FFF has got it pretty much spot on, but I don't understand how adding heat to the airflow would make the burn more uniform. This is more dependant on the ratio of the fuel to air rather than as a function of the charge temperature. The design of most light aircraft engines means that they are in no way optimised for either efficiency or power outputs when compared to modern engine designs. Low compression ratios, manual mixture control, air cooling, 2 valves per cylinder, push rods etc...........
If all we had to do was to increase the temperature of the mix to increase combustion efficiency then life would be very easy for engine designers!! You really want as much air as possible going into the cylinders, therefore the colder the better as it is more dense and maybe add a turbo/supercharger for effect aswell. If increased heat aids combustion, then why do we have intercoolers to cool the charge down and help increase power outputs?
Cold air=good power, hot air=less power.
Where did you come across this idea?