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Yeah, I guess I'm mixing up two things I don't know much about and trying to make it as simple as possible. Thanks for the clairification on detonation. So for the record, what is pre-ignition? I always assumed it meant lighting the fuel before the plug.

scanevalexec wrote:Yeah, I guess I'm mixing up two things I don't know much about and trying to make it as simple as possible. Thanks for the clairification on detonation. So for the record, what is pre-ignition? I always assumed it meant lighting the fuel before the plug.

Source: http://www.streetrodstuff.com/Articles/ ... Page_2.php

Key Definitions

Detonation
Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug.

Pre-ignition
Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite prior to the spark plug event it is classified as pre-ignition. The two are completely different and abnormal phenomenon.




I guess i was wrong a bit.

scanevalexec wrote:Yeah, I guess I'm mixing up two things I don't know much about and trying to make it as simple as possible. Thanks for the clairification on detonation. So for the record, what is pre-ignition? I always assumed it meant lighting the fuel before the plug.

It's at the end of the second, long-winded paragraph. Pre-ignition is almost always caused by carbon deposits that have become red-hot. It does mean lighting the fuel before the spark, it's just that the cause of ignition is different than with detonation. A higher octane fuel won't help much if you have pre-ignition.