Function

The exhaust gas recirculation should mainly decrease the combustion temperature to reduce the harmful nitrogen dioxide in the exhaust gases. However this reduces the efficiency, the torque and the power of the engine. Every such compromise is regulated for the different ranges of the engine anew, and is limited to between 20 to 30 percent of exhaust gases. In addition, the recirculated gases might be cooled down. (see the picture above).

How it works

Internal exhaust gas recirculation is possible with an increased valve overlap, while adjusting the camshaft or the electric/hydraulic valve control. The outer exhaust gas recirculation connects the exhaust system with the intake system via a pipe. The connection might either be constructed the short way – inside the cylinder head – or outside in between the exhaust pipe and the intake pipe. An exhaust gas regulation valve in the pipe regulates the quantity. An electro magnet (see figure) in the valve receives electrical signals from the control unit to regulate the pressure box which opens or closes the pipe for the exhaust gas recirculation. See figure 2 below the electrical connection. During full load the exhaust gas recirculation must be ceased to ensure the surplus of oxygen, because the engine would soot.