| 摘要 |
PURPOSE:To prevent excessive lowering of charging efficiency in the low opening area of a throttle valve and to improve the running efficiency of an engine, by a method wherein a branch pipe, having the closed one end, is communicated in the middle between a throttle valve and a suction valve in the intake air passage of an overhead-valve type engine. CONSTITUTION:In an overhead-valve type engine having poppet type suction and exhaust valves 21 and 22 mounted to a cylinder head 4 by which a combustion chamber 5 is partitioned, an intake air passage 7 opened and closed by means of the suction valve 21 is communicated with a carburetter 15 equipped with a throttle valve 14 through a spacer 13. A pipe 17, having a closed tip and forming a branch pipe 18 in association with the pipe 16, is formed to the pipe 16, engaged with the spacer 13. The sectional area of the portion of the pipe 16 is minimized, and the internal volume of the branch pipe 18 is set to about 1/6 or more of the volume of the intake air passage situated down a line from the throttle valve 14. This constitution enables prevention of a decrease in an output along with lowering of charging efficiency in the low opening area of the throttle valve 14, and execution of high efficient running throughout a wide rotation range.
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