I'm not certain what heating the air would do but further reduce the air density which would theoretically mean you would need less fuel to maintain the same air/fuel ratio - so that might reduce the risk (to a piston engine) of running tool lean - but would still cut down the fuel consumption by permitting less fuel and yet maintain the same air/fuel ratio.

 

The only down side I have notice in  flying WOT (at cruise altitudes) with reduced air/fuel ratio is that the engine occasionally will miss - not enough to worry about (unless you worry about things like that {:>), generally just enriched the fuel mixture a bit stops it.

 

Having said that - I have never compared operating at reduced throttle setting to WOT so can't say how much (if any) difference it makes - theoretically, it should make some difference.

 

FWIW that's my $0.02

 

Ed

Everything Ed said, and:

 

A) Wide open throttle keeps cylinder filling closer to 100% which means effective compression ratio stays higher, which means that more heat of compression is available to maintain vaporization which means more of the available fuel gets burned.

 

B) Adding heat to the intake air raises heat of compression and improves vaporization and allows for an even leaner mixture to burn completely.

 

C) Although detonation is charge temperature dependant, super lean mixtures produce slower flame front speeds and mimic ultra high octane fuels, so detonation should not be a factor.

 

This is not at all damaging to the engine. Less fuel per revolution means lower temperatures and less stress.

All big radial engines were run well lean of peak EGT. Lest TWA would never have made it across the Atlantic. Lest the P-38s would never have made the round trip to kill Yamamoto. Even works on supercharged and turbo charged engines.

 

Lynn E. Hanover