Intake system for an automotive engine

Claim 1

An intake system for an automotive engine having cylinders comprising: primary intake ports communicated with said cylinders; secondary intake ports communicated with said cylinders; each of said primary and secondary intake ports being communicated with a corresponding cylinder at a common intake valve; each primary intake port being disposed in a tangential direction so as to provide a swirl of inducted mixture, and sectional area of each primary intake port being reduced; a primary intake manifold communicated with said primary intake ports; a secondary intake manifold communicated with said secondary intake ports; a primary carburetor having a throttle valve provided in said primary intake manifold; a secondary carburetor having a throttle valve provided in said secondary intake manifold; said throttle valve of the secondary carburetor being so arranged to be opened after the throttle valve of the primary carburetor has been fully opened; a first valve provided in each branch of said secondary intake manifold for preventing a counter flow of inducted mixture; said first valve being operatively connected to said throttle valve of the secondary carburetor so as to be opened together with the throttle valve; a bypass provided at a position downstream of said first valve for communicating the primary intake manifold with the adjacent secondary intake manifold; and a second valve provided to close said bypass and arranged to be operated to open said bypass when load on the engine exceeds a predetermined partial load.