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 integral backpressure transducer EGR valve which combines inputs of backpressure and EGR port vacuum into one unit. Both inputs are required for EGR valve to operate.