EXHAUST PASSAGE STRUCTURE OF INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To prevent amplitude of exhaust pulsation from being changed, when the passage cross-sectional area largely changes in a confluent part of an exhaust port. SOLUTION: This exhaust passage structure of an internal combustion engine is constituted by connecting an exhaust port confluent part 5 connecting one end 2a of a plurality of exhaust ports 2 to one combustion chamber and merging the other end 2b of the plurality of these exhaust ports 2 to an exhaust manifold 3, and is characterized in that the respective exhaust ports 2 and 2 have a curved part 6 on the upstream side of the exhaust port confluent part 5, and a projection part 8 continuing over between a predetermined section in the exhaust passage direction, is formed in a part continuing in the exhaust passage direction with a curved outer peripheral side part of the curved part 6 among an inner wall surface of the exhaust port confluent part 5. Thus, change in the cross-sectional area in the exhaust port confluent part 5 is restrained by the projection part 8, and the amplitude of the exhaust pulsation can be maintained. COPYRIGHT: (C)2007,JPO&INPIT