My Wild Az Guess? FS may be stuck with some primitive fixed pitch paramaters. Certainly the development of CHT seems mainly linked to RPM, which for a constant speed prop is the height of goofiness. By changing the RPM of a constant speed prop you are changing it's rotational momentum, so perhaps the sim is responding to that. My experience with real planes? should be a pretty small effect if preceptable at all. I hadn't noticed this, particulat aircraft?
Sparks or any ACES guys have any insight on some of this stuff?
Cheers: T.