Should I go to freshwater cooling?
yacht_...@hotmail.com
We are probably going to put a Sen-Dure freshwater cooling kit on our
Volvo MD-2B. We are replacing the heads and cylinders and thought it a
good time to do it before they get full of rust.
Any thoughts pro or con? It did last 13 years and 3,400 hours with
saltwater cooling. Is spending a lot of money to buy more stuff to
maintain a bad idea? I always wished we had put on freshwater cooling,
but perhaps I was lucky that I had not.
-------------------==== Posted via Deja News ====-----------------------
http://www.dejanews.com/ Search, Read, Post to Usenet
_DEFAULT
I purchases a new boat several years ago and cotemplated a closed cooling
system instead of sea water coolong.I was advised against it as they
informed me that the operating temps of closed systems tend to be 40-50
deg. warmer than open systems.their studies showed a 1/3 loss of engine
life>
hidda
yacht_...@hotmail.com wrote:
>
> We are probably going to put a Sen-Dure freshwater cooling kit on our
> Volvo MD-2B. We are replacing the heads and cylinders and thought it a
> good time to do it before they get full of rust.
>
> Any thoughts pro or con? It did last 13 years and 3,400 hours with
> saltwater cooling. Is spending a lot of money to buy more stuff to
> maintain a bad idea? I always wished we had put on freshwater cooling,
> but perhaps I was lucky that I had not.
>
> http://www.dejanews.com/ Search, Read, Post to Usenet
A properly sized and engineered Fresh Water Cooling system will do a
couple of important things. First, FWC will help prevent rusting in the
engine because you'll be running an antifreeze solution. A side effect
of this will be that your winterizing of the block will be simple.
None. You'll just have to drain whatever has saltwater in it and the
block will be protected by the antifreeze. Second, the thermostat
should be replaced with a higher temp one. This will increase operating
efficiency of the engine. This increase in temperature has another
benefit too. Volatiles and moisture in the oil (real killers in an
engine) will boil off much faster. Most all modern engines are designed
to operate at a minimum of 180 degrees. Most raw water cooled engines
run at 140.
Anders Svensson
_DEFAULT wrote:
>
> I purchases a new boat several years ago and cotemplated a closed cooling
> system instead of sea water coolong.I was advised against it as they
> informed me that the operating temps of closed systems tend to be 40-50
> deg. warmer than open systems.their studies showed a 1/3 loss of engine
> life>
IMHO, this sounds like a misunderstanding. Sea water cooled diesels tend
to run too cold, and would *benefit* from a heat exchanger system in
this respect. A good time to install it would be with new (or clean,
rather) cylinders and cylinder heads.
Anders
Mak37
I've yet to see an engine wear out because the cooling water passages in the
block have corroded through (although I'm sure it happens). I have seen many
boaters stranded because their fresh water cooling system (extra pump, hoses,
belts, heat exchanger, etc...) has broken down. Give me the more reliable, less
expensive, cooler running, raw water cooling system and I'll wear my engine out
just like 99% of all boaters from lack of use, lack of maintenance and rust and
corrosion of all the other parts.
Ken Cooperstein
I think the best solution is aftermarket aluminum manifolds and
stainless risers. These are the two components that fail in salt
water.
An additional precaution is flushing the cooling system with fresh
water and Salt Away. If you have a trailerable, this is no problem.
If not, then you can provide for pumping fresh water with Salt Away
into the cooling system from your water tank after she is tied up.
Ken
Andrew Jagger
In <01bd388e$0c5747c0$28286420@default> "_DEFAULT"
<_DEF...@prodigy.net> writes:
>
>I purchases a new boat several years ago and cotemplated a closed
cooling
>system instead of sea water coolong.I was advised against it as they
>informed me that the operating temps of closed systems tend to be
40-50
>deg. warmer than open systems.their studies showed a 1/3 loss of
engine
>life>
Conventional wisdom says that most engines run a bit hotter with fresh
water cooling and therefore run more efficiently. I've never heard
about shorter life.
Aerts
Fresh Water Cooling is a Great Idea..not a good idea...thus the cost...I
would never go back to raw water cooling...and I live in the Northwest
Territories, Canada. Go for it and don't look back.
yacht_...@hotmail.com wrote in message
<887378063...@dejanews.com>...
>We are probably going to put a Sen-Dure freshwater cooling kit on our
>Volvo MD-2B.
>saltwater cooling. Is spending a lot of money to buy more stuff to
>maintain a bad idea>
Martin
> >We are probably going to put a Sen-Dure freshwater cooling kit on our
> >Volvo MD-2B.
> >Any thoughts pro or con? It did last 13 years and 3,400 hours with
> >saltwater cooling. Is spending a lot of money to buy more stuff to
> >maintain a bad idea>
My MD2B is 25 years old without fresh water cooling. The only problem I have
had is with electrics, now solved by replacing most of them! I am on the
third voltage regulator and the second alternator.
Pat H.
yacht_...@hotmail.com wrote:
>
> We are probably going to put a Sen-Dure freshwater cooling kit on our
> good time to do it before they get full of rust.
>
> saltwater cooling. Is spending a lot of money to buy more stuff to
> but perhaps I was lucky that I had not.
I'm installing a new Volvo engine in my boat and would NEVER think of
using raw water cooling. The old engine had fresh water cooling, a
blocked intake on this system caused a boil over, with no harm since the
engine block was never dry itself. Had we had raw water cooling the
engine would have seized. This was with me watching the temp gauge, it
only took seconds for the temp to go from normal to over-temp even with
the fresh water cooling.
The engine temp will run in a more efficient range of 180-190 degrees
rather than the much too cold range of 140-150 degres with raw water
cooling. This is even more important for a diesel than for gas engine
like mine. Engine life will be LONGER, with all things maintained per
factory specs, NOT shorter, if fresh water cooling is used.
Pat
Bob
I don't believe you can run a salt water cooled system beyond a certain
temperature without the risk of having the salt solidify and block the
cooling passages of the engine. With a closed system, this concern goes
away and you may run the engine at the much more efficient higher
temperature.
I think it may be reasonable to say that running the engine below its
designed operating temperature could shorten its life.
JJames915
I got news for you, having raw or fresh water cooling doesn't make a difference
on the engine seizing when overheated. It all depends on how long it's running
overheated. Im either case if you stop removing heat the engine will overheat
very quickly.
Paul and Cindy Kruse
b...@car.lot (Bob) wrote:
< I don't believe you can run a salt water cooled system
< beyond a certain temperature without the risk of
< having the salt solidify and block the cooling
< passages of the engine. With a closed system, this
< concern goes away and you may run the engine at
< the much more efficient higher temperature.
< I think it may be reasonable to say that running
< the engine below its designed operating temperature
< could shorten its life.
I have been watching this thread with some interest, since
our family has operated and maintained a number of boats
with raw water cooling, and also with fresh water cooling.
We have never bought a new engine for any boat. They have
all been well used when we bought them. In this way, we
got a much better idea of how different boats hold up in
the long run, and what sort of maintenance they require.
Let's think about what you just said here. No matter what
the temperature of the sea water, it will be warmer inside
of the engine. Therefore, if the salt is in solution in
the sea water, it simply cannot fall out of solution
inside the engine while the engine is running. The
accumulation of salt deposits has nothing to do with the
temperature of the sea water.
Salt deposits inside the engine are caused when the water
evaporates. Normally, this happens when you shut the
engine down and do not run it again for a while. Salt
deposits in the exhaust system are another matter, but
that is not relevant to this discussion because the
exhaust is always raw water cooled -- whether the engine
is fresh water cooled or not.
We have always been very successful in keeping the salt
deposits out of our engines. I know this because I have
seen the inside of many of them, but salt deposits have
never been the reason for tearing one down. We do this by
either running them frequently, or by flushing them out
after using them when they will not be run for a while.
All in all, our engines with fresh water cooling have cost
us a great deal more heart ache than our raw water cooled
engines. We have always spent a great deal more time and
money maintaining the fresh water cooling system than we
have correcting problems caused by raw water cooling in
our other engines. I doubt that I will ever buy a boat
with a fresh water cooled gas engine again. (A diesel is
another matter.)
As for the difference in operating temperatures, I have
never seen much of a difference one way or another. If
you do have a problem with engine temperatures being too
low, it should not be that much of a problem to fix by
restricting the water flow with either a thermostat, an
orifice, or a valve.
I have recently talked with several mechanics who maintain
commercial fishing boats, to get their opinions on this
raw/fresh water cooling debate. Their opinions seem to be
mixed, though all admit that many large commercial marine
diesels are being cooled by raw water with few problems.
They do not suffer from salt deposits, but corrosion is a
concern. While this is useful data, we must also
understand it in its context. Commercial fishermen use
their engines a WHOLE lot more than any recreational
boater. All this really shows is that the engines will
not develop salt deposits if they are used frequently.
(It should also be noted that most these commercial
fishing boats that these mechanics are working on are
running a dry stack. Salt deposits are therefore no
concern in the exhaust manifold.)
A large diesel is not a "throw-away" engine, which you
discard when the boat or the engine wears out. Corrosion
can be a problem on an engine that you expect to hold up
for twenty or thirty years. For that reason, I would
consider fresh water cooling in this case. I am actually
planning to use air cooled diesels on the boat I am
building; but if I were to change my mind and use a water
cooled engine, then I would not use a conventional heat
exchanger sold for that purpose. I have just never seen
on hold up like I think it should. Rather, I would use
either a keel cooler or a water box, or both.
One note about keel coolers: They do not work so well
when you are running the engine at the dock or at a
mooring in shallow water. The problem is even worse when
you have very little space between the keel and the
bottom. They need the water to be flowing past the keel.
If you are a cruiser who has to run your main engine or
you generator for long periods of time while the boat is
at rest in shallow water, then do not depend upon a keel
cooler to keep the engine cool.
While I do monitor this newsgroup, my server is
famous for losing Usenet articles. If you reply to
this posting, please also route a copy to me via E-mail.
Have a great day,
plk...@iu.net (Paul Kruse)
Bob Fifer
The salts precipitating out of salt water at elevated temperatures are
salts of magnesium and calcium carbonate, not sodium chloride.
They begin to precipitate out when salt water rises above 140 deg F. At
elevated temperatures the carbonate <->bicarbonate <-> carbon dioxide
balance is shifted, and these carbonate salts fall out of solution. These
deposists are relatively insoluable, and will probably require a dilute
acidic flushing solution to remove from inside of cooling system
passageways. Oxalic acid automotive radiator flush is one way to remove
these salts, but should be done within the manufacturers guidelines for
engine flushing. These salt precipitates accumulate over time and not all
at once due to an occasional overheating incident.
Most raw water cooled engines are set up to run cooler, i.e. injector
timing and volume. A thermostat is usually set to open at about 120 deg.
F. With clean fuel and frequent oil changes, proper winterization
flushing, as well as attention to zinc anodes where appropriate, a raw
water cooled engine should last 20 years.
In article <NY1G.1$ro2....@news1.atlantic.net>, plk...@iu.net (Paul and
Cindy Kruse) wrote:
--
Remove anti-spam tags from address when replying.
edgar cove
In article <01bd388e$0c5747c0$28286420@default>, _DEFAULT
<_DEF...@prodigy.net> writes
>I purchases a new boat several years ago and cotemplated a closed cooling
>system instead of sea water coolong.I was advised against it as they
>informed me that the operating temps of closed systems tend to be 40-50
>deg. warmer than open systems.their studies showed a 1/3 loss of engine
>life>
>> http://www.dejanews.com/ Search, Read, Post to Usenet
>>
pointed out that engines used in boats fall into two distinct
categories:-
1. Those designed specifically for marine use with salt water cooling.
For reasons connected with the size of the market such engines are
relatively uncommon in smaller sizes. Such engines tend to operate at
lower ratings to keep temperatures down and have wider cooling
passages. In combination these factors add up to a motor that can be
cooled directly by salt water without undue wear. It is true that salt
water cooled engines have to work at lower temperatures to avoid
deposits and in such engines the designed clearances e.g. of piston in
cylinder take account of this. It is not sensible to take an engine of
this type and fit fresh water cooling and boost the operating
temperature to say 180 degrees f. even though in theory 180 degrees is a
more efficient temperature. See next paragraph.
2. For economic reasons many of the smaller engines used in boats,
particularly yachts, are 'marinised' versions of engines mass produced
for the industrial engine market. It has not escaped the notice of the
manufacturers that a yacht engine is doing pretty well if it exceeds 100
running hours annually and accordingly they run such engines at a high
rating that equates to a relatively short engine life in terms of total
hours run. Since the engines were not designed for marine use, which is
a small sector of the market, the cooling passages are small and
intended to be cooled by fresh water only and the internal clearances
are based on operating at the most efficient temperature, which for an
engine of this sort is about 180 degrees f. or even more if the system
is pressurised. To cool such an engine with salt water is a recipe for
trouble.
Basically therefore you should adhere to the manufacturers
recommendations for the engine in question.
--
edgar-(remove nospam from return address for e-mail)
Paul and Cindy Kruse
Hello, Bob; and thanks very much for the additional information.
At 01:30 PM 2/17/98 -0500, you wrote:
>The salts precipitating out of salt water at elevated temperatures are
>salts of magnesium and calcium carbonate, not sodium chloride.
>
>They begin to precipitate out when salt water rises above 140 deg F. At
>elevated temperatures the carbonate <->bicarbonate <-> carbon dioxide
>balance is shifted, and these carbonate salts fall out of solution.
Let me make sure that I understand what you are saying: The solubility of these
salts of magnesium and calcium carbonate decreases as the temperature increases,
like the solubility of a gas in water?
>These
>deposists are relatively insoluable, and will probably require a dilute
>acidic flushing solution to remove from inside of cooling system
>passageways. Oxalic acid automotive radiator flush is one way to remove
>these salts, but should be done within the manufacturers guidelines for
>engine flushing. These salt precipitates accumulate over time and not all
>at once due to an occasional overheating incident.
I have always wondered why it was so difficult to get rid of these salt deposits
in exhaust manifolds. The only way to do it is to remove the manifold and soak
it in acid. Now I know.
>Most raw water cooled engines are set up to run cooler, i.e. injector
>timing and volume. A thermostat is usually set to open at about 120 deg.
>F. With clean fuel and frequent oil changes, proper winterization
>flushing, as well as attention to zinc anodes where appropriate, a raw
>water cooled engine should last 20 years.
Again, I repeat something back to you to make sure I understand you correctly:
You are saying that the reason I have not had a problem with salt deposits in my
raw water cooled engines is because they are set up to run with cooler water?
Peter Jerkewitz
There are some other minor considerations on the fresh vs salt water
cooling.
Consider winteriazation, closed loop system only the raw water pump and
heat exchanger need be protected.
Consider hot water heaters, higher engine temps mean more hot water for
the family.
Can't think of any more, the important issues have been covered.
Peter ( Salt Water Sailor )
Pat H.
Actually there is a substantial difference in the length of time one
has to shut the engine down when the heat guage reacts to a lack of
cooling when comparing fresh vs raw water cooling.
By empirical example without water in the engine block and heads you
have from 10-25 seconds to shut down the engine, less if it has aluminum
heads.
With water/coolant in the block and heads the engine might fun for
around 60 to 120 seconds before a total boil over, depending on the
ambient air/water temperature.
An example: A friend of mine was driving his 1970 Ford Mach 1 Mustang
flat out in Montana back when that was socially acceptable<G>. His
lower radiator hose broke, dumping his coolant, which he didn't notice
immediately (why I don't remember). This is the same thing you get with
a totally blocked raw water intake on a marine engine. His temp guage
went to full hot then dropped most of the way to zero, with no coolant
to sense. 10 to twenty seconds into this the engine began to run
erratically, and seized completely before he coasted to a stop.
A boat with no airflow to partially cool the engine will seize faster.
I'm certain that there are many people that have example of raw water
cooling doing the job, particularly those that use their boats a lot.
It seems that those of us, me in particular, that don't used our boats
more than 2-10 hours per month have engines that suffer much more
severely in salt water. The previous owner of my boat had raw water
cooling on the first engine. When it had to be replaced due to severe
corrosion from sitting for extended periods partially full of salt
water, he made the move to fresh water cooling. The second engine,
which has had its problems, has NEVER had a problem from the fresh water
cooling system.
The new engine will have fresh water cooling, and that's that.
Pat
Ted H
yacht_...@hotmail.com wrote:
>
> We are probably going to put a Sen-Dure freshwater cooling kit on our
> Volvo MD-2B. We are replacing the heads and cylinders and thought it a
> good time to do it before they get full of rust.
>
I've always been a proponent of raw water cooling in a recreational
inboard boat engine (particularly when it wasn't mine!).
*However*, I recently purchased a new inboard powered boat (ordered with
raw water cooling - against the dealer's rec). After going thru it's
first winter's layup procedure, I decided to install fresh water
cooling. The winterizing process becomes much less messy when you don't
have to worry about the engine block.
The engine currently has ~20 hrs on it and I just installed the factory
FWC kit (did it myself, what a pain in the butt!). I used the boat
exclusively in salt water (to this date) and religiously flushed the
engine with fresh water for at least 10 minutes after each outing.
After seeing the film of rust deposits in the intake manifold and hoses,
I don't regret my decision to convert. As a plus, the engine will now
operate at ~180 deg. F (instead of 140), which will allow it to run more
efficiently and keep the build-up of crud in the oil to a minimum.
I'd go for the FW cooling if it were my re-build. Just my $0.02
Regards - Ted H
SolarFry
>Subject: Re: Should I go to freshwater cooling?
>From: edgar cove <ed...@nospam.demon.co.uk>
>Date: Tue, Feb 17, 1998 14:35 EST
>Message-id: <jMMz7AAV...@coves.demon.co.uk>
fresh water cooling you will be replacing the
heat exchanger manifold every 2-3years. They rust out and let
water into the engine via the exhaust port.
hidda
SolarFry wrote:
<Snipped>
> >
> In addition you will probably not keep the boat more than 6 or 7 years and with
> fresh water cooling you will be replacing the
> heat exchanger manifold every 2-3years. They rust out and let
> water into the engine via the exhaust port.
You know folks, in over 20 years with various I/O engines, Merc, OMC,
and Volvo, I have never experienced a rusted out exhaust manifold that
let saltwater back into the cylinders. I have had cracked manifolds
where it let the exhaust and NOISE into the engine compartment. I have
had clogged manifolds and risers (due to scaling), but I've never had
one let water back into the engine.
Usually, going by my experience, when coolant flow through the exhaust
manifolds and risers slows down, it's due to scaling in the coolant
passages. This is a warning for you to change them.
RE: FWC It's worth every penny. Unless you modify the engine to
increase the raw water flow, which probably includes a bigger raw water
pump, you'd do well to get FWC if you push your engines like I do. With
raw salt water cooling, I experienced precipitation of salts that caused
scaling in the heads around the valves. On subsequent full throttle
runs, the valves over heated and burned which resulted in compression
loss and a repair bill. Even when we enlarged the water passageways in
the heads, we still experienced burned valves.
When we repowered and spec's FWC, the burned valve problem stopped.
We have had clogged exhaust manifolds on this engine. Temperature rise
was slow, even at high rpms. In a previouse Merc, we also experienced a
clogged manifold. Temperature rise was dramatic. Decrease in power was
the first indication something was wrong. By that time, temp guage was
pegged. Luckily, engine was fine and temp dropped when we cut back on
the throttle.
In salt water, no question. FWC is worth the money for the majority of
us. I'd probably spec FWC even if I was in fresh water. Running
anti-freeze in an engine just makes so much sense to me. A lot to be
said for a pressurized cooling system with anti-freeze. Oh yeah, 5
minutes of flushing is enough. Don't even have to wait for hot water to
come out. With raw water cooling, you have to wait for the thermostat
to open up before you can even begin flushing out the engine.
Remember, the longer you run the engine out of water, the hotter the leg
will get and the better the chances of you blowing out a seal. If you
run the engine a long time on the ear muffs, make sure you run water
over the leg too.
James W. Hebert
In article <jMMz7AAV...@coves.demon.co.uk>, edgar
<ed...@nospam.coves.demon.co.uk> wrote:
[regarding raw water cooling of marine engines
versus closed loop cooling]
> It is not sensible to take an engine of
> this type and fit fresh water cooling and boost the operating
> temperature to say 180 degrees f. even though in theory 180 degrees is a
> more efficient temperature.
The notion that an internal combustion engine operates
"better" or "more efficiently" at elevated temperatures
does not seem to me to be apparent at first glance.
Could someone explain what law of nature wants an
internal combustion engine to operate around 180-deg.
Farenheit?
I think there might be some other, non-natural, laws
influencing this tendency, like the pollution laws
of the US regarding automotive engine emissions.
If I observe two machines, both producing the same
amount of work or output, and one of them operates
at 180-degrees while the second operates at 100-degrees,
I am tempted to predict that the machine that will
last longer is the one operating at the lower
temperature. At least that is my experience
with many other "machines" that I have seen,
particularly anything involving electronics.
--jim
Jim Hebert, K8SS | C O N T I N U O U S
Beverly Hills, Michigan | W A V E
ji...@w8hd.org | http://tango.w8hd.org
John Matott
This is a really good question. I can think of three reasons that might be
valid...at low temperatures, the pistons and rings may not fully expand and
seat to the cylinder walls at their design clearances...the viscosity of
fuel decreases rapidly with its temperature, so it might not atomize
properly at low temperatures...the amount of cooling apparatus needed to
bring the water jacket temperature of a fully loaded engine down a hundred
degrees might be excessive. These are just guesses.
Harry Krause
From: edgar cove <ed...@nospam.demon.co.uk>
In article <01bd388e$0c5747c0$28286420@default>, _DEFAULT
<_DEF...@prodigy.net> writes
>I purchases a new boat several years ago and cotemplated a closed cooling
>system instead of sea water coolong.I was advised against it as they
>informed me that the operating temps of closed systems tend to be 40-50
>deg. warmer than open systems.their studies showed a 1/3 loss of engine
>life>
>
>>
I have been following this thread with interest but nobody has yet
pointed out that engines used in boats fall into two distinct
categories:-
2. For economic reasons many of the smaller engines used in boats,
particularly yachts, are 'marinised' versions of engines mass produced
for the industrial engine market. It has not escaped the notice of the
manufacturers that a yacht engine is doing pretty well if it exceeds 100
running hours annually and accordingly they run such engines at a high
rating that equates to a relatively short engine life in terms of total
hours run.
What's your definition of a "yacht" or a "yacht engine?" Most of the modern
yachts I've seen are powered by diesels that are rated to perform for thousands
of hours a year.
If you have a choice, you should fresh-water cool any inboard engine in a
conventional pleasure craft. With a closed cooling system, the only real area
subject to corrosion is in the heat exchanger. With an open system, seawater can
go where it wants and do the damage for which it is so notorious.
Since the engines were not designed for marine use, which is
a small sector of the market, the cooling passages are small and
intended to be cooled by fresh water only and the internal clearances
are based on operating at the most efficient temperature, which for an
engine of this sort is about 180 degrees f. or even more if the system
is pressurised. To cool such an engine with salt water is a recipe for
trouble.
--
To respond via EMAIL to a newsgroup post, remove -nospam from my address.
- - - - - -
"But honey, we need a 2 gig drive for word processing!"
Terry Schell
ji...@w8hd.org (James W. Hebert) writes:
<snip>
>The notion that an internal combustion engine operates
>"better" or "more efficiently" at elevated temperatures
>does not seem to me to be apparent at first glance.
The simple story: because any carnot cycle engine is producing power
as a function of the difference in temp between the air intake and the
peak cyl. temp. Running with higher water jacket temps allows you to
slightly increase this ratio without adding more fuel. This higher
temp creates greater pressure, which creates more torque.
As far as wear, the limit at 180 deg F is due to longevity. It
is a function of the boiling point of coolant at normal pressures. If
you were willing to run exotic coolants and synth oils (and play with
tuning to prevent preignition) you could increase this temp and
improve efficiency further. You don't have to worry about heat induced
metal fatigue until temps get quite high... so long as you don't start
losing coolant or having your oil break down.
Terry "gear-head" Schell
edgar cove
In article <34ED84CC...@gate.net>, Harry Krause <hkr...@gate.net>
writes
<snipped>
>What's your definition of a "yacht" or a "yacht engine?" Most of the modern
>yachts I've seen are powered by diesels that are rated to perform for thousands
>of hours a year.
small engines which are offered for salt water cooling. My answer to
the question of whether it is worth fresh water cooling such an engine
was basically 'not if it was designed for salt water cooling'. Remember
that unless you go for a keel cooler freshwater cooling involves the
complication of an extra water pump.
Your comment obviously concerns engines of much higher power fitted in
much bigger yachts. They -may- be rated for thousands of hours per year
but to my knowledge most manufacturers offer higher ratings for pleasure
craft than for workboats because they know quite well that pleasure
craft spend most of their time on their moorings and do not run very
many hours each season. Such engines are invariably fresh water cooled
because they are highly rated and need to run at 180-190 degrees to
avoid wear and such temperatures demand a pressurised system.
Furthermore they are almost invariably marinised versions of a basic
engine produced for industrial or automotive uses .
>If you have a choice, you should fresh-water cool any inboard engine in a
>conventional pleasure craft. With a closed cooling system, the only real area
>subject to corrosion is in the heat exchanger. With an open system, seawater
>can
>go where it wants and do the damage for which it is so notorious.
Too wide a generalisation. I have been using salt water cooled small
engines all my life without such problems-but the engines were simple,
reliable, modestly rated and-above all-designed for marine use with
direct cooling.
BTW - your comment about your (or is it my?) hard drive. Personal
choice really-I prefer not to spend time deleting spam from mine so use
a spam filter. There may be some people who enjoy reading spam. That's
OK by me!
hidda
edgar cove wrote:
<Snipped>
Remember
> that unless you go for a keel cooler freshwater cooling involves the
> complication of an extra water pump.
Not true. My FWC Volvo has two water pumps like everybody else. One is
the circulating pump that's integral with the engine, just like
everybody else (except somebody like Mr. Heon) and a raw water pump with
a rubber impeller, just like everybody else. The difference is a heat
exchanger, a few more hoses, and a different water distribution manifold
on the engine. I'd guess the system adds about 40 lbs, probably less.
Gould 0738
James Herbert wrote:
>same
>amount of work or output, and one of them operates
>at 180-degrees while the second operates at 100-degrees,
>I am tempted to predict that the machine that will
>last longer is the one operating at the lower
>temperature. At least that is my experience
>with many other "machines" that I have seen,
>particularly anything involving electronics.
I am not a mechanical engineer and I know doodem squat about electronics,
except for the fact that resistors, capacitors, etc don't have moving parts
lubricated by oil from a sump.
Run an engine as cold as 100 degrees and you'll have big time "poison oil"
problems.
The waters and acids that collect in the crankcase won't dissipate at such a
low operating temperature and a lot of premature engine wear to bearings and
other critical parts will occur. Sick oil makes sick engines.
Garry Heon
Gould 0738 wrote:
SNIP
> I am not a mechanical engineer and I know doodem squat about electronics,
> except for the fact that resistors, capacitors, etc don't have moving parts
> lubricated by oil from a sump.
>
> Run an engine as cold as 100 degrees and you'll have big time "poison oil"
> problems.
> The waters and acids that collect in the crankcase won't dissipate at such a
> low operating temperature and a lot of premature engine wear to bearings and
> other critical parts will occur. Sick oil makes sick engines.
Since Hidda mentioned my name in this thread I'll add my $0.02, actually
with my engines it's more like $1.02 We are talking water temp here
not oil temp. Most boats do not come equipped with an oil temp
gauge. My cooling setup eliminates the circulating pump and the
thermostat. The water flows from the sea water pump to a y pipe
where the circulating pump normally sits. From there to the back of
the block up to the heads and out through the intake, where the
T-stat normally sits. I flow ALOT of water. Although my water temp
NEVER reaches more than 110 degrees F the oil temp runs just at
200 degrees F at normal cruise, 4000 rpm, and will push 230 at
extended periods of WOT. As for oil sickness and changes, I just
went through this with the folks at Teague Custom Marine, who build
some of the finest professional race engines. My recommended change
interval is 20 hours, again this is high performance, so I asked
about running synthetic. I was told that I would still have to
change the oil every 20 hours since all the byproducts that make
it into conventional oil will still get into the synthetic. Although
the oil may not break down it's loaded with acids that will kill the
bearings. With the 12 qt pans I think I'll stick with conventional
oil.
The current power is the first time I've run cold water temp and
changed the oil every 20 hours. They have about 400 hours on them,
my Mercs only made it 300, and I'll be pulling them apart in April.
Although there is nothing wrong with the bottom end I figured I'd
pull them apart since I'll be installing new heads and cam. Going
over the bottom is cheap insurance at this point.
Garry Heon
http://home.att.net/~firststepp
I'll inspect for wear and corrosion and report what I find
Chris Campbell
I can add only a little... I know from reading car magazines (no technical
info to back this up) that internal combustion engines are more efficient at
higher temperatures. To this end much research has been done into high
temperature ceramics which would allow a piston engine built from them to run
at very high temperatures. Again, I can't describe why that is, but evidently
it is the case...
edgar cove
In article <34EDEB...@mauigateway.com>, hidda
<hi...@mauigateway.com> writes
Despite disagreeing with me you go on to confirm what I said! OK, so
your FWC Volvo has -two-water pumps. If it was SWC it would only need
one.
--
edgar cove
Charlie Mayne
edgar cove <ed...@nospam.demon.co.uk> writes:
My SWC installation has two pumps, just as (I think) "hidda" writes. I
think this is pretty much standard: two pumps for FWC or SWC.
Cheers,
Charlie
CS30 "Sprite"
--
Charlie Mayne | Motorola Incorporated
char...@pets.sps.mot.com | Microprocessor Products Group
| Austin, Texas 78735-8598
"I am concerned about my memory. But, for the life of me, I can't recall why."
hidda
edgar cove wrote:
>
> In article <34EDEB...@mauigateway.com>, hidda
> <hi...@mauigateway.com> writes
> >edgar cove wrote:
> ><Snipped>
> > Remember
> >> that unless you go for a keel cooler freshwater cooling involves the
> >> complication of an extra water pump.
> ><Snipped>
> >
> >Not true. My FWC Volvo has two water pumps like everybody else. One is
> >the circulating pump that's integral with the engine, just like
> >everybody else (except somebody like Mr. Heon) and a raw water pump with
> >a rubber impeller, just like everybody else. The difference is a heat
> >exchanger, a few more hoses, and a different water distribution manifold
> >on the engine. I'd guess the system adds about 40 lbs, probably less.
>
> Despite disagreeing with me you go on to confirm what I said! OK, so
> your FWC Volvo has -two-water pumps. If it was SWC it would only need
> one.
> edgar cove
You mean your engine doesn't have a circulating pump like a car has? Is
your engine a high performance engine? If it's a Merc, OMC, or Volvo,
and not an exotic engine like Garry Heon has in his boat, then you
should have two water pumps. One to circulate the water in the engine
and one to lift the water from the intake to the engine.
What kind of engine do you have? The vast majority of I/O engines in
boats have two water pumps. Even if my Volvo had raw water cooling, it
would still have two pumps. Every Merc I've ever seen had two water
pumps. So has every OMC and every other inboard engine I've ever seen.
Garry's is the first one I ever saw (picture on his website) that didn't
have a circulating pump. When I saw that, I asked him about it.
Dennis
edgar cove
In article <34F274...@mauigateway.com>, hidda
<hi...@mauigateway.com> writes
<earlier notes snipped>
>You mean your engine doesn't have a circulating pump like a car has? Is
>your engine a high performance engine? If it's a Merc, OMC, or Volvo,
>and not an exotic engine like Garry Heon has in his boat, then you
>should have two water pumps. One to circulate the water in the engine
>and one to lift the water from the intake to the engine.
>
>What kind of engine do you have? The vast majority of I/O engines in
>boats have two water pumps. Even if my Volvo had raw water cooling, it
>would still have two pumps. Every Merc I've ever seen had two water
>pumps. So has every OMC and every other inboard engine I've ever seen.
>Garry's is the first one I ever saw (picture on his website) that didn't
>have a circulating pump. When I saw that, I asked him about it.
>
>Dennis
We are not comparing like with like here. The engines you describe are
high performance ones and these would never have SWC because the cooling
passages will be relatively narrow. There are always local hot spots
internally, particularly within the cylinder head, and these will be at
a higher temperature than the mean outlet temperature of the cooling
water. They also tend to be the narrowest places e.g. between the
valves, and would quickly become blocked with the deposits which SW
makes if heated over about 130 degrees. Moreover cylinder wear on a high
rated engine would be very high if you ran it at a low temperature.
Hence FW cooling is essential for high performance engines.
The SWC engines I have dealt with were Volvo MD 2, Kelvin, Sabb, Lister
and Gardner 5L3, plus many types of small gasoline engines. All these
were low rated compared to yours and were designed for SWC and only had
one pump. My opinion is that the additional cost and complication of
fitting FWC to such is not worth while (except perhaps the Gardner)as
they have a very long service life, as mentioned earlier, due to lower
ratings and generously sized cooling passages.
--
edgar
Garry Heon
edgar cove wrote:
SNIP
> >Dennis
>
> We are not comparing like with like here. The engines you describe are
> high performance ones and these would never have SWC because the cooling
> passages will be relatively narrow. There are always local hot spots
> internally, particularly within the cylinder head, and these will be
Actually all the high performance engines I've seen, don't think I
could begin to count them, have all been SWC. The problem with FWC
in high performance engines is getting rid of the heat they generate.
The typical heat enchanger is not up to the task. I have one friend
that built 750 hp motors, steel block with aluminum heads (Brodix).
He went to FWC for those engines. After many tries at custom built
heat exchangers he finally got it right. The heat exchanger is
38" long and 6" in dia. He is now able to keep the engines cool.
I'll have to take pic of the setup and post it on my we page, looks
like he his making moonshine in his engine compartment.
> a higher temperature than the mean outlet temperature of the cooling
> water. They also tend to be the narrowest places e.g. between the
> valves, and would quickly become blocked with the deposits which SW
> makes if heated over about 130 degrees. Moreover cylinder wear on a high
> rated engine would be very high if you ran it at a low temperature.
Hmmm, maybe you should talk to a few builders like Teague, Pfaff,
Chief, Zul, Innovation......and ask them why they run the engines
cold. My water temp is always cold, according to the gauge, and
you can hold your hand under the dumps. It's nice Jacuzzi temp. The
oil runs at what most would consider normal though.
snip
> edgar
Garry Heon
http://home.att.net/~firststepp
hidda
edgar cove wrote:
<Snipped>
>
> We are not comparing like with like here. The engines you describe are
> high performance ones and these would never have SWC because the cooling
> passages will be relatively narrow. There are always local hot spots
> a higher temperature than the mean outlet temperature of the cooling
> water. They also tend to be the narrowest places e.g. between the
> valves, and would quickly become blocked with the deposits which SW
> makes if heated over about 130 degrees. Moreover cylinder wear on a high
> rated engine would be very high if you ran it at a low temperature.
> The SWC engines I have dealt with were Volvo MD 2, Kelvin, Sabb, Lister
> and Gardner 5L3, plus many types of small gasoline engines. All these
> were low rated compared to yours and were designed for SWC and only had
> one pump. My opinion is that the additional cost and complication of
> fitting FWC to such is not worth while (except perhaps the Gardner)as
> they have a very long service life, as mentioned earlier, due to lower
> ratings and generously sized cooling passages.
> --
> edgar
Well, the engines you mentioned are not all that popular in the US. The
majority of the engines (gas) are converted truck and car engines.
These all have two pumps with the exception of some high performance
engines. Diesels, such as the popular lightweight models from Volvo,
Yanmar, Cummins all have two pumps. The heavy diesels, such as those
from Cummins, Caterpillar, Detroit, etc. all have two pumps as far as
the ones I've seen.
The exception to this is the high perf engines, usually built on GM
blocks and usually pumping out 500+ horsepower. The water passages are
bored out and I've even heard some have the water flow reversed through
the engine like they now do with the new Corvettes. These high perf
engines are designed to operate with just the intake pump. The
circulating pump is removed.
I've done some research on this after seeing Garry Heon's engines on his
page. Interesting how they engineered the system to prevent scaling in
the engines. The intake pumps are huge compared to what normal boats
would use. Water temp stays low, but oil temp runs at normal high
temps. These engines pump out so much power that there's just so much
heat that needs to be dumped. FWC just can't cut it in these cases. If
they actually designed an FWC system for these engines, it would be
huge. Besides, the bottom line is these engines are removed, torn down,
and rebuilt in just a few hours. Corrosion and scaling is not a
problem. It doesn't have a chance to become a problem.
Dennis
James Basara
Let me take a stab at this;
The fact that an engine runs more efficiently at a higher temperature is
because it was designed to operate at that specific temperature as a
minimum. You see, if the operating temperature can be controlled, the
internal component clearances can also be controlled, thus the efficiency of
the engine can be optimized. The designed operating temperature is selected
based on a minimum controllable set-point which is based on the intended
operating environment and the thermo-dynamic efficiency of the cooling
system plus a fudge factor for errors. It would be useless to set an
operating temperature of say 120 deg. if that temperature could not be
maintained under the worst case conditions. Even though that lower
temperature would be less harmful to the internal engine components,
lubricants, seals, etc. So you see, the set-point of 180-195 degrees is the
minimum operating temperature of an internal combustion engine in an
automobile using a standard radiator cooling system at the worst case
condition (under high load in a high ambient) and thus all designs in an
automobile are based on worst case conditions. The thermostat is the
temperature regulating component in a cooling system and it maintains the
set-point operating temperature. Since many marine engines are based on
automobile engines you will find 190 degrees a common thermostat
temperature.
As far as marine engines go, I think open cooling systems that use raw
seawater are more efficient therefore the engines can operate at lower
set-point temperatures, thus increasing the service life of an engine. On
the other hand, corrosion and cooling passage obstruction can be a big
problem in the salt water environment, hence the closed cooling system and
higher operating temperatures. If I were considering a closed cooling
system. I would determine the specified operating temperature of the engine
first. If it's designed to run at 140-160 than you might be wise to leave it
alone because you may not get that level of efficiency out of a heat
exchanger. Check the thermostat rating.
James Basara
James W. Hebert wrote in message ...
>In article <jMMz7AAV...@coves.demon.co.uk>, edgar
><ed...@nospam.coves.demon.co.uk> wrote:
>
>[regarding raw water cooling of marine engines
>versus closed loop cooling]
>
>> It is not sensible to take an engine of
>> this type and fit fresh water cooling and boost the operating
>> temperature to say 180 degrees f. even though in theory 180 degrees is a
>> more efficient temperature.
>
>The notion that an internal combustion engine operates
>"better" or "more efficiently" at elevated temperatures
>does not seem to me to be apparent at first glance.
>
>Could someone explain what law of nature wants an
>internal combustion engine to operate around 180-deg.
>Farenheit?
>
>I think there might be some other, non-natural, laws
>influencing this tendency, like the pollution laws
>of the US regarding automotive engine emissions.
>
>If I observe two machines, both producing the same
>amount of work or output, and one of them operates
>at 180-degrees while the second operates at 100-degrees,
>I am tempted to predict that the machine that will
>last longer is the one operating at the lower
>temperature. At least that is my experience
>with many other "machines" that I have seen,
>particularly anything involving electronics.
>
Bruce Ardern
James Basara <BAS...@prodigy.net> wrote in article
<6d8a18$57bq$1...@newssvr03-int.news.prodigy.com>...
> Let me take a stab at this;
>
> The fact that an engine runs more efficiently at a higher temperature is
> because it was designed to operate at that specific temperature as a
James, what are your thoughts relating to using raw sea water for cooling
an ex automotive diesel (Nissan LD28 or similar) in a trailer borne boat
where unlimited fresh water can be introduced to the sea water intake after
each use of the boat in the sea? Mostly this boat would be in the sea for
two days at a time or less. I am thinking particularly of comments people
have made relating to small passages within the engine and their tendency
to become blocked with salt crystals at high opeating temeratures, and of
the corrosion question when raw sea water cooling is used.
regards, Bruce Ardern
Katikati, Bay of Plenty, New Zealand
Mark Whatman
Bruce Ardern wrote:
> James Basara <BAS...@prodigy.net> wrote in article
> <6d8a18$57bq$1...@newssvr03-int.news.prodigy.com>...
> > Let me take a stab at this;
> >
> > The fact that an engine runs more efficiently at a higher temperature is
> > because it was designed to operate at that specific temperature as a
> > minimum. etc.
>
<snip>
Let me add my $0.02. I have asked this question of a few engine builders and
manufacturers and here is the response.
1. The salt in salt water crystalizes at 170 deg F. to prevent this
crystalization Merc, Volvo, etc. set their thermostats between 140 and 160 deg
F to reduce the likelyhood that salt will crystalize and block engine passages.
2. The automotive engines used in most marine applications run at their most
efficient arround 195 deg F. This is primarily due to the basic laws of
physics. The same amount of heat is created internally regardless of the water
temp, hence Garry's observation that the oil temp in his motors runs 200 - 230
deg F. This energy can be disipated in many ways, some that produce power and
some that don't. Passing this heat energy to the water in the passages is a
method that does not produce power. This transfer of energy to the coolong
water is wasted. That being said, this amount of energy is minimal and can be
easuly made up for by a richer mixture, thus adding a little more energy to the
initial creation of the heat to compensate for the loss to the outside. This
explains the comment that 195 deg F is a more efficient temp to be running at
because you use slightly less fuel to produce the same amount of power.
3. If the actual internal temp of the water passages is kept below 170 deg F
then the corrosion caused by the water is identical to a boat run in fresh
water. It's what happens AFTER the engine is shut off and left to cool that
causes the corrosion. Flushing the motor imediately after use in salt water,
making sure to run it until the thermostat opens so you actually get fresh
water into the block, will net the same result as running it in fresh water.
What makes salt water motors, outdrives, etc. corrode faster is the fact that
almost no one flushed the system imediately after each use. The boat is
launched, used for the day or weekend, let sit for hours on end and then pulled
at the end of the day or weekend or week and then flushed. The corrosive
nature of salt water has had hours and even days to work before it's flushed.
Hence the salt system will corrode at a higher rate than the fresh water
system. Reality, other things will fail, causing an overhaul, before this
extra corrosion takes it toll. (assuming a 750 - 1000 hour service interval)
4. It's the antifreeze/coolant/rust inhibitor that is used in a closed system
that will actually reduce the corrosion. Water, fresh or salt, left in the
passages where air can get to it to react is what kills the internals. That's
one of the reasons antifreeze is used to winterize a boat, aside from the
desire to prevent cracking of the block due to expansion. You can simply drain
he water from the engine to prevent cracking but the exposed passages will be
terribly rusted come spring unless they are coated with a rust inhibitor.
All that being said. FWC is the way to go in situation where it's difficult to
flush the engine or it will sit for weeks or months without use. If you run
the boat every week and flush it after each use (assuming salt water use) you
will not see any more corrosion related failures than the identical FWC setup.
The extra "efficiency" will never pay for the cost of the FWC setup.
--
Mark Whatman
mwha...@worldnet.att.net
http://home.att.net/~mwhatman
JDavis1277
Closed cooling has many pluses as well as minuses. From following this thread
I believe most have been discussed. However, for salt water boaters closed
cooling (FWC) can be a blessing. Not only does sea water corrode engines, but
in small water (coolant) passage ways which become extremely hot, the salt may
plate to the passage way because of spot flash boiling (cavitation?) of the raw
sea water. Over a fairly short period, an engine can be rendered inoperable.
Pretty undesireable if operating off shore. Thanks, Butch Davis-
Terry Schell
"James Basara" <BAS...@prodigy.net> writes:
<snip>
>As far as marine engines go, I think open cooling systems that use raw
>seawater are more efficient therefore the engines can operate at lower
>set-point temperatures, thus increasing the service life of an engine. On
>the other hand, corrosion and cooling passage obstruction can be a big
>problem in the salt water environment, hence the closed cooling system and
>higher operating temperatures. If I were considering a closed cooling
>system. I would determine the specified operating temperature of the engine
>first. If it's designed to run at 140-160 than you might be wise to leave it
>alone because you may not get that level of efficiency out of a heat
>exchanger. Check the thermostat rating.
<snip>
I disagree with your central claim that the efficiency advantage is
due to internal engine clearances. Any basic book on the
thermodynamics of internal compustion engines will cover this topic.
As far as efficiency goes, there are undenyable advantages to
maintaining the highest possible internal temp while still controling
the time when ignition occurs.
You will not increase service life of an engine by running it at a
lower temp so long as your lubricants are designed for the original
operating temp. What parts do you think will gain an increased
"service life" with a lower temp?
Sincerely,
Terry
Fritz;Ree
I agree with Terry. The worst thing for an engine is to run below its rated
temp. 160 to 190 is best for most engines. I would take fresh cooling over
salt every time!
regards; Fritz
Terry Schell wrote in message <6d9fpe$oso$1...@vixen.cso.uiuc.edu>...
PCR
Our boat is kept at a marina about six miles up a freshwater river. We
take it down the river and into a brackish lake (about 28 miles) and
then into the Gulf of Mexico. It does not have a closed system. Is
there enough natural "flushing" with thirty or so minutes of freshwater
operation to undo the harmful effects of the saltwater?
Thanks.
edgar cove
In article <34F339...@lucent.com>, Garry Heon <he...@lucent.com>
writes
>edgar cove wrote:
><snipped>
>. Moreover cylinder wear on a high
>> rated engine would be very high if you ran it at a low temperature.
>
>Chief, Zul, Innovation......and ask them why they run the engines
>cold. My water temp is always cold, according to the gauge, and
>you can hold your hand under the dumps. It's nice Jacuzzi temp. The
>oil runs at what most would consider normal though.
>
>http://home.att.net/~firststepp
Never heard of any of these makers. Are they gasoline or diesel? I
would think they must be pretty low rated motors designed for SWC and
therefore intended to run as cold as that. By low rating I mean low
bmep not necessarily low power output.
--
edgar cove
hidda
Bruce Ardern wrote:
>
> James Basara <BAS...@prodigy.net> wrote in article
> <6d8a18$57bq$1...@newssvr03-int.news.prodigy.com>...
> > Let me take a stab at this;
> >
> > The fact that an engine runs more efficiently at a higher temperature is
> > because it was designed to operate at that specific temperature as a
> > minimum. etc.
>
> an ex automotive diesel (Nissan LD28 or similar) in a trailer borne boat
> where unlimited fresh water can be introduced to the sea water intake after
> each use of the boat in the sea? Mostly this boat would be in the sea for
> two days at a time or less. I am thinking particularly of comments people
> have made relating to small passages within the engine and their tendency
> to become blocked with salt crystals at high opeating temeratures, and of
> the corrosion question when raw sea water cooling is used.
>
> regards, Bruce Ardern
> Katikati, Bay of Plenty, New Zealand
It's not the salt (sodium chloride) that's the problem. It's the other
stuff that precipitates at high temps and forms scale in the engine,
especially around the valves in the heads. This scale (non-soluble)
then insulates the metal and the next time it gets hot, steam forms
between the scale and the metal. The steam further insulates the metal
from the cooling salt water. This results in increased operating
tempratures of the exhaust valves. This then leads to valve failure and
you need to pull the heads and repair them. This doesn't happen if you
don't run your boat at full loads and at full throttle all the time.
However, if you do, then either modifications to the raw water cooling
system designed to eliminate this problem are called for or you can go
with FWC which eliminates the problem and has other benefits too.
The problem of using a modified raw water system is it's not designed to
operate at slow speeds. The engine will get too much cooling and you
end up creating other problems.
For the majority of us operating in salt water, FWC offers more
advantages than disadvantages. However, if you all wish to stick with
raw water cooling, then that's fine with me. I won't try to convince
you otherwise. On the other hand, I'm one of those people who have been
known to push their boats and engines to the limit and have had problems
with raw water cooling. It's not fun pulling the heads to get the
valves done every two or three years. And yes, we tried everything you
can think of to increase water flow, including boring out the cooling
passages, removing the thermostat, etc. We even went with the best
valves available. Spent a ton of money for nothing. The only thing
that helped was FWC.
Marcus G Bell
Garry Heon (he...@lucent.com) wrote:
> Hmmm, maybe you should talk to a few builders like Teague, Pfaff,
> Chief, Zul, Innovation......and ask them why they run the engines
> cold. My water temp is always cold, according to the gauge, and
> you can hold your hand under the dumps. It's nice Jacuzzi temp. The
> oil runs at what most would consider normal though.
OK, that's a key element there, the oil being normal temp. The oil
comes into direct contact with the internal parts of the engine, the
water does not. For the water to remove heat, the heat must conduct
through the water jacket walls and then be absorbed by the water. The
rate of heat conduction through the jacket wall is related to the
difference in temp between the water and the engine internals and to
the thermal diffusivity of the jacket material (cast iron has a low
coefficient, aluminum is much higher). As such, the water temp doesn't
really tell you the internal engine temp.
If heat is being generated very rapidly inside the engine, the water
must be cooler to remove the heat. A hi-po engine would thus require a
lower water temp than a "normal" engine based on the same engine
block. Garry, I think your situation is not especially applicable to
that of most pleasure boaters in this regard.
--
--
Marcus. ( be...@mail.med.upenn.edu )
James Basara
>I disagree with your central claim that the efficiency advantage is
>due to internal engine clearances. Any basic book on the
>thermodynamics of internal compustion engines will cover this topic.
>As far as efficiency goes, there are undenyable advantages to
>maintaining the highest possible internal temp while still controling
>the time when ignition occurs.
Well then, you're disagreeing with an engine builder and an automotive test
engineer.
What about air/fuel charge temperature and density?
What about viscousity breakdown and service life of lubricants?
Trust me, if you could run an engine at 32 degrees Ferenheit (an example),
it would be preferable.
Terry Schell
"James Basara" <BAS...@prodigy.net> writes:
>>I disagree with your central claim that the efficiency advantage is
>>due to internal engine clearances. Any basic book on the
>>thermodynamics of internal compustion engines will cover this topic.
>>As far as efficiency goes, there are undenyable advantages to
>>maintaining the highest possible internal temp while still controling
>>the time when ignition occurs.
>Well then, you're disagreeing with an engine builder and an automotive test
>engineer.
I suggest you pick up *any* text covering the thermodynamics of a
carnot-cycle internal combustion engine. I have my copy of Taylor open
right now... looking at a couple of formulae showing how many HP are
lost through the cooling system as a function of coolant temp. and gas
temp at the top of the compression stroke.
>What about air/fuel charge temperature and density?
That is why I mentioned the bit about "while still controlling the
time when ignition occurs."
>What about viscousity breakdown and service life of lubricants?
You *might* need to change the oil a bit more often if you run the
engine 20 degrees hotter... but not much. Modern engine oils don't
break down until they are a couple hundred degrees hotter than the
water jacket. If you were actually concerned with this problem, you
wouldn't lower the water jacket temp you would add an oil cooler. The
water jacket temp has very little effect on oil temp.
>Trust me, if you could run an engine at 32 degrees Ferenheit (an example),
>it would be preferable.
I don't trust you. I trust a pile of engineering texts. Can you point to
a single reference that supports your 32 degrees claim for efficiency? for
longevity? I can point to a number of textbooks and engine manufacturer's
service bulletins that disagree with you (everything from GM to Cummins
to Lycoming). Why don't we just remove the thermostat if the engine
would be more efficient and have less wear at lower temps? (Don't
forget, thermostats are there to *raise* not lower water jacket temps)
Why have all automotive manufacturers gone to 190 degree thermostats
(three decades ago 160 was a relatively normal thermostat)?
Any heat removed from the combustion chamber before or during the
expansion stroke must reduce efficiency. You cannot cheat carnot.
Terry
Steve Danaher
I do not know where the supposed experts got their information that
cooler is better. I have been a mechanic and have studied engine
design for 20 years. Almost all automotive engine oils are designed
to operate at at least 176 degrees F. One of the things that happen
when engines run cold is that there is a problem with sludge
formation.
Also, most engine metals are at their strongest at about 400 degrees
Farenheit.
Regarding engine clearances, a machinist can dial in any clearance he
wants to most engine parts. The supposed increase in engine
efficiency with tighter tolerances is extremely theoretical. If there
was an increase in efficiency, it would be fantastically minor. I
realize that if the engine was cooler, then the incoming fuel and air
could also be cooler and therefore denser. However, any gain would
most likely be more than offset with poorer combustion due to energy
needed to get the combustion burn process going.
If you had spent considerable time taking apart both 140 degree
engines and 180 degree engines, you would not be impressed with what
running cooler does.
A freshwater cooled engine can have any thermostat installed. For
the inside of the engine, 180 degrees has been the standard for quite
some time. I am sure considerable amounts of time and money have been
spent analyzing the effect of various running temperatures. This
would be historically and for the modern goals of fuel efficiency and
emissions control. Newer automotive engines have usually had 195
degree thermostats to help meet those modern goals. However, there is
somewhat more trouble with head gaskets and other heat related issues
at this temperature.
---Steve D. in CA
Pat Ford
>I do not know where the supposed experts got their information
<snips>
I hereby nominate this thread for the stupidest to come down the pike
in many a moon. Seconds?
Question:
Is it better for a marine engine to be raw water cooled or fresh water
cooled?
Answer:
Fresh water. Some large engines can perhaps tolerate raw water
cooling well, but certainly pleasure boats engines are preferably
fresh water cooled.
Case Closed!
Go on about your business. Thank you.
Marcus G Bell
Pat Ford (pf...@halcyon.com) wrote:
> I hereby nominate this thread for the stupidest to come down the pike
> in many a moon. Seconds?
I'll have a second beer, if that's what you mean :-)
I take it you're not real big on understanding the theory behind any
of this, you just want the bottom line?
> Question: Is it better for a marine engine to be raw water cooled or
> fresh water cooled? Answer: Fresh water.
So if there's disagreement, is it not useful to divine the source and
reach a better understanding?
Myles J. Swift
Terry Schell wrote:
>
> "James Basara" <BAS...@prodigy.net> writes:
> <snip>
> >As far as marine engines go, I think open cooling systems that use raw
> >seawater are more efficient therefore the engines can operate at lower
> >set-point temperatures, thus increasing the service life of an engine.
>
> I disagree with your central claim that the efficiency advantage is
> due to internal engine clearances. Any basic book on the
> thermodynamics of internal compustion engines will cover this topic.
> As far as efficiency goes, there are undenyable advantages to
> maintaining the highest possible internal temp while still controling
> the time when ignition occurs.
>
> Sincerely,
> Terry
I used to test automotive engines for fuel efficiency (one less pit stop
can win a race) On an Alfa-Romeo mileage would go from about 30mpg at
160 degrees to near 40mpg at 205 degrees. Saab has built some
experimental models running ceramic blocks running at over 300 degress
with the whole engine heavily insulated. They were getting in the mid
40mpg but they have not yet been able to control the more complex
emmissions generated at those temperatures.
***********************************************************************
Myles J. Swift - Computer Assistance Inc. - Microcomputer specialists
since 1977. Makers of GarageKeeper and Motive Power software for
automotive and other mechanical repair and service businesses.
sami...@bix.com
On 1 Mar 1998 04:16:09 GMT Marcus G Bell of University of Pennsylvania
wrote this re Re: Should I go to freshwater cooling?:
>As such, the water temp doesn't
>really tell you the internal engine temp.
constraint on minimum temperature worth mentioning. If the peak sustained
oil temperature does not rise above the vaporization temperature of water
condensate in the oil, you will have a problem.
Scott A. Miller
sami...@bix.com sami...@cyberenet.net
Have a new Java product? Annouce it @ www.javalobby.org/javawire
Incoming fire has the right of way
sami...@bix.com
On Sat, 28 Feb 1998 13:31:00 -1000 hidda of Stop the Spamming! wrote this
re Re: Should I go to freshwater cooling?:
>stuff that precipitates at high temps and forms scale in the engine,
>especially around the valves in the heads. This scale (non-soluble)
>then insulates the metal and the next time it gets hot, steam forms
>between the scale and the metal. The steam further insulates the metal
>from the cooling salt water.
your engine, you may wish to have your cylinder head magnafluxed ;>)
edgar cove
In article <34fa3fe0...@news.2xtreme.net>, Steve Danaher
<sdanahe...@2xtreme.net> writes
>I do not know where the supposed experts got their information that
>cooler is better. I have been a mechanic and have studied engine
>design for 20 years. Almost all automotive engine oils are designed
>to operate at at least 176 degrees F. One of the things that happen
>when engines run cold is that there is a problem with sludge
>formation.
major diesel manufacturers mainly on the tchnical side (yes, and on
cooling system design!). The original post on this subject was from
someone who obviously had an SWC engine and wondered whether it would be
worth going to FWC. The answer is 'no' to that since his engine was
obviously a low-tech one designed for SWC.
><snipped a bit>
>I realize that if the engine was cooler, then the incoming fuel and air
>could also be cooler and therefore denser. However, any gain would
>most likely be more than offset with poorer combustion due to energy
>needed to get the combustion burn process going.
>Dont agree with this. The jacket temperature will have little or no
effect on inlet air temperature. Combustion burn at lower air temps is
no problem-look at the efficiency of intercooled turbocharged engines.
>If you had spent considerable time taking apart both 140 degree
>engines and 180 degree engines, you would not be impressed with what
>running cooler does.
>
> A freshwater cooled engine can have any thermostat installed. For
>the inside of the engine, 180 degrees has been the standard for quite
>some time. I am sure considerable amounts of time and money have been
>spent analyzing the effect of various running temperatures. This
>would be historically and for the modern goals of fuel efficiency and
>emissions control. Newer automotive engines have usually had 195
>degree thermostats to help meet those modern goals. However, there is
>somewhat more trouble with head gaskets and other heat related issues
>at this temperature.
He is right. To the people who came on line to say they were bored with
this-go read something else. Those who were interested in the subject
and asked for information are getting expert opinion for free, which is
what ng's are about IMO.
--
edgar-(remove nospam from return address for e-mail)
atperretta
Marcus G Bell
> On Sat, 28 Feb 1998 13:31:00 -1000 hidda of Stop the Spamming! wrote this
> >It's not the salt (sodium chloride) that's the problem. It's the other
> >stuff that precipitates at high temps and forms scale in the engine,
> >especially around the valves in the heads.
sami...@BIX.com wrote:
> If this implies that the coolant is in direct contact with the valves in
> your engine, you may wish to have your cylinder head magnafluxed ;>)
Heh heh. Good point :-)
Probably he means the part of the water jacket most adjacent the
valves, esp. the exhaust. "Around" as in "near", not literally
"attached directly to the perimeter."
Magnafuxed & Zyglowed.
Anders Svensson
Myles J. Swift wrote:
> I used to test automotive engines for fuel efficiency (one less pit stop
> can win a race) On an Alfa-Romeo mileage would go from about 30mpg at
> 160 degrees to near 40mpg at 205 degrees. Saab has built some
> experimental models running ceramic blocks running at over 300 degress
> with the whole engine heavily insulated. They were getting in the mid
> 40mpg but they have not yet been able to control the more complex
> emmissions generated at those temperatures.
>
> ***********************************************************************
> Myles J. Swift - Computer Assistance Inc. - Microcomputer specialists
> since 1977. Makers of GarageKeeper and Motive Power software for
> automotive and other mechanical repair and service businesses.
The internal combustion engine IS more effecient at higher temperatures.
The relatively low temp that todays engines run under is dictated by the
technology we use. Exhaust valves and piston tops are usually the weak
points.
Reasons for using SWC on a powerful boat engine could simply be saving
30 HP (on a 425 hp gasoline engine) by excluding a power consuming
pump/intercooler unit. Running a Chevy (or similar) big block automotive
engine for maybe 100 hours on SWC is not a problem. It would then be
beneficial to keep temperature down ON THE COOLING WATER, not on the
engine itself - but that is fairly easy to achieve.
A engine like a 427 Chevy is not designed to have 'optimum tolerances'
at working temperature. It is IMO a fairly crude (but good, strong and
long lasting) engine with a conservative power output in relation to
cylinder volume. I see no problem running that engine on sea water,
aside for longevity.
However, put a truly advanced engine, (sorry, all Chevy fans) same HP,
less than half the displacement and no turbo...) with aluminium heads
and block, computer designed cooling water flow pattern and hot spot
control, moving parts designed to heat swell into tolerances - even go
from oval to round (not unusual at all for pistons) - then a precisely
controlled thermal environment would not only be beneficial but
necessary.
The high output outboards is proving that seawater cooling works very
good, given that it is a design parameter from the beginning.
Anders
Terry Schell
"atperretta" <atper...@worldnet.att.net> writes:
<snip>
>Terry wrote: ....I disagree...there are undenyable advantages to =
>maintaining the highest...internal temp...
>[end of earlier messages in part]
HEY! you chopped up my quote so it says something very different than
I originally wrote! The advantages are in efficiency; there may
be disadvantages to higher water jacket temps... but they aren't related
to efficiency (unless you lose control of ignition or combusion).
BTW... this doesn't mean you should go out and get rid of your raw
water cooling.
Terry
James Basara
The temp diff equation in Carnot's theorem is in reference to the gas temp
before ignition and at peak heat. It has nothing to do with the temperature
of the engine. If fuel economy improves with increase in engine temperature
than go ahead and block air flow to your radiators. See what kind of mileage
you get. The only factor involving engine temp would be fuel atomization and
instantaneous mixture charge cooling. Both those factors are easily taken
care of by normal cylinder heat after a few combustion cycles.
The earlier post claiming a nearly 10 mpg fuel economy increase for a 20
degree engine temp increase is totally ridiculous. If that were the case
than we would all be swapping thermostats tomorrow. Boy, some of you people
will swallow any old bilge water. Thermostats were originally placed in
engines to provide warmer air for cabin occupants, not engine efficiency.
There is no magical law of thermodynamics that states an engine runs better
at higher operating temperatures! I challenge anyone to find one. Carnot's
laws have nothing to do with operating temperatures.
atperretta wrote in message <6df6ad$l...@bgtnsc03.worldnet.att.net>...
I know nothing about this subject, but that's never stopped me before.
Isn't the efficiency of a theoretical Carnot cycle a function only of
temperature differentials [according to something like E = (T2 - T0)/(T1 -
T0)?] After 35 or so years I don't recall precise definitions nor exact
formulae, but I recall the principle. It explains Terry's referenced fuel
consumption figures and a few other things, such as manufacturers'
specifications and recommendations. Evidently running an engine at higher
temps is more efficient (in theory), but at around 5000 K it (and your boat)
will melt. An engine, like a boat and her captain, is a practical
compromise.
[earlier messages in part]
James Basara writes: ...I think open cooling systems that use..can
operate at lower...temperatures..[and be more efficient]...
Terry wrote: ....I disagree...there are undenyable advantages to
James Basara
Terry, You might want to reread your text books. Carnot's theorem of delta T
pertains to the temp of air/fuel mixture before ignition and the peak temp
of combustion gases. It has nothing to do with engine temp. In fact, in a
Carnot system, heat removal from the cylinder is crucial.
Go ahead a keep researching, you will not find a formula to explain your
claims.
Let me restate for clarification; If so designed, an internal combustion
engine will run more efficiently and have a longer service life at lower
operating temperatures. I stress the, if so designed, part. Just look at
drag racers, they run their engines cold! Nothing pisses a racer off more
than a hot engine, why?
Garry Heon
Steve Danaher wrote:
>
> I do not know where the supposed experts got their information that
> cooler is better. I have been a mechanic and have studied engine
> design for 20 years. Almost all automotive engine oils are designed
> to operate at at least 176 degrees F. One of the things that happen
> when engines run cold is that there is a problem with sludge
> formation.
You have the point exactly. I could care less how cool my water temp
is, I like it at 100 - 110 degrees F. However, my oil temp always runs
up to at least 200 degrees F. To me that's the "real" temp of the
engine.
>
> A freshwater cooled engine can have any thermostat installed. For
> the inside of the engine, 180 degrees has been the standard for quite
> some time. I am sure considerable amounts of time and money have been
> spent analyzing the effect of various running temperatures. This
> would be historically and for the modern goals of fuel efficiency and
> emissions control. Newer automotive engines have usually had 195
> degree thermostats to help meet those modern goals.
Correct but those goals are more than just pure performance. The
auto industry has to worry about emmisions, we don't, yet. On
a pure performance engines I've seen, they are run cold.
Garry Heon
http://home.att.net/~firststepp
Garry Heon
edgar cove wrote:
>
> In article <34F339...@lucent.com>, Garry Heon <he...@lucent.com>
> writes
> >edgar cove wrote:
> ><snipped>
> >. Moreover cylinder wear on a high
> >> rated engine would be very high if you ran it at a low temperature.
> >
> >Chief, Zul, Innovation......and ask them why they run the engines
> >cold. My water temp is always cold, according to the gauge, and
> >you can hold your hand under the dumps. It's nice Jacuzzi temp. The
> >oil runs at what most would consider normal though.
> >
> >http://home.att.net/~firststepp
> Never heard of any of these makers. Are they gasoline or diesel? I
> would think they must be pretty low rated motors designed for SWC and
> therefore intended to run as cold as that. By low rating I mean low
> bmep not necessarily low power output.
Check out www.chiefengines.com and you'll get an idea of the type
of builders I speak of. They build high performance gas engines
where the lowest price engine is $8576 300 hp 350 cubic inches and the
most expensive engine is a $60,000 1400 hp 705 cubic inches. These
guys are at the top of the game when it comes to performance engines.
The others don't have web sites.
Garry Heon
> --
> edgar cove
Fritz
Right on Garry, A cold running won't last long;
regards; Fritz
James Basara wrote in message
<6dcs9g$qpq$1...@newssvr07-int.news.prodigy.com>...
>
>>I disagree with your central claim that the efficiency advantage is
>>due to internal engine clearances. Any basic book on the
>>thermodynamics of internal compustion engines will cover this topic.
>>As far as efficiency goes, there are undenyable advantages to
>>maintaining the highest possible internal temp while still controling
>>the time when ignition occurs.
>
>Well then, you're disagreeing with an engine builder and an automotive test
>engineer.
>What about air/fuel charge temperature and density?
>What about viscousity breakdown and service life of lubricants?
>Trust me, if you could run an engine at 32 degrees Ferenheit (an example),
>it would be preferable.
>>
James W. Hebert
In article <34fa5856....@news.halcyon.com>, pf...@halcyon.com (Pat
Ford) wrote:
> Question:
> Is it better for a marine engine to be raw water cooled or fresh water
> cooled?
Kudos for using "raw water" cooled instead of "salt water" cooled.
But there are thousands of boats on the Great Lakes that are raw water
cooled with fresh water.
One ought to say "raw water cooled" and "closed loop cooled" or something
similar to distinquish between to the two approaches.
--jim
Jim Hebert, K8SS | C O N T I N U O U S
Beverly Hills, Michigan | W A V E
ji...@w8hd.org | http://tango.w8hd.org
JJames915
Actually there have been experiments with high temp engines that have shown
remarkable efficiencies in power produced for fuel consumed. The engines had
no cooling systems at all. When a cooling system removes heat it is removing
energy. Think about it, a normal engine pro-actively disperses heat, simply
creating a condition where the burning fuel then wants to heat it back up. If
you let the engine heat up to a higher temp then less of the energy released by
burning the fuel goes into heating the engine parts. You just have to design
the systems to operate at the higher temps. In practice they did have
difficulties with longevity, controlling ignition, and costs though. Certainly
won't see any of these in our boats.
Marcus G Bell
James Basara (BAS...@prodigy.net) wrote:
> Terry, You might want to reread your text books. Carnot's theorem of
> delta T pertains to the temp of air/fuel mixture before ignition and
> the peak temp of combustion gases. It has nothing to do with engine
> temp. In fact, in a Carnot system, heat removal from the cylinder is
> crucial.
Does it matter how the heat is removed?
How about we open the exhaust valve at 10 degrees ATDC and let all
that heat out. No good? How about we rapidly cool the burnt gasses in
the cylinder by conducting heat away through the cylinder walls, such
that by the time the piston reaches 10 deg. ATDC, the temp of the
gasses is the same as ambient. OK, you've removed a lot of heat. Is
your engine efficient?
I suggest that the Carnot system has strict requirements for how the
heat is removed. A good way to remove heat is to let the gasses expand
while the piston is driven downward in the power stroke. Heat removed
by any other means is waste (unless recovered by some other means).
> Let me restate for clarification; If so designed, an internal
> combustion engine will run more efficiently and have a longer
> service life at lower operating temperatures. I stress the, if so
> designed, part.
This sounds good. But there must be a reason why there'a been all this
experimentation into ceramic engine parts for higher temps. If running
cool is so great, why not just design engines with massive heat
exchangers to dump all that heat? Heating the cabin of my auto is not
a good enough reason to regulate engine temp to such high levels.
There must be something else....
> Just look at drag racers, they run their engines cold! Nothing
> pisses a racer off more than a hot engine, why?
I wouldn't look to drag racers to be models of efficiency. They might
extract huge amounts of power from their engines, but they burn a lot
of fuel in the process.
Just to be sure, we're defining efficiency as ratio of power out vs.
rate of fuel burn, right? You don't mean HP/displacement, do you?
Marcus G Bell
James Basara (BAS...@prodigy.net) wrote:
> Terry, You might want to reread your text books. Carnot's theorem of delta T
> pertains to the temp of air/fuel mixture before ignition and the peak temp
> of combustion gases.
Folks, this topic is fascinating. I do believe however that it may
have drifted far enough away from the topic of fresh vs. raw water
cooling to warant starting a new thread. Please see the new "Engine
Efficiency" thread.
Marcus G Bell
Garry Heon (he...@lucent.com) wrote:
> You have the point exactly. I could care less how cool my water
> temp is, I like it at 100 - 110 degrees F. However, my oil temp
> always runs up to at least 200 degrees F. To me that's the "real"
> temp of the engine.
Right.
> The auto industry has to worry about emmisions, we don't, yet. On a
> pure performance engines I've seen, they are run cold.
The auto industry does have to worry about efficiency, though. Do
hi-po engine builders have the same concerns in that area? Also, when
you say the performance engine runs cold, are you refering to water or
oil temp? That seems to be an important distinction. My feeling is
that the hi-po engines are built around blocks that were not designed
with a view towards the continuous high power output they are
subjected to after modification for hi performance. This means running
the water cooler to keep the guts at a reasonable temp so it doesn't
have a meltdown.
Terry Schell
"James Basara" <BAS...@prodigy.net> writes:
>The temp diff equation in Carnot's theorem is in reference to the gas temp
>before ignition and at peak heat. It has nothing to do with the temperature
>of the engine.
Where the heck do you think the heat in the water jacket comes from?
It is extracted from the *gas* inside the cyl... almost all of it is
removed from the cyl between the top of the compression stroke and the
end of the expansion stroke. Unless a physical law governing the
relationship between gas temp and pressure has been repealled, cyl
pressure will be reduced. This will necessarily decrease torque and
therefore, less HP will be available.
>If fuel economy improves with increase in engine temperature
>than go ahead and block air flow to your radiators. See what kind of mileage
>you get.
I have clearly stated a caveat that the efficiency of the engine will
only increase with increasing temps if you can maintain control of
combustion. If you want to see the effect of decreasing temps, pull
your thermo out and drive without it.
<snip>
>The earlier post claiming a nearly 10 mpg fuel economy increase for a 20
>degree engine temp increase is totally ridiculous. If that were the case
>than we would all be swapping thermostats tomorrow.
Well, in a sense we all *have* swapped thermostats. Newer cars have
thermos that are 15-25 degrees hotter than in the 60's. There are
good reasons not to go even hotter, but they have more to do with the
properties of the coolant, not the engine efficiency directly.
>Boy, some of you people
>will swallow any old bilge water. Thermostats were originally placed in
>engines to provide warmer air for cabin occupants, not engine efficiency.
Provide a reference. I can show you countless engines that have
thermostats even though they are not used for cabin heat. Look at any
of the high-efficiency industrial engines.
>There is no magical law of thermodynamics that states an engine runs better
>at higher operating temperatures! I challenge anyone to find one. Carnot's
>laws have nothing to do with operating temperatures.
I accept your challenge! It isn't too hard because there are 20+ books
at your local university library that cover this topic. You
might start with one of the most common textbooks on the subject "The
Internal-Combustion Engine in Theory and Practice: Thermodynamics,
Fluid Flow, Performance Vol 1" by C.F. Taylor. ISBN: 0262700263.
When you are done with that, you can move on to volume II. "The
Internal-Combustion Engine in Theory and Practice: Combustion, Fuels,
Materials, Design Vol 2" These are both current and in print so it
shouldn't be hard to find them.
Perhaps I failed your challenge because it isn't a "magic" law... just
your garden variety law of thermodynamics.
Sincerely,
Terry "gearhead/geek" Schell
Terry Schell
>engine will run more efficiently and have a longer service life at lower
>drag racers, they run their engines cold! Nothing pisses a racer off more
>than a hot engine, why?
Top fuel drag racers have *no* cooling system. None. Nada. Zip. No
radiator, no cooling fins. They are designed to run for a set
time to warm up, then to go! If they don't go right away, the engine
overheats (head temps in excess of 800 degrees F) and they get severe
pre-ignition and have to shut it down. Everyone gets pissed when
their engine overheats... but that doesn't mean that your are best off
with your engine as cool as possible.
Sincerely,
Terry
Ed
On Mon, 2 Mar 1998 18:34:36 -0500, "James Basara"
<BAS...@prodigy.net> wrote:
Snip:
>operating temperatures. I stress the, if so designed, part. Just look at
>drag racers, they run their engines cold! Nothing pisses a racer off more
>than a hot engine, why?
>
>
I would have stayed completely out of this one except for that last
statement. In drag racing, it is considered common knowledge that a
hotter engine runs better up to the point of detonation and/or parts
failure.
The hottest (no pun intended) cooling system for a dedicated racing
engine includes a VW Scirrocco (excuse the spelling) radiator. And
this is after the lower part of the water jacket has been filled with
the automotive equivelant of cement to add stiffness to the block.
In racing, the goal is to control the heat, not stop it. You want to
keep it in the combustion chambers and we even wrap the headers in
insulation to keep the heat in, but you don't want it in the crank
case. The car needs to come up to operating temperature as fast as
possible but not overheat and start detonating or breaking down the
oil before you get to the end of the track. A really well setup
system will let you drive (instead of towing) back to the pits without
overheating, but barely. Then the electric water pump goes on, a
large fan is usually pointed at the radiator and someone starts
squirting down the radiator with water to cool the motor enough for
another round round.
Move up to Top Fuel and you lose the radiator alltogether.
What you may be thinking of is the fuel charge. There is an effort to
try to keep the fuel mixture cool as you can to be able to cram more
of it into engine (higher density). Hood scoops pull cool air in from
outside of the engine compartment. There are even dry ice coolers
that you can run your fuel lines through for this purpose.
I do agree with the idea that how the engine is built has a lot to do
with what temperature it will operate at. Try the above without the
parts and preparation that goes into a racing engine, and it wouldn't
last a single round (or a single hour in a boat)
-Ed
Terry Schell
Garry Heon <he...@lucent.com> writes:
<snip>
>Check out www.chiefengines.com and you'll get an idea of the type
>of builders I speak of. They build high performance gas engines
>where the lowest price engine is $8576 300 hp 350 cubic inches and the
>most expensive engine is a $60,000 1400 hp 705 cubic inches. These
>guys are at the top of the game when it comes to performance engines.
>The others don't have web sites.
These engine run cool because they are trying to get max HP per in^3.
When you try to do this, you run into severe problems with detonation
and preignition if you don't keep the combustion chamber cool. This
is why I have repeatedly stated that you are more efficient running
hotter so long as you can maintain control of combusion.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Please read the Taylor books I have referenced earlier in this thread;
they will explain in painful detail what factors influence ideal operation
temps.
atperretta
Sorry if I misrepresented your original statement. I thought the formula I
gave actually supported your original statement. Remember, I stated at the
outset that I know nothing about the subject, and it seems I've proved that.
Theory aside and from practical experience alone, the reason my original
Volvo was replaced (with a larger, fresh water cooled Volvo) was due to
corrosion related to a freshwater cooling system. The response from Sweden
was something like:
"Well, the engine was designed for our waters. They are cold enough so that
salt precipitation and consequent corrosion are not serious problems.
That's why we use fresh water cooling."
As you can see, the response from Sweden was meaningless and not helpful. I
sail the boat offshore and in tropical waters and after about 4000 hours the
original engine went. I will not use fresh water cooling in the future.
Again, my apology.
[Terry Schell wrote: ... HEY! you chopped up my quote so it says something
very different than I originally wrote!]
James Basara
What is the vaporization temperature of water and is it necessary for drying
my laundry?
sami...@BIX.com wrote in message <6df28h$8...@lotho.delphi.com>...
>On 1 Mar 1998 04:16:09 GMT Marcus G Bell of University of Pennsylvania
>wrote this re Re: Should I go to freshwater cooling?:
>>As such, the water temp doesn't
>>really tell you the internal engine temp.
>Finally, someone mentions the "other" fluid temperature. There is another
>constraint on minimum temperature worth mentioning. If the peak sustained
>oil temperature does not rise above the vaporization temperature of water
>condensate in the oil, you will have a problem.
JDavis1277
Most people who choose FWC are not concerned with efficiency; they are
concerned with engine life. Try to find a diesel powered boat without FWC.
The reason you can't is because of the high cost to replace a diesel engine.
FWC preserves engines. It is particularly helpful in a sea water environment.
Don't buy it to get better fuel economy. You would have to put a lot of hours
on an engine to save enough fuel to justify the higher cost of FWC. Having
said that, I retrofitted FWC on my 260 Mercruiser and my fuel usage decreased.
I operate in a sea water environment, so I benefit two ways.
Thanks, Butch Davis-
Mike Burke
point of this thread. Fresh water cooling
keeps the internals of the engine clean
avoiding posible blockage of waterjackets or
hot spots in the engine. that is the single
purpose. An engine doesn;t run effeciently
untill its brought up to some temperature
(design). on FW engines this can be
controlled by a thermostat (usually 160-190
degrees) I've never seen a raw water setup
but it should also have a thermostat to allow
the engine to build up to some temp. As far
as performance goes the race engines that I
build use fresh water in the radiator so that
the engine can be cooled between runs by
hooking it to a garden hose. However the
reason isn't that the engine is too hot its
because I want the air to the engine as cool
as possible. My intake sucks air through ice
and my fuel line runs through ice as well.
This allows a denser air/fuel charge (nitrous
does the same thing but adds some O2 to the
mix.)giving more power. Without a thermostat
or at least a flow restrictor the Raw water
would pass throught he engine so quickly it
wouldn't transfer enough heat from the engine
and you would coke the oil seizing the
engine.
--
################
Mike Burke
MSP Support
Ajilon/TI
Marcus G Bell
atperretta (atper...@worldnet.att.net) wrote:
> Theory aside and from practical experience alone, the reason my
> original Volvo was replaced (with a larger, fresh water cooled
> Volvo) was due to corrosion related to a freshwater cooling system.
> The response from Sweden was something like:
> "Well, the engine was designed for our waters. They are cold enough
> so that salt precipitation and consequent corrosion are not serious
> problems. That's why we use fresh water cooling."
> [snip] I will not use fresh water cooling in the future.
Uh, do you mean to say "raw water cooling"? Do you mean "fresh" in the
sense of "non-recirculated"? We've been using "fresh" in the sense of
"not salty", "not raw water", or more precisely, "recirculated".
Recirculated cooling ("fresh water cooling" in this thread) is
supposed to fight corrosion.
I agree with others who have said that the nomenclature leaves a tad
to be desired. Maybe we should try to shift away from using "fresh"
and instead stick to "recirculated" and "raw", as they are more
precise and less ambiguous.
Marcus G Bell
Mike Burke (mbu...@msp.sc.ti.com) wrote:
> I'm sorry but I really don't understand the point of this thread.
> Fresh water cooling keeps the internals of the engine clean avoiding
> posible blockage of waterjackets or hot spots in the engine. that
> is the single purpose.
Sounds good. That's where the thread originated. Then it took a left
turn towards discussing thermodynamics and efficiency.
> An engine doesn;t run effeciently untill its brought up to some
> temperature (design). on FW engines this can be controlled by a
> thermostat (usually 160-190 degrees) I've never seen a raw water
> setup but it should also have a thermostat to allow the engine to
> build up to some temp.
And that temp would be high enough to precipitate minerals in the raw
water, as others in the thread have indicated. Thus, the raw water
cooled engine is run cooler.
> As far as performance goes the race engines that I build use fresh
> water in the radiator so that the engine can be cooled between runs
> by hooking it to a garden hose. However the reason isn't that the
> engine is too hot its because I want the air to the engine as cool
> as possible. My intake sucks air through ice and my fuel line runs
> through ice as well. This allows a denser air/fuel charge (nitrous
> does the same thing but adds some O2 to the mix.)giving more power.
Sounds good.
> Without a thermostat or at least a flow restrictor the Raw water
> would pass throught he engine so quickly it wouldn't transfer enough
> heat from the engine and you would coke the oil seizing the engine.
Can you explain what coolant flow rate has to do with rate of heat
removal, in the sense you've indicated that faster flowing coolant
leads to slower heat removal? It seems counter-intuitive.
Dave Brown
Marcus G Bell wrote:
> I agree with others who have said that the nomenclature leaves a tad
> to be desired. Maybe we should try to shift away from using "fresh"
> and instead stick to "recirculated" and "raw", as they are more
> precise and less ambiguous.
I'd go one further and vote for 'closed' and 'open' cooling.
Regards,
Dave Brown
Brown's Marina
atperretta
Thanks for the, uh, clarification. Uh, I mean a system that pumps saltwater
through the whole block,not just the heat exchanger. Uh, guess "raw water
cooling" is current usage. Uh, thanks again. Uh, good luck.
s/v Kerry Deare of Barnegat
Marcus G Bell wrote: ...Uh, do you mean to say "raw water cooling"?... >
Marcus G Bell
atperretta (atper...@worldnet.att.net) wrote:
> Thanks for the, uh, clarification. Uh, I mean a system that pumps
> saltwater through the whole block,not just the heat exchanger. Uh,
> guess "raw water cooling" is current usage. Uh, thanks again. Uh,
> good luck.
Uh, I guess you noticed my slight hesitation in searching for, uh,
clarification, as I was uh, a bit confused but still needed to
entertain the notion that I was uh, simply wrong and you were uh,
actually meaning what you said and were using the exact same uh,
terminology everybody else was using. I guess it's all uh, clear
now. Thanxabunch. Mmmbuhbye now. Catchyalater.
sami...@bix.com
On Mon, 02 Mar 1998 23:28:49 -0500 James W. Hebert of CW Communications
wrote this re Re: Should I go to freshwater cooling?:
>similar to distinquish between to the two approaches.
Scott A. Miller
sami...@bix.com sami...@cyberenet.net[new]
sami...@bellatlantic.net[going away]
George Jefferson
:Well then, you're disagreeing with an engine builder and an automotive test
:engineer.
:Trust me, if you could run an engine at 32 degrees Ferenheit (an example),
:it would be preferable.
recomend you discuss this with your engineer friend before putting
words in his mouth.
--
george jefferson : geo...@sol1.lrsm.upenn.edu
to reply simply press "r"
-- I hate editing addresses more than I hate the spam!
Marcus G Bell
> On Mon, 02 Mar 1998 23:28:49 -0500 James W. Hebert of CW Communications
> wrote this re Re: Should I go to freshwater cooling?:
> >One ought to say "raw water cooled" and "closed loop cooled" or something
> >similar to distinquish between to the two approaches.
sami...@BIX.com wrote:
> How about just "open loop" and "closed loop" ;?)
"Open loop" and "closed loop" have other meanings in control systems.
Thermoregulation is such a system. An open loop system would run the
same amount of coolant regardless of the temperature. Clearly this is
not the case with raw-water-cooled engines with thermostats. A
thermostat senses the temperature and provides feedback to control the
coolant flow. Thus, a raw-water-cooled engine with a thermostat is a
closed-loop system. Clear as mud?
"Raw-water" and "recirculated" are probably the least ambiguous in my
opinion.
hidda
Marcus G Bell wrote:
>
> atperretta (atper...@worldnet.att.net) wrote:
>
> > Theory aside and from practical experience alone, the reason my
> > original Volvo was replaced (with a larger, fresh water cooled
> > Volvo) was due to corrosion related to a freshwater cooling system.
> > The response from Sweden was something like:
>
> > "Well, the engine was designed for our waters. They are cold enough
> > so that salt precipitation and consequent corrosion are not serious
> > problems. That's why we use fresh water cooling."
>
> > [snip] I will not use fresh water cooling in the future.
>
> Uh, do you mean to say "raw water cooling"? Do you mean "fresh" in the
> sense of "non-recirculated"? We've been using "fresh" in the sense of
> "not salty", "not raw water", or more precisely, "recirculated".
>
> Recirculated cooling ("fresh water cooling" in this thread) is
> supposed to fight corrosion.
>
> to be desired. Maybe we should try to shift away from using "fresh"
> and instead stick to "recirculated" and "raw", as they are more
> precise and less ambiguous.
>
Then you'd have the problem of:
RWC = Recirculated Water Cooling
RWC = Raw Water Cooling
Phil Washburn
Boats with keel coolers do not need a second pump provided they are running a dry
exhaust
system with the stack running straight up from the engine like tugs do. If you are
running a wet
exhaust system like the majority of pleasure boats, you need the second pump to
pump raw water
into the exhaust system to cool it. Otherwise the exhaust system will burn up,
taking the boat
with it.
Charlie Mayne wrote:
> edgar cove <ed...@nospam.demon.co.uk> writes:
>
> >In article <34EDEB...@mauigateway.com>, hidda
> ><hi...@mauigateway.com> writes
> >>edgar cove wrote:
> >><Snipped>
> >> Remember
> >>> that unless you go for a keel cooler freshwater cooling involves the
> >>> complication of an extra water pump.
> >><Snipped>
> >>
> >>Not true. My FWC Volvo has two water pumps like everybody else. One is
> >>the circulating pump that's integral with the engine, just like
> >>everybody else (except somebody like Mr. Heon) and a raw water pump with
> >>a rubber impeller, just like everybody else. The difference is a heat
> >>exchanger, a few more hoses, and a different water distribution manifold
> >>on the engine. I'd guess the system adds about 40 lbs, probably less.
>
> >Despite disagreeing with me you go on to confirm what I said! OK, so
> >your FWC Volvo has -two-water pumps. If it was SWC it would only need
> >one.
>
> My SWC installation has two pumps, just as (I think) "hidda" writes. I
> think this is pretty much standard: two pumps for FWC or SWC.
>
> Cheers,
>
> Charlie
> CS30 "Sprite"
>
> --
> Charlie Mayne | Motorola Incorporated
> char...@pets.sps.mot.com | Microprocessor Products Group
> | Austin, Texas 78735-8598
> "I am concerned about my memory. But, for the life of me, I can't recall why."
Martin
I have a Volvo MD2B with raw water cooling. The thing I have noticed is that in these
hot tropical Dutch waters, it never runs at a constant temperature.
The engine temperature slowly rises until the thermostat opens and lets in a flood of
cold water, at which point the exhaust emits a cloud of steam and the engine
temperature plummets. When I first had the boat 20 odd years ago, I replaced the
thermostat. This had absolutely no effect. I then checked both the old and new
thermostats to make sure they opened and closed at the specified temperature. They both
did and also the impeller pump works perfectly and has been properly maintained. As
everything else seemed normal. I have ignored this phenomena. The engine can obviously
take these temperature fluctuations, which are worst in spring when the raw water must
be be about 6-8 DegC. BUT the engine must run better with a heat exchanger and at the
correct constant temperature?
With the engine now 25 years old maybe it is safe to leave things as they are? It's
certainly cheaper!
James Basara
What you need is a flow restrictor in your coolant flow path. (PID tuning of
the coolant system response.)
James Basara
Anders Svensson
A fancy word for the effect you see is hysteresis. That means that the
thermostate have one temperature when it starts to open going from cold
to hot, and one other (most certainly higher) when it closes going from
hot to cold.
Note, that the temperature difference can be high on closed cirquit
cooled setups too, for example could a antifreeze treated cooling system
on a car have a -30C water/glycol mix in the radiator and +90C in the
block, without getting these effects.
It is also a fact that the water in the heat exchanger would be close to
the seawater temperature. Because it is a heat exchanger, it will not be
exactly the same, but it will come down fairly close.
So your little problem may have some other explanation.
My shot is that the thermostat is especially hysteresic (not hysteric)
i.e. prone to stay open for a long time instead of opening and closing
smoothly and gradually. You may want to consult a Volvo specialist in
Holland and ask him if there is a 'smoother' thermostath available.
Anders
James Basara
For the last time and only to clarify my position as to the original
question of why engine thermostat temperatures are set at 195 degrees.
Increased engine efficiency (which may or may not even exist) at higher
temperatures is NOT the reason modern gasoline engines operate at 205
degrees (the actual thermostat rating is where the thermostat begins to
open, not where it is fully open). The actual reasons are:
1) Range of operating conditions, with specific regard to worst case
temperature scenarios (high ambient temp @ high load).
2) Styling and economical factors (smaller and lighter cooling components,
lower hood lines, smaller grill openings, etc.).
3) SAE standards (which may be the biggest reason)
4) A host of practical design considerations based on past experience.
All these factors come into play when an engine is designed. Thermodynamic
theories aside, if engines ran better at higher temperatures, then they
would be designing engines that run at higher temperatures. The fact is that
residual heat has for more negative impacts than some minor gain in
efficiency. Excessive residual heat is an undesirable by-product of an
internal combustion engine and is removed at great expense to the overall
efficiency. 205 degrees F is the LOWEST PRACTICAL operating temperature for
a modern automotive engine thus the marine engine which is based on it.
Someone used top fuel dragsters as an example. Those engines burn alcohol.
Alcohol produces far less heat than gasoline. Many studies have shown that a
properly setup engine, burning alcohol can run cooler and more efficiently
than a gasoline engine. It's service life is increased dramatically, all
because of the lower combustion temperatures and resultant lower operating
temperatures.
At lower temperatures, thinner oil can be used (look at trans fluid) and
therefore the internal friction losses are reduced. I can go on and on but I
think I've made my point. I help design automotive drivetrain systems and
despite your stack of theory, I am correct.
James Basara
Automotive Test Engineer
Mike Burke
>
> > Without a thermostat or at least a flow restrictor the Raw water
> > would pass throught he engine so quickly it wouldn't transfer enough
> > heat from the engine and you would coke the oil seizing the engine.
>
> Can you explain what coolant flow rate has to do with rate of heat
> removal, in the sense you've indicated that faster flowing coolant
> leads to slower heat removal? It seems counter-intuitive.
>
a stove. Turn on the heat. Imediately touch
the water. It's still cold. The flame is
hot enogh to burn but enough heat hasn't
transfered to the water to raise the temp
much. Now put a metal spoon in the flame for
a second or two. touch the spoon . It's hot
enough to burn. Now heat the spoon till it
red hot. Put it in the water for ten
seconds. touch the spoon. It's still hot
enough to burn. Heat xfer is a measure of
the conductivity of a object. Water is
mildly/moderatly conductive to heat xfer.
Therefore to maximize the heat xfer water
must stay in contact longer than say metal.
There is a lot of math that goes along with
this that I'm not able to expalain. However
I have see many a racer make this mistake.
Thinking that the engine will run cooler they
remove the thermostat from their engine and
the oil temp goes through the roof. The
reason is simple the water moves so quickly
from the engine to the radiator that it
doesn't remove enough heat from the metal
engine. While the engine is removing heat at
an excellent rate from the combustion
chambers.
Mike Burke
Martin wrote:
>
> I have a Volvo MD2B with raw water cooling. The thing I have noticed is that in these
> hot tropical Dutch waters, it never runs at a constant temperature.
> The engine temperature slowly rises until the thermostat opens and lets in a flood of
> cold water, at which point the exhaust emits a cloud of steam and the engine
> temperature plummets. When I first had the boat 20 odd years ago, I replaced the
> thermostat. This had absolutely no effect. I then checked both the old and new
> thermostats to make sure they opened and closed at the specified temperature. They both
> did and also the impeller pump works perfectly and has been properly maintained. As
> everything else seemed normal. I have ignored this phenomena. The engine can obviously
> take these temperature fluctuations, which are worst in spring when the raw water must
> be be about 6-8 DegC. BUT the engine must run better with a heat exchanger and at the
> correct constant temperature?
> With the engine now 25 years old maybe it is safe to leave things as they are? It's
> certainly cheaper!
give a constant flow of water at a reduced
rate. this will help to stablize the temps.
though the engine will run cooler in colder
water and warmer in warmer water. you can
make one from thin sheet metal. Use the
gasket as a guide. start with the hole about
half the diameter of the thermostat hole.
Hope this helps
Mike Burke
> At lower temperatures, thinner oil can be used (look at trans fluid) and
> therefore the internal friction losses are reduced. I can go on and on but I
> think I've made my point. I help design automotive drivetrain systems and
> despite your stack of theory, I am correct.
>
> James Basara
> Automotive Test Engineer
know squat about racing. Top fuel dragsters
burn Nitro methane. Alcohol dragsters burn
Alcohol. AND AUTOMATIC TRANSMISSIONS USE A
COOLER IN THE RADIATOR WHICH MEANS THAT THEY
RUN THE SAME TEMP AS THE ENGINE SMARTASS.
YOU CAN'T POSSIBLE DO ANYTHING WITH AN ENGINE
CAUSE YOU DONT KNOW THE BASICS. IF YOU
WORKED FOR ME ID FIRE YOUR ASS.
Marcus G Bell
Mike Burke (mbu...@msp.sc.ti.com) wrote:
> > > Without a thermostat or at least a flow restrictor the Raw water
> > > would pass throught he engine so quickly it wouldn't transfer enough
> > > heat from the engine and you would coke the oil seizing the engine.
> >
I wrote:
> > Can you explain what coolant flow rate has to do with rate of heat
> > removal, in the sense you've indicated that faster flowing coolant
> > leads to slower heat removal? It seems counter-intuitive.
Mike Burke (mbu...@msp.sc.ti.com) wrote:
> [stove and spoon experiment snipped]
> Water is mildly/moderatly conductive to heat xfer. Therefore to
> maximize the heat xfer water must stay in contact longer than say
> metal.
This is somewhat true, but the thermal diffusivity of water is pretty
good, as is the heat capacity, though there are certainly better and
worse materials in both regards.
Consider that the water is in contact with the heated object whether
the water is flowing or standing still. So "needing to stay in contact
longer" is not the reason.
Having the water flow rapidly through the system is a great way to
keep the temperature more even within the system, as long as laminar
flow is maintained. However, when water flows too rapidly through
convoluted passageways, it sets up turbulent flow with eddies which
trap pockets of air, or if things are hot enough, pockets of
steam. Then, the liquid is no longer in contact with the metal, and
heat transfer between the metal and liquid is greatly compromised in
those spots.
> There is a lot of math that goes along with this that I'm not able
> to expalain.
Does the math include anything about rate of bulk fluid movement?
> However I have see many a racer make this mistake. Thinking that
> the engine will run cooler they remove the thermostat from their
> engine and the oil temp goes through the roof. The reason is simple
> the water moves so quickly from the engine to the radiator that it
> doesn't remove enough heat from the metal engine. While the engine
> is removing heat at an excellent rate from the combustion chambers.
I'd say that they have turbulent flow in their systems which were
designed with lower coolant flow rates in mind. It's not the fast
flowing coolant which compromises heat transfer per se, its the fast
flowing liquid that leaves voids where the coolant doesn't contact the
metal of the engine.
Another interesting thing I'm told that racers do is use almost pure
water in their systems. This helps keep the track from getting
slippery like it would with a healthy dose of ethylene glycol in the
system, should the radiator get punctured in a crash. But water also
has a higher heat capacity than ethylene glycol, so it can remove heat
more efficiently than H2O/EG mix. However, water's surface tension
makes it more likely to leave voids of unwetted metal, so "wetting
agents" are introduced to lower the surface tension and increase the
coolant's contact with the metal. Or so I'm told.
Over.
Mike Burke
-- Another interesting thing I'm told that
racers do is use almost pure
> water in their systems. This helps keep the track from getting
> slippery like it would with a healthy dose of ethylene glycol in the
> system,
perhaps but I use pure water to facilitate
cool downs between runs. (cold water from a
garden hose connected to top radiator hose)
I'd say that they have turbulent flow in
their systems which were
> designed with lower coolant flow rates in mind. It's not the fast
> flowing coolant which compromises heat transfer per se,
Also perhaps partly true...
But I do know from my beer brewing that
after the beer has been boiled it must be
cooled to <90 degrees so that yeast may be
added without killing it. This must be done
as fast as possible to keep the beer from
being infected with an unwanted bacteria. We
use twenty feet of soft copper tubing with
cold tap water flowing thru. If the water is
pushed thru at full force it cools the beer
slower (~20 mins) than if its pushed thru at
a moderate (1/3rd of full ) rate (cool time
of 12-15 minutes.) There is not a lot of
turbulence within the smooth copper coil
Nelson
>Sure, Imagine if you will a pot of water on
>a stove. Turn on the heat. Imediately touch
>the water. It's still cold. The flame is
>hot enogh to burn but enough heat hasn't
>transfered to the water to raise the temp
>much. Now put a metal spoon in the flame for
>a second or two. touch the spoon . It's hot
>enough to burn. Now heat the spoon till it
>red hot. Put it in the water for ten
>seconds. touch the spoon. It's still hot
>enough to burn. Heat xfer is a measure of
>the conductivity of a object. Water is
>mildly/moderatly conductive to heat xfer.
>Therefore to maximize the heat xfer water
>must stay in contact longer than say metal.
>There is a lot of math that goes along with
>this that I'm not able to expalain. However
>I have see many a racer make this mistake.
>Thinking that the engine will run cooler they
>remove the thermostat from their engine and
>the oil temp goes through the roof. The
>reason is simple the water moves so quickly
>from the engine to the radiator that it
>doesn't remove enough heat from the metal
>engine. While the engine is removing heat at
>an excellent rate from the combustion
>chambers.
>--
>################
>Mike Burke
>MSP Support
>Ajilon/TI
Some of your theory is good some not,some is backwards.
Your idea that the longer the water stays in contact the more heat
will be transfered would be correct if the object were to heat the
water, but the object is to cool the metal (engine) not heat the
coolant.
Using your red hot spoon example, if you place the spoon under running
water it will cool much faster than dipping it in a pan of water.
Eventualy the water in the pan will get hot. If you were to keep water
running through the pan it would never get hot.. The faster that you
run cold water over any surface, the more heat will be absorbed
The reason that a race engine will run hotter without the thermostat
is not because the water isn't taking enough heat from the engine but
because the water isn't staying in the radiator long enough to be
cooled.
Nelson
James Basara
Heat transfer rate inversely proportional to velocity? I've heard that
removing the thermostat from a race engine will make it overheat and that
guys install flow restrictors to prevent that but then why remove the
thermostat?
I think that there are other factors involved including the heat transfer
efficiency of the radiator at a given rate of flow (inlet vs. outlet
temperatures), this is because of the aeration of the fluid at high flow
rates within the cooling system. The coolant contains air pockets which act
as tiny insulators. If a certain percentage of fluid is replaced with air,
an equal percentage of that fluids thermal efficiency will be lost. A higher
flow rate will induce an abnormal amount of aeration thus causing the loss
of cooling efficiency.
As far as the cooling pipes and the beer story, poppycock! I have hydraulic
pump heat exchangers that require maximum cold water flow rates or the
hydraulic fluid would quickly overheat. It would be insane to reduce the
flow rates to increase cooling efficiency and you can argue that one with
the heat exchanger manufacturer.
James Basara
Mike Burke wrote in message <34FD71D0...@msp.sc.ti.com>...
>--
>################
>Mike Burke
>MSP Support
>Ajilon/TI
#1 I believe Nitro Methane has very similar burn characteristics to Alcohol.
#2 Trans fluid is cooled in the portion of the radiator that the outlet is
attached to and thus at a much lower temperature than the coolant flowing
into the radiator, not the engine temp. Transmission lubricants operate at
much lower temps than engine lubricants under normal load conditions and
under higher load conditions we add an external trans cooler.
Please don't scream at me, I do hate belligerence.
sami...@bix.com
On 3 Mar 1998 15:59:30 GMT Marcus G Bell of University of Pennsylvania
wrote this re Re: Should I go to freshwater cooling?:
>water, as others in the thread have indicated. Thus, the raw water
>cooled engine is run cooler.
>
which case soluble minerals would obviously be deposited, how is it that
increasing the water temperature is supposed to _decrease_ the capacity of
that fluid to hold minerals in solution, rather than _increasing_ it, which
is what I'm reasonably certain I learned in HS chemistry?
>removal, in the sense you've indicated that faster flowing coolant
>leads to slower heat removal? It seems counter-intuitive.
>