If the fuel ignites before the ignition fires, it’s called preignition. Detonation is caused by excessive heat and/or pressure. It occurs after the spark plug wires. Octane is only a measure of the fuel’s ability to resist detonation. It has nothing to do with making HP. Raising the compression ratio makes more HP, and sometimes you need more octane to prevent detonation. Detonation is a real HP killer!