Abstract: Disclosed herein is a back pressure control type EGR system for an internal combustion engine, wherein a vacuum modulator has an air introducing chamber which is selectively opened, in accordance with the pressure of recirculated exhaust gas, to a vacuum line connecting an EGR port with a vacuum operated flow control valve. The air introducing chamber is further connected to another vacuum port formed slightly above the EGR port via another vacuum line. Switching valve devices responsive to the temperature of the engine are located on the vacuum lines for stopping the EGR operation when the engine is cold.

Abstract: Disclosed herein is an internal combustion engine provided with an exhaust gas recirculation system of so-called back pressure control type. The exhaust gas recirculation system is provided with a vacuum line connecting a so-called EGR port with a vacuum operated flow control valve, and a modulator valve having a control chamber selectively opened to the vacuum line in response to the pressure of recirculated exhaust gas for controlling vacuum signal level of the flow control valve. The control chamber of the modulator is connected to another vacuum signal port located slightly above the EGR port.