EGR Valve: Description and Operation

PURPOSE
- To reintroduce exhaust gases into the combustion cycle causing lower combustion chamber temperatures, thereby reducing the formation of nitrous oxide.

OPERATION
- In the "Sonic" Exhaust Gas Recirculation (EGR) system, the EGR valve is a conventional vacuum actuated valve. As vacuum applied to the EGR valve diaphragm overcomes the spring force, the valve begins to open.

- As the vacuum signal weakens, at 1.6 in (41mm) Hg or less, the spring force closes the valve. The EGR valve is fully open at about 4.5 in (114 mm) Hg.

CONSTRUCTION
- The EGR valve consists of a housing, a diaphragm, a spring, a vacuum port and a pintle.