Ancient History

[Darrell Norquay]

At 12:45 AM 9/8/96 -0500, John Faubion wrote:

>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.

Granted, the change of fuel makes a big difference, but the point was that
28:1 AFR is Very Lean, even for methane.  I did not say it was making
anywhere near maximum power at this AFR, again, it was making just enough
power for it's intended (constant) load.

>Mainly by reducing frictional losses at the lower RPM.

This would be more of a factor with a big block, since it has higher
frictional losses due to increased bore, stroke, stc.

>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.  :)

I wasn't aware of the magic number of 5252 RPM, how did you arrive at it? 
I can't see this applying to ALL internal combustion engines across the board...
As far as best cruise RPM, depends if it's a Honda 750cc four or a 512ci
Caddy, doesn't it?  You're right, I shouldn't have included HP in that list,
but the point was, that if all you're interested in is enough horsepower to
cruise, it doesn't matter how much horsepower you can make at some other
RPM.  Horsepower is proportional to RPM, so in theory, the higher the RPM,
the higher the horsepower.  Of course, this is ultimately limited by engine
design, VE, and a whole host of other things.






regards
dn
dnorquay at awinc.com