A method for adaption of clutch torque in an electromagnetic clutch for an auxiliary rotating unit such as a supercharger or an AC compressor by means of an engine control unit, wherein engagement of said electromagnetic clutch is achieved by means of a coil control current being applied to an electromagnetic coil which pulls a clutch armature disc connected to the auxiliary rotating unit into engagement with a clutch rotor operatively connected to an internal combustion engine which is provided with a crank speed sensor for feeding a crank speed signal to the engine control unit, characterized in that said method comprises the following steps: - step 1: intermittently performing an adaption engagement of the clutch initiated by the engine control unit under predetermined operational conditions outside of regular operation of the auxiliary rotating unit; - step 2: recording crank speed signal disturbance data from a disturbance in said crank speed signal following clutch speed synchronization by recording an actual location in time (t 1, t 2, t 3) of a peak in the crank speed signal caused by the point of clutch speed synchronisation between the clutch rotor and the clutch armature disc occurring during said adaption engagement and comparing said actual location in time (t 1, t 2, t 3) with a reference location in time (t 0) for clutch speed synchronisation of a known nominal electromagnetic clutch and recording a crank speed peak value (n 1, n 2, n 3) for said peak during said adaption engagement, said crank speed signal disturbance data containing information about actual clutch torque during the adaption engagement; - step 3: entering said crank speed signal disturbance data into a look-up table or an equation yielding an adaption factor based on a relative comparison between deduced actual clutch torque of the electromagnetic clutch and expected clutch torque for a known nominal electromagnetic clutch; - step 4: multiplying said adaption factor with a previously stored torque adaption factor yielding a new torque adaption factor; - step 5: applying said new torque adaption factor to a nominal clutch torque table yielding an adapted coil control current/actual clutch torque relationship for achieving a smoother engagement of the clutch in the next following clutch engagement; and - step 6: iterating steps 1 through 5 until the remaining relative error between deduced actual clutch torque and expected nominal clutch torque is reduced to an accepted predetermined level. - step 1: intermittently performing an adaption engagement of the clutch initiated by the engine control unit under predetermined operational conditions outside of regular operation of the auxiliary rotating unit; - step 2: recording crank speed signal disturbance data from a disturbance in said crank speed signal following clutch speed synchronization by recording an actual location in time (t 1, t 2, t 3) of a peak in the crank speed signal caused by the point of clutch speed synchronisation between the clutch rotor and the clutch armature disc occurring during said adaption engagement and comparing said actual location in time (t 1, t 2, t 3) with a reference location in time (t 0) for clutch speed synchronisation of a known nominal electromagnetic clutch and recording a crank speed peak value (n 1, n 2, n 3) for said peak during said adaption engagement, said crank speed signal disturbance data containing information about actual clutch torque during the adaption engagement; - step 3: entering said crank speed signal disturbance data into a look-up table or an equation yielding an adaption factor based on a relative comparison between deduced actual clutch torque of the electromagnetic clutch and expected clutch torque for a known nominal electromagnetic clutch; - step 4: multiplying said adaption factor with a previously stored torque adaption factor yielding a new torque adaption factor; - step 5: applying said new torque adaption factor to a nominal clutch torque table yielding an adapted coil control current/actual clutch torque relationship for achieving a smoother engagement of the clutch in the next following clutch engagement; and - step 6: iterating steps 1 through 5 until the remaining relative error between deduced actual clutch torque and expected nominal clutch torque is reduced to an accepted predetermined level.