EC/Emission Control Systems — Exhaust Gas Recirculation (EGR) System (7M-GE), page 12

EC-12     EMISSION CONTROL SYSTEMS — Exhaust Gas Recirculation (EGR) System (7M-GE)

EXHAUST GAS RECIRCULATION (EGR) SYSTEM (7M-GE)

(1)
EGR Port    R Port    EGR Vacuum Modulator
                      EGR Valve

VSV

EC3033

(2)
EGR Port
R Port

ECU
VSV
EGR Cooler
EGR Vacuum Modulator
EGR Valve

EC3034

(3)
EGR Port
R Port

ECU
VSV
EGR Cooler
EGR Vacuum Modulator
EGR Valve

EC3035

To reduce NOx emissions, part of the exhaust gases are recirculated through the EGR valve to the intake manifold to lower the maximum combustion temperature.

Coolant Temp. | *Engine RPM | VSV | Throttle Valve Opening Angle | Pressure in the EGR Valve Pressure Chamber | EGR Vacuum Modulator | EGR Valve | Exhaust Gas

Below 57°C (135°F) | - | OPEN | - | - | - | CLOSED | Not recirculated

Above 57°C (135°F) | Above 4,000 rpm | OPEN | - | - | - | CLOSED | Not recirculated

 | Below 4,000 rpm | CLOSED | Positioned below EGR port | (1) LOW | ** Pressure constantly alternating between low and high | OPENS passage to atmosphere CLOSES passage to atmosphere | CLOSED | Not recirculated

Above 65°C (149°F) | | | Positioned between EGR port and R port | (2) HIGH | | | OPEN | Recirculated

 | | | Positioned above R port | (3) HIGH | *** | | OPEN | Recirculated (Increased)

* Engine RPM control is for Calif. only.
** Pressure increase ——— Modulator closes ——— EGR valve opens ——— Pressure drops
    EGR valve close ——— Modulator opens ———
*** When the throttle valve is positioned above the R port, the EGR vacuum modulator will close the atmosphere passage and open the EGR valve to increase the EGR gas, even if the exhaust pressure is insufficiently low.