On Thu, 31 May 2007 00:25:09 GMT, Jerry Wass
wrote:

GeorgeB wrote:
On Wed, 30 May 2007 15:10:29 GMT, Jerry Wass
wrote:

Don't like to beat a dead horse, but--

As C.S. Nixon said--"let me make myself perfectly clear"

I agree that a gallon of Mogas has more btu's than a gallon of Avgas


The main reason being--1 gal mogas= 7.422 lbs.
1 gal avgas= 6.978 lbs.

Q.E.D.

Per Wikipedia, and my friends who do weight/balance calcs, the avgasd
number above is alittle, like 18%, off ...

Avgas has a density of 6.02 lb/US gallon at 15 °C, or 0.72 kg/l, and
this density is commonly used for weight and balance computation.
Density increases to 6.40 lb/US gallon at -40 °C, and decreases by
about 0.5% per 5 °C increase in temperature.[3]

[3] is # ^ MacDonald, Sandy A. F.; Isabel L. Peppler [1941] (2004).
"Chapter 10. Airmanship", From The Ground Up, Millennium Edition,
Ottawa, Ontario, Canada: Aviation Publishers Co. Limited, pp. 265,
261. ISBN 0-9680390-5-7.

AirBP says "AVGAS 100LL: Aviation Gasoline for Reciprocating Engines
with lower maximum lead content. Color: Blue. Flash point: Below 0
degrees F. API gravity: 64-7. Relative density: .6582-.7238".

Water is likely the density of 1.000, and is about 8.34 lb/gal
suggesting the 6 lb/gal is a pretty good number.

I'd like to know the source for your 6.978 ...

My Sources a a 5 gal can of Avgas bought for break-in purposes on my
rebuilt engine--about two weeks ago, and kept in a S.Steel can of the
variety used for holding Coke/Pepsi syrup at vending booths.--air tight.
good for 125 psi(has to hold the CO2 pressure)

a 5 gal jug of Mogas bought a week ago for my lawnmower.

a 250 CC graduated Lab-type beaker, & a metric balance type scale
accurate to 0.1 gm.

The Avgas weighed 168.3 gms/250cc---The Mogas weighed 179.0gm/250cc----

Please let me know If I made any mistakes in the conversion----If not,
I'll re-weigh two more samples tomorrow..

Sounds right to me. SG has an effect on the energy content, but it is
NOT an indicator of octane. MoGas has a higher energy density than
AvGas (generally).

--
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