Venturi Vacuum Control System

Vacuum is tapped at the throat of the carburetor venturi or air flow sensor (EFI) to provide control vacuum to the vacuum amplifier. This low amplitude signal is increased in the amplifier to a level which will operate the EGR valve. A 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 affected by intake vacuum and exhaust gas pressure.