| 摘要 |
PROBLEM TO BE SOLVED: To reduce the heat capacity of a plate material constituting an exhaust manifold and early activate a catalyst just after starting by connecting a plurality of plate materials to form the exhaust manifold, and setting the thickness of the plate material, of the both, which is located on the front side of the air flow within an engine room and satisfactorily cooled relatively small. SOLUTION: This exhaust manifold is formed by connecting at least two plates. For example, it is formed of a branch pipe 26 consisting of a cylindrical plate material, and an upper case part 28 and lower case part 30 formed of a bent plate material. The thickness t1 of the upper case part 28 located on the front side of the airflow in an engine room 4 is set relatively smaller than the thickness t2 of the lower case part 30 located on the rear side. According to this, the upper case part 28 is satisfactorily cooled with the airflow to increase the allowable stress, so that it can be thinned without deteriorating the strength. Accordingly, the heat capacity of the upper case part 28 can be reduced to prevent the reduction in exhaust air temperature, and the catalyst can be early activated just after starting. |
