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Re: Ignition timing

To: MG Board <mgs@autox.team.net>
Subject: Re: Ignition timing
From: Float-by Shooter <packrat@orca.cordovanet.com>
Date: Thu, 26 Aug 1999 17:36:03 -0800 (AKDT)
On Thu, 26 Aug 1999, Larry Colen wrote:

I hear it said all the time that avgas is not good for ground
applications, but I have yet to hear a satisfactory answer for why this is
true.  My brother had to drain his airplane tanks a couple years ago when
disassembling it, and he put the avgas into his OCP (old chevy pickup).
Claimed that it ran better than ever before.  That is probably also a
commentary on the quality of our automotive fuel here in Cordova, AK.

> The reason that avgas is a BadIdea (tm) is that it has a lot of additives
> in it so that it will work at a wide range of altitudes and temperatures.
> The effect of this is that:
>  1) it is not optimized for near sealevel at reasonable temperatures, 
> as autogas is and 

One of the more common light plane accident patterns involves misjudging
the amount of power/lift available for takeoff vs. available runway
length.  I am quite certain that if avgas was truely not optimized for
maximum performance at sea level and word got out, there would be an
uproar over this in the aviation community.

>  2) the additives do nasty things to rubber and plastic parts in your
> fuel system, unless they are TrickAviationParts (read:$$$$) that are
> specially designed to not disolve in AvGas.

Since I am building my own aircraft, I have researched fuel compatibility
issues somewhat and my findings have been opposite yours.  There have been
a number of problems with the additives in autogas wreaking havoc on some
aircraft fuel system, most notably composite fuel tanks.  It's been awhile
but I think I read about this at the canard aviators website, at
www.canard.com.

AFAIK, the most notable attitives in avgas are stabilizors to keep the
fuel from going bad if it sits in the tanks for a while, and lead.  If you
have a modern vehicle with an oxygen sensor you should NOT use avgas since
it will foul the sensor.

> > could go to a racing fuel
> > or octane booster.  Note that aviation fuel will not work

I have been told that 100LL avgas averages about 103-104 octane, if you
need more than that you will have to get a special racing fuel.

But don't take my word for it, do some research on the issue for yourself.

Just my opinion as a low-time private pilot.

======================================
Del Rawlins--  packrat@cordovanet.com
http://www.cordovanet.com/~packrat/        
"I'd like to find your inner child and 
kick its little ass"  --The Eagles



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