What Does Engine Knock Mean?

[LeilaFitz]

Engine knock is an abnormal combustion phenomenon that occurs when pressure and temperature inside the engine increase, causing atomized gasoline to explode without being ignited, resulting in severe engine vibration. Vehicles are equipped with knock sensors, which serve the following purposes: 1. To measure engine vibration levels and adjust the ignition timing when engine knock occurs; 2. To function as an AC signal generator, detecting the speed and position of the crankshaft. Knock sensors consist of: a magnetic core, permanent magnets, and induction coils. The working principle of a knock sensor is: when vibration or knocking occurs, it generates a voltage peak. The greater the knocking or vibration, the higher the peak voltage produced by the knock sensor. A certain high frequency indicates knock or vibration, and knock sensors can measure frequencies in the range of 5 to 15 kHz. When the control unit receives these frequencies, the computer readjusts the ignition timing to prevent further knocking.