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Trigger Wheel, Ignition Advance, and Octane


There has been a lot of discussion/debate about the right octane to use for the Trigger Wheel.  Most people have reported either audible detonation or "pepper" spots on the spark plugs when attempting to run regular or mid-grade gas.  The pepper spots are carbon deposits in the engine that have been dislodged by the violence of the explosion created by autoignition.

From the April 1995 edition of Muscle Mustangs and Fast Fords (p.40):

". . .  the worst kind of detonation is the kind you can't even hear. . .

In automotive terms, detonation is uncontrolled combustion.  Under normal conditions, the burning of the air/fuel mixture is controlled by the ignition timing and compression ratio.  Under ideal conditions, the cylinder pressure would be peaking just as the piston reaches top dead center.  At this point, the mixture is fired and the exploding gas forces the piston down.  It's when the pressure peaks when the piston is still coming up that detonation begins.  In this case, when the timing is too far advanced, the spark is firing far before TDC and the exploded gas tries to resist the upward motion of the piston.  Instead of waiting for it to cross TDC and force it down the bore, it's trying to force it back before it even reaches TDC.  Because the piston is fighting the explosion, cylinder pressure escalates catastrophically."

My advice:  Run premium.  If you want to play...

 Timothy Skelton - all rights reserved  F6Rider Webzine    ShopTalk    Just Pics    Valkyrie Hot Links