When a piece of sharp glowing piece metal or glowing ember of carbon lights the fuel mixture before it is time to it is called pre-ignition. Pre-Ignition does not nessecerily do damage to the engine apart from giving poor performance for the fuel used, but there can be a flow-on effect from Pre-igntiion. It can cause two fires to light in the combustion chamber. With the two fires aproaching eachother from different directions, the mixture trapped between them is squeezed between them quickly building heat and pressure until it detonates. Pinging is an often used term to describe an engine rattle when accellerating. The term "pinging" is often confused between Pre-Ignition and Detonation. Pre-Ignition will cause a loss of performance as the pressure rise that does the work is mistimed. Detonation is an severe impact taken inside the cylinder, more like an explosion than a controlled burning of gases.