The Murphy Builders Site

I haven't picked up the Kitplanes yet but...
150/160 isn't the issue per se with car or av gas.
The issue there is
compression. Higher compression increases tendency
to predetonate or
knock and higher octane helps avoid this. As long
as compression is not
raised above mid 8:1 I believe, high octane (91,92)
car gas should suffice
(this from a conversation I had once with Lycon.) I
believe the typical
160 "high compression" piston 0320s is higher than
9:1 -- I know it precludes
use of car gas anyway.

The issue of water (from ethanol) is a separate one.
Some believe it is
acceptable in Lycomings due to the carb intake
routing, not acceptable in
Continentals. I don't think anyone would argue
ethanol doesn't add at least
some risk for carb icing -- why the heck would there
be carb heat on a Lyc
designed for non-ethanol fuel in the first place.
But, I've heard plenty argue
that some ethanol is acceptable if carb heat
practices are ardently followed --
and depends on climate too --- but for what level
of ethanol I don't know.
It seems reasonable to me to weigh the up/down sides
of ethanol against the
longer term up/down sides of lead.

Gas additives (besides ethanol) is yet a third
issue.
Gotta go pick up that Kitplanes article!
-Ben

I read the fuel article in Kitplanes. What I got

from it is that lead is not

the issue with airplane engines, but octane, and

ethanol is definately bad

because it traps water in the fuel which can

freeze. It went on to say that

we could run on lower octane gas with improved

ignition systems with

variable timing.
How does the 150/160 hp, car gas/avgas

relationship tie in? Is car gas only

approved in 150 hp engines because detonation

caused by lower octane
car gas

is less damaging to those engines? Are any 160hp

engines ok with car gas?

Thanks
Jesse

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If you check Peterson's AutofuelSTC site you will find
that 0-320 160hp can use autogas with the stipulation
it is 91 octane or higher. Some 0-360's are also
included that have this stipulation.
Keith R661

From: Ken <klehman@albedo.net>
Reply-To: <rebel-builders@dcsol.com>
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] RE: engines/fuel
Date: Thu, 11 May 2006 22:49:21 -0400

That makes sense as the highest compression normally aspirated aircraft
engine that I'm aware of is still lower than car engines that typically
require high octane mogas. High octane avgas was really developed for
highly boosted engines and arguably that was after many of the certified
piston engines were designed...

Even ignoring environmental issues and fuel cost, I truly believe that
maintenance will be substantially cheaper for engines that run much less
lead than pure 100LL. It is too easy to blame auto fuel for any
unrelated problems that develop while using it. Alcohol can be nasty
though if it separates and exposes some gaskets, hoses, or metals to
high concentrations while the aircraft sits unused.
Ken

Keith Leitch wrote:

If you check Peterson's AutofuelSTC site you will find
that 0-320 160hp can use autogas with the stipulation
it is 91 octane or higher. Some 0-360's are also
included that have this stipulation.
Keith R661

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