Exhaust Gas Recirculation: Description and Operation

The Exhaust Gas Recirculation system (EGR system) consists of a valve, a vacuum regulator valve, a tube and a differential pressure sensor.

The EGR system recycles measured quantities of exhaust gas back through the engine where they mix with the incoming air/fuel charge.

The powertrain control module controls the vacuum regulator valve with grounding pulses. This regulates the amount and duration of the vacuum signal supplied to the EGR valve and thus the valve lift and opening time are controlled.

The differential pressure sensor provides the module with data relating to the exact amount of exhaust gas being recirculated by measuring the differential pressure across a calibrated orifice in the supply hose. Thus closed loop control is achieved.

The use of the new variable camshaft timing optimize the combustion procedure by improving gas exchange in the cylinders. As a result of this the exhaust emissions regulations can be met without the use of a pulse air system or an EGR system.