The design and orientation of the intake manifold is a elder means in the volumetric efficiency of an engine. Crude contour changes provoke pressure drops, resulting in less air (and/or fuel) entering the combustion chamber; high-performance manifolds have smooth contours and gradual transitions between adjacent segments.

Venturi eventuality - At bottommost rpm, the speed of the airflow is increased by directing the air through a path with local capacity (cross-sectional area). The imposing Headers path opens when the load increases so that a greater magnitude of address can enter the chamber. In dual overhead cam designs, the atmosphere paths are often connected to separate intake valves so the shorter path can be excluded by deactivating the intake valve itself.