EGR Control Valves

Increased EGR flow, required to meet emission standards, adversely affects driveability. To overcome this problem, this EGR system increases EGR flow during high load operations and decreased EGR flow during low load operations. Two EGR valves are used to accomplish this.

The main EGR valve is controlled by carburetor vacuum, which is governed by throttle openings. Vacuum level at idle and wide open throttle is low; therefore, no EGR operation occurs in these modes. A thermo valve also controls vacuum application to this valve.

The sub EGR control valve is mounted so it is directly linked to throttle valve and thus mechanically controlled. See Figure. This valve more closely modulates EGR flow in response to throttle valve position.