Proportional EGR System (Turbo)
Proportional EGR system is operated by vacuum and pressure. Hoses are connected upstream of throttle valve and to thermostatic valve. Thermostatic valve prevents EGR operation when engine temperature is below 68°F (20°C).
Signal converter is used to control EGR valve due to engine load. During idle, both vacuum and pressure connections are upstream of throttle valve. See Fig 1 . Pressure differential remains the same which allows EGR valve to remain closed.
On partial load application, throttle valve is partially open and turbocharger is charging. Pressure differential on each side of throttle valve will open EGR valve. On full load, pressure signal is approximately equal causing EGR valve to remain closed.
On low load, pressure connection on rear of throttle valve supplies vacuum to signal converter. Signal converter operates allowing EGR to open.