running without thermostat
Danny Gaudenti
thermostat? Other than not letting the engine warm up as fast, is
there anything wrong with doing that? I don't have an overheating
problem or anything like that. A couple of friends at work were
talking about it today and I heard some strange possible problems.
One possiblity mentioned is that the engine will run _hotter_ without
the thermostat.
Thanks for any info,
Danny
Roy W. Forgy
cars. On older cars I would suggest that if you want to run without
one you just cut the middle out so the hole is the same size. If you
remove it all together the hole is bigger and the water will flow
through the radiator faster thus not cooling it as much.
On Sun, 12 Jul 1998 00:59:08 GMT, gau...@qnet.com (Danny Gaudenti)
wrote:
Roy W. Forgy
Hollywood Beach
Oxnard, CA
Ode
higher flow = higher heat transfer. You may even get discussion about laminar
and turbulent flow, bla, bla, bla. The water pump generates plenty of turbulence
and the paths through the engine are quite narrow anyway.
However, with the thermostat out, if you drive under "severe service"
conditions, not letting the temperature come up and stay up before shutting it
off, you may need to change your oil more often. The contaminants (acids, water,
etc.) will not have time at temp to boil off, possibly causing accelerated
engine wear.
Also, although a lower temperature will enable you to advance the timing a
little further (if you are only making short runs, if the engine comes up to
temp, this will result in detonantion) and get a cooler, denser air/fuel charge,
this will NEHATIVELY effect efficiency; power will increase slightly during the
warm-up period, mileage will decrease, more than slightly during the warm-up
period.
The engine will still run the same after warm-up, which of course will take
longer without the thermostat. My advice, don't drive a STREET car without a
thermostat, unless the one you have is stuck closed and you have to take it out
to use the car to go get a new one . . .
Danny Gaudenti wrote:
> Does anybody know anything about running an engine without a
> thermostat? Other than not letting the engine warm up as fast, is
> there anything wrong with doing that? I don't have an overheating
> problem or anything like that. A couple of friends at work were
> talking about it today and I heard some strange possible problems.
> One possiblity mentioned is that the engine will run _hotter_ without
> the thermostat.
>
> Thanks for any info,
>
> Danny
--
-----------------------------------------------------------------------------------
Ode
S.G. Ouderkirk
Ouderkirk Audio
Oude...@mci2000.com
"The government exists solely to protect the rights of its people.
To protect from threats both foreign and domestic. Should a
government endeavor fail to meet this goal, it should be eliminated.
The government exists to protect; not to provide, not to serve.
The government should provide nothing but the protection from the
violation of the rights of its people. It is a right to pursue happiness;
it is not a right to have it, nor is it a right to have assistance in
pursuing it." -- S.G. Ouderkirk
------------------------------------------------------------------------------------
Gennady Samokhin
Ode wrote:
> The engine will still run the same after warm-up, which of course will take
> longer without the thermostat.
I have a feeling that depending on paricular car some engines without thermostat will
never reach the working temperature unless you will run it sitting without air flow
through radiator. The thermostat function is not only to allow to reach working
temperature faster, but also to control it after it is reached.
Gennady
Bob.
>
>Does anybody know anything about running an engine without a
>thermostat? Other than not letting the engine warm up as fast, is
>there anything wrong with doing that? I don't have an overheating
>problem or anything like that. A couple of friends at work were
>talking about it today and I heard some strange possible problems.
>One possiblity mentioned is that the engine will run _hotter_ without
>the thermostat.
>
the radiator cools it. Some engines (espesially Oldsmobiles) can dump
water into the radiator faster than it can cool it off if there is no
thermostat. water leaving the radiator at , or close to , the temp it
entered is not a good thing.
Lakes
Running moderately modified cars in Australia, I experimented a little with
the need for thermostats.
A thermostat is designed to slow the cooling process - it cannot enhance
cooling. It is an intelligent block to the cooling of your engine so that
it will reach operating temp as soon as possible; then stay there.
So if it is removed, car will slowly get up to a temperature which is
suitable for the air temperature of the day & probably not an optimal
running temp.
Only exception is when air temp is very high and thermostat body is
introducing a restriction (ie poor design).
Conclusions: If it's too hot (car or temp), you need a bigger radiator.
Bob. <bob...@efortress.com> wrote in article
<6ofvat$d0k$1...@usenet49.supernews.com>...
rat...@hotmail.com
automobile with a 318 CID engine. That engine would definately run hot
without a thermostat. Yes, the radiator was clean as were the water jackets.
It must have been because the thermostat was acting as a baffle, forcing
coolant to the rear of the block and heads. The path of least resistance
will be taken by the coolant. I presume in this case it was through the
water pump and directly back to the radiator. I replaced the thermostat and
the engine heated to a normal temperature. I removed the thermostat to see
if it would run hot again. It did. That was the end of my experiment.
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
T. Postel
>Does anybody know anything about running an engine without a
>thermostat? Other than not letting the engine warm up as fast, is
>there anything wrong with doing that? I don't have an overheating
>problem or anything like that. A couple of friends at work were
>talking about it today and I heard some strange possible problems.
>One possiblity mentioned is that the engine will run _hotter_ without
>the thermostat.
>
>
>Danny
First, if the engine does not warm up this will cause greatly accelerated engine wear. The
products of combustion include water and oxides of sulphur, carbon and nitrogen. If the
water is not evaporated quickly and condenses on the internal engine parts, these oxides
form acids readily and cause corrosive wear. Motor oils contain emulsifiers to keep any
water away from the parts it would attack, when the emulsifiers are saturated the oil can
foam, which reduces or eliminates its lubricating ability. Even small amounts of moisture
will damage most oil filters. Motor oils are meant to operate at around 200 deg F, and so
the detergent and sequestrant additives may not perform at lower temps.
Second, it can cause overheating. In many engines the water pump is designed to pump
against some flow resistance, such as an open thermostat. If you look at one, you'll see
that the area the water goes through is quite a restriction. The small flow resistance is
enough to prevent cavitation in the pump at high rpm. Cavitation, if sever, will destroy
the pump, and even if mild will reduce the flow of coolant. Placing the restiction at the
outlet of the engine helps to balance coolant flow through the engine which reduces hot
spots. It also ensures circulation through the heater core, but that doesn't contribute to
overheating.
-m
Shawn
The GS I used to have would run warmer period without a thermostat. Will every car do
this? No. But you can leave the thermodynamics at home because formulas assume too much
and dont account for all systems. As such you cant generalize your assumption from a
formula alone. You may be right you may be wrong... I guess Im saying ANY example of
temperature change can occurr. Othewise we agree.
A lower thermostat isnt 'just' for increased timing. I run less timing, but more boost
for the GN. You are dead on when you say detonation though. In addition, I look for a
lower air inlet temp from lower underhood temps. Lower air temp = HP for me!!
Shawn GNa...@feist.com
Ode wrote:
> The idea that it will run hotter is flawed. Elementary Thermodynamics,
> higher flow = higher heat transfer. You may even get discussion about laminar
> and turbulent flow, bla, bla, bla. The water pump generates plenty of turbulence
> and the paths through the engine are quite narrow anyway.
>
> However, with the thermostat out, if you drive under "severe service"
> conditions, not letting the temperature come up and stay up before shutting it
> off, you may need to change your oil more often. The contaminants (acids, water,
> etc.) will not have time at temp to boil off, possibly causing accelerated
> engine wear.
>
> Also, although a lower temperature will enable you to advance the timing a
> little further (if you are only making short runs, if the engine comes up to
> temp, this will result in detonantion) and get a cooler, denser air/fuel charge,
> this will NEHATIVELY effect efficiency; power will increase slightly during the
> warm-up period, mileage will decrease, more than slightly during the warm-up
> period.
>
> The engine will still run the same after warm-up, which of course will take
> longer without the thermostat. My advice, don't drive a STREET car without a
> thermostat, unless the one you have is stuck closed and you have to take it out
> to use the car to go get a new one . . .
>
> Danny Gaudenti wrote:
>
> > Does anybody know anything about running an engine without a
> > thermostat? Other than not letting the engine warm up as fast, is
> > there anything wrong with doing that? I don't have an overheating
> > problem or anything like that. A couple of friends at work were
> > talking about it today and I heard some strange possible problems.
> > One possiblity mentioned is that the engine will run _hotter_ without
> > the thermostat.
> >
> > Thanks for any info,
> >
> > Danny
>
StinkyP...@hotmail.com
gau...@qnet.com (Danny Gaudenti) wrote:
> Does anybody know anything about running an engine without a
> thermostat? Other than not letting the engine warm up as fast, is
> there anything wrong with doing that? I don't have an overheating
> problem or anything like that. A couple of friends at work were
> talking about it today and I heard some strange possible problems.
> One possiblity mentioned is that the engine will run _hotter_ without
> the thermostat.
It will run too cool. Deposits and sludge are two of the results.
Stinky
Gary Derian
the bypass when the engine is hot. Removing this type of thermostat will
really screw up the water flow and probably cause overheating.
--
Gary Derian <gde...@cybergate.net>
Victor Olkhovets
You may want to find my old (1 mo old) post about driving with thermostat blocked open,
and the following discussion.
The engine remained _cold_ after 2 hr fwy driving (I had to touch it to believe the
temp sensor! - and I _could_ touch it).
My friends and I were impressed.
Victor
> > Does anybody know anything about running an engine without a
> > thermostat? ... A couple of friends at work were
Bob.
>
>About the "running hotter":
>
>You may want to find my old (1 mo old) post about driving with thermostat blocked open,
>and the following discussion.
>The engine remained _cold_ after 2 hr fwy driving (I had to touch it to believe the
>temp sensor! - and I _could_ touch it).
freeway driving is optimal for cooling .
Try the same experiment in city traffic.
Some engines WILL run cooler without a thermistat,but take one out of a
Oldsmobile or Buick V8 and it WILL overheat in traffic.
C Riecke
Since coolant temp. is one of the inputs to the cars computer
it would seem the the wise thing to do would be put in a ther. of the
proper temp. range and let the computer do its thing.
Ode
cools down, it will close again, assuring the engine stays ABOVE a certain temperature,
it does not help cooling.
Gennady Samokhin wrote:
> Ode wrote:
>
> > The engine will still run the same after warm-up, which of course will take
> > longer without the thermostat.
>
> I have a feeling that depending on paricular car some engines without thermostat will
> never reach the working temperature unless you will run it sitting without air flow
> through radiator. The thermostat function is not only to allow to reach working
> temperature faster, but also to control it after it is reached.
>
> Gennady
--
Ode
even throughout the radiator and engine, this is not a bad thing, it is ideal. A
bad thing is very little flow, then the water entering the radiator is very hot
and leaves very cool. This looks great on a spec sheet, and it cools the water
in the radiator great, and this may show up on your temp gauge depending on
where the sending unit it is, but the engine is HOTTER.
If you are transfering more heat away from the engine and your sending unit
is in the engine or between it and the radiator, it will indicate HOTTER, but
the engine temp will be COOLER. This is the whole point of the cooling system,
to take the heat FROM the engine by transfering it TO the coolant. More flow may
very well equal hotter coolant temperature, but MORE FLOW WILL NOT RESULT IN
HOTTER ENGINE TEMPERATURE.
Anyone stating that moving the water slower provides better cooling has very
limited (or no) knowledge of thermodynamics. The coolant is supposed to get hot,
that is the point, to transfer the heat from the engine to the coolant. In some
vehicles with poorly designed cooling systems, the transfer of more heat may
cause boilover, but the cylinder head and block temperature will be LOWER. Your
engine temperature is hotter than the coolant, or the coolant would not cool it.
The faster the coolant flows, if the radiator is too small, the hotter the
coolant will get, but this does not change the fact that the engine is COOLER.
The faster coolant flows, the closer the engine temperature will be to the
temperature of the coolant.
MORE FLOW = LOWER ENGINE TEMPERATURE, PERIOD.
Bob. wrote:
> In article <35a8089...@news.av.qnet.com>, gau...@qnet.com says...
> >
> >Does anybody know anything about running an engine without a
> >thermostat? Other than not letting the engine warm up as fast, is
> >there anything wrong with doing that? I don't have an overheating
> >problem or anything like that. A couple of friends at work were
> >talking about it today and I heard some strange possible problems.
> >One possiblity mentioned is that the engine will run _hotter_ without
> >the thermostat.
> >
> Yes, it can run hotter. as the engine dumps water into the radiator
> the radiator cools it. Some engines (espesially Oldsmobiles) can dump
> water into the radiator faster than it can cool it off if there is no
> thermostat. water leaving the radiator at , or close to , the temp it
> entered is not a good thing.
--
Bryan Conrad
>
>
>
I cannot comment on oldsmobiles,but certain caterpillar engines will
definately run hotter when the thermostat or regulator is removed.
This is due to the thermostat being designed to perform two
simultaneous functions.
The thermostat in these engines isolates the engine coolant
from the radiator AND opens the radiator bypass circuit to enable
coolant to flow in a short circuit through the engine block and cyl
head excluding the radiator.
When the coolant has warmed sufficiently the thermostat opens
to the radiator AND closes the radiator bypass circuit,forcing the
coolant to circulate through the radiator core.
When "mr fixit" removes the thermostat to cure all the
engine's woes,the removal of the obstruction in the bypass circuit
makes this passage the line of least resistance for engine
coolant,and,as a consequence the engine overheats due to little or no
flow through the radiator as the radiator presents more restriction to
flow than the bypass circuit.
I now have two horribly deformed fingers,crippled by RSI......
Clyde
Buggered if I know...............
Cavemen are people too!
Remove s from bconrads to E-Mail.
Gennady Samokhin
Ode wrote:
> Once the temperature of the thermostat is reached, it does nothing but stay open. If it
> cools down, it will close again, assuring the engine stays ABOVE a certain temperature,
> it does not help cooling.
>
That is exactly what I meant speaking about the control of the temperature: not to help
cooling, but not to allow it cool down below the temperature specified for particular
thermostat! And that is what may happen without thermostat - the engine will run cooler.
Gennady
dbug
wrote:
>Does anybody know anything about running an engine without a
>thermostat? Other than not letting the engine warm up as fast, is
>there anything wrong with doing that? I don't have an overheating
>problem or anything like that. A couple of friends at work were
>talking about it today and I heard some strange possible problems.
>One possiblity mentioned is that the engine will run _hotter_ without
>the thermostat.
>
>Thanks for any info,
>
>Danny
An engine should always have a properly working thermostat. It is
true that some engines can overheat without a thermostat. I have a
Ford Cleveland that will indicate a low temperature without a
thermostat while the radiator boils over. The thermostat is an
integral part of directing the flow of water in the engine. I suppose
an orifice washer could be used to serve the same function without
actually regulating temperature.
Shawn
the theory that the coolant wouldn't have sufficient time to dissipate heat. The problem with
this is that it also spends less time being "heated".
I do stand by my restriction statements! I did forget about cavitation...
I was reminded of this when I was talking to a buddy of mine (owns a rad shop) and he
corrected my mistake of "fast flow". Two great sources are Tony DeQuick and Kenny Holm.
So in summary... T. Postel said it best and put it in a way I could not. Kinda explains
erratic readings also :D
Shawn GNa...@feist.com
T. Postel wrote:
> gau...@qnet.com (Danny Gaudenti) wrote:
> >Does anybody know anything about running an engine without a
> >thermostat? Other than not letting the engine warm up as fast, is
> >there anything wrong with doing that? I don't have an overheating
> >problem or anything like that. A couple of friends at work were
> >talking about it today and I heard some strange possible problems.
> >One possiblity mentioned is that the engine will run _hotter_ without
> >the thermostat.
> >
> >Thanks for any info,
> >
> >Danny
>
Bob.
>I cannot comment on oldsmobiles,but certain caterpillar engines will
>definately run hotter when the thermostat or regulator is removed.
> This is due to the thermostat being designed to perform two
>simultaneous functions.
> The thermostat in these engines isolates the engine coolant
>from the radiator AND opens the radiator bypass circuit to enable
>coolant to flow in a short circuit through the engine block and cyl
>head excluding the radiator.
> When the coolant has warmed sufficiently the thermostat opens
>to the radiator AND closes the radiator bypass circuit,forcing the
>coolant to circulate through the radiator core.
> When "mr fixit" removes the thermostat to cure all the
>engine's woes,the removal of the obstruction in the bypass circuit
>makes this passage the line of least resistance for engine
>coolant,and,as a consequence the engine overheats due to little or no
>flow through the radiator as the radiator presents more restriction to
>flow than the bypass circuit.
>
This is one of the reason Olds engines overheat without a thermistat.
The waterneck has 2 outlets. 1 is the upper radiator hose and the other
is a 3/4" hose that goes directly back to the water pump. Do these CAT
engines have a simular steup?
Shawn
the thermostat with one side stating the importance of the restriction the thermostat
provides.
Shawn GNa...@feist.com
Victor Olkhovets wrote:
> About the "running hotter":
>
> You may want to find my old (1 mo old) post about driving with thermostat blocked open,
> and the following discussion.
> The engine remained _cold_ after 2 hr fwy driving (I had to touch it to believe the
> temp sensor! - and I _could_ touch it).
>
> My friends and I were impressed.
>
> Victor
>
> > > Does anybody know anything about running an engine without a
> > > thermostat? ... A couple of friends at work were
Ode
mean removing the thermostat. I do not mean removing the thermostat and the
bypass valve; just as I do not mean removing the thermostat and the radiator. I
mean removing JUST the thermostat.
And once again let me repeat myself, MORE FLOW = COOLER ENGINE.
And I do NOT recommend running without a thermostat in a street vehicle.
Bryan Conrad wrote:
> On Wed, 15 Jul 1998 09:07:15 GMT, Ode <Oude...@mci2000.com> wrote:
>
> >
> >
> >
> I cannot comment on oldsmobiles,but certain caterpillar engines will
> definately run hotter when the thermostat or regulator is removed.
> This is due to the thermostat being designed to perform two
> simultaneous functions.
> The thermostat in these engines isolates the engine coolant
> from the radiator AND opens the radiator bypass circuit to enable
> coolant to flow in a short circuit through the engine block and cyl
> head excluding the radiator.
> When the coolant has warmed sufficiently the thermostat opens
> to the radiator AND closes the radiator bypass circuit,forcing the
> coolant to circulate through the radiator core.
> When "mr fixit" removes the thermostat to cure all the
> engine's woes,the removal of the obstruction in the bypass circuit
> makes this passage the line of least resistance for engine
> coolant,and,as a consequence the engine overheats due to little or no
> flow through the radiator as the radiator presents more restriction to
> flow than the bypass circuit.
> I now have two horribly deformed fingers,crippled by RSI......
>
>
> Clyde
> Buggered if I know...............
> Cavemen are people too!
> Remove s from bconrads to E-Mail.
--
Ode
know what I think. More flow = cooler engine, period. If you transfer more heat from the
engine, sure the coolant may run hotter, but the engine will be cooler.
Shawn wrote:
--
Shawn
practical experience to base all automotive systems/situations on? On paper and by definition
this works out but wont ALWAYS fly in the real world. Victor stated "blocked open" not removed
btw.
I say you may run into a hotter running engine (peak) with the tstat REMOVED. Ive done it. No
formula needed it just worked out that way. Some as they have posted elsewhere ran cooler (I
have had this happen also but only at lower speeds). You miss the point.... you are using
thermodynamics with no realworld examples to explain that every car in every situation will
never(?) have its peak temp increase with the tstat removed.
When I say the restriction improves cooling, its not to find fault in the "laws" of thermodymics
but the restriction CAN affect overall system performance. See the difference? Remember we
are trying to maintain pressure in the system also.
Shawn GNa...@feist.com
Victor Olkhovets
Let me ask the group, what's called thermostat. (I'm not sure we mean the same thing now).
Is it the same in all cars (a valve near a radiator hose, which is close below, say, 190F and
opens above)?
I don't know about other types, but:
Can it be a valve opening/closing the bypass hose?
Or a 3-way valve (from engine -> to radiator / bypass)?
Or an electrically/vacuum operated valve, using an external sensor and el. unit?
The same set of questions about the waterpump.
Are they different? (I don't mean size, of course)
Is there any evidence that some of them work better (volume/time) against a pressure (blockage)?
Can a waterpump refuse to pump without resistance?
Victor
----------------------------------------------------------------------------
----------------------------------------------------------------------------
BTW, a good source of radiators in L. A.
"Radiator haus", 213 730 1666
They sell new "noname" radiators with 2yr warranty for $90-100.
(this is not a paid advertisement)
dino
condensation in the oil and subsiquent contamantion of oil. also the tolarences of major
engine parts like piston to bore are made to be run at a certain temp, running cold will wear
the engine more, also more unburnt hydrocarbons will be sent to the CAT stressing that thing.
and you will get shitty milage.
if you have a compuiter controled auto and it does not reach 'operation tempature' in a
certain ammount of time you will get a error code on the CPU and MIL lights will flash and
car will run like shit.
better off with an properly maintained cooling system than removeing thermo-stat
NOSPAM...@ibm.net
hotter with the thermostat removed, what does this really mean? Is there
a head temp gauge or an oil temp gauge, or is it just the water temp
gauge that runs hotter? That I am ready to believe, but I wouldn't call
it the engine temp.
Victor Olkhovets
Please don't take it personally, but it seems to me, you missed Zuckier' point.
The question now is:
"well, if we open the radiator hose wider, without changing anything else, the engine should be
cooler.
I guess we all agree on it.
But some people continue reporting higher temp gage reading
with the thermostat removed.
Let's accept it as an experimental fact, that is yet to be explained.
Some possible explanations are:
- Waterpump won't pump without an 'orifice', or will pump slower.
- Removing the thermostat (at least on some vehicles) opens the bypass wider.
[in other words, removing the thermostat changes not only radiator resistance]
- The gage shows the water temperature, not the block/head temperature
[this the Zuckier' explanation]
-Too high flow (with therm removed) causes cavitation/bubbles or other unpleasant side effects =>
again lower heat transfer.
-other explanations could also be possible...
Of the above, I would agree with the Zuckier's version (if we remove the thermostat, the engine will
go colder, but the temp sensor can indicate higher temperature, because it installed at some unlucky
point on some cars).
But other explanations could also be correct for some vehicles.
Victor
--------------------------------------------------------------------------------------
Ode wrote:
> I would call it engine temperature, the block and heads are pretty much what most of us would
> refer to as "the engine". When you totally rebuild an engine (new pistons, rings, valves, pumps,
> etc.) what is left to rebuild? The block and heads, that is the engine, that is what you are
> rebuilding; this is what you are trying to cool with coolant. The pistons are cooled (believe it
> or not) by the intake charge of gasoline, that is why running the thing lean will burn piston(s).
> Oil cools all lubricated parts . . . Coolant cools the stationary metal parts of the engine.
>
> More flow = Cooler engine.
>
> I do NOT recommend running a street vehicle without a thermostat.
Ode
refer to as "the engine". When you totally rebuild an engine (new pistons, rings, valves, pumps,
etc.) what is left to rebuild? The block and heads, that is the engine, that is what you are
rebuilding; this is what you are trying to cool with coolant. The pistons are cooled (believe it
or not) by the intake charge of gasoline, that is why running the thing lean will burn piston(s).
Oil cools all lubricated parts . . . Coolant cools the stationary metal parts of the engine.
More flow = Cooler engine.
I do NOT recommend running a street vehicle without a thermostat.
NOSPAM...@ibm.net wrote:
> ------------------------------------------------------------------------------------
> Yeah, that brings up the question of: when people say the engine runs
> hotter with the thermostat removed, what does this really mean? Is there
> a head temp gauge or an oil temp gauge, or is it just the water temp
> gauge that runs hotter? That I am ready to believe, but I wouldn't call
> it the engine temp.
--
Ode
cooler with higher flow, period. In a mrginal cooling system this may indeed cause the COOLANT to
run hotter, but will NOT cause the engine to run hotter. The faster the coolant flows, the lower the
difference in coolant and engine temperature, and the more total heat that is stripped from the
engine. The higher the gradient bewteen the radiator and air, the more heat is transfered out of the
vehicle. In a marginal or poorly designed cooling system this may indeed cause booilover, but the
engine temperature will be COOLER. Your temperature gauge tells you the temperature of the COOLANT,
NOT the engine. You want proof? Install a cylinder head temperature gauage (available at most hi-po
stores).
And once more, let me restate:
More flow = lower engine temperature
And I do NOT recommend running a street vehicle without a thermostat.
Shawn wrote:
> Lemme guess... thermodynamics again. Did you just learn this stuff in a class? Do you have any
> practical experience to base all automotive systems/situations on? On paper and by definition
> this works out but wont ALWAYS fly in the real world. Victor stated "blocked open" not removed
> btw.
>
> I say you may run into a hotter running engine (peak) with the tstat REMOVED. Ive done it. No
> formula needed it just worked out that way. Some as they have posted elsewhere ran cooler (I
> have had this happen also but only at lower speeds). You miss the point.... you are using
> thermodynamics with no realworld examples to explain that every car in every situation will
> never(?) have its peak temp increase with the tstat removed.
>
> When I say the restriction improves cooling, its not to find fault in the "laws" of thermodymics
> but the restriction CAN affect overall system performance. See the difference? Remember we
> are trying to maintain pressure in the system also.
>
> Shawn GNa...@feist.com
>
> Ode wrote:
>
> > The idea that a blockage in the cooling system, of any kind improves cooling is, well, you
> > know what I think. More flow = cooler engine, period. If you transfer more heat from the
> > engine, sure the coolant may run hotter, but the engine will be cooler.
> >
> > Shawn wrote:
> >
> > > blocked? or without? Multiple theories right now. The discussion is about the removal of
> > > the thermostat with one side stating the importance of the restriction the thermostat
> > > provides.
> > > Shawn GNa...@feist.com
> > >
> > > Victor Olkhovets wrote:
> > >
> > > > About the "running hotter":
> > > >
> > > > You may want to find my old (1 mo old) post about driving with thermostat blocked open,
> > > > and the following discussion.
> > > > The engine remained _cold_ after 2 hr fwy driving (I had to touch it to believe the
> > > > temp sensor! - and I _could_ touch it).
> > > >
> > > > My friends and I were impressed.
> > > >
> > > > Victor
> > > >
> > > > > > Does anybody know anything about running an engine without a
> > > > > > thermostat? ... A couple of friends at work were
> > > > > > talking about it today and I heard some strange possible problems.
> > > > > > One possiblity mentioned is that the engine will run _hotter_ without
> > > > > > the thermostat.
> > > > > >
> >
Ode
Victor Olkhovets wrote:
> Please don't take it personally, but it seems to me, you missed Zuckier' point.
I don't think I did. I think you are confusing what he said with what I said.
> The question now is:
> "well, if we open the radiator hose wider, without changing anything else, the engine should be
> cooler.
Assuming the current size hose is restrictive in some way, or even if it is not, the point is it would
certainly not cause the temperature of the engine to RISE by putting in a bigger hose.
> I guess we all agree on it.
We wouldn't be having this discussion if we agreed on it.
> But some people continue reporting higher temp gage reading
> with the thermostat removed.
> Let's accept it as an experimental fact, that is yet to be explained.
Except that I have repeatedly explained this.
> Some possible explanations are:
>
> - Waterpump won't pump without an 'orifice', or will pump slower.
The only way the water pump would need a restriction for maximum pumping is if there were air in the
system. If so it needs to be bled out, not restricted to keep air from the area around the impeller.
> - Removing the thermostat (at least on some vehicles) opens the bypass wider.
This would be considered more than a thermostat.
> [in other words, removing the thermostat changes not only radiator resistance]
>
> - The gage shows the water temperature, not the block/head temperature
> [this the Zuckier' explanation]
No, this is my explanation. I think you are loosing track here.
> -Too high flow (with therm removed) causes cavitation/bubbles or other unpleasant side effects =>
> again lower heat transfer.
Piece of crap impeller (poorly designed or malfunctioning) and/or air in the system. And just to clarify
your statement, if there were cavitation or boubles, flow would be LOWER, not higher. This should not be
a problem unless the water pump is garbage.
> -other explanations could also be possible...
>
> Of the above, I would agree with the Zuckier's version (if we remove the thermostat, the engine will
> go colder,
Once again, this is MY explanation.
> but the temp sensor can indicate higher temperature, because it installed at some unlucky
> point on some cars).
I have said this repeatedly.
> But other explanations could also be correct for some vehicles.
MORE FLOW = LOWER ENGINE TEMPERATURE
I do NOT recommend running a street vehicle without a thermostat.
Ode
1. The radiator will radiate MORE heat the hotter the coolant is in the radiator. (don't think anyone
will argue with this one)
2. So if the coolant temperature is higher after taking the thermostat out, where is the extra heat
coming from?
3. The only explanation for MORE flow is that MORE heat is being transfered into the coolant from the
engine than before the thermostat was removed.
4. MORE FLOW = COOLER ENGINE
5. The other explanation is LOWER FLOW after thermostat removal. Lower flow will of course result in
a smaller gradient on the radiator side and less heat dissapation, which of course would cause a higher
reading if the sending unit is in certain spots. Lower flow after thermostat removal is supposed could be
caused by 6&7:
6. Cavitation is more likely to happen in a restrictive system than in a free flowing system
(elementary fluid dynamics).
7. Air in the system (which it is supposed may surround the impeller after thermostat is removed)
needs to be removed, thermostat or no.
8. Now, if the aggregate engine-coolant differential is greater than the aggregate coolant-air
(radiator) differential, speeding up the coolant will cause a DECREASE in engine temperature and an INCREASE
in coolant temperature.
9. On the flip side, if the aggregate engine-coolant differential is smaller than the aggregate
coolant-air (radiator) differential, speeding up the coolant will cause a DECREASE in engine temperature and
a DECREASE in coolant temperature.
10. Either way, an increase in flow DECREASES engine (block, head) temperature, and removing the
thermostat will cause an INCREASE in flow.
Terbo
Where is the temperature gauge getting its reading from? Where is the sensor
located? Assume that the flow increases when the thermostat is removed. The
coolant spends less time in the radiator and cools less. If the sensor is
located near the coolant return to the engine, the temperature of the coolant
might very well be reported as hotter. The overall average temp of the engine
is actually lower... only hotter at the location its reported from.
With the thermostat installed, the sensor is reporting a misleadingly *low*
temperature. The coolant spends more time in the radiator and is cooler when it
hits the sensor. The average engine temperature would be *hotter* if measured
where the coolant leaves the engine.
did that make any sense?
Isaac Ethan Fox
higher temperature, and that this would go along with a cooler engine
temperature. Obviously, if you idle the motor with the thermostat in it and
measure the temperature, then remove the thermostat and run the engine under
max. load for an hour, the engine temperature without the thermostat (under
full load)would be higher. What a dumb way to gauge the effects of a
thermostat.
I can imagine a situation where a thermostat was used to close off some sort
of an engine bypass hose, thus increasing flow through the engine when the
'stat closed. I have never seen or heard of an actual automobile with this
configuration.
> The pistons are cooled (believe it
>or not) by the intake charge of gasoline, that is why running the thing
lean will >burn piston(s)
only on an ancient motor! Modern gas engines (without direct injection) run
very near to stoichiometric mixtures, except under transient conditions
(sudden accel. / decel., warm-up, etc.)
Yes, this could mean higher temperatures within the cylinder. Luckily, they
invented EGR (exhaust gas recirc.) to keep the engine temperatures (and thus
NOx production) lower.
Bryan Conrad
>
>This is one of the reason Olds engines overheat without a thermistat.
>The waterneck has 2 outlets. 1 is the upper radiator hose and the other
>is a 3/4" hose that goes directly back to the water pump. Do these CAT
>engines have a simular steup?
>
Yeah,we are essentially speaking of the same bypass circuit.
Bryan Conrad
The thermostats I refer to perform both functions,they are inseparable
without altering the design of the thermostat or system.
>Ode
>S.G. Ouderkirk
>Ouderkirk Audio
>Oude...@mci2000.com
>
>"The government exists solely to protect the rights of its people.
>To protect from threats both foreign and domestic. Should a
>government endeavor fail to meet this goal, it should be eliminated.
>The government exists to protect; not to provide, not to serve.
>The government should provide nothing but the protection from the
>violation of the rights of its people. It is a right to pursue happiness;
>it is not a right to have it, nor is it a right to have assistance in
>pursuing it." -- S.G. Ouderkirk
>
>------------------------------------------------------------------------------------
>
>
>
>
Clyde
dbug
Many automobile engines use a bypass system when the engine is cold
and the stat closed. The small block Ford is one that recirculates
water internally until the stat opens to allow coolant to stat
circulating thru the radiator. You don't want to just block the flow
of the coolant. That would take unnecessary power to turn the pump
and guarantee that the engine did not warm uniformly. I can't think
of any engine that does not recirculate (bypass the radiator) when the
stat is closed.
Shawn
running "cooler" and running too cold as the "design temp" has a range not a set point. I know
you know that I know (hehe) but others may not.
My mileage is excellent (better than OEM) but then again I dont run colder than 160 after
warmup. Of course I have a thermostat...
Shawn GNa...@feist.com
Gennady Samokhin
Terbo wrote:
It did make sense, but you are considering only one side of the equation. Less time
in the rad - higher temp at the exit. This is true if the temp at the entrance is
the same. But it is not. Higher flow means that coolant spends less time in the
engine, so the temp at the entrance to the rad will be lower. Essentially by this
consideration you just can not predict, what will actually happen.
Gennady
Ode
Terbo wrote:
> submitted for speculation:
>
> Where is the temperature gauge getting its reading from? Where is the sensor
> located? Assume that the flow increases when the thermostat is removed. The
> coolant spends less time in the radiator and cools less. If the sensor is
> located near the coolant return to the engine, the temperature of the coolant
> might very well be reported as hotter. The overall average temp of the engine
> is actually lower... only hotter at the location its reported from.
>
> With the thermostat installed, the sensor is reporting a misleadingly *low*
> temperature. The coolant spends more time in the radiator and is cooler when it
> hits the sensor. The average engine temperature would be *hotter* if measured
> where the coolant leaves the engine.
>
> did that make any sense?
--
-----------------------------------------------------------------------------------
Ode
Isaac Ethan Fox wrote:
> I agree that removing the thermostat could cause the coolant to have a
> higher temperature, and that this would go along with a cooler engine
> temperature. Obviously, if you idle the motor with the thermostat in it and
> measure the temperature, then remove the thermostat and run the engine under
> max. load for an hour, the engine temperature without the thermostat (under
> full load)would be higher. What a dumb way to gauge the effects of a
> thermostat.
>
> I can imagine a situation where a thermostat was used to close off some sort
> of an engine bypass hose, thus increasing flow through the engine when the
> 'stat closed. I have never seen or heard of an actual automobile with this
> configuration.
>
> > The pistons are cooled (believe it
> >or not) by the intake charge of gasoline, that is why running the thing
> lean will >burn piston(s)
>
> only on an ancient motor! Modern gas engines (without direct injection) run
> very near to stoichiometric mixtures, except under transient conditions
> (sudden accel. / decel., warm-up, etc.)
>
Yes, but a modern engine by doing so PREVENTS the engine from running lean. If
you run it lean it will still run hot, even in a modern engine. A modern engine
is just less likely to run lean.
> Yes, this could mean higher temperatures within the cylinder. Luckily, they
> invented EGR (exhaust gas recirc.) to keep the engine temperatures (and thus
> NOx production) lower.
--
Ode
Gennady Samokhin wrote:
> Terbo wrote:
>
> > submitted for speculation:
> >
> > Where is the temperature gauge getting its reading from? Where is the sensor
> > located? Assume that the flow increases when the thermostat is removed. The
> > coolant spends less time in the radiator and cools less. If the sensor is
> > located near the coolant return to the engine, the temperature of the coolant
> > might very well be reported as hotter. The overall average temp of the engine
> > is actually lower... only hotter at the location its reported from.
> >
> > With the thermostat installed, the sensor is reporting a misleadingly *low*
> > temperature. The coolant spends more time in the radiator and is cooler when it
> > hits the sensor. The average engine temperature would be *hotter* if measured
> > where the coolant leaves the engine.
> >
> > did that make any sense?
>
> It did make sense, but you are considering only one side of the equation. Less time
> in the rad - higher temp at the exit. This is true if the temp at the entrance is
> the same. But it is not. Higher flow means that coolant spends less time in the
> engine, so the temp at the entrance to the rad will be lower. Essentially by this
> consideration you just can not predict, what will actually happen.
>
> Gennady
--
Ode
it if you did not put your own words in place of what I wrote, attributing whatever
information or misinformation you wish to relay to my name. Thanks.
Bryan Conrad wrote:
> On Wed, 15 Jul 1998 20:19:11 GMT, Ode <Oude...@mci2000.com> wrote:
>
> The thermostats I refer to perform both functions,they are inseparable
> without altering the design of the thermostat or system.
> >Ode
> >S.G. Ouderkirk
> >Ouderkirk Audio
> >Oude...@mci2000.com
> >
> >"The government exists solely to protect the rights of its people.
> >To protect from threats both foreign and domestic. Should a
> >government endeavor fail to meet this goal, it should be eliminated.
> >The government exists to protect; not to provide, not to serve.
> >The government should provide nothing but the protection from the
> >violation of the rights of its people. It is a right to pursue happiness;
> >it is not a right to have it, nor is it a right to have assistance in
> >pursuing it." -- S.G. Ouderkirk
> >
> >------------------------------------------------------------------------------------
> >
> >
> >
> >
>
> Clyde
> Buggered if I know...............
> Cavemen are people too!
> Remove s from bconrads to E-Mail.
--
T. Postel
> 6. Cavitation is more likely to happen in a restrictive system than in a
> free flowing system
>(elementary fluid dynamics).
This slightly off, and I think you are underestimating the effects and likelihood of
cavitation. Cavitation is dependent on the total fluid pressure on trailing face of the
impeller, and to the local turbulence of the fluid. When the pressure in this region is
reduced to that of the vapor pressure of the fluid at the fluid temperature the fluid will
"boil" locally. If the number and size of these bubbles is sufficient then the drag on
the impeller will be reduced enough to increase its speed. This leads to runaway
cavitation, and while the pump continues to turn, fluid flow can drop by as much as 90%
Increasing the pressure head by restricing the output will increase the temperature at
which cavitation begins for any given rate of flow. Expecting the pressure rise, due to
the radiator pressure cap, to prevent cavitation is naive. The pressure is developed by
the expansion of the fluid with temperature. And the cooling system is not rigid. The
rubber hoses, and copper, brass, aluminum or plastic radiator parts expand with pressure.
This makes the pressure increase more slowly than the temperature. Therefore cavitation
is more likely in a hot, pressurized system than in a cool one. At room temperature, and
1 foot of head, cavitation starts when the peripheral speed of the impeller tips exceeds
12,000 fpm in water. If the impeller in your pump is 4 inches across, then cavitation
will start at about 12,000 rpm (pump shaft), at room temperature with no throttling of the
outlet. Obviously, when the water is near its boiling temperature it will cavitate very
easily. A 50% glycol & water mixture, and the proper thermostat are the best protection
against cavitation.
What I am saying when the coolant flow decreases the engine temperature increases.
Witout a thermostat, at high rpm and no other major restrictions in the coolant
passageways, many water pumps will start to cavitate. This will lead to a reduction in
coolant flow, and an increase in engine (and coolant) temperature. If not corrected this
increase in temperature will make the cavitation worse...
-m
Tu...@gis.net
Ode
T. Postel wrote:
> Oude...@mci2000.com wrote:
>
> > 6. Cavitation is more likely to happen in a restrictive system than in a
> > free flowing system
> >(elementary fluid dynamics).
>
> This slightly off, and I think you are underestimating the effects and likelihood of
> cavitation. Cavitation is dependent on the total fluid pressure on trailing face of the
> impeller,
Depends on pressure around the impeller on ALL sides. Having no pressure on the trailing face
and enormous pressure on the high side will not cause runaway cavitation.
> and to the local turbulence of the fluid.
The faster the impeller goes and/or the slower the fluid moves, the more turbulence. The
faster the fluid moves (take out the retsriction of the thermostat) the LESS turbulence.
> When the pressure in this region is
> reduced to that of the vapor pressure of the fluid at the fluid temperature the fluid will
> "boil" locally.
This would only happen under low pressure (before warm-up) with air present in the cooling
system. Air should be removed, and once it warms up (pressurizes) this will not happen.
> If the number and size of these bubbles is sufficient then the drag on
> the impeller will be reduced enough to increase its speed. This leads to runaway
> cavitation, and while the pump continues to turn, fluid flow can drop by as much as 90%
This is why bleading a cooling system is recommended. This should not happen in a properly
bled system with properly functioning pressure cap.
> Increasing the pressure head by restricing the output will increase the temperature at
> which cavitation begins for any given rate of flow.
When the system is warm and free of air, it has sufficient pressure to prevent this.
> Expecting the pressure rise, due to
> the radiator pressure cap, to prevent cavitation is naive.
I agree, the radiator pressure cap does not raise pressure, it limits it (caps it, if you
will) to at or below rated pressure. I do not believe I ever said the pressure cap would
somehow magically increase the pressure of the system.
> The pressure is developed by
> the expansion of the fluid with temperature. And the cooling system is not rigid.
Correct.
> The
> rubber hoses, and copper, brass, aluminum or plastic radiator parts expand with pressure.
Correct.
> This makes the pressure increase more slowly than the temperature.
Two different scales, please eaxplain what you mean more quickly. Are you talking
geometrically?
> Therefore cavitation
> is more likely in a hot, pressurized system than in a cool one. At room temperature, and
> 1 foot of head,
Closed system with NO AIR, how can you say 1 foot of head?
> cavitation starts when the peripheral speed of the impeller tips exceeds
> 12,000 fpm in water. If the impeller in your pump is 4 inches across, then cavitation
> will start at about 12,000 rpm (pump shaft), at room temperature with no throttling of the
> outlet.
Irrelevent information, you cannot assume 1 foot of head. What an impeller does 1 foot below
the surface of a lake is totally different than what it does in a closed system with no air.
> Obviously, when the water is near its boiling temperature it will cavitate very
> easily.
Correct, but like I said, this should not happen if the system's pressure cap is working and
the system is properly bled.
> A 50% glycol & water mixture, and the proper thermostat are the best protection
> against cavitation.
Bleading the system of air and insuring the pressure cap is working proplerly is the best
protection against cavitation.
> What I am saying when the coolant flow decreases the engine temperature increases.
Yes.
> Witout a thermostat, at high rpm and no other major restrictions in the coolant
> passageways,
Wow, that's a pretty big assumption, the entire system is pretty restrictive, such as the
radiator itself in a bled system, also the tight channels through the block and heads are
fairly restrictive.
> many water pumps will start to cavitate.
I disagree.
> This will lead to a reduction in
> coolant flow,
If it were true, yes it would, but I disagree.
> and an increase in engine (and coolant) temperature. If not corrected this
> increase in temperature will make the cavitation worse...
Make sure the cap is working and the system is bled, and let me repeat for those that have not
read this full thread . . .
I do NOT recommend running a street vehicle without a thermostat.
--
Bryan Conrad
>I did not write what is below "Ode <Oude...@mci2000.com> wrote:", so I would appreciate
>it if you did not put your own words in place of what I wrote, attributing whatever
>information or misinformation you wish to relay to my name. Thanks.
No need to get narky,this is due to my having deleted almost all of
your previous message in order to avoid an error message when I
submitted my reply.I am new to this game(the game I refer to being
newsgroups,NOT mechanics).
While we are on this subject,you may be able to help me.When
replying to a posting,if the previous message is longer than my reply
I get an error message when posting,I'm using free agent,is there a
way around this?(other than deleting most of the previous message)
As far as the likelihood of my info being misinfo goes,the
engines I refer to have been my profession for the past 17yrs,if you
would like to substantiate my claims,get in touch with your cat
dealer,and ask for a diagram of a 3306 coolant temp regulator,the
lower portion of the thermostat,upon opening,moves downward,closing
the bypass circuit as I stated in my previous posting.
Bryan Conrad
>This sounds reasonable and logical. But when I say removing the thermostat, I
>mean removing the thermostat. I do not mean removing the thermostat and the
>bypass valve; just as I do not mean removing the thermostat and the radiator. I
>mean removing JUST the thermostat.
If you read my posting,you will note I refer ONLY to the
thermostat.
T. Postel
>Responses interlaced below . . .
Nice reply, thanks.
However you seem to believe that cavitation is dependent on there being air or bubbles in
the system. Of course you can't get all the air out, but even if you could a pump will
still cavitate. The existance of dissolved air or air bubbles has no effect on the
formation of the vapor cavities, which is what reduces pump delivery. When there is air
in the flow then the destructive nature of the recompression of the vapor bubbles is
magnified. But I'm not referring to the destruction of the pump, I'm referring to the
reduction in coolant flow. Local turbulance tends to decrease the cavitation temperature.
Cavitation occurs in the lowest pressure regions of the eddies on the trailing face of the
impeller. If that pressure is below the vapor pressure of the fluid it will boil
regardless of the pressure on the opposite side of the vane. Increasing the outlet
pressure, by adding a restriction, reduces cavitation by increasing the pressure on the
inlet side of the vanes as fluid short-circuits around the vanes.
You said that my 12,000 fpm description was irrelevant! What do you think the pressure at
the intake of a water pump is when the water is 70 deg F.? I don't have an equation which
predicts cavitation in a 50% glycol & water mixture at normal operating temperatures,
considering the drag of the radiator, block & head water passages and themostat. So I
used a handy rule of thumb, used widely by pump designers. And I think, it shows that
most automotive pumps are pretty close to cavitation. Ya know, when I look at the engine
in my car, the pump seems to be about a foot below the radiator cap.
In any case you've offered no plausable mechanism for the cases of overheating which occur
when the thermostat is removed from an otherwise properly operating cooling system.
Cavitation is a known problem, which is mentioned as a rare but possible cause of
overheating in most repair books and is a real concern for someone who designs high speed
liquid pumps.
Now some more points you made:
>> This makes the pressure increase more slowly than the temperature.
>
>Two different scales, please eaxplain what you mean more quickly. Are you
> talking geometrically?
No I meant that that PV is not constant. In a rigid closed system containing an ideal gas
PV = nRT: if the temperature increases the pressure increases exactly proportionally. I
meant that this relationship does not apply in an automotive style cooling system, and
that the pressure in the system increases more slowly with increasing temperature than it
would if the system were rigid and contained an ideal gas. Did you really misunderstand?
Will I have to dumb this down even more?
later you say:
>When the system is warm and free of air, it has sufficient pressure to prevent
> this.
See, this is what I mean. The pressure maintained by the pressure cap does not reduce the
pump rpm at which cavitation begins, since the pressure of the fluid does not rise as fast
as the vapor pressure does with increasing temperature. At full pressure the pump is
closer to cavitation than at atmospheric. (Provided the pressurization is caused by the
temperature increase, not by pressurizing the system with some other source.) If there
were no pressure cap the pump would cavitate at an even lower speed.
-m
Shawn
Hmm... cant say I can keep up with you two (apologies to Ode for rudeness) on this but your
explaination of high speed in the below text might fit my experience. I still maintain that
removing the thermostat can indeed cause more heat. Not everytime mind you, just that its
possible. THAT is what I disagree with Ode about.
One can argue if its coolant only but hey, all I have to guage most cars is my coolant temp!
Sorry! For one of my cars without thermostat it would raise coolant temp to well over 200degF
on the highway, to me this is too much (I like slightly under - but Im anal!). Now I dont
care if all the lab work in the world says my actual engine temp is lower (I do agree w/this)
it cant be so much lower that I think the system is doing "better" at that coolant temp. The
same car would run just under to just over 200degF with thermostat. Whew!
I think the thermostat makes a pressure difference. I was told via NG that basically - NO it
doesnt. However thinking out loud here, doesnt the change in flow (being a restriction)
affect pressure? Kinda like thumb on the garden hose/AirCond orifice tube/Air compressor
lines etc... note I dont make reference to the radiator cap or the other restrictions in the
system. I mention this because while designing the cooling system initially on a given car, I
think the "other restrictions" are factored in. Thermostats of the same rating with the same
outside diameter can have completely different inside diameters and plungers.
FWIW - Use a VDO guage along with the factory temp sensor in my GN. I monitor the temp
reported by the ECM via laptop and they read 10-11degF difference accross the scale. Mounted
in two different locations.
Shawn GNa...@feist.com
T. Postel wrote:
> Oude...@mci2000.com wrote:
> >Responses interlaced below . . .
>
> >> This makes the pressure increase more slowly than the temperature.
> >
> >Two different scales, please eaxplain what you mean more quickly. Are you
> > talking geometrically?
>
> No I meant that that PV is not constant. In a rigid closed system containing an ideal gas
> PV = nRT: if the temperature increases the pressure increases exactly proportionally. I
> meant that this relationship does not apply in an automotive style cooling system, and
> that the pressure in the system increases more slowly with increasing temperature than it
> would if the system were rigid and contained an ideal gas. Did you really misunderstand?
> Will I have to dumb this down even more?
>
> later you say:
> >When the system is warm and free of air, it has sufficient pressure to prevent
> > this.
>
Joe Bays
<ol...@hotmail.com> wrote:
> As soon as anybody mentiones overheating/overcooling/temperature, the
same argument reappears.
> Let me ask the group, what's called thermostat. (I'm not sure we mean
the same thing now).
>
> Is it the same in all cars (a valve near a radiator hose, which is close
below, say, 190F and
> opens above)?
> I don't know about other types, but:
>
> Can it be a valve opening/closing the bypass hose?
> Or a 3-way valve (from engine -> to radiator / bypass)?
> Or an electrically/vacuum operated valve, using an external sensor and
el. unit?
>
>
> The same set of questions about the waterpump.
> Are they different? (I don't mean size, of course)
> Is there any evidence that some of them work better (volume/time)
against a pressure (blockage)?
>
> Can a waterpump refuse to pump without resistance?
>
> Victor
My answers, assuming relatively ordinary cars, are:
No, almost always No, No, No, No, and Yes (using murphy's law here). I am
pretty sure I saw one otherwise ordinary thermostat configured as a 3 way
valve.
--
Joe Bays
my e-mail address is jnbays at tricon dot net
Paul Mendes
Something really strange happened to me earlier tonight while
driving my car. I have a 93 Ford Probe GT 5-speed, which has been fairly
trouble free. As I was driving home around 25 MPH (cop behind me), and I took
a turn, the car stalled completely. I pulled over and noticed the "Anti-lock",
"check engine" and "fuel cutout" lights lit. Normally the check engine light
does come on should it stall or not fully start, as well as the anti-lock
light. Not sure about the fuel cutout light though. I tried starting it, it
would crank, but not start. Almost as if no fuel was getting to the engine
(kinda of like those fuel cutoff switches some people use as
theft-deterrents). Everything works (lights, etc) and all the gauges look
fine. Nothing overheating, and I was only driving about 15 minutes.The 93+
Probes have a fuel cutoff switch inside on the left side of the trunk. This is
in case of any rear end collision, it would cut off the fuel to the engine.
The manual mentions that this switch can be tripped even in parking lot bumps
and by hitting potholes, none of which I did. I did go over some bumps, but it
was earlier in my drive. When the engine cut off, the road was exceptionally
smooth. You can reset the switch by pressing it, and that should do it. I
tried, but when I try to start the car, "fuel cutout" still lights up and the
car cranks and cranks, with no luck. It's not flooded, and all the fuses are
fine too. I even tried having someone press the reset button in while I
started it, with no luck. Does anyione have any ideas as to what might have
happened and what I should do to get my car started?? Has anyone else
experienced this and know what to do? I don't normally have access to this
newsgroup, so I would sincerly appreciate it if anyone can e-mail me with any
help. My address is: pau...@ix.netcom.com
Thanks so much for any responses that can help me out. I really appreciate it.
Paul Mendes
Pawtucket, RI, USA
pau...@ix.netcom.com
Ode
started posting that this NG should change it's name to rec.autos.physics! Anyway, more
responses below . . .
T. Postel wrote:
> Nice reply, thanks.
> However you seem to believe that cavitation is dependent on there being air or bubbles in
> the system. Of course you can't get all the air out, but even if you could a pump will
> still cavitate. The existance of dissolved air or air bubbles has no effect on the
> formation of the vapor cavities, which is what reduces pump delivery. When there is air
> in the flow then the destructive nature of the recompression of the vapor bubbles is
> magnified. But I'm not referring to the destruction of the pump, I'm referring to the
> reduction in coolant flow. Local turbulance tends to decrease the cavitation temperature.
> Cavitation occurs in the lowest pressure regions of the eddies on the trailing face of the
> impeller. If that pressure is below the vapor pressure of the fluid it will boil
> regardless of the pressure on the opposite side of the vane. Increasing the outlet
> pressure, by adding a restriction, reduces cavitation by increasing the pressure on the
> inlet side of the vanes as fluid short-circuits around the vanes.
>
> You said that my 12,000 fpm description was irrelevant!
I said it was irrelevant because you can not assume 1 foot of head, a closed system is very
different than a lake or other body of open water.
> What do you think the pressure at
> the intake of a water pump is when the water is 70 deg F.? I don't have an equation which
> predicts cavitation in a 50% glycol & water mixture at normal operating temperatures,
> considering the drag of the radiator, block & head water passages and themostat. So I
> used a handy rule of thumb, used widely by pump designers. And I think, it shows that
> most automotive pumps are pretty close to cavitation. Ya know, when I look at the engine
> in my car, the pump seems to be about a foot below the radiator cap.
Like I said, this is irrelevant in a closed system, this is not an open body of water. The
pressure at 1 foot of head in a lake is WAY lower than the pressure of an automotive cooling
system at temperature.
> In any case you've offered no plausable mechanism for the cases of overheating which occur
> when the thermostat is removed from an otherwise properly operating cooling system.
I indeed have, think you need to check my previous posts. I have already repeated it several
times (and no offense) but I don't particularly care to type it all in again when it is
readily available in the thread several times already.
> Cavitation is a known problem, which is mentioned as a rare but possible cause of
> overheating in most repair books and is a real concern for someone who designs high speed
> liquid pumps.
A water pump in an automotive cooling system is hardly a high speed pump.
> Now some more points you made:
> >> This makes the pressure increase more slowly than the temperature.
> >
> >Two different scales, please eaxplain what you mean more quickly. Are you
> > talking geometrically?
>
> No I meant that that PV is not constant.
Not with fluids, and not in a non-ideal world.
> In a rigid closed system containing an ideal gas
> PV = nRT: if the temperature increases the pressure increases exactly proportionally.
You said it, IDEAL GAS LAW, well, this is a NON-IDEAL FLUID, once again I fail to see the
relevance of an ideal gas law in a non-ideal fluid system.
> I
> meant that this relationship does not apply in an automotive style cooling system, and
> that the pressure in the system increases more slowly with increasing temperature than it
> would if the system were rigid and contained an ideal gas. Did you really misunderstand?
Yes, I did misunderstand and still do; why is an ideal gas law relevant in a non-ideal fluid
system?
> Will I have to dumb this down even more?
I would simply appreciate less ambiguity.
> later you say:
> >When the system is warm and free of air, it has sufficient pressure to prevent
> > this.
>
> See, this is what I mean. The pressure maintained by the pressure cap does not reduce the
> pump rpm at which cavitation begins, since the pressure of the fluid does not rise as fast
> as the vapor pressure does with increasing temperature. At full pressure the pump is
> closer to cavitation than at atmospheric. (Provided the pressurization is caused by the
> temperature increase, not by pressurizing the system with some other source.) If there
> were no pressure cap the pump would cavitate at an even lower speed.
I agree, but I still disagree that cavitation is a problem and still contend that higher flow
= cooler engine and that increased heat transfer to the coolant from the engine and
corresponding, but not as great in magnitude, increased heat transfer from coolant to radiator
to air explains why the coolant may run hotter in some vehicle.
Designing a pump to need a restriction to prevent cavitation seems like wasting energy to
me. Why would you not reduce the restriction (higher flow (maybe larger diameter) thermostat)
and pump speed, thereby reducing horsepower draw on the engine, resulting in more power and
more efficiency? Seems like putting in a high speed pump and then adding the restriction to
prevent cavitation would be pretty wasteful. Pump speed can be easily varied by pulley size.
If cavitation were a problem, don't you think this would be a very poor design?
It's a good exchange and I appreciate the continuing thought provoking discussion . . .
Ode
Shawn wrote:
> Postal and Group,
> Hmm... cant say I can keep up with you two
> (apologies to Ode for rudeness)
???????
> on this but your
> explaination of high speed in the below text might fit my experience. I still maintain that
> removing the thermostat can indeed cause more heat.
In the coolant, not the block/heads.
> Not everytime mind you, just that its
> possible.
Correct, it depends if increasing the speed increases the transfer into or out of the coolant
more. If the increase in coolant flow increases heat transfer engine-coolant more than
coolant-air, the coolant will be hotter, the other way around the coolant will be cooler; either
way the engine will be cooler.
> THAT is what I disagree with Ode about.
It's the coolant, not the engine that indicates hotter.
> One can argue if its coolant only but hey, all I have to guage most cars is my coolant temp!
What about your oil temp? Cooler block/heads = cooler oil.
> Sorry! For one of my cars without thermostat it would raise coolant temp to well over 200degF
> on the highway, to me this is too much (I like slightly under - but Im anal!). Now I dont
> care if all the lab work in the world says my actual engine temp is lower (I do agree w/this)
> it cant be so much lower that I think the system is doing "better" at that coolant temp.
Why not? Put in a cylinder head temp gauge if you wish to prove it to yourself. (An oil temp gauge
may even work).
> The
> same car would run just under to just over 200degF with thermostat. Whew!
>
> I think the thermostat makes a pressure difference. I was told via NG that basically - NO it
> doesnt.
A well designed, properly functioning, open thermostat should add no significant restriction to
the cooling system and thus no significant localized pressure, immediately aft of the thermostat.
> However thinking out loud here, doesnt the change in flow (being a restriction)
> affect pressure? Kinda like thumb on the garden hose/AirCond orifice tube/Air compressor
> lines etc... note I dont make reference to the radiator cap or the other restrictions in the
> system.
Why would you want to restrict your cooling system with a restrictive thermostat? Try putting in
smaller hoses, do you think this will help cooling?
> I mention this because while designing the cooling system initially on a given car, I
> think the "other restrictions" are factored in. Thermostats of the same rating with the same
> outside diameter can have completely different inside diameters and plungers.
>
> FWIW - Use a VDO guage along with the factory temp sensor in my GN. I monitor the temp
> reported by the ECM via laptop and they read 10-11degF difference accross the scale. Mounted
> in two different locations.
--
Ode
No offense was intended, just trying to clear it up. And no, I didn't mean you were giving
misinformation, it was just a general statement "information or misinformation". I have no
experience with CAT engines and in no way challenge (or confirm) the authenticity of the
information (or misinformation) you provided.
As for your newsgroup troubles, I am not familiar with "free agent" so I can't really help
you there. Personally use Netscape Communicator Professional Edition, and it works flawlessly.
I have taken no offense, I just like to keep it clean and precise when it comes to quotes.
I spend ample time in this newsgroup defending what I say, I don't want to waste time
defending what I didn't say because someone misquoted me. Just be careful, no offense taken,
no offense meant, good to have someone with your experience here . . .
Bryan Conrad wrote:
> Clyde
> Buggered if I know...............
> Cavemen are people too!
> Remove s from bconrads to E-Mail.
--
Ode
Bryan Conrad
> I have taken no offense, I just like to keep it clean and precise when it comes to quotes.
>I spend ample time in this newsgroup defending what I say, I don't want to waste time
>defending what I didn't say because someone misquoted me. Just be careful, no offense taken,
>no offense meant, good to have someone with your experience here . . .
OK,you will note I have not referred to thermodynamics as I have no
training/knowledge of its laws and,as a result,am not qualified to
state it's vitues.I am aware,however, that,among other things,the temp
differential between the coolant and the ambient air affects heat
transfer rate.The higher the differential,the higher the transfer rate
of heat energy.
I tend to agree with your statement of more flow=more cooling
capacity,as the temp differential between the cyl head water passages
and coolant will be very high,therefore,you would need to circulate
the coolant very quickly indeed to exceed the transfer rate and reduce
the heat transfer to the coolant.( this is probably physically
impossible).
I have found that reduced flow through the radiator(caused by
internal scaling) will result in higher temp differential between top
and bottom rad tanks due to coolant having more time to offload heat.
This,though,seems perplexing,as scale is reportedly a very
good insulator,and should in theory negate the above effects.
Something else I have puzzled over in the past,is the transfer
rate of heat between laminates-eg combustion gas,cast
iron,scale,coolant,scale,copper,paint,air.It seems to be a rather
complex job to calculate all the various rates involved so I guess
there must be a standard average allowance made for these effects?
How would you calculate,for instance,the air speed required to
pass air through a particular radiator core to achieve a desired
offloading of x horsepower?This would depend on many variariables(very
bloody variable!)including air temp,rad design(staggered or inline
tubes),rad area,coolant temp,paint characteristics and thickness,the
list goes on and on..................
Maybe I can pick up a few things here.It always seems to me I
pick up one answer and about twenty new questions with it!!
Thanks to all for an interesting thread.
Shawn
> > (apologies to Ode for rudeness)
> ???????
then nevermind! :D
> > on this but your
> > explaination of high speed in the below text might fit my experience. I still maintain that
> > removing the thermostat can indeed cause more heat.
>
> In the coolant, not the block/heads.
>
Already got schooled on my choice of words... Ill change it to coolant temp, but that it
generatedmore underhood temp overall in my case. My engines arent used in lab work to prove formulas
so
all I have to go on is actuall experience. If coolant temp (seperate from engine just to be clear) is
high
and engine temp is low then you assume TOO much in the real world for expectations. Read what I
said again. If temps (coolant only) are saaaayyy 300 with stat removed and only 180 with the stat in
place, you will never convince me that the system is performing better. Afterall how many points would
we need a reading from to find actual engine temp. No this didnt happen with the temps described...
:D
> > Not everytime mind you, just that its
> > possible.
>
> Correct, it depends if increasing the speed increases the transfer into or out of the coolant
> more. If the increase in coolant flow increases heat transfer engine-coolant more than
> coolant-air, the coolant will be hotter, the other way around the coolant will be cooler; either
> way the engine will be cooler.
>
> > THAT is what I disagree with Ode about.
>
> It's the coolant, not the engine that indicates hotter.
>
> > One can argue if its coolant only but hey, all I have to guage most cars is my coolant temp!
Not many folks run around with oil temp guages. Im trying to stay realistic here. The thread
NEVERstarted with the ASSumption you would be measuring the temp of the blockand heads (only coolant).
See where Im going? Does it make ANY difference to anyone I dont wanna argue formulas? In the
daily grind of things folks are going to be a little messed up if they have to change
the scale of what is "normal" temp if they HAVE to ASSume that the engine is ALWAYS going to be
running cooler than the actual coolant. Otherwise we are looking at installing wwaaayy too many
guages.
Head temp can differ from the jackets in the block etc...
>
>
> What about your oil temp? Cooler block/heads = cooler oil.
My car has a factory oil cooler that uses the radiator to help cool the oil. With this "nevermind the
real world" way ofthinking, removal of the thermostat is gonna jack my oil temp up. Therby perhaps
the ENGINE temp wont be lowered as
much. ;D
> > Sorry! For one of my cars without thermostat it would raise coolant temp to well over 200degF
> > on the highway, to me this is too much (I like slightly under - but Im anal!). Now I dont
> > care if all the lab work in the world says my actual engine temp is lower (I do agree w/this)
> > it cant be so much lower that I think the system is doing "better" at that coolant temp.
>
> Why not? Put in a cylinder head temp gauge if you wish to prove it to yourself. (An oil temp gauge
> may even work).
Sooo... lemme get this. Im to measure coolant temp in the heads or just the head? Either way how far
back do I have to go?I ASSume you can take the heat transfer laws all the way back to the source of
heat. What heat transfers to might always be hotter
than what it transfered from. Anybody out there runnin a valve face temp guage? I need to borrow
one.
> > The
> > same car would run just under to just over 200degF with thermostat. Whew!
> >
> > I think the thermostat makes a pressure difference. I was told via NG that basically - NO it
> > doesnt.
>
> A well designed, properly functioning, open thermostat should add no significant restriction to
> the cooling system and thus no significant localized pressure, immediately aft of the thermostat.
>
> > However thinking out loud here, doesnt the change in flow (being a restriction)
> > affect pressure? Kinda like thumb on the garden hose/AirCond orifice tube/Air compressor
> > lines etc... note I dont make reference to the radiator cap or the other restrictions in the
> > system.
>
> Why would you want to restrict your cooling system with a restrictive thermostat? Try putting in
> smaller hoses, do you think this will help cooling?
I have no proof that it would.... just seems to me this MUST change the cooling system behavior insome
way. Same outside diameter, different inside diamater, same temp thermostat found in two different
systems. Considering my experience I am willing to look at this as a source of why I had more
underhood heat
making the car not perform as well. Good thing the block was cooler though.
You guys love arguing the math side of this. Its pointless because with only a guage to measure
coolant temp Im layin money on a lower number (average Joe doesnt have tons-o-guages). Another
example:
My GN runs 177degF down the highway with A/C on. Soo... I take out thermostat. Now just for sake
of example it now runs according to coolant temp sayyy 200degF Hmmmm engine MUST BE RUNNING
ooohh say 150???? Hell I can only guess!! Actually if we even COULD agree on where to measure
ENGINE temp Ill bet it would be ??? See the problem? You want this to be global. Different cars
do diff things. I cant explain it and dont pretend I can via formula but my car didnt like the temp
(coolant!) change.
The car didnt run the same, registered a higher coolant temp, and ticked on shutdown. Now your going
to tell me
the engine was too cold.
Shawn GNa...@feist.com
snip!
Ode
First and foremost, while the engine is at temperature, it is always HOTTER than the coolant. The faster
the coolant flows, the less difference there will be between the engine and coolant temperatures. If you
had an infinite flow cooling system, the temp of the engine and coolant in the entire system (including
the radiator) would be the same. Now, as you slow the coolant flow down, the temperature of the coolant
coming into the radiator rises, the temperature of the coolant exiting the radiator may rise or drop
(depends on whether the tenperature gradient was greater at the engine or radiator before you speed the
coolant up) and the temperature of the engine rises. The slower you move the coolant the greater the
difference in temp between the in and out temp of the radiator, and the less total heat taken from the
engine. The hotter the incoming coolant to the radiator, the more heat the radiator will dissapate. In an
infinite speed (or a faster speed) coolant flow, this assures the maximum possible (or greater)
temperature gradient at the radiator and the most possible (or more) heat transfered away from the engine.
As for generating more underhood temp, aggregate it should be the less. Same amount of heat generated,
more heat is in the coolant, less heat in the block/heads and more total heat dissapated through the
radiator. As for a temp. of 300 thermostat out and 180 thermostat in . . . you either have other problems
in the system or a very poorly designed cooling system.
As for measuring the coolant temperature in the heads, that is not what I mean, I am talking about
measuring the temperature of the head, of the metal, not the coolnat in the head/block.
As for the coolant temperature being your indicator of how cool your engine is and negating the
argument for lower engine block/head temperature because you can't see that, let me ask you this, what is
the point of the cooling system? If it were to keep the coolant cool, you could just take the water pump
out and put the tempo gauge in the radiator. The entire purpose of the cooling system is to cool the
engine block/heads, now in doing so, this may or may not cause cooling temperature to increase. Now,
speeding up the coolant is going to cause and increase in the amount of heat transfered into the coolnat
from the engine and an increase in the amount of heat transfered out of the coolant to the radiator and
the air. Now if speeding up the coolant causes a greater increase in transfer in than the increase in
transfer out, the coolant will be hotter; nevertheless block/head temperature will be cooler. Hope this
clears it up, if you have any other questions, let me know and I will try to clear them up for you if I
know (I do not have ALL the answers) . . .
And let me repeat myself again for anyone not reading this entire thread:
Higher coolant flow = lower engine temperature.
AND:
I DO NOT RECOMMEND RUNNING A STREET VEHICLE WITHOUT A THERMOSTAT.
Shawn wrote:
--
Ode
Bryan Conrad wrote:
> OK,you will note I have not referred to thermodynamics as I have no
> training/knowledge of its laws and,as a result,am not qualified to
> state it's vitues.I am aware,however, that,among other things,the temp
> differential between the coolant and the ambient air affects heat
> transfer rate.The higher the differential,the higher the transfer rate
> of heat energy.
Correct.
> I tend to agree with your statement of more flow=more cooling
> capacity,as the temp differential between the cyl head water passages
> and coolant will be very high, therefore,you would need to circulate
> the coolant very quickly indeed to exceed the transfer rate and reduce
> the heat transfer to the coolant.( this is probably physically
> impossible).
Yes, in an infinite flowing system the head temp and coolant temp would be the same, it is
impossible to get the head cooler than the coolant without some external means.
> I have found that reduced flow through the radiator(caused by
> internal scaling) will result in higher temp differential between top
> and bottom rad tanks due to coolant having more time to offload heat.
Yes, and less total heat taken out of the system.
> This,though,seems perplexing,as scale is reportedly a very
> good insulator,and should in theory negate the above effects.
It's not good enough of an insulator to negate the effect, apparently.
> Something else I have puzzled over in the past,is the transfer
> rate of heat between laminates-eg combustion gas,cast
> iron,scale,coolant,scale,copper,paint,air.It seems to be a rather
> complex job to calculate all the various rates involved so I guess
> there must be a standard average allowance made for these effects?
No, no standard averaging method unless the system has already been designed and you can calculate
an aggregate specific to that engine and that engine only. And yes it is complicated.
> How would you calculate,for instance,the air speed required to
> pass air through a particular radiator core to achieve a desired
> offloading of x horsepower?This would depend on many variariables(very
> bloody variable!)including air temp,rad design(staggered or inline
> tubes),rad area,coolant temp,paint characteristics and thickness,the
> list goes on and on..................
Yes, it's pretty ugly. Computers are very much your friend. Numerical methods are a wonderful thing
when you have a machine to do the serious, recursive number crunching.
> Maybe I can pick up a few things here.It always seems to me I
> pick up one answer and about twenty new questions with it!!
The more you learn, the more you learn how much more there is to learn. I have learned a lot in my
life, and the more I learn, the more I agree with the coining, "Ignorance is bliss". The less you
know, the less you worry about, and the happier you are. I personally, am miserable and have so
much more to learn.
> Thanks to all for an interesting thread.
I quite enjoy the discussion as well.
T. Postel
> Anyway, more
>responses below . . .
>
>T. Postel wrote:
>> You said that my 12,000 fpm description was irrelevant!
>I said it was irrelevant because you can not assume 1 foot of head, a closed
> system is very different than a lake or other body of open water.
>> What do you think the pressure at
>> the intake of a water pump is when the water is 70 deg F.?
>Like I said, this is irrelevant in a closed system, this is not an open body of
>water. The pressure at 1 foot of head in a lake is WAY lower than the
>pressure of an automotive cooling system at temperature.
At 70 deg F. a cooling system will be unpressurized - remove the radiator cap, no
kablooie. So the system will behave exactly like an open system, and look the pump is
about 1 foot below the top of the radiator, so I think as a first approximation it works
pretty well. Consider that under some conditions the lower radiator hose will collapse if
it is not reinforced by a wire spring. That means that the pump inlet is below
atmospheric pressure. My point was that at engine start-up the pump can be run at 40% of
the cavitation speed (at red line). That is pretty close, and it gets closer as the
temperature of the coolant rises.
>
>>In any case you've offered no plausible mechanism for the cases of
>>overheating which occur when the thermostat is removed from an otherwise
>>properly operating cooling system.
>
>I indeed have, think you need to check my previous posts. I have already
>repeated it several times (and no offense) but I don't particularly care
>to type it all in again when it is readily available in the thread several times
>already.
This?
-> In some vehicles with poorly designed cooling systems, the transfer of more
-> heat may cause boilover, but the cylinder head and block temperature will be LOWER.
I found it in one of your 20 or so posts in this thread, so you're not repeating yourself
as much as you think. Anyway I said plausible...
>A water pump in an automotive cooling system is hardly a high speed pump.
>
Oog! high speed for centifugal pumps is over 1800 rpm see "Centrifugal Pumps" by L.C.
Lowenstein or any text book on pump design.
>Yes, I did misunderstand and still do; why is an ideal gas law relevant in a
> non-ideal fluid system?
>
Sheesh! The ideal gas law defines the limit of behavior of any system that contains a gas.
If the system is closed, non rigid and contains mostly liquids, but some gas or vapor, it
will never have as high a pressure change due to temperature change as a closed rigid
system containing an ideal gas. If it is too tiresome to compute the actual thermal
behavior of a system, you use the ideal gas law (Charles' Law) and you know it will always
have a lower thermal coefficient of pressure change. My point is that as the temperature
of the coolant rises, the pump rpm where cavitation begins gets lower. The pressurization
of the cooling system does not prevent this.
>Designing a pump to need a restriction to prevent cavitation seems like
> wasting energy to me.
The required flow through the engine is about 50 gallons per bhp per hour. The pressure
developed by the pump is on the order of 2 or 3 psi. So the power required to pump the
coolant of a 200 hp engine is about 0.3 hp. Under the most extreme conditions, a large
engine won't need 1 hp for the pump.
As with virtually every engineering problem in automotive design, the solution involves
cost. You could design a pump that did not require a restriction to eliminate cavitation.
To keep the peripheral speed lower and deliver the same flow, the impeller would need to
be thicker, the vanes would need to be stronger. If the pump is to be belt driven with a
longer "snout", then the housing will need to be stronger too. Maybe the best solution
uses several staged pumps to deliver more or less flow depending on coolant temperature.
Electric motor driven pumps, operating at a constant speed could be designed to achieve
impressive efficiencies with no possible cavitation. Would a redesign increase
reliability and reduce cost? Would the energy savings be worth it?
-m
Terry Krug
>
> Ode wrote:
>
>>snip<<
>
> That is exactly what I meant speaking about the control of the temperature: not to help
> cooling,
>>snip<<
>
> > > Ode wrote:
> > > >
> > > I have a feeling that depending on paricular car some engines without thermostat will
> > > never reach the working temperature unless you will run it sitting without air flow
> > > through radiator. The thermostat function is not only to allow to reach working
> > > temperature faster, but also to control it after it is reached.
> > >
> > > Gennady
I have been following this discussion for a while now. If having a
thermostat maintains the engine at operating temperature, I have a
question. I had an 81 Monte Carlo that I put an older 307 into. I found
a real nice heavy duty radiator at the junk yard that fit. The car ran
real well and was fun to drive. The first winter I had a big problem.
When the temperature outside got low, like below 40, the engine would
never heat up. I could not get an hot air out of the heater core. If I
understand all you arguements correctly, the coolant is supposed to run
through the heater core (bypass mode) when the thermo is closed. The
thermo is supposed to create enough restriction to allow coolant to
continue to circulate through the heater core even when the thermo is
open. If this is the case, why did this engine never heat up? I could
let it idle for a few minutes until it did warm up, then as quick as I
would take off, flow air over the rad., the thing would cool off and no
heat. Someone finally suggested that I block part of the rad, like the
big trucks do, which did the trick. If the coolant is only cooled by the
rad. when the thermo is open, why would the big rad. make this engine
stay stone cold? Just curious.
Ode
something to restrict the flow to prevent cavitation and damage to the pump, drawing extra
horsepower from the engine and then restricting the flow is a poorly designed system. The pump
could be slowed and the restriction eliminated, causing less draw on the engine, thus better
rear wheel horsepower and better mileage. In an era where 1000's of dollars go into an
automobile to get that last bit of mileage and lower emissions, do you really think a designer
would waste power like this?
T. Postel wrote:
> The required flow through the engine is about 50 gallons per bhp per hour. The pressure
> developed by the pump is on the order of 2 or 3 psi. So the power required to pump the
> coolant of a 200 hp engine is about 0.3 hp.
A water pump absorbs more horsepower than this, perhaps due to the restriction created by the
thermostat. And a car of course is not an ideal system.
> Under the most extreme conditions, a large
> engine won't need 1 hp for the pump.
You're kidding yourself if you expect this (only 1 hp lossed to water pump) in the real world.
> As with virtually every engineering problem in automotive design, the solution involves
> cost. You could design a pump that did not require a restriction to eliminate cavitation.
> To keep the peripheral speed lower and deliver the same flow, the impeller would need to
> be thicker, the vanes would need to be stronger.
Add thermostat (restriction) to intake side of pump, pressure on intake side = lower,
cavitation would be MORE likely. Add thermostat (restriction) to output side of pump, pressure
on intake side = ?????, flow = lower (if flow was the same, this would mean no pressure
increase on output side and the thermostat would not be a restriction). Adding this
restriction is going to lower the pressure on the far side of the thermostat, which of course,
comes through the radiator and back to the impeller intake side. So the only way the
restriction could RAISE the pressure on the intake side is if by slowing the coolant to reduce
the Bernouli effect. So take the restriction out, lower the pump speed to the flow rate [of
higher pump speed with restriction]. This preserves the same Bernouli effect as the system
with the restriction and higher pump speed. The pump is now turning more slowly, requires less
horsepower, and is less stressed. The same pump can be used at a slower speed to provide the
same flow without cavitation. Why would a slower moving pump operating against less pressure
need a thicker impeller and stronger vanes? You could use a weaker impeller and corresponding
lower cost.
T. Postel
> First off, any system that is designed to kill itself by overpumping and
> then uses something to restrict the flow to prevent cavitation and damage to the pump,
> drawing extra horsepower from the engine and then restricting the flow is a poorly designed
> system. The pump could be slowed and the restriction eliminated, causing less draw on the
> engine, thus better rear wheel horsepower and better mileage. In an era where 1000's of dollars go
> into an automobile to get that last bit of mileage and lower emissions, do you really
> think a designer would waste power like this?
>
The best efficiency in a centrifugal pump occurs when the impeller diameter,
in inches is about
D=(1800*h^0.5)/rpm. h is output pressure in ft. The 1800 is a conversion
factor, which varies by +/- 10% for different impeller shapes. However, for
small impeller diameters the internal losses rise. While the most efficient
pump for a given head and rpm will have a small impeller diameter, its
efficiency will be lower than a pump with a larger impeller capable of higher
ouput pressures, even with an in line restriction. So a larger diameter pump
will produce a higher quantity of flow at lower hp. That is, the best pump
for exactly 4 psi may have an efficiency of only 15%, whereas a pump designed
for 16 psi may have an efficiency of 50%, and throttled to 4 psi, 40%. So in
the real world, the best pump is a little bigger in diameter than the lowest
pressure design would predict. This pump gets dangerously close to
cavitation, so the output is restricted and the efficiency is reduced, but the
horsepower to move the coolant through this pump is still lower than the power
required by a smaller diameter impeller. Reduce the rpm, for a given head,
and the most efficient pump will have a larger diameter impeller, which will
cavitate at a lower temperature. So your design can avoid cavitation only by
using a much less efficient pump. See? (It is a non-ideal system in the real
world...)
>T. Postel wrote:
>> So the power required to pump the coolant of a 200 hp engine is
>>about 0.3 hp.
>
>A water pump absorbs more horsepower than this,
>
Now you are getting on my nerves. >:|
This isn't discussion or argument, it's just the automatic gainsaying of
anything I write. (source: Monty Python)
In my last post I wrote that the cooling system needs to move about
50 gph per bhp. That was a luxuriously conservative estimate, and you rejected
it. So here is a "real world" exercise:
A modern, conventional automobile engine requires the water jacket to remove
about the same amount of heat as is used to produce horsepower at the
flywheel. The following chart is average values, based on actual measurements
of engines, of the heat balance.
bhp 24%
coolant 24%
exhaust 44%
radiation & etc 8%
The cooling system is removing the same amount of heat as the crankshaft.
That is 1 hp/hp or 2547 btu/hp*hr
The maximum radiator temperature should not exceed 220 deg. F. and the coolant
returning from the radiator maybe 200 F. (worst case: hot day, A/C, tailwind)
The amount of coolant (cp about 0.7 btu/lb/deg F.) per hour is
2547/(220-200)/0.7=182 lb/hr/hp = 22 gph/hp
For a 150 hp engine that is 54 gpm.
The hp required to pump a liquid:
HP=GPM*PSI*Sp. Gr./1715 Sp. Gr. is the specific gravity, (which for
water+glycol coolant is about 1.1).
That comes to 0.14 hp at 4 psi
I have used very conservative numbers here, but I will include a 100% safety
margin: 0.3 hp to pump the coolant.
Pumps of this size usually have better than 40% efficiency, so the pumping hp
is about 0.75 hp.
>A water pump absorbs more horsepower than this, perhaps due to the
>restriction created by the thermostat. And a car of course is not an
>ideal system.
If the flow or the head pressure are reduced the required HP falls. In a pump
with a large short circuit flow, as are used in cars, if the outlet is
restricted the head pressure only increases slightly, it mostly causes more
leakage around the impeller. At a constant rpm and a variable restriction in
the pump outlet, the HP required drops with reduced flow. (Real world.)
>> Under the most extreme conditions, a large
>> engine won't need 1 hp for the pump.
>
>You're kidding yourself if you expect this (only 1 hp lossed to water
>pump) in the real world.
No, I'm not kidding. I know some water jackets and radiators have much more
drag and the pumps on those cooling systems must produce considerable
pressure. You can do it in your head: the pumping hp required is proportional
to the outlet pressure. Assume 200 gpm and 3 psi then the power is 0.35 HP.
What if a high drag system needed 9 psi - then 1.05 HP. But remember 9 psi is
20 feet of head. Do you think the pump on your car can make a 20 foot high
fountain?
No, most of the power for the pump goes into the waterproof seal on the pump
shaft. It must resist upto 15 psi at 230 F. of slippery coolant, with no
leakage, for 3000 in use hours, over the rpm range of the engine, including
extended periods of no movement, and cold starts below 0 F. No mater how good
your pump is, if is driven by a belt, it will need that seal. If you think
you can save gas by reducing the horsepower going to the pump, you
should invent a lower drag seal. Or maybe a mag-drive, to eliminate the seal?
High efficiency, low drag, but kinda pricey.
>Adding this restriction is going to lower the pressure on the far side
>of the thermostat, which of course, comes through the radiator and
>back to the impeller intake side. So the only way the restriction
>could RAISE the pressure on the intake side is if by slowing the
>coolant to reduce the Bernouli effect.
Bernoulli effect indeed! For water in a conduit the Bernoulli effect is
exactly h=v^2/(2*g) h is ft of head, v is the velocity in ft/sec and g is
the gravitaional constant 32.2 ft/(sec^2). It shows that for a reduction in
pressure the VELOCITY of the fluid increases (and vice versa). But the
VELOCITY is most important in the drag of the water pipes, galleries, radiator
core and hoses. The pressure drop required to overcome drag is proportional
to the square of the velocity. Are you sure you want to invoke Bernoulli?
A restriction in the outlet of a pump increases the pressure on the downstream
side of the impeller vanes and reduces the velocity of the outflow from the
pump. There is an increase in pressure in the pump from the conversion of
velocity to pressure inside the volute (the Bernoulli effect!) This pressure
pushes some extra leakage around the vanes, additionally coolant flows through
the bypass hose and heater core directly to the pump inlet.
> Why would a slower moving pump operating against less pressure
>need a thicker impeller and stronger vanes? You could use a weaker
>impeller and corresponding lower cost.
You think a little slower, a few percent maybe would do, huh? Sorry, to
eliminate the possibility of cavitation when the coolant is at its maximum
temperature, the peripheral speed of an unrestricted pump must be kept below
about 2000 fpm. Assuming the current design uses a 4 inch diameter impeller
and the engine red line is 4000 rpm, the thermostat restriction allows a
higher peripheral speed, about 4000 fpm, without cavitation. This is
speculation on my part, since cavitation behavior at elevated temperatures has
yet to be characterized well enough to make predictions. See:
http://www.thw.wb.utwente.nl/people/kruyt/niels.htm
for recent research on numerical simulation of pump operation at STP
conditions.
How about running the same diameter pump half as fast? Then the pump volume
would have to be doubled to deliver the same quantity of liquid. For a given
diameter, the pump would need to be twice as thick. The pressure developed by
a centrifugal pump is proportional to the square of the peripheral speed,
(Bernoulli) so the outlet pressure would be one fourth as big, I hope that's
ok. The impeller is twice as deep, the vanes are twice as long, the pump
housing is twice as deep. These things act mechanically as cantilevers, The
vanes are supported at their root, the pump snout resists the side force of
the drive belt, through the casing to the mounting surface. The moment
increases with the length of the cantilever section for concentrated loads,
like the drive belt on the pump casing. It increases as the square of the load
for uniform loads, like the pressure on the impeller vanes. So these parts
will need to be made stronger.
A pump with a smaller diameter impeller running at the original rpm would need
to have about the same internal volume to deliver the required flow. Since
the diameter would be reduced from 4 in to 2 inches the depth would need to be
quadrupled. So the vanes would need to stick up from the hub four times as
far, and therefore be about 16 times as strong at the root. The pump housing
snout would be 4 times longer, less the seal and bearing spaces, and so you
see... In addition smaller pumps have higher rotation losses, and so are not
as efficient. Oh, that's were I started!
-m
Shawn
T. Postel wrote:
> Oude...@mci2000.com wrote:
> snip!
>
> >A water pump absorbs more horsepower than this, perhaps due to the
> >restriction created by the thermostat. And a car of course is not an
> >ideal system.
> Postel wrote:
> If the flow or the head pressure are reduced the required HP falls. In a pump
> with a large short circuit flow, as are used in cars, if the outlet is
> restricted the head pressure only increases slightly, it mostly causes more
> leakage around the impeller. At a constant rpm and a variable restriction in
> the pump outlet, the HP required drops with reduced flow. (Real world.)
***
Wow! You guys have taken this to a whole new level! :D I wonder if HP loss as reported in say a
engine dyno test might be higher due to ?? Belt design or pully size? I am guessing the Ode is adding
these losses in the HP required estimates. Seems to me that the formula accounts for HP losses for the
pump ONLY?
***
>
>
> SNIP!!
>
> >Adding this restriction is going to lower the pressure on the far side
> >of the thermostat, which of course, comes through the radiator and
> >back to the impeller intake side. So the only way the restriction
> >could RAISE the pressure on the intake side is if by slowing the
> >coolant to reduce the Bernouli effect.
>
> Bernoulli effect indeed! For water in a conduit the Bernoulli effect is
> exactly h=v^2/(2*g) h is ft of head, v is the velocity in ft/sec and g is
> the gravitaional constant 32.2 ft/(sec^2). It shows that for a reduction in
> pressure the VELOCITY of the fluid increases (and vice versa). But the
> VELOCITY is most important in the drag of the water pipes, galleries, radiator
> core and hoses. The pressure drop required to overcome drag is proportional
> to the square of the velocity. Are you sure you want to invoke Bernoulli?
>
> A restriction in the outlet of a pump increases the pressure on the downstream
> side of the impeller vanes and reduces the velocity of the outflow from the
> pump. There is an increase in pressure in the pump from the conversion of
> velocity to pressure inside the volute (the Bernoulli effect!) This pressure
> pushes some extra leakage around the vanes, additionally coolant flows through
> the bypass hose and heater core directly to the pump inlet.
***Keep it coming Postel/Ode I find all this interesting. I just seems natural to me for the need for
PUMP pressure in the system I may have stated incorrectly in an earlier post that the thermostat
"maintains" the pressure. I meant above a certain lower limit not a steady one... is there a global
accepted value for this? Something like this might explain the issues I had with the thermostats having
same outside/different inside diameters for the same temp rating.
***
Shawn GNa...@feist.com
Ode
week later and ask the question again; like the last few physics/fluid dynamics/thermodyamics
discussions, or the Water Wetter discussion, whew, that one took a while. More below . . .
T. Postel wrote:
> Oude...@mci2000.com wrote:
> > First off, any system that is designed to kill itself by overpumping and
> > then uses something to restrict the flow to prevent cavitation and damage to the pump,
> > drawing extra horsepower from the engine and then restricting the flow is a poorly designed
> > system. The pump could be slowed and the restriction eliminated, causing less draw on the
> > engine, thus better rear wheel horsepower and better mileage. In an era where 1000's of dollars go
> > into an automobile to get that last bit of mileage and lower emissions, do you really
> > think a designer would waste power like this?
> >
> I don't get "kill itself" The pump is not damaged by the thermostat.
I was talking about designing the system so that cavitation would cause it to kill itself by pumping
itself to death, and then adding the restriction (thermostat) to cure this problem. From the very page
you linked to in your last response:
"Downstream in the impeller these bubbles cavitation implode as a result of the higher pressure.
This can cause damage to the blades, the so-called cavitation erosion, which reduces their life
expectancy."
> The best efficiency in a centrifugal pump occurs when the impeller diameter,
> in inches is about
> D=(1800*h^0.5)/rpm. h is output pressure in ft. The 1800 is a conversion
> factor, which varies by +/- 10% for different impeller shapes.
OK, so adding the restriction (thermostat) flow drops, Bernoulli effect = pressure increase, so you need
a larger diameter impeller for maximum efficiency, I can see that. But I don't see why you would not be
better off removing the restriction and using a smaller impeller (less chance of cavitation with smaller
impeller) to get the same flow with less power from the engine.
> However, for
> small impeller diameters the internal losses rise. While the most efficient
> pump for a given head and rpm will have a small impeller diameter, its
> efficiency will be lower than a pump with a larger impeller capable of higher ouput pressures, even
> with an in line restriction.
This is a fairly general statement. Surely reducing impeller size from 4.00 to 3.99 inches would not be
enough of a drop in efficiency to overcome the added restriction. The thermostat, not being a brick wall
restriction and not being totally open, where is the cut off.
> So a larger diameter pump
> will produce a higher quantity of flow at lower hp.
Ok, so use the larger impeller, remove the restriction, run an underdrive pulley, does this not yield
the same flow with less horsepower draw?
> That is, the best pump
> for exactly 4 psi may have an efficiency of only 15%, whereas a pump designed
> for 16 psi may have an efficiency of 50%, and throttled to 4 psi, 40%.
OK.
> So in
> the real world, the best pump is a little bigger in diameter than the lowest
> pressure design would predict. This pump gets dangerously close to
> cavitation, so the output is restricted and the efficiency is reduced,
Why restrict to slow flow, why not just reduce impeller speed?
> but the horsepower to move the coolant through this pump is still lower than the power required by a
> smaller diameter impeller. Reduce the rpm, for a given head, and the most efficient pump will have a
> larger diameter impeller, which will cavitate at a lower temperature.
OK. so why not do this, no restriction?
> So your design can avoid cavitation only by using a much less efficient pump. See? (It is a non-ideal
> system in the real world...)
OK, this still does not explain why you would rather run higher impeller RPM and a restriction rather
than lower RPM and no restriction.
> >T. Postel wrote:
> >> So the power required to pump the coolant of a 200 hp engine is
> >>about 0.3 hp.
> >
> >A water pump absorbs more horsepower than this,
> >
> Now you are getting on my nerves. >:|
> This isn't discussion or argument, it's just the automatic gainsaying of
> anything I write. (source: Monty Python)
On your nerves? If I had an engine on a stand and belt bypass the water pump, use an electric pump
powered by 120 VAC so as not to draw HP from the engine, I will only see a .3 hp increase over driving
the pump off of the engine? I don't think so.
> In my last post I wrote that the cooling system needs to move about
> 50 gph per bhp. That was a luxuriously conservative estimate, and you rejected it. So here is a "real
> world" exercise:
> A modern, conventional automobile engine requires the water jacket to remove about the same amount of
> heat as is used to produce horsepower at the flywheel. The following chart is average values, based on
> actual measurements of engines, of the heat balance.
> bhp 24%
> coolant 24%
> exhaust 44%
> radiation & etc 8%
> The cooling system is removing the same amount of heat as the crankshaft.
> That is 1 hp/hp or 2547 btu/hp*hr
> The maximum radiator temperature should not exceed 220 deg. F. and the coolant
> returning from the radiator maybe 200 F. (worst case: hot day, A/C, tailwind)
> The amount of coolant (cp about 0.7 btu/lb/deg F.) per hour is
> 2547/(220-200)/0.7=182 lb/hr/hp = 22 gph/hp
> For a 150 hp engine that is 54 gpm.
> The hp required to pump a liquid:
> HP=GPM*PSI*Sp. Gr./1715 Sp. Gr. is the specific gravity, (which for
> water+glycol coolant is about 1.1).
> That comes to 0.14 hp at 4 psi
Restriction (thermostat) on the ouput side of the pump = slower flow = more pressure, most systems about
10-14 lbs, where do you get a measely 4 PSI on output? Definitely can not neglect the restriction caused
by the radiator either, or the restriction of the path through the water jacket. Also keep in mind that
most vehicles you would want to take the thermostat out of (racing) run a hell of a lot more than 150
hp.
> I have used very conservative numbers here, but I will include a 100% safety
> margin: 0.3 hp to pump the coolant.
> Pumps of this size usually have better than 40% efficiency, so the pumping hp
> is about 0.75 hp.
>
> >A water pump absorbs more horsepower than this, perhaps due to the
> >restriction created by the thermostat. And a car of course is not an
> >ideal system.
>
> If the flow or the head pressure are reduced the required HP falls.
Yes, pump is slowed, required hp falls.
> In a pump
> with a large short circuit flow, as are used in cars, if the outlet is
> restricted the head pressure only increases slightly, it mostly causes more
> leakage around the impeller. At a constant rpm and a variable restriction in the pump outlet, the HP
> required drops with reduced flow. (Real world.)
If a restriction is added (thermostat), less flow = more pressure (Bernoulli) = higher PSI, higher HP
draw in a restricted system. A pump pumps harder when outlet is restricted. If the flow is slowed by
slowing the the pump instead of adding a restriction, HP draw is reduced.
> >> Under the most extreme conditions, a large
> >> engine won't need 1 hp for the pump.
> >
> >You're kidding yourself if you expect this (only 1 hp lossed to water
> >pump) in the real world.
>
> No, I'm not kidding. I know some water jackets and radiators have much more
> drag and the pumps on those cooling systems must produce considerable
> pressure. You can do it in your head: the pumping hp required is proportional
> to the outlet pressure. Assume 200 gpm and 3 psi then the power is 0.35 HP.
> What if a high drag system needed 9 psi - then 1.05 HP. But remember 9 psi is
> 20 feet of head. Do you think the pump on your car can make a 20 foot high
> fountain?
It is not a fountain, all it needs to do is pump the water to 20 feet through a rigid hose. A fountain
has to impart enough momentum to the water to travel 20 feet vertical with no hose. A water pump in an
automobile can do that (20 feet vertical through a non-expansive hose), but you are not going to make a
fountain out of it 20 ft. high. Hope this was either an oversight or a joke on your part, not a flaw in
your understanding.
> No, most of the power for the pump goes into the waterproof seal on the pump
> shaft. It must resist upto 15 psi at 230 F. of slippery coolant, with no
> leakage, for 3000 in use hours, over the rpm range of the engine, including
> extended periods of no movement, and cold starts below 0 F. No mater how good
> your pump is, if is driven by a belt, it will need that seal. If you think
> you can save gas by reducing the horsepower going to the pump, you
> should invent a lower drag seal. Or maybe a mag-drive, to eliminate the seal?
> High efficiency, low drag, but kinda pricey.
Well, as long as were going all out, let's just go for the ultimate, cavitation free design; a
magneto-hydrodynamic pump!
> >Adding this restriction is going to lower the pressure on the far side
> >of the thermostat, which of course, comes through the radiator and
> >back to the impeller intake side. So the only way the restriction
> >could RAISE the pressure on the intake side is if by slowing the
> >coolant to reduce the Bernouli effect.
>
> Bernoulli effect indeed! For water in a conduit the Bernoulli effect is
> exactly h=v^2/(2*g) h is ft of head, v is the velocity in ft/sec and g is
> the gravitaional constant 32.2 ft/(sec^2). It shows that for a reduction in
> pressure the VELOCITY of the fluid increases (and vice versa).
That's what I said.
> But the
> VELOCITY is most important in the drag of the water pipes, galleries, radiator
> core and hoses. The pressure drop required to overcome drag is proportional
> to the square of the velocity. Are you sure you want to invoke Bernoulli?
There's nothing to "invoke" it is an integral part of the understanding of the system.
> A restriction in the outlet of a pump increases the pressure on the downstream
> side of the impeller vanes and reduces the velocity of the outflow from the
> pump. There is an increase in pressure in the pump from the conversion of
> velocity to pressure inside the volute (the Bernoulli effect!)
Yes.
> This pressure
> pushes some extra leakage around the vanes, additionally coolant flows through
> the bypass hose and heater core directly to the pump inlet.
Yes, this works. Still don't see why you wouldn't just take out the restriction and slow the pump down
so that the flow was the same. Same flow = same pressure.
> > Why would a slower moving pump operating against less pressure
> >need a thicker impeller and stronger vanes? You could use a weaker
> >impeller and corresponding lower cost.
>
> You think a little slower, a few percent maybe would do, huh? Sorry, to
> eliminate the possibility of cavitation when the coolant is at its maximum
> temperature, the peripheral speed of an unrestricted pump must be kept below about 2000 fpm. Assuming
> the current design uses a 4 inch diameter impeller and the engine red line is 4000 rpm, the thermostat
> restriction allows a higher peripheral speed, about 4000 fpm, without cavitation. This is speculation
> on my part, since cavitation behavior at elevated temperatures has yet to be characterized well enough
> to make predictions. See:
> http://www.thw.wb.utwente.nl/people/kruyt/niels.htm
> for recent research on numerical simulation of pump operation at STP
> conditions.
>
> How about running the same diameter pump half as fast? Then the pump volume
> would have to be doubled to deliver the same quantity of liquid.
What?! You are telling me you would have to pump twice as much after taking the restriction OUT to get
the same flow!? Take the restriction out, slow the pump until the original flow volume is reached!
---- (snip) ---- (presumption is on which snipped is based is incorrect, you do not need to pump twice
as much volume to get the same volume if you take the restriction out!)
OK, let's try this plain as day . . .
Step 1: Measure flow rate through upper radiator hose with thermostat installed in the water
outlet, at temp, thermostat open.
Step 2: Remove Thermostat (restriction).
Step 3: Underdrive water pump enough that original flow level is restored.
Same flow, same Bernoulli effect, same size impeller, same pump, less horsepower draw on the engine,
it could not be any more obvious . . .
Ode
engine. Remember the engine is metal and if air is being blown across it at 50 mph at -20 F,
it's not going to get very warm. Also what little flow the heater core allows, is probably
enough to keep the whole thing cool with such a large heat dissapator (radiator). You could
also try increasing your anti-freeze % during the winter to 70/30, this will make the engine
less able to dissapate heat, as well as protect against colder temperatures. Although simply
blocking some of the airflow into the engine compartment will work just fine, just don't forget
to remove the blockage when the weather gets warmer . . .
Terry Krug wrote:
--
T. Postel
>***
>Wow! You guys have taken this to a whole new level! :D I wonder if HP loss
> as reported in say a
>engine dyno test might be higher due to ?? Belt design or pully size? I am
> guessing the Ode is adding
>these losses in the HP required estimates. Seems to me that the formula
> accounts for HP losses for the
>pump ONLY?
Oh, I goofed up, I wrote 4 psi, and meant 40 psi, then used 4 in my figures.
3 hp is a more realistic number for the total power to pump the coolant. In a
150 hp engine (blah - blah)
And I'm talking pump losses only. The bearing - belt - pully - seal losses
are quite large, but they will be about the same with a really good pump or a
really bad one.
>*
>***Keep it coming Postel/Ode I find all this interesting. I just seems natural
> to me for the need for
>PUMP pressure in the system I may have stated incorrectly in an earlier post
> that the thermostat
>"maintains" the pressure. I meant above a certain lower limit not a steady
> one... is there a global
>accepted value for this? Something like this might explain the issues I had
> with the thermostats having
>same outside/different inside diameters for the same temp rating.
>***
>
>
>Shawn GNa...@feist.com
>
I don't know of any universal design guidelines for the pressures at any point
in an internal combustion engine cooling system. It shouldn't be so high that
it leaks, and it can't be so low that the coolant boils, locally, near the
exhaust valves for instance.
Why do your thermostats look different? I really don't know... Just
speculation: Two thermostats could have different inside diameters, if I am
following you here, and still represent the same amount of restriction. If
these thermostats are like the kind I'm acquainted with, they have a wax
pellet encased in a brass, or copper, "bullet". When the wax gets hot, it
melts & expands, pushing on an SS rod which pushes the valve open. If the
bullet had a larger diameter, or did not clear the valve space as far, then
the "inside diameter" of the valve would need to be bigger so that the annulus
had the proper cross section to the flow. - Sound plausible?
-m
T. Postel
for the pump maximum pressure, when I should have used 40 psi. -- Very sorry.
It doesn't really alter the argument. Just multiply all pressure related
figures by 10. ie hp to pump water is less then 10 hp for 200 hp engine.
Now back to the story so far...
I thought you had understood that the reason for the restriction in the outlet
of the pump is just to raise the inlet pressure.
A pump sucks liquid in one hole and pushes it out another. But at high
temperatures, near the boiling point of the fluid being pumped, the pressure
in the pump can go lower than the vapor pressure of the coolant. For most pump
applications the Net Positive Suction Head (NPSH) can be correlated with the
inception of cavitation. The question is how can you most efficiently keep the
NPSH above the point at which cavitation begins? There are only 2 ways, suck
less, or allow some leakage from the highest pressure area to the lowest
pressure area. To achieve the required flow with less suction, you would need
a larger inlet for the impeller. To achieve a given quantity of flow requires
a certain displacement. Therefore if the inlet increases, and the outlet
diameter stays the same, at the same rpm, then the impeller depth must
increase. Deeper impeller blades must be stonger, etc... In addition, can
you guess? A pump with a thin ring for an impeller is less efficient than a
wide ring or disk. The inlet pipe must not be smaller than the impeller inlet,
or the pipe will act as a restriction which will reduce the NPSH. Taken
together, these limitations are difficult to surmount efficiently and
economically.
It is more economical to restrict the outlet. If some of the pump capacity is
diverted from the outlet back into the inlet, that leakage will displace some
of the inlet liquid, proportionally to the square root of the difference in
pressure. That means when the pressure at the inlet is close to the outlet
pressure, there is little leakage. But when the impeller is near cavitating
more liquid flows, and if it is enough, it completely eliminates cavitation.
Before replying to specific points, I'll try to get to what seems to be the
root of your argument:
You believe that the thermostat restricion (if it is there to reduce
cavitation) raises the pressure at the pump outlet, and reduces the pump flow
enough to waste measurable horsepower. And that a suitable pump, using less
engine power can deliver the required pressure and flow without the
restriction.
You say that your pump is more efficient than mine, since you don't waste any
pressure through the restriction. Yes: some of the energy used in my pump
goes to increasing the pump inlet pressure. However your design does not
eliminate cavitation, because there is no way to increase the npsh.
> Oude...@mci2000.com wrote:
> > First off, any system that is designed to kill itself by overpumping...
I still don't get "kill itself" The pump doesn't cavitate, because of the
restricion caused by the thermostat.
>>Reduce the rpm, for a given head, and the most efficient pump will have a
>>larger diameter impeller, which will cavitate at a lower temperature.
>OK. so why not do this, no restriction
Read it again: lower temperature. Lower is bad.
>> So your design can avoid cavitation only by using a much less efficient
>>pump. See? (It is a non-ideal system in the real world...)
>OK, this still does not explain why you would rather run higher impeller
>RPM and a restriction rather than lower RPM and no restriction.
You will need some way to keep the inlet pressure above the vapor pressure of
the coolant. Without the restriction, a slower pump will cavitate too.
>Restriction (thermostat) on the ouput side of the pump = slower flow = more
>pressure, most systems about 10-14 lbs, where do you get a measely 4 PSI on
>output? Definitely can not neglect the restriction caused by the radiator
>either, or the restriction of the path through the water jacket.
Yes, that was an error, I should have used 40 psi.
>Also keep in mind that most vehicles you would want to take the thermostat
>out of (racing) run a hell of a lot more than 150 hp.
This IS irrellevant. Are you now talking about race cars or passenger cars, I
have always been talking about production passenger cars. Every race engine
I've worked on that had a belt driven water pump underwent extensive testing
to guarantee no cavitation at maximum rpm and maximum coolant temperature.
Nearly all used some restriction in the water jacket outlet.
Now, talking about production passenger cars, of course it depends on the car,
between 30 and 50 psi. The pump doesn't produce the pressure seen by the
radiator cap. It doesn't matter what the static pressure is, except in as much
as it helps raise the temperature of cavitation. The pump only has to produce
enough pressure to move the coolant through the water jacket, radiator and
thermostat.
>> If the flow or the head pressure are reduced the required HP falls.
>Yes, pump is slowed, required hp falls.
NO! Constant rpm. If either head or flow is reduced the power falls.
>If a restriction is added (thermostat), less flow = more pressure
>(Bernoulli) = higher PSI, higher HP draw in a restricted system. A pump
>pumps harder when outlet is restricted. If the flow is slowed by slowing
>the the pump instead of adding a restriction, HP draw is reduced.
No, and no. Try again: The Bernoulli effect applies to VELOCITY (ft./sec.)
not quantity of flow (cu. ft./sec. or gpm) When I write "flow," "flow rate,"
"quantity of flow" and things like that I mean the volume per time, like gpm
or cfs. The thermostat acts like an orifice, the pressure drop, h, depends on
the quantity of flow and area of the orifice:
h=k*q^2/(2*g*a^2) k is the the reciprocal of the "discharge coefficient." For
a given flow rate, the orifice causes a pressure drop in the fluid flowing
through the orifice. The pump must deliver q gpm. The change of velocity
through the restriction is V=(2*g*h)^0.5 (Bernoulli). That is through the
thermostat. For the rest of the cooling system the velocity is unchanged. The
velocity through a pipe is the quantity of flow divided by the cross sectional
area. Neither of these change. The quantity of flow must be the same or else
the heat balance changes, and you have said nothing about making the hoses or
cooling passages bigger or smaller.
The pump design determines the amount that the outlet pressure increases with
flow rate, or does not. For most pumps the pressure does increase with flow,
but for some it is nearly constant over a range of from no flow to 150% of the
design rate. (at constant rpm). To say, "A pump pumps harder when outlet is
restricted. " may or may not be true. Most centrifugal pumps are designed to
operate against some pressure. At a lower than design pressure, any number of
problems can arise: the delivery and load may fluctuate; the impeller may see
an imbalance and start to wobble; if the load is not in the range that the
driver was designed for, the driver may be overloaded; or it may over speed...
>>Do you think the pump on your car can make a 20 foot high fountain?
>It is not a fountain, all it needs to do is pump the water to 20 feet
>through a rigid hose. A fountain has to impart enough momentum to the water
>to travel 20 feet vertical with no hose. A water pump in an automobile can
>do that (20 feet vertical through a non-expansive hose), but you are not
>going to make a fountain out of it 20 ft. high. Hope this was either an
>oversight or a joke on your part, not a flaw in your understanding.
BZZZZZZZZT!
Now I shouldn't do this, but you seem to misunderstand pressure. The head
pressure in a conduit or reservoir will push a free flow to the height of the
pressure measured in ft of head. Assume a vessel containing a liquid with
pressure, h, (in ft of head). The pressure can be from the height of a column
of liquid or from pressurization by pumping. If the vessel is pierced with an
orifice, the liquid will exit through the orifice with a velocity,
V=(2*g*h)^0.5. (hey look: it's Bernoulli again!) The jet will have that
velocity in any direction. If issuing vertically the jet will rise nearly to
the height h ft above the orifice. This is exactly what it means to have 20
ft of head pressure: that a free stream of water with that pressure at its
source will rise that many feet above its source. Indeed, if the hose goes
straight up the pump will fill it too, And it means the exact same thing. It
just seems that it is easier for most people to get a feel for pressure by
imagining the fountain. And it seems that you too think a 20 foot fountain
represents more pressure than a 20 foot pipe. I'll use 40 psi for my figures,
to insure that I overestimate the power and pressure losses, yet I don't think
anybody expects their water pump to make a 100 ft fountain.
>>a magneto-hydrodynamic pump!
Have you checked out the efficiency of those? I think you'll need a Mr.
Fusion.
>> How about running the same diameter pump half as fast? Then the pump
>>volume would have to be doubled to deliver the same quantity of liquid.
>What?! You are telling me you would have to pump twice as much after taking
>the restriction OUT to get the same flow!? Take the restriction out, slow
>the pump until the original flow volume is reached!
No I'm saying that to get the same quantity of flow your pump must have
approximately same displacement per time. The pressure change does not effect
the pump displacement very much, since water, or coolant, is practically
incompressible.
>---- (snip) ---- (presumption is on which snipped is based is incorrect, you
>do not need to pump twice as much volume to get the same volume if you take
>the restriction out!)
My analysis is correct. You do need the same pump displacement per time. If
the rpm is reduced by a factor of 2, please note:
"The pressure developed by a centrifugal pump is proportional to the square of
the peripheral speed, so the outlet pressure would be one fourth as big, I
hope that's ok." At 1/2 speed the pump delivers 1/4 the pressure, that is
your allowance for removing the restriction, and the pump MUST have twice the
displacement to deliver the original quantity of flow at 1/2 speed. Imagine
that in one revolution the pump can discharge 1 gallon of liquid. At 1 rpm it
is delivering 1 gal./min. At 2 rpm it can deliver 2 gpm See? if the pump goes
half as fast it would need twice the displacement to deliver the original
flow. Well, actually a little more than twice, since the peripheral speed
contributes to the quantity of flow by conversion of the potential head. (All
together: Bernoulli!)
>OK, let's try this plain as day . . .
With two small additions...
> Step 1: Measure flow rate through upper radiator hose with >thermostat
installed in the water outlet, at temp, thermostat open
>
Step 1a: Measure pressure at pump inlet.
>
> Step 2: Remove Thermostat (restriction).
>
> Step 3: Underdrive water pump enough that original flow level is
>restored.
>
Step 4: Measure pressure at pump inlet.
>
> Same flow, same Bernoulli effect, same size impeller, same pump, less
>horsepower draw on the engine,
>it could not be any more obvious . . .
Oh look, the pump inlet pressure is falling! Soon the coolant will be
boiling on the vanes. What are you going to do? Slow the pump down some more?
Oh, oh the coolant is getting hotter, it's starting to boil. Better slow the
pump down some more... No, maybe speed the pump up. Oh, no the pressure is
falling even more, more coolant is boiling...
YOU MUST RAISE THE INLET PRESSURE.
-m
Ode
T. Postel wrote:
> An error on my part has lead some misinformation, in particular I used 4 psi
> for the pump maximum pressure, when I should have used 40 psi. -- Very sorry.
> It doesn't really alter the argument. Just multiply all pressure related
> figures by 10. ie hp to pump water is less then 10 hp for 200 hp engine.
That's a hell of a lot more believeable! I can see that.
Less restriction = slower impeller speed for same flow. More restriction = higher
impeller speed for same flow. Bernoulli effect = same. Pressure at inlet = same.
Same chance for cavitation.
>
>
> > Oude...@mci2000.com wrote:
> > > First off, any system that is designed to kill itself by overpumping...
>
> I still don't get "kill itself" The pump doesn't cavitate, because of the
> restricion caused by the thermostat.
Right. As per design it will cavitate without a restriction and thus would destroy
itself unless a restriction is added.
> >>Reduce the rpm, for a given head, and the most efficient pump will have a
> >>larger diameter impeller, which will cavitate at a lower temperature.
>
> >OK. so why not do this, no restriction
>
> Read it again: lower temperature. Lower is bad.
Same pump, no restriction, slower impeller speed, same flow, same inlet pressure.
> >> So your design can avoid cavitation only by using a much less efficient
> >>pump. See? (It is a non-ideal system in the real world...)
>
> >OK, this still does not explain why you would rather run higher impeller
> >RPM and a restriction rather than lower RPM and no restriction.
>
> You will need some way to keep the inlet pressure above the vapor pressure of
> the coolant. Without the restriction, a slower pump will cavitate too.
No retsriction, Same inlet pressure, slower impeller speed, pump is LESS likely to
cavitate.
> >Restriction (thermostat) on the ouput side of the pump = slower flow = more
> >pressure, most systems about 10-14 lbs, where do you get a measely 4 PSI on
> >output? Definitely can not neglect the restriction caused by the radiator
> >either, or the restriction of the path through the water jacket.
>
> Yes, that was an error, I should have used 40 psi.
>
> >Also keep in mind that most vehicles you would want to take the thermostat
> >out of (racing) run a hell of a lot more than 150 hp.
>
> This IS irrellevant. Are you now talking about race cars or passenger cars, I
> have always been talking about production passenger cars. Every race engine
> I've worked on that had a belt driven water pump underwent extensive testing
> to guarantee no cavitation at maximum rpm and maximum coolant temperature.
> Nearly all used some restriction in the water jacket outlet.
>
> Now, talking about production passenger cars, of course it depends on the car,
> between 30 and 50 psi. The pump doesn't produce the pressure seen by the
> radiator cap. It doesn't matter what the static pressure is, except in as much
> as it helps raise the temperature of cavitation. The pump only has to produce
> enough pressure to move the coolant through the water jacket, radiator and
> thermostat.
>
> >> If the flow or the head pressure are reduced the required HP falls.
>
> >Yes, pump is slowed, required hp falls.
>
> NO! Constant rpm. If either head or flow is reduced the power falls.
Yes, but without a restriction a slower impeller speed will yield the same flow.
> >If a restriction is added (thermostat), less flow = more pressure
> >(Bernoulli) = higher PSI, higher HP draw in a restricted system. A pump
> >pumps harder when outlet is restricted. If the flow is slowed by slowing
> >the the pump instead of adding a restriction, HP draw is reduced.
>
> No, and no. Try again: The Bernoulli effect applies to VELOCITY (ft./sec.)
> not quantity of flow (cu. ft./sec. or gpm)
More flow = more velocity, we are not changing the size of the piping here.
> When I write "flow," "flow rate,"
> "quantity of flow" and things like that I mean the volume per time, like gpm
> or cfs.
More volume per unit time = more velocity in the same system.
> The thermostat acts like an orifice, the pressure drop, h, depends on
> the quantity of flow and area of the orifice:
> h=k*q^2/(2*g*a^2) k is the the reciprocal of the "discharge coefficient." For
> a given flow rate, the orifice causes a pressure drop in the fluid flowing
> through the orifice. The pump must deliver q gpm. The change of velocity
> through the restriction is V=(2*g*h)^0.5 (Bernoulli). That is through
> thethermostat. For the rest of the cooling system the velocity is unchanged.
Hey we're talking fantasy, so far I haven't seen one that would even fit under the
hood!
In the situation I describe WHY would inlet pressure fall? Same flow, same pump,
slower impeller speed, no restriction. Same flow=same volume of coolant going
through the pump, why would INLET pressure be any different? I can see why OUTLET
pressure would be different, what causes an inlet pressure drop with the same
flow, no restrisction?
(Sure would be easier with hand gestures, diagrams, a couple of cold ones, etc,
too bad we can only type back and forth (this is taking forever)) . . .
Howard Sockryder
in 1989. Slowed accessories down and they didn't use as much HP. Bet they
still do it.
Shawn wrote in message <35B6CDBF...@feist.com>...
Shawn
T. Postel wrote:
> *SNIP!!* Something like this might explain the issues I had
> > with the thermostats having
> >same outside/different inside diameters for the same temp rating.
> >***
> >
> >
> >Shawn GNa...@feist.com
> >
> I don't know of any universal design guidelines for the pressures at any point
> in an internal combustion engine cooling system. It shouldn't be so high that
> it leaks, and it can't be so low that the coolant boils, locally, near the
> exhaust valves for instance.
>
> Why do your thermostats look different? I really don't know... Just
> speculation: Two thermostats could have different inside diameters, if I am
> following you here, and still represent the same amount of restriction. If
> these thermostats are like the kind I'm acquainted with, they have a wax
> pellet encased in a brass, or copper, "bullet". When the wax gets hot, it
> melts & expands, pushing on an SS rod which pushes the valve open. If the
> bullet had a larger diameter, or did not clear the valve space as far, then
> the "inside diameter" of the valve would need to be bigger so that the annulus
> had the proper cross section to the flow. - Sound plausible?
> -m
Yes. I didnt mean for the same application however. The bullet can vary as well as
the actuall inside diameter, hmmm... makes this a riddle tough to solve. I forgot
about the bullet plunger thingamabob.
Shawn GNa...@feist.com
T. Postel
>pump, slower impeller speed, no restriction. Same flow=same volume of coolant
>going through the pump, why would INLET pressure be any different? I can see
>why OUTLET pressure would be different, what causes an inlet pressure drop
>with the same flow, no restrisction?
>
inlet. Imagine this simple (idealized) picture: coolant enters the pump inlet, with
velocity Vi, and comes in contact with the moving impeller vanes. Inlet vanes are moving at
rpm*PI*Di, Di is the impeller inner vane diameter. Due to the viscosity of the coolant, it
tends to acquire the rotary motion of the impeller. "Centrifugal" force moves each bit of
coolant into larger circular paths, which due to the influence of the vanes increases the
velocity of the coolant. The velocity of the vanes at the outlet is rpm*PI*Do, Do is the
outer diameter of the impeller. So the outlet velocity of the coolant, Vo, is nearly
Vi+rpm*PI*(Do-Di). If the rpm decreases the only way that Vo can be the same is if Vi
increases. In a closed system Vi can be increased only by the conversion of pressure:
V=(2*g*h)^0.5 at the inlet. I.E. a lower inlet pressure, and the pump is more likely to
cavitate.
-m
Ode
on whether cavitation is a problem in a well designed cooling system, but will consider the
possibility in the future. I'm sure some newcomer to the group will bring up the question again
in . . . well, I give it a week . . .
T. Postel
> The discussion has been an interesting and educational exchange. We probably still disagree
>on whether cavitation is a problem in a well designed cooling system, but will consider the
>possibility in the future. I'm sure some newcomer to the group will bring up the question again
>in . . . well, I give it a week . . .
>
I have been running cooling system simulations. For any given heat input to the water jacket, and
radiator with constant characteristics, if the quantity of coolant flow is increased its temperature
drops. By coolant temperature, I mean at the thermostat location, the radiator outlet, and the
radiator average temps increase. This applies to cold start & run-up to temperature, with high flow
run vs. low flow run, and hot running with a sudden change of flow. Except for brief transient
fluctuations, the coolant temperature is always lower with higher flow. If the radiator is just big
enough for a certain heat input, (I.E. the coolant will overheat with any increase in input) its
capacity will increase with a higher flow.
"More flow = cooler engine, period."
-m
Ode
enjoyed it and much to the chagrin of the rest of the group, I'm sure we'll have more physics
discussions in the future. Take care of yourself, and stick around . . .
T. Postel wrote:
--
Trapper
> Amen, brother, that's what I said to start this whole mess! Thanks for the discussion, I quite
>enjoyed it and much to the chagrin of the rest of the group, I'm sure we'll have more physics
>discussions in the future. Take care of yourself, and stick around . . .
>
I've been lurking on this posting since it started and I am amazed at
the twists and spin put onto what is simple thermodynamic theory.
Most people were confused between heat and temperature. The purpose of
the cooling system is to move heat from the engine to the atmosphere.
Larger radiators, higher volume water pumps etc enable the system to
move the heat at a lower temperature. As the thermostat is a
restriction in the system then removing it should increase the coolant
flow and reduce the overall temperature, however the amount of
temperature decrease will be insignificant in terms of the engine's
capability to handle temperature. The sole purpose of the thermostat
is to bring the engine temperature up to it's minimum operating
temperature as quickly as possible after that it's effectively out of
the heat transfer equation. That's the way I see it.
Looking forward to the next scientific?? debate. Maybe I should start
one on is there a substitute for horsepower?
Trapper in Calgary, Alberta
rath...@netcom.ca
Ode
Greg Zelna wrote:
> I think its possible to flow TOO fast thru a radiator, or any
> themodynamic system forseeking the best possible heat transfer. I recall
> many years ago at Pratt Whitney (jet engine mfr) that in the 'paired
> turbine vanes' which were essentially a hollow blade shape with a second,
> slightly smaller one inserted inside it and an airgap between the two they
> actually SLOWED the flow of coolant (air) thru parts of the engine.
> The outer surface of the inner vane had little bumps fabricated onto it,
> called 'trip strips' thier sole purpose was to disrupt the flow of (cooling)
> air past that vane, slowing it down to transfer more heat from the vane to
> the air....
There is a difference between turbulent and laminar flow. The bumps would be to enhance
turbulence; turbulence effectively pushes more air into direct contact with the radiating
surface.
> At some point I believe you could push so much water thru an
> engine's radiator that it'd no longer reduce the engine temp to the desired level but
> instead slowly heat up to an unacceptable level...
More flow = cooler engine.
> Along the lines of more is better. I installed an oversized radiator in my '67
> Mustang. Ran GREAT highway, almost too cold. However, idling in hot weather,
> well the 6-cylinder sized fan couldn't pull enough air across the larger
> radiator and it'd slowly build up heat.
Most likely some other problem. Did you use a larger shroud for the new radiator, with
good fit/seal between the radiator and shroud and the proper diameter opening for your
fan? It would slowly build up heat? It should do this in the city, but did it get too
hot, or did it just run warmer than on the freeway?
> Coulda tried a flex fan I suppose,
> sold the car long ago.
More flow = cooler engine.
Stephen M. Henning
> More flow = cooler engine.
This seems very logical but it is false. On some race engines where
overheating is very likely and fatal, they remove the thermostat and
insert a constriction plate that has a hole of optimum size to insure
maximum cooling. They arrive at the size of the hole empirically. I
guess when you think about it there are such things as wind burn where a
wind can be so strong it causes heat rather than removing it. The race
mechanics describe the water as going too fast to cool if you don't put in
the constriction plate. I think that it is a case of the relative area of
the engine and radiator is reduced by eddy-pools where the same hot water
keeps eddying in a loop and never makes it out.
--
Cheers, Steve Henning, Reading, Pennsylvania, USA
Correct email address is shen...@fast.net (Please forgive my spam deterrent)
Visit my home page at http://www.users.fast.net/~shenning
Shawn
true. I "still" dont think its the whole story to a cooling system tho.
Shawn GNa...@feist.com
T. Postel
>
>There is a difference between turbulent and laminar flow. The bumps would be to
>enhance turbulence; turbulence effectively pushes more air into direct contact
>with the radiating surface.
>
>
>More flow = cooler engine.
>
Yes, and it can be even more complicated. Reynolds criterion = VDs/u (V is the
velocity, D is the mean diameter, s is the specific gravity, and u is the
viscosity) In a given pipe with a certain cross sectional shape and area well
below the velocity at which "Reynolds Criterion" is less than about 2000 in cgs
units the flow will be laminar. If the velocity of flow is much greater then the
flow will be turbulant. In between the flow does not abruply change, but the
core of the pipe, where flow is not slowed by drag from the walls, flows a
little faster, and becomes turbulent first. As the velocity continues to
increase, the turbulent core expands, and the laminar flow near the walls gets
thinner. For some applications, this segregation can allow the turbulent core
to move through the heat exchanger with virtually no change in temperature,
while the laminar part drops right down to the minimum exchange temp (or up to
the max). If the core takes up the majority of the cross sectional area then
the heat exchanger will show a greatly diminished capacity for that flow
velocity. If this can happen, the designer will incorporate "spoilers" to
generate turbulance throughout the cross section of the flow. It can happen in
the liquid carrying tubes in a radiator, or through the air conducting fins.
Thin elongated tubes are almost immune to this transition effect. Straight,
circular tubing is likely to suffer a loss of heat exchanging capacity for a
narrow range of flow velocities. That is why circular tube radiators have chaff
in the tubes. While this is a real effect, it is never seen in automotive
radiators, because it is easy to design around.
-m
T. Postel
>In article <35C227BB...@mci2000.com>, Oude...@mci2000.com wrote:
>
>
>overheating is very likely and fatal, they remove the thermostat and
>insert a constriction plate that has a hole of optimum size to insure
>maximum cooling. They arrive at the size of the hole empirically. I
>guess when you think about it there are such things as wind burn where a
>wind can be so strong it causes heat rather than removing it. The race
>mechanics describe the water as going too fast to cool if you don't put in
>the constriction plate. I think that it is a case of the relative area of
>the engine and radiator is reduced by eddy-pools where the same hot water
>keeps eddying in a loop and never makes it out.
>
with. (bored to death) The constriction is to eliminate pump cavitation.
Cavitation reduces the quantity of coolant flow. Less flow = hotter engine.
Look at this thread on http://www.dejanews.com/home_ps.shtml, try from 07-16-98
on...
Man, Ode, it wasn't even 1 day!
-m
Tune.gis.net
Drop the thread.
'52 GMC longstep 228 T-5 NO Thermostat!
1959 Chevrolet Apache 235 Four Speed NO thermostat!
Ode
up. I guess I was wrong, I guessed it would be a week before somebody started it
up again . . . it only took about 24 hours!
Tune.gis.net wrote:
--
Ode
. . .
Stephen M. Henning wrote:
> In article <35C227BB...@mci2000.com>, Oude...@mci2000.com wrote:
>
> > More flow = cooler engine.
>
> This seems very logical but it is false.
Afraid not.
> On some race engines where
> overheating is very likely and fatal, they remove the thermostat and
> insert a constriction plate that has a hole of optimum size to insure
> maximum cooling. They arrive at the size of the hole empirically. I
> guess when you think about it there are such things as wind burn
This isn't an SR-71, the heating effects of air at 200 mph are less than the heat
that kind of airflow draws off. At 200 mph, most race cars run very SMALL
radiators because that is all they need and a smaller radiator represents less
drag. Notice most Indy cars are built this way and run hot in the pits and
nominal at speed. This is why a small restriction such as a plastic bag on the
airflow to the radiator can cause overheating and engine destruction, and why
NASCAR crews clean the radiator airflow grills of rubber (from tires wearing out
in "the groove" on the track") and other debris during each pit stop.
> where a
> wind can be so strong it causes heat rather than removing it.
This is not an SR-71, at 200 mph, the air carries away MUCH more heat than
friction provides to a radiator.
> The race
> mechanics describe the water as going too fast to cool if you don't put in
> the constriction plate.
That's bullshit. Even if I have been arguing with T. Postel about whether or not
cavitation is a significant concern in a properly designed cooling system in a
street car, I will NOT argue that cavitation is of concern in a low volume, high
RPM cooling system such as that found in a Ferrari V-10 Formula One engine that
cranks over 17,000 RPM and doesn't have a whole lot of coolant in the system. At
this speed (both engine and fluid speed) cavitation is without a doubt a very big
concern in a cooling system!
> I think that it is a case of the relative area of
> the engine and radiator is reduced by eddy-pools where the same hot water
> keeps eddying in a loop and never makes it out.
Eddy currents? Have you ever considered the shape of the water channels in the
block/heads, there are no pockets for water to pool. There are straight or curved
channels, that's it. And outside the engine, this is a VERTICAL system. Coolant
enters the top and pours down the radiator by gravity.
P.S. I am really not ready to further discuss the subject, as T. Postel and I
have beat the subject to death the past few weeks . . .
Ode
T. Postel wrote:
> Man, Ode, it wasn't even 1 day!
> -m
--