Functional analysis
Valve timing

The pressure drop generated by the flow depends on the permeability of the intake and exhaust systems. This is determined by the geometry (diameters, lengths, elbows, etc.) and by the presence of components such as air filters, flowmeters, catalytic converters, silencers, etc.). At high gas velocities, low permeability can limit engine filling.

This paragraph deals with the permeability of the sub-assembly consisting of the part of the duct located in the cylinder head, the seat and the valve. The minimum flow cross-section is defined, at the start of opening, by the portion of the cone released between the seat and the valve 2.1.1...