I am willing to wager that there are more discussions about octane than
most know about the subject.
While this isn't "rocket science" (we don't use gasoline), it is still
known to the members of the SAE, and
well rounded enthusiast.
"octane", per se, is correctly known as the ability of a fuel to resist
pre detonation. But how is it determined?
There are actually two approved methods. The "Research Method", which
uses the chemical make-up of the
fuel, and the "Motor Method", which is the result of direct precision
engine testing. The number on the gas
pump is the arithmetic average of both test methods.
The "Motor Method", having performed it in college, requires a precision
built test motor to rigorous standards.
The motor is a simple one cylinder (as I recall) precision engine with
screw adjustable compression ratio, a
dynamometer to run under load, and a minimum of two calibration runs,
and a fuel test run.
The calibration runs are made with N-normal heptane, defined as "0"
octane, and with Iso-octane, defined as 100 Octane.
During these calibrations, the engine is under load, and the compression
ratio is adjusted just below the ping level. These are defined as the
"0" and "100" octane levels. the fuel being tested is then run, and the
compression ratio increased to pinging. The test fuel's octane level is
the equivalent ratio between the "0" octane and the "100" octane tests.
Most states, that require labeling, use the average result between the
Motor Method and the Research method.
For what it is worth.
For more information, the SAE has this section of 1757 discussions of
"Octane". If the link is not working, try typing
in the reference, or searching "Google.com" for "SAE"
http://www.sae.org/servlets/SiteSearch?charset=iso-8859-1&ht=0&qp=&col=portal&qs=&sae_qt1=&qc=&pw=100%2525&ws=0&la=en&qm=0&st=1&nh=25&lk=1&rf=0&oq=&rq=0&si=1&ql=&jsp_name=simplesearch.jsp&qt=octane&x=0&y=0&ofType=ALL
<http://www.sae.org/servlets/SiteSearch?charset=iso-8859-1&ht=0&qp=&col=portal&qs=&sae_qt1=&qc=&pw=100%2525&ws=0&la=en&qm=0&st=1&nh=25&lk=1&rf=0&oq=&rq=0&si=1&ql=&jsp_name=simplesearch.jsp&qt=octane&x=0&y=0&ofType=ALL>
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Steve Laifman
Editor - TigersUnited.com
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