Sorry that it seems I beat this thing to death but I want to add some new infos after a call from Honda Germany and another talk with my techie.
Honda technical service man says: Possible reasons for overheating a NSX on the track are:
Stock radiator isn't capable of enough cooling for heavy track use - that's why they changed also to an aftermarket radiator at the 24 hours Nuerburgring NSX-R (just mentioned in another thread) which was bigger and thicker. They even altered some of the parts in the front compartment to give the radiator more room. My techie agrees - new radiator will be mounted.
Honda techie says: If the oil temperature exceeds 140 C the ECU reduces max rpm and even go into limp mode to avoid Vtec and other engine problems. My techie agrees and says his measurements show oil temps in the region of 145 C in my engine. That's why we add an oil cooler.
Honda techie says: Maybe the engine is running lean because the Lambda sensor gives false measurements to the ECU (my cats are removed). Lean running leads to more heat. My techie says: Rubbish - normal cats work only up to 60% of full load, afterwards (and I'm running always full load at the track) the ECU always sets the Lambda 1 relation (I guess it's 7:1) no matter which sensor measurements. His conclusion: Engine is not running lean at full load.
Honda techie says: Leak down or compression tests are not necessary in my case - if I have no combustion in the coolant (I have not after changing the head gaskets), no coolant leaks, no power loss, no oil leaks etc. I would have no engine problem like cracked blocks or blown gaskets. Serious engine problems would be remarkable very fast under heavy track use. My techie agrees.
Honda techie suggests installing an oil temp gauge - we will do that together with the installing of an oil cooler. After all this modifying the car will be brought on a dyno - not only to test the power but also if it overheats under full load with not much streaming air (At the dyno they usualy only have fans in front of the car to give about 90 km/h airstream).
