What does combustion knock, commonly known as ping, result from?

Combustion knock, commonly referred to as ping, occurs due to detonation in the combustion chamber of an engine. Detonation is an uncontrolled explosion of the air-fuel mixture that happens after the spark plug has fired, rather than in a smooth and controlled manner. This phenomenon can lead to sharp pressure spikes and vibrations in the engine, which is what is felt as knock or pinging sounds.

When detonation occurs, it contrasts sharply with the normal combustion process, where the fuel burns in a steady manner once ignited, contributing to smoother engine operation and power delivery. Detonation can be detrimental because it can cause severe engine damage over time if it persists.

While factors like ignition timing, fuel mixture, and oil pressure affect engine performance, the specific cause of combustion knock is primarily linked to the ignition and rapid combustion characteristics associated with detonation.