Valves
In a four-stroke internal combustion engine, valves play a crucial role by controlling gas exchange and ensuring the combustion chamber’s seal during the compression and power strokes. There are two types of valves: intake valves, which regulate the flow of air or the air-fuel mixture into the cylinder, and exhaust valves, which release the spent gases from the cylinder.

Modern automotive four-stroke engines use poppet valves, consisting of a stem and a valve head. The working surface of the valve head is ground at a specific angle to match the corresponding angle on the valve seat, ensuring the necessary seal when the valve seats in the valve seat. The end of the valve stem typically has grooves for valve keepers that secure the valve spring retainer.

A sealed combustion chamber is essential for achieving high pressure during the combustion of the air-fuel mixture, which directly impacts the engine’s efficiency and power.

Materials and Manufacturing

Valves are made from heat-resistant and corrosion-resistant steels. This is necessary because, during engine operation, the valve head, especially the exhaust valve, heats up to very high temperatures:

• For gasoline engines: 900-1000℃;
• For diesel engines: 700-900℃.