Why in hot air engines produce less power?

Question

I read here that at hot temp's engines produce less power. why?

Answer 1

Couple of reasons. When air, or any fluid for that matter, is heated, the molecules separate and the air becomes less dense. So one of the reasons engines produce less power is that in effect it is taking in less air for combustion. The other reason is the effect that the less dense air has on such things as fans and propellers. There is simply less air for the blades to bite into and produce the thrust needed for propulsion.

Answer 2

Basically, on a hot day the air molecules move further apart. (Just the same as heated iron- it expands) If the air molecules are further apart, the air density is lowered.

Low air density means less mass (air) for the engines to compress and turn into power.

Humidity also has the same affect. Because of the moisture the air density is reduced.

Lift is also reduced because the air is effectivley thinner.

Answer 3

Hot air is thinner {has less oxygen modules} than cold air. That is why you commonly add a intercooler to a turbo system to extract more power. The denser the charge of air the more power.

Answer 4

In short, the hot air is less dense than the cold air... the cold air has more oxygen and because oxygen is highly flamable, the combustion in the engines is more intense and that means more power out the back end... it gets more complicated than that when you have to deal with atmospheric pressure and pressure altitude... but that is the basic idea...

Answer 5

Because air expands. When it expands, there are less air molecules and there are less molecules to ignite the fuel.