Patent ID: 7324888

Claim:
A method for estimating friction torque for an internal combustion engine in a powertrain of an automotive vehicle, the engine having an idle state, a fueled power-on state and a fuel cut-off state, the engine having a crankshaft, engine crankshaft speed being higher during operation in a fuel cut-off state than in an idle state, the powertrain including an engine control unit with memory registers in which a friction torque look-up table resides, the look-up table having input variables comprising engine speed and indicated engine torque, the method comprising the steps of: measuring engine crankshaft speed and indicated engine torque when the engine operation in the fuel cut-off state; measuring engine crankshaft speed fluctuations in the engine fuel cut-off state; reconstructing a first harmonic of a periodic signal to recover an amplitude that corresponds to engine friction losses using engine crankshaft speed measurements during operation of the engine in a fuel cut-off state; and updating the engine friction look-up table when new measurements of the engine friction torque obtained from an amplitude signal in the fuel cut-off state are available.