To improve the exhaust gas cleaning performance while preventing the absorption of thermal stress, generation of thermal deflection and crack in an exhaust manifold for multi-cylinder internal combustion engine and while improving the exhaust gas temperature retaining performance.
Downstream ends 17-1, 17-4; 17-2, 17-3 of each pair of branch pipes 4-1, 4-4; 4-2, 4-3 continuously provided to each exhaust port of a pair of cylinder having an exhaust stroke displaced from each other among branch pipes 4-1, 4-2, 4-3, 4-4 of a thin branch pipe of an exhaust manifold 1 are provided continuously to collecting pipes 5-1, 5-2, and the collecting pipes 5-1, 5-2 are collected so that the whole of the branch pipes 4-1-4-4 and the downstream ends 17-1-17-4 are collected so as to have a nearly circular cross section. Plate cases 6 (6-1, 6-2) are installed in the branch pipes 4-1-4-4 and the branch upstream ends 26-1-26-4 of the case 6 are welded to an upstream flange 2, and the collecting pipes 5-1, 5-2 and the downstream ends of the case 6 are welded to a downstream flange 3.
NAITO MASAZUMI
FUJIMORI KOICHI
HASHIMOTO HIROSHI
