PURPOSE: To reduce the intake air and to prevent knocking by providing a gate valve in the operating pressure path for opening/closing the secondary valve of carburetor thereby closing the valve upon occurrence of knocking thus closing the secondary valve.
CONSTITUTION: The secondary valve 8 of carburetor 6 having a supercharger in the upstream will respond to the pressure from the supercharge pressure lead-in path 10 and opened against a spring 9c when said pressure is high. Upon detection of knocking through a knocking detector 41, a waist gate valve 15 will open first and it knocking continues, the ignition timing is lagged by small amount through an ignition timing regulator 44 and if knocking is still continuing, the valve 39 will close to close the secondary valve 8 through the spring 9c thus to reduce the intake air and to prevent knocking. Since considerable lagging of ignition timing the thickening of the air/fuel ratio are not performed upon occurrence of knocking, the fuel consumption is improved.
SAKATA YUUZOU
IIDA MIKIO
