The induction valve is the end point of the intake system. The air-fuel mixture, necessary for the proper functioning of the engine, is pushed through the induction valve into the combustion chamber. A camshaft controls the opening and closing of the induction valve. The structure of the metal of the induction valve (especially the bottom - "the plate") differs significantly from the one of the outlet valve. This is determined by different thermal conditions of functioning.

The power of the engine is directly proportional to the amount of the combustible mixture and fuel that enters the cylinder through the inlet valve, as well as the quality of the cleaning the cylinder from smog through the outlet (exhaust) valves. In order to improve the filling of the engine, the inlet valve diameter is larger than the one of the outlet valve. During descent, the flow speed of the wasted mixture is higher than at the intake of the fresh one, due to the fact that the smog is pushed out by a piston.

The diameter of the inlet valve deals with the possibility of placing it in the cylinder head, and the piston height - with the forces of the valve mechanism performance.