Just who invented this imaginary term "Pre-Detonation"? There's "pre-ignition" which is a flame front that begins somewhere other than at the tip of the spark plug, and "detonation" which is uncontrolled, possibly explosive burning of the fuel/air mixture. How did those terms get combined? In over 60 years of tinkering with engines and spending decades teaching the mechanical trade, I've never heard that one before!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!