Negative Backpressure EGR Valve

Negative backpressure EGR valve assembly has an internal vacuum bleed feature to regulate EGR based upon engine load. Bleed valve spring is moved from above the diaphragm to below, and valve is normally closed. Flow of valve is controlled by manifold vacuum, negative exhaust backpressure and carburetor ported vacuum signal.

When carburetor ported vacuum signal is applied to main vacuum chamber, partially opening valve, vacuum signal from manifold side (reduced by exhaust backpressure) is transmitted up the hollow stem of valve. This enables the signal to act on diaphragm, opening bleed and causing transducer to modulate, providing a specific flow. Thus, flow past the valve is a constant percentage of engine airflow.