Internal Combustion Engines
The fuel valve in a four stroke cycle diesel engine

Opens at 15° before top dead center and closes at 20° after top dead center
Opens at 15° after top dead center and closes at 20° before bottom dead center
May open and close anywhere
Opens at top dead center and closes at bottom dead center

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Internal Combustion Engines
The exhaust valve in a four stroke cycle petrol engine

Opens at 50° before bottom dead center and closes at 15° after top dead center
Opens at 50° after bottom dead center and closes at 15° before top dead center
May open and close anywhere
Opens at bottom dead center and closes at top dead center

ANSWER DOWNLOAD EXAMIANS APP