Knock sensors such as the Ford knock sensor are small piezoelectric microphones that are embedded on the engine block to detect engine knock. A knock sensor is connected to the electronic control unit of the engine. When engine knock is detected, the knock sensor sends electrical signals to the ECU. In turn, the ECU makes proper adjustments by reducing the ignition timing. Ignition timing is reduced by slowing down the firing of the sparkplugs and by reducing fuel injection. Engine knock has a characteristic frequency that can be detected by the knock sensor. When engine knock occurs, its shockwaves reverberates throughout the engine block. Engine knock vibration can be picked up by the knock senor even at lower intensity.
Engine knocking occurs when the fuel/air mixture explodes during ignition instead of rapidly being burned. Engine knock disrupts the normal combustion process of the engine. Consequently, power will be lost. When engine knocking occurs, the smooth burning of the fuel/air mixture is interrupted. Residual fuel will be left unburned. Hence, fuel efficiency is drastically affected. The pistons will not have enough time to adjust to the sudden explosion. Ironically, although engine knocking or fuel detonation is more energetic than normal combustion, it does not optimize the energy of the fuel. It causes sudden and premature buildup of pressure that disrupt the four stroke cycle of a gasoline engine.
Under normal combustion, the fuel/air mixture is ignited at a controlled and orderly manner. However, when engine knock occurs, this order is disrupted. Typically, combustion is initiated by the sparkplug during power stroke right after compression stroke. Combustion occurs when the crankshaft is at 15 to 40 degrees position prior to TDC or top dead center. Top dead center refers to the point of maximum compression. Maximum compression allows the fuel and air to thoroughly mix. This minimizes any residual or unburned fuel. However, engine knock prevents the optimal combustion of fuel. Consequently, fuel energy is wasted and residual fuel is formed.
Engine knocking or fuel detonation is detrimental to the normal function of the engine. The rapid buildup of pressure at the wrong time creates problems. Since pressure seeks to be released, it may cause the gaskets to rupture. In extreme cases, the pistons and crankshaft might become dislocated. The damage is sometime irreversible. However, this scenario can be prevented if a knock sensor is installed on the engine. A knock sensor monitors and helps in counteracting engine knocking. If you are looking for reliable knock sensors, Parts Train is the ideal online store to do your shopping.