I use the term "overheat timer" to describe in a few words how overheat usually works in IL2.
In reality, for every second spent at higher than spec temperatures you run the risk of something breaking. This risk doesn't always just go away if you throttle back, because in some cases damage could be cumulative. You could badly overboost your engine for a minure or two longer than you should and nothing would seem wrong, only to have it break down half an hour later because of a tiny crack in one of the cylinders that serves as a starting point for a cascade of damaging events.
In IL2, what we lack is the accumulation of this damage. As long as you manage to cool the engine within a certain timeframe (before you hear the engine sound changing to the sample used for damaged engines), the engine is once more as good as a brand spanking new piece delivered straight from the factory. It's like the engine "resets" to its default undamaged state erasing any previous damage and the reason is that there isn't really any damage modelled yet at that point. It has to reach the point where you see your RPMs drop and the sound sample change to actually register damage.
I hope i explained it clear enough to make sense
