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

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

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Internal Combustion Engines
In a typical medium speed 4-stroke cycle diesel engines

Exhaust valve opens at bottom dead center and closes at top dead center
Exhaust valve opens at 35° before bottom dead center and closes at 20° after top dead center
Exhaust valve opens just after bottom dead center and closes just before top dead center
May open and close anywhere

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