-:::Valve Timing for Four Stroke Petrol Engine Cycle:::-
The petrol engines are also known as a spark-ignition engines. The valve timing diagram for a four-stroke cycle petrol engine.
The following particulars are important for a four-stroke cycle engine regarding the valve timing
A) The inlet valve opens (IVO) at 10-20 degree before the top dead center (BDC).
B) The compression of charge starts at 30-40 degree after BDC and ends at 20-30 degree before TDC.
C) The ignition(IGN) of charge takes place at 20-30 degree before TDC.
D) The expansion starts at 20-30 degree before TDC and ends at 30-50 degree before BDC.
E) The exhaust valve opes (EVO) at 30-50 degree before and closes at 10-15 degree after TDC.
Notes- i) The inlet valve of a four-stroke I.C engine remains open for 230 degree
ii) The charge is compressed when both the valves (.i.e, inlet valve, and exhaust valve) are closed.
iii) The charge is ignited with the help of a spark plug.
iv) The pressure inside the engine cylinder is above the atmospheric pressure during the stroke.