EGR Valve: Description and Operation

EGR System:

PURPOSE
The EGR system lowers combustion temperatures to reduce oxides of nitrogen.

DESCRIPTION
The system consists of the EGR valve, exhaust recirculation lines, 70°C thermovalve, vacuum ports on the throttle valve, and vacuum lines.

OPERATION
The EGR system is operational when the engine temperature is above 70°C (122°F). If engine temperature drops below 60°C (122°F) the thermovalve prevents application of vacuum to the EGR valve. The EGR valve is operational under all load conditions except idle (closed throttle) and full load.

A vacuum signal from the throttle valve controls a proportional opening of the EGR valve. The EGR valve introduces inert exhaust gases into the intake system. This action lowers the temperature in the combustion chambers therefore reducing oxides of nitrogen in the exhaust gases.