Importance

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Abstract

In an exhaust manifold 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 improves by shortening a total length of the exhaust manifold 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 θ1 being equal to or below 20 degrees to form a first convergent exhaust manifold branch 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. The first and the second convergent exhaust manifold branches are thereafter convergent at a convergence angle θ3 from 0 degrees to 20 degrees.

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First Claim