VENTURI Vacuum Control System
Vacuum is tapped at throat of carburetor venturi or air flow sensor to provide control vacuum to vacuum amplifier. This low amplitude vacuum signal is increased in amplifier to a level which will operate EGR valve.
Dump diaphragm compares venturi and manifold vacuum to prevent EGR operation at wide open throttle. EGR operation is determined primarily by venturi signal, but is also effected by intake manifold vacuum and exhaust gas pressure.