4.11 and Engine Overheat

[julian265]

Originally Posted by Arrow

I don't agree that it is proportional to MAP. Take the prop away from an engine and run it even on low MAP, you will see that it will overheat and explode just in seconds.

If you have killed an engine in a few seconds by over-revving it, then the engine has suffered mechanical failure, which in this case has nothing to do with coolant or oil temperature.

Originally Posted by greybeard1

Actually, heat to waste in internal combustion engine is about three times power developed and this latter is directly proportional to MAP, not to RPM, which is a consequence (that's to say an output, not an input) and, secondarily, by mixture, that contributes to take away some warm before the cooling system does.

I agree... in the scope of normal operating speeds.

Imagine two identical engines, each producing the SAME SHAFT POWER. One is running at 2500 RPM, and higher MAP, the other at 3000 RPM, and lower MAP.
The engine running at 3000 rpm will be producing more heat, due mainly to decreased efficiency at the higher rpm. It is the efficiency change which determines how much more heat is generated. Without knowing what it is, we're all just guessing, however I don't think the difference between 2500 and 3000 would be more than around 20%, meaning that MAP is still the main factor in heat generation... Which is why i disagree with "Pre 4.11 engine temps were effected more by manifold pressure than by engine RPMs or mixture settings, which simply is not realistic at all.".

Does anyone have an efficiency (or BSFC) chart for one of these aero engines?