see detonation knock sensor Koni
Noise which results from the spontaneous ignition of a portion of the air-fuel mixture in the engine cylinder caused by overly advanced ignition timing or use of incorrectly low octane fuel for that engine.
Detonation occurring in an engine's combustion chamber due to uncontrolled burning of the last portion of the air-fuel mixture. Knock results in the development of sudden excessive pressures, reduces engine efficiency, and can destroy engine parts.
"Technically detonation—in internal combustion engines occurs when fuel in the cylinder is ignited by the firing of the spark plug and smooth burning proceeds but some of the unburned mixture in the combustion chamber explodes before the flame front can reach it, combusting suddenly before the optimum moment of the four-stroke cycle. The resulting shockwave reverberates in the combustion chamber creating a characteristic metallic ""pinging"" sound.
the sound of knocking (as on a door or in an engine or bearing); "the knocking grew louder"
sound like a car engine that is firing too early; "the car pinged when I put in low-octane gasoline"; "The car pinked when the ignition was too far retarded"
The sharp, metallic sound produced when two pressure, or flame fronts collide in the combustion chamber. This could be the result of incorrect ignition timing, incorrect air/fuel mixtures, or the wrong grade (octane rating) of gas. Also known as Detonation.
1] A general term used to describe various noises occurring in an engine; may be used to describe noises made by loose or worn mechanical parts.  Preignition, or detonation. Also see anti-knock agent, carbon knock, diesel knock, engine knock, fuel knock, and spark knock
Characteristic metallic noise caused by the fuel mixture detonating.
Engine noise caused by detonation. See also: DETONATION.
A noise within an engine generally caused by detonation or preignition.