Intake system for internal combustion engines

Internal combustion engine comprising cylinder means having cylinder bore means, piston means disposed in said cylinder bore means for reciprocating movement so as to define combustion chamber means therein, intake port means having a center and provided in said cylinder means to open to said combustion chamber means, first and second intake passage means which are separated one from the other and communicate with said intake port means, said first intake passage means being smaller in cross-sectional area than the second intake passage means, wall means extending radially of said intake port means and separating said first and second intake passage means at said intake port means, means for closing said second intake passage means at least under light load engine operation, intake valve means having a back contour and provided for closing said intake port means, said first intake passage means having a centroid in a cross-section at the intake port means and being so located that a line passing through the centroid and the center of the intake port means intersects a projection of said cylinder bore means at a point of intersection and makes an angle of 50.degree. to 80.degree. with a tangential line of said projection of the cylinder bore means at said point of intersection, whereby the first intake passage means is located with respect to the axis of said cylinder bore means radially outwardly of said second intake passage means at said intake port means.