Internal Combustion Engines
By higher octane number of spark ignition fuel, it is meant that the fuel has

Higher heating value
Higher flash point
Longer ignition delay
Lower volatility

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

Starts at 40° before bottom dead centre and ends at 30° after bottom dead centre
Starts at 40° after bottom dead centre and ends at 30° before top dead centre
Starts at bottom dead centre and ends at top dead centre
May start and end anywhere

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