Ancient History

[John Faubion]

> power from the engine is a bad idea.  Different story at light loads or
> cruise. I have seen industrial methane powered stationary engines running
at
> AFR's of 28:1, and they last a longggg time.  Once you get the engine

Whoa! As soon as you changed fuel (methane) you changed the stoichiometric
ratio! So your comparison of 28:1 on methane means absolutely nothing when
related to gasoline. Its an apples to oranges. In addition you wouldn't
want to lean out an engine to reach maximum power. Max power will occur
with a slightly richer than stoich mixture. While best efficiency will
occur leaner than stoich.

> etc).  Ask any pilot, he will tell you that as a plane reaches cruise
> altitude and speed, you lean it out until the engine is just making
enough
> power to maintain cruise conditions.  This gives maximum fuel economy.

True.

> right, a low numerical rear end ratio or overdrive does increase mileage,
> but lowering RPM would also decrease HP and VE, and thus overall engine

Mainly by reducing frictional losses at the lower RPM.

> output. If you set it all up jesssstt raaht, so that VE, torque, and HP
all
> peak at a low enough RPM, which also coincides with your normal cruising
> speed, voila`, mega-MPG.  

Of course the ONLY rpm where torque, horsepower and VE could all peak at
the same time is at 5252 rpm. Not exactly most people's idea of a best
cruise speed! Now if your cam duration is short enough keep the engine
speed down, reducing the overall frictional losses (which are exponential
with regard to rpm) and then geared for this lower peak torque (at which VE
also peaks and usually BSFC) than you could have great mileage. I know this
is sort of what you were eluding to but just not getting there on the same
track.  :)

John Faubion
jfaubion at beaches.net