| 摘要 |
PURPOSE:To aim at enhancing the fuel consumption of an engine provided with an intake-air port arrangement in which a helical passage and a straight passage are formed, by increasing an intake-air control valve for opening the straight passage, in accordance with increase in load so that the air-fuel ratio of a mixture is enriched. CONSTITUTION:Negative pressure in a negative pressure chamber 64 or the atmospheric pressure from a port 30 is selectively introduced into a diaphragm chamber 59 for controlling an intake-air control valve 17 disposed in a straight passage 14 and as well into an operating chamber 59 for controlling the opening and closing of an enrich valve port 54 in a carburettor, by means of a selective control valve 27. Venturi negative pressure from a venturi negative pressure port 70 is introduced into a diaphragm chamber in the selective control valve 27 through an induction pipe 69, and the atmospheric pressure is introduced into the diaphragm chamber 20 and the operating chamber 59 when the venturi negative pressure is increased in accordance with increase in load, so that the intake-air control valve 17 and the enrich port valve 17 are opened. |
