Secondary Throttle System

When the primary throttle valve is almost completely open (greater than 54 degrees), venturi vacuum created in the primary carburetor bore reacts upon the one-way check valve in the vacuum line to the secondary throttle control diaphragm. Vacuum gradually bleeds through the restricted orifice in the one-way check valve to the diaphragm, causing the diaphragm to lift the actuator rod. At this time, if the primary throttle angle is further increased, secondary throttle will open at the same time, increasing air and fuel volume for high energy demands.

Diaphragm can be reacted upon instantneously through the secondary throttle control solenoid. Solenoid is regulated by the control unit based upon engine demand. When control unit signals the secondary throttle control solenoid to open, primary venturi vacuum is routed to the upper chamber of the secondary diaphragm, by-passing the restricted orifice in the one-way check valve. This allows the secondary throttle valve to respond to vacuum intensity with no delay. When primary vacuum decreases, vacuum in diaphragm is bled off by an internal release valve in the one-way check valve.