PORSCHE 912, 911T & 914/6 Engine Modification: Operation: Notes
Driving at high speed, throttles closed, causes a high vacuum in engine induction system, resulting in an over rich air/fuel mixture. To correct this, a regulating solenoid valve opens at engine speeds above 1600 RPM, allowing manifold vacuum to act upon vacuum control unit. When throttle is closed, increased manifold vacuum pulls actuating plunger of throttle valve compensator. This in turn acts upon carburetor linkage exerting a slight pull towards full throttle, keeping throttle from fully closing. Solenoid valve closes at speeds below 1500 ± 50 RPM, allowing air to enter vacuum part of control unit. As a result, actuating plunger returns into its resting place and throttles close to idle position. Regulating solenoid valve is controlled by an RPM transducer which receives its signals from contact breaker points.