1. The number of valves per cylinder noun interpretation
The number refers to the number of valves per cylinder of the engine each cylinder have a valve (including the intake and exhaust valves), there are two valves, three-valve , four valves and five valves several.
Movement of the piston
automotive engine requires the air intake valve is directly connected to an intake manifold for an engine intake mixture gas inlet, an exhaust valve is an exhaust gas discharged from the engine combustion exports.
Number of valves on the main engine head associated with the displacement and the engine speed. When the high engine speed when the engine valve opening and closing quickly, so easily lead to insufficient power of engine intake air drops, similar to one run too fast and cause hypoxia. Thus increasing the valve lift, but this is not likely to cause the valve to close in time, thus increasing the size of the intake and exhaust valves. Valve too large and need to reciprocating opening and closing the valve seat will increase the weight, inertia leads to big, big noise, big wear. So there will be multiple multiple intake and exhaust ports appear.