Exhaust Gas Recirculation: Description and Operation

Fig. 32 EGR wide open throttle control valve:

This valve, Fig. 32, which is used on some vehicles, closes the EGR valve when the engine requires maximum power at or near wide open throttle. This valve is installed in the vacuum line between the ported vacuum connection on the carburetor and EGR valve. A vacuum line from the carburetor venturi vacuum tap is connected to the top port on the valve and provides control for the valve. When venturi vacuum signal is at a predetermined level near wide open throttle, it is strong enough to overcome the calibration spring pressure and unseat the diaphragm valve, diverting EGR source vacuum to the atmosphere and causing the EGR valve to close. Normal EGR flow is resumed when there is a reduction in engine load from the wide open throttle position.