Posted by TParker (IP: 4.33.1.93) on August 05, 1999 at 20:08:23:
In Reply to: High Octane...Another point of view posted by Sparks on August 05, 1999 at 19:00:05:
: I am not a Chemist.
OK! niether am I.
: My soapbox is based on Motorcyle experience.
We were not talking about Motorcycles here.
: With only two cylinders, minor changes are more noticable, and other than Posers, most riders are very sensitive to thier machine.
you are right.
: The theory of internal combustion is that the best power can be reached when detonation takes place at Top Dead Center (TDC) or just slightly after.
True.
: Most engine tuning methods are based upon the cylinder at TDC.
True
: Reality intrudes and heat, pressure, and other factors can cause detonation to occur before TDC. Higher octane resists detonation. In a 2 cylinder engine, there is a noticable and measuarable increase in performance and mileage with the use of higher octane fuel.
True.
This is in a very clean and well tuned engine, alternating between 2 gallon tankfulls of high vs. low octane.
OK!
: In 6 or 8 cylinders, the difference may not be as pronounced, but one can logically have the theory that higer octane may have an impact on efficiency.
Very slight!
: Race fuel is High octane.
Very true, but like motorcycle engines race engines use a much high compression than ordinary car engines do. Also motorcycle use a distributor less ignition system that allows the builder/manufacture to tune these engine to operate closer to TDC than distributor engines. And motorcycle engines and race engines operate at much high RPM's which also contributes to high compression and an icreased tendance towards predetonation, which is reduced with higher octane fuel, hence better perfomance.
: Any other Points of view? T.L. I would be especially interested in hearing from.
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