Method for determination of exhaust back pressure

A method for determination of exhaust back pressure (P3) for an engine (1) with a two-staged turbocharger (2) comprises the following steps: - measuring the temperature (T3) downstream the engine (1), the temperature (T4) downstream the turbocharger (2) and/or the pressure (P4) downstream the turbocharger (2); - determining a flow parameter for exhaust mass flow; - estimating overall turbine pressure ratio (PRT) or difference with a model (15) of the turbocharger (2) on the basis of the measured and determined parameters; - determining the exhaust back pressure (P3) downstream the engine (1) with the model (15).