| 摘要 |
PURPOSE:To produce a suction control effect throughout a wide range, by providing a varying device which increases the opening period of a timing valve, located in a second intake air passage communicated to a second suction port feeding intake air in a region on the higher load side that of a first suction port, to the high speed high load side. CONSTITUTION:Supercharging of intake air is effected only through a first natural suction port 9p in a low speed low load area where a second throttle valve 17 and first and second supercharging valves 21 and 22 are closed. When the second throttle valve 17 is opened due to an increase in a load and the number of revolutions, supercharging of intake air is also effected through a second natural suction port 9s. When a load is further increased, the first supercharging valve 21 is opened to drive a supercharger 18, and supercharged air is fed through a first supercharging port 10p. Especially in high speed high load area, a switching valve 28 of a varying device 25 is opened, the opening period of a timing valve 23 in a second supercharging passage 15s is increased, and a quantities of supercharged air is supercharged high-efficiently.
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