Internal Combustion Engines
A fuel of an octane number rating of 75 matches in knocking intensity as a mixture of

75% iso-octane and 25% normal heptane
75% normal heptane and 25% iso-octane
75% petrol and 25% diesel
75% diesel and 25% petrol

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

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

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