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Originally Posted by Speedy Squirrel View Post
The reason is that the maximum surface temperature allowable is well below the autoignition temperature (around 530 F) due to the effect of the combustion process itself. The flame front starts at the plug and as it advances the pressure and temperature of the mixture in front of the advancing flame front increases. If the walls are hot enough, it will ignite and produce knock. Obviously this tendency is highly dependent on the combustion geometry, so an easy number for all engines does not exist.

Air-cooled engines have a problem here, since the hot spot is the exhaust valve, and it is a big one that is hard to cool; the fins are a long ways away. Check out a cross-section view of the Porsche cylinder head some time, and you will get an understanding of the problem.
Yes yes yes but Porsche knows a location(s) they can place a sensor and based on controlled lab testing and racing of other 911/930 based engines, often to destruction, know when this particular engine is overheating or not. That's what we are after here.

Let's accept for investigation the sensor on the 3.2L motor is in one such location. Do we have any tuners like Steve Wong who map chips for high performance street and track use?
Old 08-03-2009, 03:47 PM
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