Exhaust Gas RECIRCULATION: Operation

As throttle plate opens to partial throttle, such as during cruising, a vacuum signal is sensed by the vacuum amplifier. Here, the signal is strengthened enough to be able to open the EGR valve. As the valve opens, a controlled amount of exhaust gas is taken from the exhaust manifold and sent back into the intake manifold. The temperature control valve shuts off EGR flow when engine coolant temperature is below approximately 120°F (49°C).

At sustained low vacuum conditions, such as during heavy acceleration, no EGR occurs, since the vacuum level is too low. However, the vacuum reservoir will maintain an operable vacuum level to accommodate fluctuations in engine operation and vacuum levels.