Abstract: A method for estimating a combustion torque acting upon a crankshaft of an internal combustion engine is described. In one example, the method includes acquiring an instantaneous engine speed signal, calculating a cyclic engine speed signal based on the instantaneous engine speed signal, averaging the cyclic engine speed signal, correcting the averaged cyclic engine speed signal for engine losses, and estimating the combustion torque based on the corrected averaged cyclic engine speed signal. The description also concerns a control unit for an internal combustion engine.

Abstract: An exhaust gas recirculation system for an internal combustion engine, which comprises an intake plenum, an exhaust gas system, and a fresh-air feed line and an exhaust gas recirculation line connected to the intake plenum, includes a sensor, arranged in the intake plenum for measuring an amount of an exhaust gas component, and a controller constructed for outputting a correcting variable based on the sensor and adjusting the percentage by mass of inert gas in the intake plenum on the basis of the correcting variable. The sensor arranged in the intake plenum is a gas concentration sensor which is equipped for determining the air ratio, the oxygen concentration or the carbon dioxide concentration in the intake plenum and to output as sensor variable a variable representing the air ratio, the oxygen concentration or the carbon dioxide concentration to controller.