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Re: Spark Plugs

To: PilotRob@webtv.net (Robert E. Shlafer), gjbranch@attbi.com (Geoff Branch)
Subject: Re: Spark Plugs
Date: Thu, 13 Jun 2002 10:15:38 -0700
Cc: grbyrns@ucdavis.edu (Glen Byrns), spridgets@autox.team.net
References: <"Geoff Branch" <gjbranch@attbi.com>
Bob -

In my neighborhood (Sunland, CA) the local Chevron sells "racing fuel" that 
is available in 95, 100 and 105 octane and in no-lead or low-lead 
formulations.  It runs $4 to $6 per gallon.  A Union station nearby has a 
similar variety of "76" racing fuel.  It's sold without road tax charges 
and is not to be used in vehicles that will be operated on public roads.

Clay L.
'67 Sprite

   At 04:30 AM 6/13/2002 -0400, Robert E. Shlafer wrote:
>You know-
>Normally, I am not a proponent of Avgas
>for auto use because the formulation of these fuels are so very
>different considering the very different applications;
>Avgas being "built" for continuous low rpm
>piston operations at any pressure altitude
>up to about 30,000 feet, plus.
>The "volatility" and "burn" characteristics
>are different to the extent avgas "go's off"
>a lot sooner in the automotive application
>then auto gas of the same octane number
>so that ignition timing actually has to be
>retarded to avoid detonation in the case of
>the auto engine. To the extent this is the
>case nulifys the apparent higher octane
>number of Avgas when used for other
>internal combustion applications.
>However, at some point in the octane game the auto engine will feel an
>Fr'instance, an auto engine running on
>91PON and timed accordingly to do so
>just short of detonation/pre-ignition might
>not get the full benefit of the 9 greater
>octane number of 100LL Avgas due to the
>foregoing differences in formulation as
>previously outlined but, there might be a
>net gain of 1/2 that despite these differences. And 1/2 a loaf might be
>than none in this case, eh?
>And, Geoff is correct. 100LL is "low lead"
>as compared to the leaded Avgas of
>"yesterday", not the leaded automotive
>gas of yesterday; "low lead" comparison
>in this case, is a case of apples & oranges
>rather than apples an apples.
>The lead content of 100LL (low lead)
>Avgas is far greater than it's automotive
>"unleaded" counterpart.
>You might try mixing this stuff or using it
>"straight up" and see if you might not be
>able to run a little more advance in the
>normally aspirated applications or a little
>more boost in the case of "blown" motors
>(a la Glen Byrnes' gorgeous little Bugeye).
>What would really give one a clue as to
>"improvement" would be an Air/Fuel ratio
>monitor set-up. This would be the way to
>go and would tell the tale in objective terms, taking all of the
>guesswork out of
>this!! :)
>I'd sure be interested in hearing the results!!
>Cap'n. Bob
>     '60 :{)

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