how do I change the thread title? I was able to this before??

 

I have no idea if this is "too cold" or not. Frankly, I suspect that for racing purposes, this heat exchanger is a bit too small! Then again, other than an occasional run through the gears against some interesting car on the streets, a constest that lasts all of 10 seconds on average...my car isn't raced. They make far larger oil coolers, your size is dictated by your wallet.

I drive my 928 as if it was turbocharged. That is, I allow it to warm up to full operating temperature before I attempt any sort of full power or RPM's above 3000. I don't care for blown head gaskets-!

I'm going to finish the install that I stalled last year; I will install the oil temp gauge, the fuel pressure gauge, and the manifold pressure gauge that I bought from Nordstrom last year in the the plastic fitting that I bought from Carl Faucette. When that's done I can evaluate the oil cooler objectively.

As to being too cool...your oil needs to reach a certain temperature to insure proper lubrication at all points of the engine. If the oil temperature is too high, then we run the risk of having the crankshaft or camshaft or othe rotating surface meet the block or the head or whatever. Thin oil allows things to touch, and heat makes the oil thin. Synthetic oil resists this a very small! amount.

-Lets say you built a 928 with two radiators. One for the coolant as from the factory, and one for OIL. Oil capacity increases by a HUGE amount! And lets say you drive one mile to work each day in your 928, and one mile back, a total of 10 minutes per day.

Q: WHY would this be the worst possible scenario?

N?

 

Yes, the trans cooler serves to warm up the oil just as much as it serves to cool it. American cars for years have had at least a simple pipe which passes trans fluid through the radiator for exactly this reason. Sure, the trans will heat up eventually, more so if you're on it hard... but it heats up much slower than the engine. This is why the more knowledgeable trans techs will usually suggest you run the fluid back through the rad after it leaves the external cooler.

 

I think there's a good reason why my wife's 968 Tip has ATF lines going from the trans to a cooler built in to the radiator, and then from there to an external cooler, then back to the trans. Best of both worlds. If the warming effect from the coolant was not necessary, I doubt Porsche would have gone to the extra trouble of setting it up this way if they were already planning to install an external cooler.

Dan
'86 928S 5-spd w/LSD

 

That's interesting! I learn something new every day!

 

Dan, you say the 968 has the extrenal cooler *after* the one in the rad? Interesting...

 

I am sure my car has a thermostat in the line from the motor to the oil cooler in the radiator; so how can it warm the oil if the oil has to be warm before it is allowed to reach the radiator?

Do not know about the auto trans, maybe that has open flow - but would it not be better to keep the trans fluid cool?

Marton

 

Marton, the engine oil heats up relatively quickly. Trans fluid does not. Oil needs to be at a minimum temperature for effective performance, and a trans cooler in the rad will help it warm up quicker, then when the trans temp exceeds water temp it will help cool it.

 

You know, now that I think about it, I'm not quite sure which direction the flow is. It may very well be the external first, then the rad cooler...

Dan
'86 928S 5-spd w/LSD

 

All the 928 automatics after 1983 have an external trans fluid cooler as well as the internal heat exchangers in the radiator which are in the HOT side of the radiator. The 87> have a long thin one at the top of the a/c condensor.

 

Interesting, I found the attached pic in the 968 WSM. It goes through the rad, then the external cooler, if I'm reading this right. Wonder why they did it that way?