EGR Control Valves: Notes

The increased EGR flow required to meet emission standards adversely affects driveability. The EGR control valves compensate for the EGR's effect on driveability and are controlled by carburetor vacuum. The amount of vacuum is governed by relative throttle openings. The EGR system increases EGR flow during high load operation and decreases EGR flow during low load operation. Vacuum level at idle and wide open throttle is low and no EGR operation occurs in these modes. Two types of EGR valve systems may used to accomplish this: