| 摘要 |
PROBLEM TO BE SOLVED: To correctly detect average O2 concentration in an engine in which an O2 sensor is provided on a collecting chamber part connected to branch pipe parts communicated to respective exhaust ports by forming the axis lines of all the branch pipe parts so as to intersect at one point in the collecting chamber part, and arranging the detecting part of the O2 sensor on the one point. SOLUTION: In a four-cylinder engine, four exhaust ports are opened on the front face of a cylinder head, and an exhaust manifold M is fitted to the cylinder head. The exhaust manifold M is provided with four branch pipe parts 51 -54 respectively communicated to the respective exhaust ports and a manifold main body 7 consisting of a common collecting chamber 6 integratedly connected to the lower stream ends of the respective branch pipe parts 51 -54 . In this case, all the branch pipe parts 51 -54 are formed so that their axis lines A1 -A4 are intersected at one point P (desirably the center in the collecting chamber part 6), and the detecting part 10a of an O2 sensor 10 is arranged on the one point P. Hereby the average O2 concentration of the whole exhaust gas can be correctly detected. |
