METHOD FOR CONTROLLING INTAKE-AIR, AIR-FUEL RATIO AND IGNITION TIMING OF INTERNAL-COMBUSTION ENGINE

PURPOSE:To aim at enhancing the fuel comsumption of an engine provided with an intake-air port arrangement in which a helical passage and a straight passage are formed, by setting the angle of spark advance of ignition timing, corresponding to the allowable angle of spark advance which varies in accordance with the open degree of an intake air control valve for opening the straight passage. CONSTITUTION:A control device 110 which receives detected values from a rotational speed sensor 111, a negative pressure sensor 112, etc., controls a diaphragm device 20 for dividing an intake-air control valve 17 disposed in a straight passage 14 and a selective control valve 24 for selectively introducing negative pressure from a negative chamber 30 or the atmospheric pressure into an operating chamber 59 for controlling the opening and closing of an enrich valve port 54. Further, the control device 110 controls a selective control valve 116 for selectively introducing the atmospheric pressure or negative pressure from a negative pressure extracting port 33 into a diaphragm chamber 98 in a negative pressure type spark advancing device 91 for a distributer 90. When the volume of intake-air becomes above a predetermined value, the spark advance is increased while the intake-air control valve 17 and the valve port 54 are opened.