What happens when you increase air temperature flowing into an engine?

[liam1992]

Hi for a bit of work I have to explain the advantages and disadvantages of a higher engine intake air temperature.
I have been told that it decreases the power output of the engine but I can't seem to work out why it would decrease.
I also want to comment on how it affects the efficiency but i am unsure on this. I think that the efficiency would increase as the air has to be compressed less to ignite, is this correct?

Thanks for the help

 

[SteamKing]

What happens to the density of the intake air when it is heated?

 

[liam1992]

What happens to the density of the intake air when it is heated?

The density will decrease, surely this makes it easier to compress and therefore more efficient but there is less actual oxygen being compressed meaning less power produced by the engine. Is this correct?

 

[SteamKing]

Yes.

 

[rcgldr]

In addition to the somewhat less dense air, there's also the issue that combustion will produce less heat (energy) if the intake air is hotter.