PPRuNe Forums - Carb Heat to warm engine?

tcamiga said in the backward post:

Quote:

The application of Full Carb heat was to keep as much heat as we could in the engine internals to reduce mechanical thermal shock damage due the changes in temp when the throttle was snapped shut.

I've also heard this regarding engine warmup after start from Tim Tucker at the robbie safety course. Makes sense... warm air, warm engine.

tc also says (and I agree) that carb heat

Quote:

... also made the mixture slightly richer...

My confusion...

A richer mixture will make an engine run cooler... so, what ends up being the net result? I suppose I should have done a little experimentation when I had access to a piston heli, but right now I don't, so, what are your findings...

At a fixed throttle (say closed as it applies to throttle chops and engine warm up) does the cyl heat temp increase or decrease in response to carb heat position?

Of course as stated on TC's site, there are more important reasons for full carb heat at low throttle settings, but for engine warm up?

On a related note, I prefer to keep carb heat off during warm up, especially in conditions conducive to carb ice... that way when the student pulls it on during runup (make sure they leave it on long enough to actually melt anything), and the RPM increases 10% as the ice melts, they get a graphic demonstration of carb ice while safely on the ground.