Internal Combustion Engines
In a four stroke cycle petrol engine, the expansion

May start and end anywhere
Starts at 30° after top dead center and ends at 50° after bottom dead center
Starts at 30° before top dead center and ends at 50° before bottom dead center
Starts at top dead center and ends at bottom dead center

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Internal Combustion Engines
In a typical medium speed 4-stroke cycle diesel engine the inlet valve

Opens at 20° before top dead center and closes at 35° after the bottom dead center
Opens at top dead center and closes at bottom dead center
Opens at 10° after top dead center and closes 20° before the bottom dead center
May open or close anywhere

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Internal Combustion Engines
Detonation is harmful due to

Increase in the rate of heat transfer, there is a reduction in the power output and efficiency of the engine
High intensity of knock causes crankshaft vibration and the engine runs rough
None of these
Excessive turbulence which removes most of the insulating gas boundary layer from the cylinder walls

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