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Originally Posted by Gary in BR
I hear of detonation alot but what is it exactly??
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cars are designed to combust fuel. this means that a controlled burn of the air / fuel mixture occurs. the expansion of this reaction pushes the pistons down. this all occurs in a controlled fashion at controlled timing.
detonation occurs if the fuel ignites too early in the cycle. in some cases, pressure and heat ignite the air / fuel mixture before the spark plug fires. if the piston is far enough before top dead center, there is not enough pressure to control the burn and an explosion (detonation) occurs. this can also occur because the spark plug ignites too early due to poor tuning. this detonation is NOT controlled; it is violent, uneven and rapid. it can destroy a valvetrain or break pistons.
higher octane fuel helps to prevent this because it is less volitile and not as likely to prematurely ignite (higher flash point).