Electric EGR Motor System
Electric EGR (EEGR) motor/valve system uses exhaust gas recirculation to control Oxides of Nitrogen (NOx) emissions just like vacuum operated systems. The difference is the way in which exhaust gas is controlled. Advantages to this type of system are:
- EEGR valve is activated by an electric stepper motor not a vacuum motor. It is located at rear of engine block.
- No vacuum diaphragm is used.
- No DPFE sensor is used.
- No Orifice Tube Assembly is used.
- No EGR vacuum regulator solenoid is used.
- A new MAP sensor is used. A TMAP is used, but temperature function is not used at this time. TMAP is located on top of valve cover.
- Engine coolant is routed through the assembly, extending durability of electric motor.
EEGR system consists of an electric EGR motor/valve integrated assembly, a PCM, TMAP sensor and connecting wiring. The following list of components and their specific operation corresponds to numbers in illustration. See Fig 1.
- EEGR system receives signals from Engine Coolant Temperature (ECT) or Cylinder Head Temperature (CHT) sensor, Throttle Position (TP) sensor, Mass Airflow (MAF) sensor, Crankshaft Position (CKP) sensor and Thermal Manifold Absolute Pressure (TMAP) sensor to provide information on engine operating conditions to PCM. Engine must be warm, stable and running at a moderate load and engine speed (RPM) before EEGR system is activated. PCM will deactivate EGR during idle, extended Wide Open Throttle (WOT), or whenever a failure is detected in an EEGR component or EGR required input.
- PCM calculates desired amount of EGR for a given set of engine operating conditions.
- PCM in turn will output signals to EEGR motor to move (advance or retract) a certain number of discrete steps. Electric stepper motor will directly actuate EGR valve, independent of engine vacuum. EGR valve is commanded from 0-52 discrete increments or "steps" to move EGR valve from a fully closed to full or partially open position. The position of EGR valve determines EGR flow.
- TMAP sensor is used to measure variations in manifold pressure as exhaust gas recirculation is introduced into intake manifold. Variations in EGR being used will correlate to TMAP signal. Increasing EGR will increase manifold pressure values.
EEGR valve is a water cooled motor/valve assembly. See Fig 2 and Fig 3 . The motor is commanded to move in 52 discrete steps as it acts directly on EGR valve. Position of valve determines rate of EGR flow. The built in spring works to close valve against motor opening force.