EGR System: Description

The Exhaust Gas Recirculation (EGR) system distributes small amounts of exhaust gas into the intake mixture. This lowers combustion temperatures due to lower concentrations of oxygen. Lowering of combustion temperatures reduces amount of NOx emissions. The amount of exhaust gas recycled and timing of EGR valve opening are controlled by engine vacuum, exhaust system backpressure, altitude, temperature, throttle angle and engine speed.

Typical systems consist of an EGR valve, vacuum reservoir, check valve, Ported Vacuum Switch (PVS) and/or a Temperature Vacuum Switch (TVS). The following 5 types of EGR valves are used:

• Backpressure Variable Transducer (BVT)
• Electronic (EEGR)
• Integral Backpressure (IBP) transducer
• Ported
• Pressure Feedback Electronic (PFE)