Exhaust gas recirculation system for a compression ignition engine and a method of controlling exhaust gas recirculation in a compression ignition engine

An exhaust gas recirculation system for a compression ignition engine, comprising:

• a first pressure sensor for sensing an absolute gas pressure in an intake manifold of the engine;
• a second pressure sensor for sensing an absolute gas pressure in an exhaust manifold of the engine;
• an engine speed sensor for detecting a rotational speed of the engine crank shaft;
• a fuelling rate sensor for detecting a fuelling rate for the engine;
• an air charge temperature sensor for detecting a temperature of intake air in the intake manifold of the engine;
• a conduit for providing a fluid passage between the exhaust manifold and the intake manifold, and an exhaust gas recirculation valve disposed in the conduit to regulate a flow of exhaust gas from the exhaust manifold to the intake manifold;
• means for controlling the exhaust gas recirculation valve so that the flow of the exhaust gas through the conduit from the exhaust manifold to the intake manifold is regulated;
• and
• an electronic controller for receiving signals from the first and second pressure sensors, the engine speed sensor, the fuelling rate sensor and the air charge temperature sensor, computing an optimal ratio of the exhaust gas to be recirculated to intake air based on the signals received and computing a valve position that permits the optimal ratio of exhaust gas to intake air to flow through the conduit to the intake manifold, and actuating the means for controlling the exhaust gas recirculation valve to position the valve at the computed valve position to permit the optimal ratio of exhaust gas to intake air to flow through the conduit from the exhaust manifold to the intake manifold.