DrJupeman

I just completed my second race weekend in my 981 CS with ambient temps above 85F. Within fairly short-order (15 minutes?) the car will yell about high oil temps, I believe that warning is set at 300F. Backing off revs will cool the car to avoid the warning and have the oil temps hover in the 290 range. Water temps are around 225-235. Obviously backing off revs in a race car is a problem. I am running pure water with water wetter. The car is relatively young (5,000 miles, not that miles is a great indicator of much) and otherwise seems to run great.

I have access to data from another 981 CS running with me this past weekend and his oil temps never crested 290, were usually in 270 range and water temps below 220.

The only guess I have as a cause is my car has AC and his does not. I was not running the AC, but I'm wondering if the condensers block too much airflow. Before I rip out the condensers, does anyone have experience with this issue and a solution? I'm getting old, I'd love to keep the AC....

redmonkey928

If your warning is at 300F and your getting that within 15' something is not right. The 718 tech guide will state an oil temp over 150C will result in engine damage and to immediately stop the engine and let cool.

Something is not right if your getting that with such a short run time, and would definitely start digging into it before running the car again.

blomman

My 981 has ac, no really difference in oil/water temps When in use.
Water maximum 100c
Oil maximum 128c
Check the fans and the fuses.

38D

I was at the same race as Charlie, and my temps are much lower. My car does not have AC.

Oil Temp: 271.4 to 282.2
Water Temp: 208.7 to 214.1

This is from the last 3 laps fo the race, so the car was good and heat soaked by then

mikew968

Is there any difference in the cooling on the 981 and 718?

thuggo

Just curious, what fuel was everyone running?

DrJupeman

This has been something we considered, too. I was running 93, I think 38D was running 100.

thuggo

So just my personal experience and I didn't grab the actual oil/water temps. But a few weeks ago I was at Road Atlanta and ran 93 for the first half the day. Car felt slow. It ambient was in the mid 90's with it obviously being well over 100 on the track. Put in 100 for the 2nd half of the day and the car appeared to run where I expected it too. *shrugs*

Chris P Lewis

I have done 2 fuel octane experiments. My car has had either an AIM or Motec C125 (it now has the C125) so I have real data on the performance.

1. I ran at Road Atlanta last year in fairly warm 85F weather. I was running 93 pump gas, pumped out the tank and put in 16 gallons of 100 octane VP fuel. There was no difference in top end, which is your HP indicator. Note that these cars do respond to higher temps by making less power, see page 25 of the technical manual. At that time I was not smart enough to look at Timing Advance.

2. Last week at VIR it was also 85F, I was running Pilot 93 pump gas. We pulled up the timing advance data on the Motec and saw that it was running 30.4 degrees all day long. I also looked at April 30 2021 Timing data and it was also 30.4 degrees. The car was slower on the back straight last week because the ambient air temp was higher than April, but the timing was not pulled due to any ping detection. The straight line difference was 0.6 sec on the back straight from April to June due to increase ambient air temps.

After a 20 lap stint at VIR, 85F ambient temp, the following drivetrain temps were measured:

Oil Temp. 242.6 F
GBox Oil Temp. 249.8 F
GBox Clutch Temp. 244 F
Water Temp 204.8 F
No Alarms were indicated.
A/C on Max....I'm a wimp.

I will probably do another experiment now that I have the data pretty well set up, but I didn't see a significant change due just to fuel octane.
It is my understanding that the 718 has improved thermal management over the first generation car.

Chris

ArtF10

Not sure if it's a similar situation but last year I had sporadic elevated temps. It would get a little better if the heat was running which isn't really an option most of the season. It ended up being a sticky thermostat. We changed that and did a flush and never happened again. Coincidentally it was around the 5000 mile mark as well.