ENGINE COMPONENT AND LOCATION 105 EGR Valve This engine uses the EGR valve to recirculate exhaust gases. Engine oil operates the EGR valve. The EECU determines the desirable valve opening based on inputs from a number of sensors and commands the EGR valve solenoid to open or close the valve. Corrosion occurs in the inlet manifold if exhaust gas condenses there. This can produce both internal and external damage. To eliminate corrosion, the EECU compares engine RPM, torque load, ambient temperature, inlet manifold temperature and EGR demand to calculate the dew point in the inlet manifold. It then adjusts the EGR opening to stay above the dew point.
Additionally, surfaces within the inlet manifold and the mixing chamber are treated to resist corrosion. The EGR valve attaches to the rear section of the exhaust manifold for reliable response and turbocharger efficiency. This location also protects the EGR cooler from harmful high pressure exhaust pulses that occur during engine braking. EGR Valve Function When the EGR valve is open, exhaust gas recirculates into the combustion chamber. The valve is normally closed when engine coolant temperature is below 65°C (149°F) unless the EECU commands the valve open during automatic cooler cleaning mode.
When coolant temperature exceeds 65°C (149°F), engine load exceeds 50%, and RPM exceeds 1200, the EECU opens the EGR valve to approximately 90% of its range. At idle, the EECU monitors exhaust temperature every three minutes. If it exceeds 98°C (208°F), the valve opens to approximately 14% of its range. Otherwise, it remains closed.