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: A method of testing a fuel system of an internal combustion engine comprises measuring the instantaneous speed of a component of a pumping apparatus of the system this speed decreasing as fuel is pressurised to achieve fuel delivery to the engine as compared with the nominal engine speed due to "wind up" in the drive to the engine. The speed profiles obtained as fuel is supplied to each injection nozzle and compared to determine if the injection nozzles are working correctly.