In addition to the previously described external load moments, there are also combustion quality phenomena and internal friction moments which need to be balanced out. These change slightly, but continuously, over the entire service life of the engine.
In addition, the individual cylinders do not generate the same level of torque for the entire service life of the engine. The reason for this are the mechanical tolerances and changes which occur during the service life of the engine. All this could result in a rough-running engine, particularly at idle.
The smooth-running control system calculates the accelerations of the crankshaft via the CKP sensor after each combustion process and compares them.
Using the differences in engine speed as a basis, the injected fuel quantity for each cylinder is adjusted individually so that all the cylinders make as equal a contribution as possible to the torque produced.