EGR Control Valves: Notes

Increased EGR flow, required to meet emission standards, adversely affects driveability. To overcome this problem, the valve is controlled by carburetor vacuum, which is governed by throttle openings. The EGR system increases EGR flow during high load operations and decreases EGR flow during low load operations. Vacuum level at idle and wide open throttle is low and no EGR operation occurs in these modes. Two EGR valve combinations are used to accomplish this: