Emission Control Systems: Description and Operation

ENGINE EMISSION CONTROL

The exhaust gas recirculation (EGR) system includes:
- EGR valve actuator/pintle position sensor.
- EGR cooler assembly.

The exhaust gas recirculation (EGR) system reduces the peak combustion temperatures and oxides of nitrogen (NOx). The EGR valve is an electromechanical device that uses a linear actuator to control the relative position of the valve's pintle. This device also has a built-in pintle position sensor that functions to provide the powertrain control module (PCM) with a feedback signal. This output signal provides the information on the valve position relative to its seat. The advantage of this"closed loop"feedback is the ability to continuously vary exhaust gas flow to match operating conditions. The EGR cooler cools a portion of the engine exhaust gases and then recirculates them back into the inlet air stream. This increases the engine's tolerance for EGR and reduces the amount of smoke formed by exhaust gas dilution of the mixture.