possible engine damage due to jumps?

i notice in a few replaces i might do a jump like say the flugplatz at the nurburging and the car starts smoking for the rest of the race

it doesnt seem to diminish performance

i’ve even seen it in jumps nowhere near as big as the flugplatz

i didnt notice this at all on forza 4

I’ve never noticed anything like that in FM5.
How ever your suspension might bottom out and take damage, but that is extremely rare (much more common in FM4)

Are you sure that you aren’t downshifting while in air, which would cause overrevving of the engine when the car lands?
That would be my first guess. The damage caused might be only 1% and therefore so minor that you don’t even notice that.