Definition: Detonation (generally caused by fuel with a low octane rating) is the tendency for the fuel to pre-ignite or auto-ignite in an engine's combustion chamber. This early (before the spark plug fires) ignition of fuel creates a shock wave throughout the cylinder as the burning and expanding fuel air mixture collides with the piston that is still traveling towards top-dead-center. The resulting knock/ping is the sound of the pistons slamming against the cylinder walls. Severe detonation can break pistons and destroy engines.
Pronunciation: det-n-ey-shuh
Also Known As: pre-ignition,
auto-ignition,
pinging, or
knocking
Examples: Use of low-grade fuel can cause an engine to detonate.