Internal Combustion Engines
Pre-ignition is caused by the spontaneous combustion of the mixture before the end of the compression stroke, and is due to

Any one of the listed here
Overheated spark plug points
Red hot carbon deposits on cylinder walls
Cylinder walls being too hot

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Internal Combustion Engines
The fuel valve in a four stroke cycle diesel engine

Opens at 15° before top dead center and closes at 20° after top dead center
May open and close anywhere
Opens at 15° after top dead center and closes at 20° before bottom dead center
Opens at top dead center and closes at bottom dead center

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Internal Combustion Engines
Supercharging is the process of

Providing forced cooling air
Supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere
Supplying compressed air to remove combustion products fully
Injecting excess fuel for raising more loads

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