Venturi Vacuum Control System

The venturi vacuum control system utilizes a vacuum tap at the throat of the carburetor venturi to provide a control signal. This vacuum signal is amplified to the level required to operate the EGR control valve. Elimination of recycle at wide open throttle is accomplished by a dump diaphragm which compares venturi and manifold vacuum to determine when wide open throttle is achieved. At wide open throttle, the internal reservoir is ``dumped'', limiting output to the EGR valve to manifold vacuum. The valve opening point is set above the manifold vacuums available at wide open throttle. This system is dependent primarily on engine intake airflow as indicated by the venturi signal, and is also affected by intake vacuum and exhaust gas back pressure.