| 摘要 |
An intake manifold adapted for use with an engine having two intake ports for each cylinder and comprising an aluminum plenum chamber having an air inlet and air outlets twice the number of cylinders of the engine in number, and a plurality of branch pipes of wrought aluminum connected to the respective air outlets of the plenum chamber. One of the two branch pipes to be connected to the intake ports for each cylinder is larger in the length of the channel than the other branch pipe. The two branch pipes are equal in the cross sectional area of the pipe channel, or the branch pipe having the longer channel is smaller than the other branch pipe in the cross sectional area of the channel. The roughness of the inner surface of each branch pipe is up to 10 .mu.m, preferably up to 5 .mu.m, more preferably up to 1 .mu.m, in terms of center line average height.
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