I pulled a little data from the ECU and wanted to share and compare. Is this consistent with what you are measuring on the track? BTW, this is from my 1st Gen R53 JCW car. Edit: added RPM to graph Some easy observations to make: ECT - Sitting on grid, or sitting still anywhere for that matter, maximizes ECT - It looks like the fans kicked on around 220F and dropped the temps to 210F - Drops like a rock when you finally start moving, no surprise - Dips way down to 190F at the beginning of the Warm-up lap as rpm is still relatively low, but plenty of air is flowing - Settles at around 200F for the entire Hot track session, very steady - Approaches my typical street driving temp of 194F moving through cool-down and exiting track to park - Starts to climb again after parked and sitting still IAT - Steadily cooks more and more while sitting still - Cools nicely during the relatively mild warm-up - Avg, or rather RMS temp continues to increase through entire session, starting around 150F (i.e. Ta + 65F) and ending around 170F (i.e. Ta + 85F). So, engine performance is just getting lower and lower with each lap. - Same story as with ECT for the cool-down, track exit, and parking Relevant Car details: - Water Wetter and about 30% OEM coolant - OEM thermostat - OEM IC with large after market scoop - Aero grill, yeah it is relevant as it definitely flows more air So, the Engine Coolant system seems to be working just fine and seems adequate. However, the Intercooler seems not quite good enough and a Meth kit or any other IAT lowering method would certainly help track performance. I am guessing the IATs would look much worse without the large hood scoop, this may even affect ECTs. Again, is this data and observations consistent with what you are seeing?