What causes engine pinging?
Eric Alter
causes the engine to start to ping under heavy load?
A year+ ago one of my cars started to have engine ping under heavy
acceleration. Is there any way to correct this?
--
Eric Alter
Ravanasamudram Venkatachalam
Generally speaking, engine pinging occurs only in larger size engines
such as the 8 cylinders.It usually occurs in engines that have a good
amount of wear on them, and under heavy loads or heavy acceleration.
This occurs because the fuel burns ahead of time in the cylinder, and
jars the piston which doesn't quite fit the cylinder anymore. In the
days of the 8 cylinder vehicles, I remember this to start occuring when
the engines usually have put in about 80 to 100 k miles. This is usually
an indication, that the engine needs to be rebuilt, i.e. larger size
piston rings need to be installed. It generally doesn't occur in the
smaller engines because they run at a higher rpm.
Venkatachalam
Mark Forbes
>In rec.autos.tech, al...@rchland.vnet.ibm.com (Eric Alter) writes:
>>I know that 1 solution to engine ping is to buy higher octane gas but what
>>causes the engine to start to ping under heavy load?
>>
>>A year+ ago one of my cars started to have engine ping under heavy
>>acceleration. Is there any way to correct this?
>such as the 8 cylinders.It usually occurs in engines that have a good
>amount of wear on them, and under heavy loads or heavy acceleration.
>This occurs because the fuel burns ahead of time in the cylinder, and
>jars the piston which doesn't quite fit the cylinder anymore. In the
>days of the 8 cylinder vehicles, I remember this to start occuring when
>the engines usually have put in about 80 to 100 k miles. This is usually
>an indication, that the engine needs to be rebuilt, i.e. larger size
>piston rings need to be installed. It generally doesn't occur in the
>smaller engines because they run at a higher rpm.
Sorry. Wrong. Time for a tutorial on pinging.
Pinging is caused by *detonation* of the fuel/air mixture. In this it is
different than normal combustion, because it happens at a point in front
of the advancing flame front as it propagates away from the spark plug.
Detonation occurs whenever the combination of heat and pressure is
sufficient to initiate combustion in the mixture without an external source.
Fuels with higher octane numbers are more resistant to detonation.
Cylinder pressure and temperature are the driving factors, and they are
in turn determined by the amount of mixture in the cylinder, and the
timing of the ignition spark.
As the cylinder approaches top-dead-center on the compression stroke, a
spark is fired. It is fired at a time prior to TDC, such that the peak
of the cylinder *pressure* will occur at or slightly after TDC. If the
spark fires late, burning continues to occur after TDC and the exhaust
stream heats up. This waste heat represents lost power and fuel economy.
If the spark fires early, the pressure peak happens before the piston
has finished its upward stroke. In combination with an open-throttle
condition, this can lead to extremely high cylinder pressures and
temperatures. The extreme conditions cause bits of the mixture not yet
reached by the flame front to detonate and begin burning outward from
the detonation locus. Eventually these flame fronts collide.
Flame front collision causes shock waves, which are heard as a high-
frequency 'knock' or 'ping'. Pinging is the less severe form of the
two. In addition, extreme turbulence is induced in the burned mixture,
which greatly increases the rate of heat transfer into the cylinder
walls and piston crown. This hot, pressurized, turbulent mixture is
what causes engine damage with chronic pinging, because it exceeds the
combustion chamber's designed capacity to remove waste heat. Burned
pistons will result from severe pinging or knocking. The mechanical
shock of the detonation and shock waves also can degrade bearings,
and the power output of the engine drops precipitously because the
pressure peak occurs while the piston is still on an upward stroke.
Black smoke is often seen when preignition occurs. Contrary to popular
belief, this is *not* "blowing out the carbon". The turbulent conditions
in the chamber result in incomplete combustion of the mixture, and
the unburned gases create black smoke.
The solution is simple; reduce the cylinder pressure, and retard the
timing. Unfortunately, both of these reduce the engine efficiency and
hence the resulting gas mileage. Recent vehicles have computer-controlled
ignition timing, and incorporate knock sensors which can detect the
onset of preignition and adjust the timing accordingly. With adequate
sensors, the timing can be run at 'just on the edge' of pinging, where
efficiency is at a maximum and no damage will occur. Feedback systems
of this type are much less sensitive to fuel variations, as well.
Piston slap, caused by the skirt of the piston whacking against the
cylinder walls, is a different creature entirely. It doesn't have anything
to do with preignition, although engine wear does have an effect.
Small engines have the same sorts of problems with pinging as large
engines, and in fact even two-strokes and single-cylinder engines
can ping if you misadjust the timing.
Ignition timing is a whole subject in itself, but the important thing
to remember is that it's not static; it changes depending on the speed
and load on the engine. At low speeds the spark fires later (in degrees)
because the *time* required to complete the burn takes fewer degrees
of rotation to complete. As the engine speeds up, you have to start the
spark earlier, in order to complete the burn on schedule. Cylinder
pressure also influences the burn speed, so you have to compensate
for that using manifold pressure as a control. (Vacuum advance/retard)
For people like me, with a 1966 Volvo, all I get is mechanical spark
advance. It's nothing more than two spring-compensated counterweights
mounted on the distributor shaft, which advance the spark as the
speed increases. Low speed, 10 degrees of advance. High speed, as
much as 50 degrees of advance. It varies in between. No load compensation,
so I'm not as efficient as I could be. I leave my distributor clamp
just slightly loose, so that I can adjust the timing by tapping the
distributor back and forth. If I get a load of low-octane gas, I give
it a whack (or two) in the 'retard' direction until it just barely
pings at full throttle in fourth gear at about 40 miles per hour. When
I get better gas, I advance the spark to achieve comparable performance.
Back in the good old days, there used to be a dial mounted on the
distributor. It was labeled "Octane Selector" and you set the pointer
to whatever the octane rating of the fuel was. Gasoline wasn't
standardized well enough to be consistent, so a tankful had a rating
posted on it, and you'd adjust for it at fill-up time. These days we
have computers to take care of such things.
Anybody know of aftermarket electronic timing systems? I've been contemplating
building one with a microcontroller, but I just don't have the time
right now.....
Mark G. Forbes | for...@atlantis.cs.orst.edu
Corvallis, OR | 503 754 3104 home phone | Hardware R & D
"Never ascribe to malice that which can be blamed on the engineer."
James P. Callison
>In rec.autos.tech, al...@rchland.vnet.ibm.com (Eric Alter) writes:
>>I know that 1 solution to engine ping is to buy higher octane gas but what
>>causes the engine to start to ping under heavy load?
>>A year+ ago one of my cars started to have engine ping under heavy
>>acceleration. Is there any way to correct this?
>
>such as the 8 cylinders.It usually occurs in engines that have a good
>amount of wear on them, and under heavy loads or heavy acceleration.
>This occurs because the fuel burns ahead of time in the cylinder, and
>jars the piston which doesn't quite fit the cylinder anymore. In the
>days of the 8 cylinder vehicles, I remember this to start occuring when
>the engines usually have put in about 80 to 100 k miles. This is usually
>an indication, that the engine needs to be rebuilt, i.e. larger size
>piston rings need to be installed. It generally doesn't occur in the
>smaller engines because they run at a higher rpm.
Knocking/pinging is caused by detonation of the fuel/air mixture, as
opposed to ignition. It is most easily fixed by changing to higher
octane-rated gas. It is _imperative_ that you rectify the situation,
as detonation (the ping/knock) burns up the valves and piston combustion
face, because of the irregularity of the detonation, and the fact that
it occurs before the piston reaches top dead center--ie, much of the
energy is wasted pushing the piston down as it is still rising through
its stroke. It also occurs before the valve are fully closed, and puts
undue stress on them.
In other words, excessive pinging/knocking is a VERY Bad Thing(tm). A
little bit of pinging every once in a while, say, when attempting to
accelerate up a hill, is normal, and the only way to avoid it is to
(a)adjust your driving habits; (b)buy the more expensive, higher-grade
gas; (c)buy 104+Octane Boost (or whatever it's called); or (d)stay
away from hills/mountains :-)
And the number of cylinders has nothing to do with it; 4-bangers will
knock just as badly as V8s. I personally hear more 4-bangers that
ping like hell than I do V8s...
James
James P. Callison Microcomputer Coordinator, U of Oklahoma Law Center
Call...@uokmax.ecn.uoknor.edu /\ Call...@aardvark.ucs.uoknor.edu
DISCLAIMER: I'm not an engineer, but I play one at work...
The forecast calls for Thunder...'89 T-Bird SC
"It's a hell of a thing, killing a man. You take away all he has
and all he'll ever have."
--Will Munny, "Unforgiven"
Bob Valentine
>I know that 1 solution to engine ping is to buy higher octane gas but what
>causes the engine to start to ping under heavy load?
My checklist (in order) would be:
1. Over-advanced timing / incorrect timing and/or control.
2. Engine running too hot. (stuck thermostat/dirty/clogged system)
3. Excessive carbon in the cylinders.
>A year+ ago one of my cars started to have engine ping under heavy
>acceleration. Is there any way to correct this?
Check above. It's probably the timing.
--> Bob Valentine <--
--> rava...@mailbox.syr.edu <--
Bob Valentine
>such as the 8 cylinders.
It's got nothing to do with the number of cylinders. ANY
engine could ping. (Well, I dunno about a 8hp Briggs&Stratton....)
>It usually occurs in engines that have a good
>amount of wear on them, and under heavy loads or heavy acceleration.
Wear is not a great factor. My 200K mile Olds 350 still don't
ping, and the timing is ADVANCED over factory. I run the cheapest gas
that can be bought.....
>This occurs because the fuel burns ahead of time in the cylinder, and
>jars the piston which doesn't quite fit the cylinder anymore.
Ah, you're talking about piston slap. Ping is technically
pre-ignition of fuel, before the spark plug fires. Often caused by
uneven fuel distribution in the cylinder, or hot spots in the
cylinder.
>In the
>days of the 8 cylinder vehicles, I remember this to start occuring when
>the engines usually have put in about 80 to 100 k miles.
Don't knock the V8 off that fast. The main reason you used to
hear it more was due to carbon build up, and out-of-spec timing.
>This is usually
>an indication, that the engine needs to be rebuilt, i.e. larger size
>piston rings need to be installed.
At worst, you have to yank the heads and clean out all the
carbon.
> It generally doesn't occur in the
>smaller engines because they run at a higher rpm.
What's your source for that? I'd like to see it.
--> Bob Valentine <--
--> rava...@mailbox.syr.edu <--
PS- I forgot to add one thing before: Malfunctioning EGR could cause
pinging also....
Jim Frost
Me too. My 1.6L 4 cylinder engine sometimes pings under heavy loads
when using cheap gas. I must be imagining it.
jim frost
ji...@centerline.com
Val Breault
Sorry. Wrong. Time for a tutorial on pinging.
Pinging is caused by *detonation* of the fuel/air mixture. In this it is
different than normal combustion, because it happens at a point in front
of the advancing flame front as it propagates away from the spark plug.
<more good stuff deleted for bandwidth sake>
Mark is right. I have deleted the balance of his post but encourage
those that have not seen it to look for it.
Mark G. Forbes | for...@atlantis.cs.orst.edu
Corvallis, OR | 503 754 3104 home phone | Hardware R & D
"Never ascribe to malice that which can be blamed on the engineer."
--
Val Breault - N8OEF - vbre...@gmr.com \ /|
Instrumentation dept GM NAO R&D Center \ / |
My opinions are not necessarily those of \ /__|
GMR nor of the General Motors Corporation \/ |___
JUN HE
Venkatachalam) writes:
>In rec.autos.tech, al...@rchland.vnet.ibm.com (Eric Alter) writes:
>>I know that 1 solution to engine ping is to buy higher octane gas but what
>>causes the engine to start to ping under heavy load?
>>
>>acceleration. Is there any way to correct this?
>>
>>
>>Eric Alter
>
>Generally speaking, engine pinging occurs only in larger size engines
>amount of wear on them, and under heavy loads or heavy acceleration.
>days of the 8 cylinder vehicles, I remember this to start occuring when
>an indication, that the engine needs to be rebuilt, i.e. larger size
>smaller engines because they run at a higher rpm.
>
>
Are we talking about the same 'pinging'? As I understand, pinging is usually
caused by detonation or preignition; when there is too much carbon deposit in
cylinders, or abnormal cooling of the cylinder head, detonation or preignition
may happen. Higher octane gas has a lower flame wave speed and therefore may
stop the pinging caused by detonation but can not help to stop preigination.
The pinging you mentioned here sounds more like piston slapping to me, which
cause by abnormal cylinder wall or piston skirt wearing.
Jun
Jeffrey E. Thompson
>Jun
I think that the confusion about higher engine rpm is due to
the unmentioned timing advance that is needed as rpm increase. Because the
flame speed for a fuel is a constant finite value (roughly) as the engine
rpm increases, the mixture must be ignited sooner so the optimal explosion
size can be reached in time. ie. the size of the explosion should be
close to the size of the combusion chamber when the piston comes to TDC. If
a car pings because of predetonation caused by a hot spot of carbon it is
possible that when the engine revs high enough the timing advances far
enough to fire the spark plug before the carbon has an effect. The reason
pinging is more pronounced under load probably has to do with the richness
of the mixture. A richer mixture may ignite easier, but I'm not sure where
the limit to that is.
Just my $0.02
Jeff
KENNETH MACALPINE
Venkatachalam) writes:
>In rec.autos.tech, al...@rchland.vnet.ibm.com (Eric Alter) writes:
>>I know that 1 solution to engine ping is to buy higher octane gas but what
>>causes the engine to start to ping under heavy load?
>>
>>A year+ ago one of my cars started to have engine ping under heavy
>>acceleration. Is there any way to correct this?
>>
>>--
>>
>>Eric Alter
>
>Generally speaking, engine pinging occurs only in larger size engines
>such as the 8 cylinders.It usually occurs in engines that have a good
>amount of wear on them, and under heavy loads or heavy acceleration.
>This occurs because the fuel burns ahead of time in the cylinder, and
>jars the piston which doesn't quite fit the cylinder anymore. In the
>days of the 8 cylinder vehicles, I remember this to start occuring when
>the engines usually have put in about 80 to 100 k miles. This is usually
>an indication, that the engine needs to be rebuilt, i.e. larger size
>piston rings need to be installed. It generally doesn't occur in the
>smaller engines because they run at a higher rpm.
>
>Venkatachalam
>
The pinging or knocking sound(in severe cases) that you are reffering to
has nothing to do with the number of cylinders an engine has, nor the mileage
the engine has. The sound you are hearing is the explosion of the gas and
fuel mixture within the cylinders. This occurs when the temperature of any
part of the piston/cylinder walls/head system exceeds the flash point of the
fuel that is being used. A fuel with a higher octane number has a higher flash
point. The flash point refers to the temperature at which the fuel explodes.
Under normal operating conditions, the fuel/air mixture is undergoing a
controlled burning which is intiated by the spark plug. If the spark does not
go off before the flash point temperature is reached, then
pre-ignition(knocking or pinging) occurs. The reson you noticed this in older
cars is because as a car gets older an accumulation of carbon deposits(unburnt
gas) forms on the top of the piston and in the combustion chamber. The
deposits do not dissapate heat quickly and therefore, under heavy loads, the
temperature of these deposits can exceed the flash point of the fuel; thereby
causing pre-ignition. If your car has spark plugs that are the wrong heat
range, the temperature of the ceramic(white)insulation in the sparkplug
can also exceed the flash point of the fuel and cause pre-ignition.
There are a few possible fixes to this pre-ignition problem. The first is to
try gas with a higher octane rating. If that doesn't work, the next method,
which will work for all cars with distributors, is to retard the timing of the
spark. If you don't know where your distributor is or if you even have one
in your car, ask a reliable mechanic to do this. Otherwise, with the engine
off losen(do not remove) the bolt or bolts that secure the distributor to the
the engine. Then, with a marker, mark the position of the distributor relative
to the housing that it fits in on the engine. Then with the engine idling,
slowly twist the distributor in one direction. The engine rpm will either
increase or decrease. If it increases, you are advancing the timing. If the
idle speed decrease,s you are retarding the timing. You want to retard the
timing relative to the mark on the housing of the distributor(about the
distance from 12:00 to 1:00 is a approximate first guess). If you retard
the timing too much, the engine will have very little power and poor fuel
economy. Tighten the bolts that secure the distributor and drive the car. If
it still knocks or pings, retard the timing a little more. If it doesn't knock
or ping, then you retarded it too much. The ideal setting is to have the
timing set at the point where the engine just barely doesn't knock under
heavy loads.
The noise that the piston makes when it hits the cylinder wall because it
doesn't fit tighly is called piston slap. It might get worse under pre-ignition
but the majority of the sound is preignition. If piston slap is very excessive
then it will produce a sound similar to that of a muted slap. If gone unchecked, pis
piston slap will not only destroy the piston rings, but it will also make the
cylinder bores oval shaped not cylindrical, which will require a reboring of
the cylinders.
Verbiage king
ken
Patrick Taylor, The Sounding Board
[detonation stuff]
>it occurs before the piston reaches top dead center--ie, much of the
>energy is wasted pushing the piston down as it is still rising through
>its stroke. It also occurs before the valve are fully closed, and puts
>undue stress on them.
Wait a minute. Are you telling me that either valve is still open during
the late part of the compressoin stroke (before TDC)? That doesn't make
sense to me. Seems like you wouldn't get any compression, then.
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Jonathan R. Lusky
>In article <C4p1x...@constellation.ecn.uoknor.edu> call...@uokmax.ecn.uoknor.edu (James P. Callison) writes:
>>its stroke. It also occurs before the valve are fully closed, and puts
>>undue stress on them.
>
>Wait a minute. Are you telling me that either valve is still open during
>the late part of the compressoin stroke (before TDC)? That doesn't make
>sense to me. Seems like you wouldn't get any compression, then.
With the blower cam I use on my 350 chevy, the intake valve doesn't close
until almost halfway through the compression stroke. And the exhaust valve
opens just over halfway through the power stroke.
--
--=< Jonathan Lusky ----- lu...@ccwf.cc.utexas.edu >=--
\ 89 Jeep Wrangler - 258/for sale! /
\ 79 Rx-7 - 12A/Holley 4bbl /
\________67 Camaro RS - 350/4spd________/
Jun Guo
>>
>Are we talking about the same 'pinging'? As I understand, pinging is usually
>caused by detonation or preignition; when there is too much carbon deposit in
>cylinders, or abnormal cooling of the cylinder head, detonation or preignition
>may happen. Higher octane gas has a lower flame wave speed and therefore may
>stop the pinging caused by detonation but can not help to stop preigination.
>The pinging you mentioned here sounds more like piston slapping to me, which
>cause by abnormal cylinder wall or piston skirt wearing.
>
>Jun
I have a Toyota 2.0L 4 cylinders, and it start to ping about one year ago.
I took the car to the dealer, they said it was caused by carbon deposit.
But three month later, the pinging is back. My question is: what caused
the carbon deposit? I use fairly decent gas, like Exxon most of the time.
Jun
--
+-----------------------------------------------------------------------------+
| Jun Guo (j0g...@tamsun.tamu.edu) | Texas A&M University |
| Department of Electrical Engineering | College Station, Texas |
+-----------------------------------------------------------------------------+
Tom Leone
(pinging) is not really the noise of two flame fronts
colliding. It is the noise from pressure waves caused by
abnormally fast combustion.
Also, higher octane gas does not burn more slowly. It goes
through pre-flame reactions more slowly. The actual flame front
propogates at the same speed as lower-octane gas.
Here's something I posted on this subject some time ago:
>If you know a thing or two about how to fix a engine that pings or
>knocks, please post.
>Thanx.
Engine knock is the audible pressure oscillation caused by a form of
abnormal combustion. Normally, the flame propogates smoothly from the
spark plug to the edges of the combustion chamber. As it does so, it
compresses the unburned gases ahead of it, which increases their
temperature and pressure. At these high temperatures, chemical reactions
in the unburned gas can lead to spontaneous, extremely rapid combustion
before the flame front arrives. This fast combustion can produce very
high (even damaging) pressures and temperatures.
There are many ways to prevent this:
(1) Slow down the pre-flame reactions--use a higher octane fuel.
(note: this does not slow down the normal flame speed)
(2) Lower the temperatures:
(a) Flush out cooling system, make sure thermostat, water pump,
and other parts are working properly. You can even install
a lower-temperature thermostat very cheaply.
(b) Check the ignition timing (too much spark advance causes
higher combustion temperatures and knock).
(c) Make sure that intake air "flapper" valve is not stuck (this
collects hot air from the exhaust manifold for cold starts).
(d) Do a general car "check-up" to look for things that might
be making the engine work harder (and hotter) than normal.
(e) Eliminate "hot spots" in the combustion chamber, like incorrect
spark plugs (these come in different "heat ranges") or burrs.
(f) Remove insulating deposits from the combustion chamber (piston
crown and cylinder head surface). This requires removal of the
cylinder head, which is a pretty big job on most cars. Some
people say you can clean them out by spraying water into the
intake air, but I've never tried this.
You may also be interested to know that engine design affects the tendency
to knock. An engine which "burns fast" gives less time for pre-flame
reactions, and therefore avoids knock. Some ways to get faster burning are
central spark plug location (and/or multiple plugs, like the Ford 2.3L
twin-plug), higher turbulence (from swirl or small-diameter valves), and
compact combustion chambers (such as the famous Chrysler "hemi"
hemispherical chamber, or pent-roof four-valve engines).
-Tom Leone <t...@slee01.srl.ford.com>
Andrew J. Huang
>I have a Toyota 2.0L 4 cylinders, and it start to ping about one year ago.
>I took the car to the dealer, they said it was caused by carbon deposit.
>But three month later, the pinging is back. My question is: what caused
>the carbon deposit? I use fairly decent gas, like Exxon most of the time.
>
>Jun
Low mixture velocity. i.e. you're not driving hard enough. With
small throttle openings, the velocity through the cylinders is low and
the mixture is not as completely burned.
Another source is driving short distances so that the engine operates
a high fraction of the time before being warmed up. An engine needs a
richer mixture to run under these conditions and this leads directly
to more deposits.
The classic way of clearing carbon is the Eye-talian tune up: 60mph
in second gear for 5mins. Once a month and immediately after every
traffic jam.
-andy
bohdan.l.bodnar
I have a 1986 Mustang with 2.3 liters engine which had an abnormal amount of
engine knock. Timing was slightly retarded without success and EGR was
operational. I conjectured carbon deposits in the cylinders were causing the
knock. I appear to have eliminated most of the deposits (and knock) via
water injection. On a warm engine, I gradually squirted in about one quart of
water while maintaining the RPM at around 1800. For kicks, I monitored the
oxygen sensor's output while squirting in the water. I did this last night.
This morning, there was virtually no knocking (although I did manage to induce
some at 65 mph, going up a hill, and accelerating -- it was NOTHING compared
to what I had yesterday morning). One observation: it appears that the oxygen
sensor was temporarily out of commission (voltage dropped to zero) during the
injection. The voltage slowly came up to "normal" several minutes after water
injection was terminated. Since the sensor's essentially an ion pump, I
conjecture that the pores in the ceramic were clogged (blown off carbon?).
An alternative way to clean the engine from carbon is to use this chemical GM
sells -- it's about $6/container. I have never used this, but the people I've
spoken with who have claim it works very well.
Regards,
Bohdan
Bob Valentine
[mucho stuff deleted]
>knock. I appear to have eliminated most of the deposits (and knock) via
>water injection. On a warm engine, I gradually squirted in about one quart of
>water while maintaining the RPM at around 1800. For kicks, I monitored the
>oxygen sensor's output while squirting in the water. I did this last night.
>to what I had yesterday morning). One observation: it appears that the oxygen
>sensor was temporarily out of commission (voltage dropped to zero) during the
>injection. The voltage slowly came up to "normal" several minutes after water
>injection was terminated. Since the sensor's essentially an ion pump, I
>conjecture that the pores in the ceramic were clogged (blown off carbon?).
Acutally, what probably happened was that the water cooled the
exhaust temperature down far enough that the 02 sensor went off line.
Of course, this is assuming a 1 wire sensor. I'd imagine a
3-wire heated type would be able to maintain proper operating
temperature.
>Bohdan
JUN HE
tes:
>I have a Toyota 2.0L 4 cylinders, and it start to ping about one year ago.
>I took the car to the dealer, they said it was caused by carbon deposit.
>But three month later, the pinging is back. My question is: what caused
>the carbon deposit? I use fairly decent gas, like Exxon most of the time.
>
>Jun
>--
>+-----------------------------------------------------------------------------+
>| Jun Guo (j0g...@tamsun.tamu.edu) | Texas A&M University |
>| Department of Electrical Engineering | College Station, Texas |
>+-----------------------------------------------------------------------------+
>
stop-and-go. A car should be used in a mixed city-highway driving, and
occationally rev the engine during highway driving. Higher operating
temperature helps to burn away carbon deposit. Know anything about an
italian tune-up?
Jun He
Paul Hovnanian
>causes the engine to start to ping under heavy load?
Higher cylinder pressures (when under higher loads) promote the conditions
for premature detonation (pinging).
>A year+ ago one of my cars started to have engine ping under heavy
>acceleration. Is there any way to correct this?
Have your ignition timing checked. If it is too far advanced it will
aggravate a pinging condition.
Assuming that it didn't ping under the same load prior to this time,
your cylinders may be carboned up, creating hot spots that encourage
pinging. Get a tune up.
Bob Campbell
> Higher cylinder pressures (when under higher loads) promote the conditions
> for premature detonation (pinging).
>
> Assuming that it didn't ping under the same load prior to this time,
> your cylinders may be carboned up, creating hot spots that encourage
> pinging. Get a tune up.
I've had my heads milled several times. Now the engine
pings all the time even though I've had it tuned. I was
thinking that the heads are now causing the compression to
be higher than normal and may be the cause of my trouble.
What do you think?
Jeffrey E. Thompson
>hovn...@iftccu.ca.boeing.com (Paul Hovnanian) writes:
I'm no expert, but I think it's a definite possibility. You may
need to lower the compression ratio with a new set of pistons. Too much
compression causes pre-ignition (pinging) which is why most supercharged
and turbo equipped cars have lower compression ratios (without the turbo).
The Devil Reincarnate
> Venkatachalam) writes:
>>In rec.autos.tech, al...@rchland.vnet.ibm.com (Eric Alter) writes:
>>>I know that 1 solution to engine ping is to buy higher octane gas but what
>>>causes the engine to start to ping under heavy load?
>>>
>>>A year+ ago one of my cars started to have engine ping under heavy
>>>acceleration. Is there any way to correct this?
>>>
>>>--
>>>
>>>Eric Alter
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Just my $0.02 :
My new Acura pings ever so slightly first thing in the morning when I
am climbing a hill with my engine cold. This is the key word for me: *cold engine*.
This is because the engine CPU advances the timing to compensate for the cold
engine. Two seconds later, the engine CPU receives input from the knock sensor
and retards the timing, and the pinging stops. Same acceleration, further up
the same hill.
I don't think pinging has anything to do with the number of cylinders,
although, I would think that since there are more cylinders, the probability
of one cylinder out of all possible cylinders pinging is increased....Whatever..
>>Generally speaking, engine pinging occurs only in larger size engines
>>such as the 8 cylinders.It usually occurs in engines that have a good
What has cylinders got to do with pinging?
What has the number of cylinders got to do with size of engine?
MX3 is V6 and has 1800cc.
Legend is V6 and has 3200cc.... what's the correlation?
gordon.d.woods
Bought new: 1978 Buick with Pontiac 301 V8.
Ran beautifully for 5K miles, started pinging on INTERMEDIATE
loads, e.g. cruising level at 55 mph. Heavy acceleration would
stop the cruise pinging for about 5 minutes after the acceleration.
(I would speed up and slow down on long trips just to get some peace.)
Tried high octane gas: no change. Checked EGR, found OK. The only
thing that would reduce it was retarding the spark to the point of poor
performance.
The kicker:
It did this for 158K miles at which point I had the engine rebuilt.
Ran beautifully for 5K miles, started pinging on INTERMEDIATE loads.
BTW, it went through a couple radiators during it's life with no
change, so I don't think it's the cooling system.
I can't see anything on Tom Leone's check list that hasn't been
covered except removing the heads to clean deposits and this
would have to be done every 5K miles to silence the engine.
BTW, the only accessories changed in the rebuild were water pump
and fuel pump; has original carb, EGR, distributor, etc.
From article <1pcia...@fmsrl7.srl.ford.com>, by t...@slee01.srl.ford.com (Tom Leone):
Mike Hughes
>Ok, you pinging experts, figure this out. [...]
[78 GM that pings under light load then stops pinging with hard accel]
I'll try. Because you say that the pinging occurs as you cruise down the
road and goes away when you stomp the gas, my bet would be on a faulty
vacuum advance unit. This car is equiped with GM's HEI system, and uses
mechanical and a vacuum-controled spark adjustments.
The mechanical adjustment is simply a weight on a spring, which spins with
the distributer shaft. As the shaft spins faster, the weight overcomes the
tention of the spring and mechanically advances the spark timing.
The vacuum adjustment uses a vacuum signal (usually timed from a port in the
carburetor) applied to one side of a rubber diaphragm. The diaphragm is
attached to a slide plate, which adjusts the timing.
As the engine cruises down the road, the vacuum signal is pretty high, which
tells the distributer to advance the timing for better power and fuel eco-
nomy. The advanced spark causes hotter temperatures, which causes detonation.
When you hit the gas, the distributer is told to retard the spark so pinging
doesn't occur, and your car stops pinging.
I suspect that the slide that the diaphragm operates is damaged, causing the
delay in advance.
Just my guess...-Mike
:Suicidal Tendencies====>: :
:Mike Hughes(301)340-0922: [Smack, smack, smack...] :
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