VALVES TYPES AND ARRANGEMENTS (EXHAUST/INTAKE V/VS)

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The majority of valves in use are poppet types and are fitted in either single large or multi small arrangements.

Large single valves.

•              simple operating gear.

•              simple valve construction.

•              simple cylinder head required.

Multiple small valves.

•              Smaller valve lift required.

•              Lower inertia since components usually much lighter.

•              Volumetric efficiency improved.

•              Combustion chamber design more flexible.

•              Lower metal temperatures.

•              Less distortion of valve lid at operating temperature.

                       

Valve springs

Springs are required to support mass of valve in the cylinder head. There are several spring arrangements in common use some employing single springs while others employ multiple springs.Single Springs

•              simplest solution.

•              vibrate at lower natural frequencies, risk of valve bounce.

•              buckling risk for long springs.

•              large diameter springs have higher stress, bending moment.

Series Springs

•              reduces bending stresses.

•              reduces buckling.

•              more complex.

Parallel Springs

•              reduced inertia.

•              more complex.

•              alters natural frequency and so avoids axial vibration.

gives safety factor in event of breakage