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From: djl@fisher.UUCP (Dan Levin  N6BZA )
Newsgroups: net.auto
Subject: Of Octane and Mothballs and such...
Message-ID: <762@fisher.UUCP>
Date: Mon, 23-Sep-85 11:01:25 EDT
Article-I.D.: fisher.762
Posted: Mon Sep 23 11:01:25 1985
Date-Received: Wed, 25-Sep-85 12:39:54 EDT
Distribution: net
Organization: Princeton University.Mathematics
Lines: 56

On the topic of octane methods (this gets bounced around now and then,
seems like time again..):

One methed (the R(esearch) method) is to calculate the theoretical octane
rating of a fuel based on its components.

The other (the M(something) method) is to take a one cylinder engine, and
change the compression until it just barely knocks on your test fuel.
Then find the iso-octane and hexane(?) mix that just knocks in the same engine.
Since the octane rating is literally the percentage of iso-octane in the
equivilent octane/hexane mixture, this rather pragmatic test will reveal
the 'true' octane rating.

The R+M/2 you see on the pumps in some states means that the octane rating
was calculated based on the average of these two methods.

About mixing fuels:

I am told by people I trust that mixing leaded and unleaded fuels produces
a very interesting resulting octane rating.  In particular, mixing leaded
regular (89 octane) in equal parts with unleaded regular (87 octane) will
result in a ~90 octane fuel.  Of more interest to older car fans, mixing
leaded regular (89) with unleaded super (92) will give you at least
92 octane fuel with enough lead in it for your valves.  Your milage may
vary based on the amount of alcohol in the unleaded gas.

I do not think that mixing leaded fuels of differing octane ratings
will do anything unexpected.

About mothballs: ( No flames from chemists on minor points please...)

Seems that gas is basically just a mixture of carbon chains (in essence at
least), the longer the average chain, the higher the effective octane
rating.  Also seems that some mothballs (there seem to be two kinds, I do
no suggest getting the wrong one!) are 100% (in fact lab grade, although
not USP) naphthalene(sp?).  Seems that naphthalene is a very long carbon
chain, and that it dissolves fairly quickly ( ~ten minutes or less) in
gas.  I have had several chemically oriented Ivy League types consider
possible bad side effects, and they all admit that naphthalene should
burn completely at combustion chamber temps, and that it is very, very
stable stuff, sufficiently so that it will not react and form any nasty
compounds in my engine.

This all boils down to saying that adding 3 real moth balls per gallon
to my tank will make my car run on leaded regular (89), which means that
it is bringing the octane up to ~92 or so.

So enough on fuels for now.  For those of you who are wondering, I drive
a '65 Mustang fastback with a 10.5:1 c.r. 289, and it doesn't like
87 octane unleaded fuel too much :-)

-- 
			***dan

{allegra,astrovax,princeton,twg}!fisher!djl
The misplaced (You call *that* a ski slope??) Californian