GryGst

Apologies if this is topic has already been addressed elsewhere on the forum. I did search, but didn't have much success...

I'd like to better understand how fluids are cooled in my 981 GTS with a 6-speed manual trans-axle. In the nose of my car, I've got three heat-exchangers. My understanding is all three are for coolant. The car has two side-intakes. At least one of them must be an air intake for the motor. But I don't have a clue if/how/where (i) engine oil and (ii) trans-axle fluid are cooled. I've also read that the gauges may be calibrated in such a way that what's reported to the driver may not represent what the sensors are actually seeing...

Questions:

1. Can someone offer up a quick primer on the fluid cooling systems -- or point out a thread that does so?

2. Where is the heat exchanger for the AC?

3. Is the engine oil cooled? If so, how/where?

4. Is the trans-axle fluid cooled? If so, how/where?

5. What coolant and oil temperatures are folks seeing on track -- and at what point are the temperatures high enough to merit truncating the session?

6. Has anyone replaced their trans-axle fluid and had it tested to see if its been degraded prematurely by high temperatures?

Thanks for your help.
Kindest,
GryGst

GryGst

At Laguna-Seca last weekend, I got the chance to observe my coolant temps and oil temps and learned that the reported coolant temp becomes sticky at 194 degrees F. (i.e., it never rises higher, regardless of the actual temperature until, I'm told, it reaches 221+ -- which, not surprisingly, never happened). In effect, the coolant gauge becomes an idiot light once the coolant has become fully warm. Oil temperatures seemed accurate but never rose anywhere close to becoming a point of concern. So this topic's no longer of great concern. Still, I find it offensive that Porsche feels the need to "reassure" owners that all is fine by installing a gauge that doesn't actually work properly!

jscott82

AC condenser is in front of the left radiator.

There is a small oil/water heat exchanger on top of the motor to cool oil.

There is no cooling for the trans. But stay tuned to my spec Cayman build thread. I have a pretty cool solution coming.

There no real cooling for the power steering. But if you look at the hardlines, Porsche put a couple of extra loops under the chassis to help. May be able to augment those rather than installing an additional radiator

I haven't run the car yet, so can't speak to expected temps. But the car will be fully instrumented to capture then when I do

GryGst

@JScott82: thanks! It's been surprisingly hard to dig up technical information about these cars. Not sure if that's because the owner demographics are different from that for other track cars I've owned or because there's a presumption that "if Porsche built it...". Regardless, I appreciate the insights.

jscott82

Agree.. we need to wake this forum up

mgent

GryGst

@MGent: FWIW, I wouldn't be concerned with oil temperatures of 260-270 degrees, provided you're using a quality synthetic. In my last track car -- tube-framed, mid-mounted LS3 motor mated to a Porsche G50 gearbox (flipped upside down) -- oil temperatures were regularly well over 275. When we had the oil tested, the results showed few chemical indicators of engine damage/wear. Might never "feel" right to you, but I think the jury is still out as to whether there's actually a problem to solve here.

jscott82

Tell us more about that car!!!

GryGst

PM sent...

zedcat

Try searching ebsracing,com. They have the GT4 technik bulletin which has high level descriptions of most systems including cooling. (I had a PDF on a hard drive but lost it...) Not sure how similar it is to other 981s but may be worth a look. And FWIW my observation is the GT4 and GTS can handle advanced/instructor group DE sessions (20 to 30 min) with no temp issues. I've driven GT4 at COTA in summer. At least for MTs. PDK in GTS I'm not certain. Another observation- this sub forum is a bit quiet. The 987-981 forum is more active and also the DE/Racing forum. Best of luck.

GryGst

@ZedCat: thanks for the post. I've been around the track scene for years, but I'm new to owning a P-car (I've driven many but never owned/maintained one). Much obliged...

badabing

If your car is PDK it should have come with the 3rd / Center radiator from the factory ???

GryGst

@MGent: Hi Mark. My understanding is that oil is cooled by an air-to-water cooler located on top of the motor, so -- given that your oil will ALWAYS be hotter than your coolant once the car is warm -- why would you expect you oil temperatures to be significantly lower with the addition of the third radiator? Maybe I'm not following the bouncing ball here...