4. Architectures and technological solutions

4.1 Influence of valve number and arrangement on combustion and performance

When designing a cylinder head, two objectives are sought: to facilitate filling and to control combustion.

For engines that are not supercharged, filling depends mainly on permeability. This depends on the shape of the passages and their cross-sections (number and size of valves, lift laws).

The combustion process depends on factors such as :

• the volumetric ratio, which requires control of dead volumes (particularly for diesel engines);

• the compactness of the combustion chamber, which reduces the flame propagation distance;

• heat exchange at the periphery...