ErnestSw

Doug,
Coming from a medical background I may have a more "organic" point of view than most. I think a car, like, for instance, the human body, is designed to work best within a fairly narrow temperature range. Both can function outside that range, but it's compensated function and it's stressful.
In absolute terms my car is not overheating. In relative terms I believe it is.
Cheers

hacker-pschorr

Any resolution to this story?

jserio

I have to agree with BC. I think it is safe to say that a reverse flushing is needed. I have seen it on many cars before and it doesn't matter the make. If you had chunks flowin in that engine then I would consider that a double gimme. I'd let a pro blow the **** out of it ( and I don't mean a Vegas pro). Okay thats my unclean one for the year

borland

When I refurbished my A/C system recently, I removed the Condensor which is located in from of the radiator. Even though I never have a problem with engine coolant temperature regulation, I spend at least an hour straightening fins and, with a tooth pick and wire hook, removing tiny pebbles from the fins of the condensor.

After cleaning the condensor, I could actually see the difference when viewing distant objects thru the condensor. Also air flow seemed to be improved, as felt by hand with the electric fans and engine running.

I also replace the two radiator side plate gaskets that improve air flow from the fans.

ErnestSw

The bottom line seems to be that the car runs at or near the top white line under all conditions of ambient temperature, air flow, and rpms. It runs there on the track, at high ambient temperature at idle in traffic, and at 40 degree ambient while cruising at 70 mph.
That tells me that the system is maintaining a dynamic equilibrium as per design with adequate "head room" for all conditions. By hearsay it appears that most GTs run hotter than most other 928s.

pappy92651

ErnestSw,

Since your engine is pinging is your car running lean? What is your AFR under full load (quick check new spark plug reading or exhaust tip color)?

Potential causes for pinging;
Chips
Brain
MAF
Oxygen Sensor
fuel filter
in tank pump
fuel regulator
low octane fuel
carbon deposits
wrong spark plugs (heat range?)

The pinging might be a symptom of something else, not the cooling system. Your temperature readings sound similar to mine except that mine fall off when the engine is unloaded. Lean conditions can heat load your engine causing exhaust valves to glow red. What is your oil pressure when the engine is hot and at idle?

Pappy

perrys4

Pappy, our mutual mechanic friend has told me the Devek radiator is to small and inefficient for the car and only reccomends the stock unit. I had heard good things about it until my converstaion. I too will be needing a radiator in the future. Whats your opinion of their setup?

worf928

One thing you didn't mention:

Old, leaky, clogged-up, bad-spraying fuel-injectors.

More than one pinging shark has been cured by way of getting the injectors cleaned and balanced.

Would not running lean cause pinging and the engine to get way too hot?

But, running too hot may not lead to pinging. Yes?

mark kibort

touch the radiator when its reading hot?? do this by touching the face of the radiator up and down the face. this will show whether the radiator fluild is circulating.
when a thermostat sticks, or the system is not burped (crush uper and lower hoses before engine is warm but running and do this when it is not running as well)

ive had over 3 sticking thermostats and issues with un-burped system.

the devek radiator is good for sytem replacement when the stock radiator is clogged or your block has some clogged passages. Ive used stock radiators on both of my race cars and they both run between the white lines in races when temps are over 90f. just cruised down to LA on hyway 5 and climbing the famous grape vine. the temps barely got to the middle (flaps always open, because they are gone)

Lean doesnt cause detonation, mixtures at 14.7:1 or near by, does (ie stoich)
(heat actually goes down past 16:1 and just before you would start missing due to lack of fuel) the engine is designed to cruise at medium power settings at 14.7 for best fuel burn, but the power setting is low enough, as to not raise engine temps. this is why at full throttle or nearby, the fuel ratios go to 12-13:1 for best power and cooler temps for reduction of the chance of detonation.

Let us know.
mk

pappy92651

Ron,

I will have to ask our friend. He does not like Devek and may have some bias. The stock radiators are also good but brand new are almost twice the cost of Devek. Mark Anderson rebuilds the stock units and resells them for a good value.


Dave,

Fuel injector problems have been known to cause detonation, true. Cleaning them is good idea.


Mark,

I agree with 90% of what you said. Why do engines that I have tested ping more as I run them leaner? If I run this test on the dyno I can get brand new engines to ping at ratios above stoich. You can see the detonations on the scope. Now If I back my timing off and run lean that is different, detonation is reduced.

Wouldn't running lean make the mixture prone to detonation? The timing is retarded in order to minimize this effect. Otherwise the mixture burns in a random pattern, rather than with controlled flame travel. A rich mixture reduces the associated cylinder temperatures and the volatility of the cylinder charge.

I'm old school. Perhaps I'm missing something.

Pappy

shaaark89

ernest,
did you ever get a chance to try the stock chips?
i had a similar pinging and running hot issue with the 89 (has chips) which was improved by adding more fuel with an adjustable regulator.
overall though, i'm not sure what you describe is truly that abnormal. all my street cars run at or just below the upper white line.
the '87s and '88 i had ran near the middle of the 2 white lines, but they have different gauges than the '89 and up cars.
if the car is pinging, you can be sure that either it doesn't have enough fuel or the timing is too advanced. as pappy eludes to, detonation will occur if the timing and fuel mixtures are not appropraite relative to one another. lean with retarded ignition may not detonate while rich with too much advance may.

worf928

I do not think you're missing anything. I think you are right on the money.

Lean combustion is hotter. Hotter can lead to (pre-)detonation.

Bad cooling can make the lump run hotter.
Lean combustion can make the lump run hotter.

Every in-good-health 928 I've seen on a dyno likes to run rich to very-rich at WOT. Even if the cooling system isn't cooling too well the rich mixture should (help) prevent pre-detonation. The cooling system in this car is new ( Modulo blocked passages.)

Ergo - it is running lean. That's where I'll place my bet.

Not directly. Lean combustion is slower and hotter. The hotter temperature is what may lead to pre-ignition of the fuel-air mixture.

Nope. Mixture does not lead directly to pre-ignition. Heat is it. The fuel-air mixture heats as it is compressed. The fuel-air mixture is heated by the engine. Too little fuel leads to lean and hotter combustion, the hotter combustion leads to pre-ignition.

ErnestSw

I no longer have any pinging. The injectors have been cleaned and the (incorrect) aftermarket chips have been replaced with the proper ones.

SharkSkin

The Devek radiator is supposed to have some 30% more cooling capacity than the stock unit...

[Edit]Correction -- 23%[/Edit]

perrys4

The Devek radiator is supposed to have some 30% more cooling capacity than the stock unit...

You did see Pappys response regarding the bias, right???? I suspected this too and was curious about his opinion. Pappys sharp and knowledgable. ( had him checked out, ha, ha )!!