Scott,

1) Does AVgas and MOgas have the same energy potential and weight?

For all practical purposes, "Yep" and "Yep".

I know diesel fuel has more potential energy but also weighs more and

needs to be considered in the calculations.

6.1 lb/gal and 19,500 BTU/LB for Diesel, 6.05 lb/gal and 20,380 BTU/LB for
Gasoline (average values)

2) Could you explain to a slow learner {:>) exactly what the octane rating

means.  Not how to calculate it but what the fuel does. (i.e. compare 100
octane to 50 octane)

Long story but higher octane means the fuel has a greater resistance to
ignition.  It's actually HARDER to ignite which lets us advance timing, run
higher compression and other fun things that increases overall engine
efficiency.  Higher octane numbers have NOTHING to do with the energy
content.  Fortunately for the gas station owners, most folks don't believe
that and run the higher priced gas thinking they are doing good things for
their car.

3) When comparing AVgas motors to MOgas engines, do we need to compensate

for weight or octane?

Nope.  Just can't tune them the same.  Higher octane will let you TUNE the
engine for higher HP (within limits).  Feeding  high octane fuel to a "low"
performance engine (your basic car engine) doesn't hurt a thing but gives
you NO advantages, just higher cost and slightly increased maintenance
(plugs and sensors).

Feeding low octane fuel to a highly "strung" engine (race car, high
performance aircraft engines, etc) and the engine will eventually self
destruct from detonation.

And Paul is absolutely correct in that O2 sensors usually die quickly if
they see ANY lead.

Also keep in mind that 100LL (Low Lead) has a VERY high lead content.  The
LL description is a hold over from when it was compared to 110 octane and
other aviation fuels seldom seen any more.

Steve Webre
Broussard, LA

Actually Steve, many modern cars will have more power with premium fuel,
latest autoweek quoted a Honda engineer as saying that the new accord V6,
while not requiring premium fuel would gain 10HP using it.

Also, the Oz sensors don't seem to die quickly at all using 100LL, according
to Tracey and others on the list.

Other than that I totally agree with you.

Hans

 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
ACRE NL web site. Copyright 1998-2002 All world wide rights reserved.
http://home.earthlink.net/~rotaryeng/            http://www.linux.org