Originally Posted by Porschefile
Well I just returned from 2 days at VIR and the cooler seems to have cooled the car effectively. I was hitting 270-280 oil temps on a cool day (67 degrees or so). I think it's safe to say that on a warm summer day the car would overheat with the AR cooler. During my last session the car went into limp mode and the SES light came on and I assume it was the transmission (oil was in normal range). The 335 steptronic is a great street car but not suitable for the track even with the oil cooler. I'll probably end up getting a spec E30 or an E36 M3 to play with.
I had problems last year with limp tracking an auto in manual mode with Dinan stage III. The problem is that all the transmission loses are rejected into to the cooling system. There are few thing s you can do to combat this.
1. Run in manual mode only.
2. Run with traction control completely off. There is really no choice in the matter.
3. Change the coolant to 30/70 mixture with a bottle of water wetter. My overall coolant temperature dropped about 18-23 F which was more enough to keep me out of limp mode on the hottest summer days. Only draw back is the coolant must be changed back for cold weather and due to mixture should be replaced yearly to prevent corrosion.
A few other people have done this as well with the same results. The science is fairly simple. The coolant mixture of 30/70 allows for more heat to be transferred at and at a higher rate than normal 50/50 mixture. This allows for much more heat to absorb at the source so you don’t get localized boiling which is the true cause of heat induced limp for this car. The other befits is the heat is rejected out also at much higher rate at the radiator so it far more efficient. A bigger radiator will help with overall heat rejection to atmosphere but it will not solve the problems at the places where heat is absorbed into the system like the head and exhaust valve area in the water jacket.