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3. Valve
A valve is typically used to control the timing and quantity of gas or vapor flow into an engine.
It consists of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end
of a shaft also called a valve stem. The portion of the hole where the plug meets with it is
referred to as the 'seat' or 'valve seat'. The shaft guides the plug portion by sliding through a
valve guide. In exhaust applications a pressure differential helps to seal the valve and in intake
valves a pressure differential helps open it. Poppet valves date from at least the 1770s, when
James Watt used them on his steam engines. [3][6]
Figure 3. Valve and components.
Figure 4. Valve terminology
GiDB|DERGi Sayı 5, 2016
