Engine Valve Timing Diagram

 

Engine Valve Timing Diagram

 

 

The inlet valve usually opens few degrees before the piston reaches TDC in its exhaust stroke. It closes after quite a few degrees of piston reaching the BDC, i.e. when the piston starts to move up the cylinder in compression stroke. In suction stroke, the air/fuel mixture or charge gets sucked into the cylinder very rapidly. This is because, the downward movement of the piston creates vacuum (or negative pressure) in the cylinder and the air-fuel mixture gets filled in the empty space.