This is a cross post from Rennlist...and sounds similar to an issue that Jerseydevil posted (though he was running a manual w/ RE71's)
I have a 2014 (981) Cayman S that I track fairly frequently. It has about 40k miles – recently changed air filter and PDK flush*, along with oil changes every 3-5k miles and brake fluid changes, and already had spark plugs changed. Using Mobil 1 0-w40*. Using Pzero tires and always use PSM. Issue only appeared recently.
On the last two sessions of a recent 3-day track event (high 80’s and sunny), I was driving the car in sports plus and allowing the car to do the shifting. Half way into the second to last half hour session, it felt as if the car went into sort of a limp mode. No fault codes/CEL, but car wouldn’t rev to redline before shifts – was short maybe 500 – 1000 RPM before shifting. I ended the session early, let the car rest, and then went back out the last session, and after 5-10 minutes laps, it “limping” again.
I was advised by someone to do a PDK/transmission flush*, which I did along with an oil change, and brought it out to the track the following week for a test (fresh PDK/transmision fluid and oil). Temps were about high-80’s / 90 degrees – on the first day, I was able to drive 3 sessions without issue, then every session afterwards, started “limping” after 10 minutes or so – when I noticed this, I did a cool down lap and pitted in. The next day, it started “limping” after 10 minutes of the first session. Called it quits and went home.
Brought the car to a Porsche dealer the next day – and they concluded that it was because I overheated my brake fluid (likely because that’s the only code they saw).
A few questions come to mind:
-I question the conclusion the dealer came up with, since I use RBF600 fluid, which was flushed beginning of the year, and bled prior to the 3-day event when the “limping” started to occur. Also, seems far fetched associating these two together…and even if I upgrade to SRF, wouldn’t the fluid still get just as hot, but not necessarily boil - setting off the high temp brake fluid sensor?
-Someone suggested it might be a cooling fan or thermostat/sensor issue, but dealer didn’t (or couldn’t) see that.
-I spoke to a very knowledgeable Cayman guru who said to get a third radiator, use Driven DI-40 oil and PDK cooler. I would have done this, had I not found out that there are other 981 Cayman S owners in the area that drive their cars harder/faster than me (at the same event), and do not have these modifications. My concern is that these modifications cost real money, and I cannot test if this would be successful unless I invest additional time and money into a track event to test it out (I can't replicate this problem safely on public roads)
-I understand alot of people don't like Mobil 1, but I've always used it in the past with no issue (and know others that are faster than me using it), and used fresh Mobil 1 oil on the test event to no benefit. I have also tracked the car in 90+ weather many times in the past with no issue.
CPO warranty is running out soon, and I’m getting frustrated throwing money and time into troubleshooting and testing the car. Was curious if anyone else had this same issue and what resolved it. Very close to selling my car and moving on in life to another hobby.