Internal Combustion Engines
In order to eliminate knocking in compression ignition engines, there should be

Low compression ratio
Short delay period
Late auto-ignition
High self ignition temperature of fuel

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

Starts at top dead center and ends at bottom dead center
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
May start and end anywhere

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