Detonasjonstopp

Detonasjonstopp is a phenomenon observed in internal combustion engines, specifically those operating on a lean air-fuel mixture. It is characterized by a rapid and uncontrolled combustion event that occurs after the normal spark ignition. This abnormal combustion is often accompanied by a sharp, metallic knocking sound, hence the name "detonasjonstopp" which translates to "detonation stop" or "detonation knock" in English.

The primary cause of detonasjonstopp is the auto-ignition of the unburned fuel-air mixture in the combustion chamber. While the spark plug initiates the main combustion event, the elevated temperature and pressure within the cylinder can cause pockets of the mixture to reach their auto-ignition point before the flame front from the spark plug arrives. This leads to secondary, spontaneous combustion waves that collide with the primary flame front, creating shock waves.

These shock waves are responsible for the characteristic knocking sound and can lead to significant stress on engine components, including pistons, connecting rods, and crankshafts. Prolonged or severe detonasjonstopp can cause severe engine damage. The phenomenon is more prevalent in engines designed for high efficiency, which often operate with leaner fuel mixtures and higher compression ratios. Factors such as engine temperature, air-fuel ratio, ignition timing, and the octane rating of the fuel all play a role in the occurrence of detonasjonstopp. Modern engine management systems often employ knock sensors to detect detonasjonstopp and adjust ignition timing or fuel delivery to prevent it.