wrote:


Is it fair to say that with a particular engine type, that SFC can be
used to estimate HP? (because that's what the equations are doing
seems to me)



Varies somewhat with an engine's efficiency. Most normally aspirated
air cooled engines are in the .42 to .45 range. That's leaned out to
best efficiency remember. Car engines are I believe, around or little
under .4 by using electronic fuel injection and low friction (narrow)
bearings etc. and the more efficient diesels in the mid .3s. IIRC, the
turbocompound radials like the R3360 were in the high .3s, among the
most efficient gas engines built, even if they didn't run like that very
long before something went south.

I think .45 lb/hp/hr will give a valid fuel consumption number, accurate
to a few percent, for pretty much any power setting that can be done at
lean mixture on just about any gasoline air cooled, carburated engine.

John