Air intake manifold for internal combustion engine

The distributor has a connecting surface (18) of radius of curvature (R) between an air inlet duct and a plenum at the vicinity of one of a set of nearer primary duct of the air inlet duct. The radius exists such that the air is guided towards the nearer duct. The surface follows a break section such that the primary ducts have similar acoustic behavior. Another surface connects between the section and the primary duct.