Intake system for internal combustion engines

An intake system for an internal combustion engine having a plurality of cylinders each having a plurality of intake ports, the opening timing of a part of said intake ports being determined so that that of each cylinder has some overlap with that of another in which the intake stroke takes place subsequently to that in the former and the opening timing of the rest of said intake ports being determined so that that of each cylinder has less overlap with that of another in which the intake stroke takes place subsequently to that in the former, said intake system comprising intake passage means each being connected to an intake port of one of said cylinders, junction means connected to said respective intake passage means, resonance intake passage means connected to said junction means at one end thereof, in which an intake pressure resonance effect is to be produced, shutter valve means provided in said respective intake passage means connected to said intake ports having the larger overlap with that of another cylinder and control means for controlling the opening timing of said shutter valve means so that said shutter valve means is closed under at least a low speed and heavy load engine operating condition.