Engine Knocking In Bike & Scooter Explained | Bike Maintenance & Mileage Tips | Engine Life Increase

Описание: Knocking is a phenomenon of generating unwanted pressure wave which create unpleasant sound and can damage engine wall during combustion in engines.

Knocking is mainly associated with SI engines. It depends on auto ignition quality of fuel. The higher auto ignition temperature causes lower down knocking tendency.
When the piston reaches at TDC after compression, the spark plug produces spark which ignite the compressed mixture and starts the combustion process. It ignites only those part of mixture which is in contact with spark plug and generates a main flame front which further ignites the whole mixture.

This will generate a high temperature and pressure force inside the cylinder.
This burnt part of mixture (combustion products) separate the fresh mixture from spark plug to the other end of the cylinder.
As this flame front expands, it compressed the unburned part of the charge.

This compression increases the temperature and pressure of unburned part of mixture. If the temperature of this part reaches its auto ignition temperature, it will ignite from other end and a new flame front starts moving towards opposite direction of main flame.
When both of these flame fronts collide, it will generate a high pressure wave which produces an unpleasant sound and also damage the cylinder wall.

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