Diesel engine exhaust gas recirculation system with greater atmospheric pressure compensation at low engine load

An exhaust gas recirculation system for a diesel engine and which includes an exhaust gas recirculation passage connecting between the exhaust system and the air intake system of the engine, an exhaust gas recirculation control valve which regulates the flow resistance of the exhaust gas recirculation passage according to the amount by which the pressure in its pressure chamber is lower than atmospheric, a mechanism for providing a supply of low pressure, an absolute pressure control valve which receives a supply of low pressure from such mechanism at its input port and provides a supply of a pressure at its output port the absolute pressure value of which is substantially fixed, and a vacuum control valve which has a pressure regulating chamber which receives supply of pressure from the output port of the absolute pressure control valve and also has an output port opening from the pressure regulating chamber. The vacuum control valve is controlled according to engine load, and bleeds the pressure regulating chamber to the atmosphere when the pressure therein is at or below a certain pressure value, this certain pressure value increasing in accordance with increasing engine load. The output port of the vacuum control valve is communicated to the pressure chamber of the exhaust gas recirculation control valve.