Exhaust Gas Recirculation: Description and Operation: Overview

In this system, exhaust gases are circulated to dilute the incoming fuel air mixture. Dilution of the incoming mixture lowers peak flame temperatures during combustion and thus limits the formation of NOx.

Fig. 39 EGR control valve. Exc.4-153, 4-156 & V6-181 engines:

An additional system is used to control the rate of exhaust gas recirculation, depending on engine model. The Venturi Vacuum Control system uses the same type exhaust gas recirculation (EGR) control valve, Fig. 39, only the method of controlling the valve is different. The valve is a vacuum actuated, poppet type unit used to modulate exhaust gas flow from the exhaust gas crossover into the incoming air/fuel mixture.