A. Opens at 20° before top dead center and closes at 35° after the bottom dead center B. Opens at top dead center and closes at bottom dead center C. Opens at 10° after top dead center and closes 20° before the bottom dead center D. May open or close anywhere
A. Air used for combustion sent under pres-sure B. Forced air for cooling cylinder C. Burnt air containing products of combustion D. Air used for forcing burnt gases out of engine’s cylinder during the exhaust period
