Gas inlet duct generating an aerodynamic movement of gas within a cylinder

A gas intake pipe for a cylinder of an internal-combustion engine, the intake pipe comprising means for diverting the gas so as to generate an aerodynamic motion of the gas within the cylinder about an axis substantially perpendicular to the axis of the cylinder, the diversion means comprising a ramp shape on the lower profile of the intake pipe, and a concave shape of the upper profile of the intake pipe, the lower and upper profiles of the intake pipe being defined in position of use of the intake pipe, characterized in that the radius of curvature R1 of lower profile forming the ramp is less than 40 mm, and in that the concave shape of the upper profile comprises an intermediate zone whose radius of curvature R3 ranges between 50 and 150 mm, and a final zone whose radius of curvature R2 ranges between 10 and 100 mm, the final zone facing the ramp shape of the lower profile.