| 摘要 |
In an exhaust manifold (2) of a four-cylinder engine four cylinders of which line up in order of cylinder (#1), cylinder (#2), cylinder (#3) and cylinder (#4), temperature rise performance of a manifold catalyst (3) improves by shortening a total length of the exhaust manifold (2) while preventing exhaust gas interference between the cylinders. Therefore, an exhaust manifold branch of cylinder (#1) and an exhaust manifold branch of cylinder (#4) in outward sides of the engine that are not fired in succession are made convergent with its convergence angle (&thetas;1) being equal to or below 20 degrees to form a first convergent exhaust manifold branch (W1) and an exhaust manifold branch of cylinder (#2) and an exhaust manifold branch of cylinder (#3) between the cylinder (#1) and cylinder (#4) that are not fired in succession are made convergent at a minimum distance having a laterally projected shape to form a second convergent exhaust manifold branch (W2). The first and the second convergent exhaust manifold branches (W1,W2) are thereafter convergent at a convergence angle (&thetas;3) from 0 degrees to 20 degrees. <IMAGE>In an exhaust manifold (2) of a four-cylinder engine four cylinders of which line up in order of cylinder (#1), cylinder (#2), cylinder (#3) and cylinder (#4), temperature rise performance of a manifold catalyst (3) improves by shortening a total length of the exhaust manifold (2) while preventing exhaust gas interference between the cylinders. Therefore, an exhaust manifold branch of cylinder (#1) and an exhaust manifold branch of cylinder (#4) in outward sides of the engine that are not fired in succession are made convergent with its convergence angle (&thetas;1) being equal to or below 20 degrees to form a first convergent exhaust manifold branch (W1) and an exhaust manifold branch of cylinder (#2) and an exhaust manifold branch of cylinder (#3) between the cylinder (#1) and cylinder (#4) that are not fired in succession are made convergent at a minimum distance having a laterally projected shape to form a second convergent exhaust manifold branch (W2). The first and the second convergent exhaust manifold branches (W1,W2) are thereafter convergent at a convergence angle (&thetas;3) from 0 degrees to 20 degrees. <IMAGE>
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