Ported & Integral BACKPRESSURE Systems
Both systems are controlled by an EGR valve which is normally closed. Vacuum signals control the opening and closing of the EGR valve. When the EGR valve is closed, no exhaust gas is allowed to enter the intake manifold. If vacuum is applied, the valve opens and exhaust gas enters the manifold passages.
Some light duty emission systems use a backpressure transducer to aid in controlling exhaust gas recirculation. This unit senses exhaust gas backpressure and modulates vacuum signal to EGR valve in response to amount of backpressure. Backpressure is used to provide information on engine operation modes. The backpressure transducer is integral with the EGR valve. See Figure .