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The objective of knock control strategies is to attempt to optimize the trade-off between protecting the engine from damaging knock events and maximizing the engine's output torque. Knock events are an independent random process. [8] It is impossible to design knock controllers in a deterministic platform. A single time history simulation or ...
LSPI events are random and infrequent, and their effects on impacted vehicles can include very high-pressure spikes, loud knocking noises and sometimes catastrophic engine damage. [4] It's commonly known as "Detonation or Knock". Engine management systems can overcome pre ignition by the means of a knock or detonation sensor.
The reduced engine speeds allow more time for autoignition chemistry to complete thus promoting the possibility of pre-ignition and so called "mega-knock". Under these circumstances, there is still significant debate as to the sources of the pre-ignition event. [3] Pre-ignition and engine knock both sharply increase combustion chamber temperatures.
To detect knock, a piezoelectric knock sensor (basically a microphone) bolted to the engine block responds to unique frequencies caused by engine knock. The sensor generates a small voltage that is sent to the electronic control unit , which processes the signal to determine if, in fact, knock is occurring.
An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs.
Engine knocking (detonation) can be caused by poor quality fuel, an engine fault or if inappropriate fuel and/or ignition settings are trialled/chosen while engine tuning is taking place. If the detonation is severe, the cylinder pressure can increase to eight times above normal pressures, [ citation needed ] which can cause the cylinder head ...
Pressure in cylinder pattern in dependence on ignition timing: (a) - misfire, (b) too soon, (c) optimal, (d) too late. In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke.
The torsional deflection of a simple cylinder cannot radiate efficiently acoustic noise, but with particular boundary conditions the stator can radiate acoustic noise under torque ripple excitation. [8] Structure-borne noise can also be generated by torque ripple when rotor shaft line vibrations propagate to the frame [9] and shaft line.