Valve Timing: What Is It And How It Affects The Engine Performance?
Engine Valve Timing Explained
Firstly, read here about how the engine valves open & close. The engine valves are just like the nose. An automotive engine uses valves for it’s ‘breathing’ (inhale/exhale) process. The engine’s camshaft opens and closes the valves at a specific interval. The timing of opening & closing of valves is specified in degrees corresponding to the position of engine’s pistons. Engine valve timing is the most critical process of IC engines.
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 the 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 the vacuum (or negative pressure) in the cylinder and the air-fuel mixture gets filled in the empty space.