Exhaust Gas RECIRCULATION: Operation: Notes

The EGR valve is a vacuum actuated poppet type valve used to control exhaust gas flow from manifold crossover into air/fuel mixture.

A vacuum tap at throat of carburetor venturi is used to provide control vacuum to the EGR amplifier. The vacuum amplifier is used to increase vacuum to the level required for EGR valve operation. Venturi vacuum signal opens EGR amplifier port, allowing manifold vacuum to operate EGR valve.

Elimination of EGR at wide open throttle is accomplished by a dump diaphragm which compares venturi and manifold vacuum to determine when wide open throttle is reached. At wide open throttle, the internal reservoir is "dumped", limiting output to EGR valve opening point. Opening point is set above manifold vacuum available at wide open throttle, allowing closure of EGR valve at wide open throttle.