A method of estimating a boost pressure of a turbocharger is disclosed. A throttle body temperature is estimated as a function of engine operating parameters. An intake air mass flow and an exhaust mass flow are estimated as a function of the throttle body temperature. A turbine inlet pressure and a turbine outlet pressure are estimated as a function of engine operating parameters. A turbine speed is estimated as a function of the intake air mass flow, exhaust mass flow and turbine inlet and outlet pressure. The boost pressure is estimated as a function of the turbine speed. Estimation of the maximum boost pressure of a turbocharged internal combustion engine is performed method cyclically as follows: estimating a throttle temperature, estimating an air mass flow and an exhaust mass flow, estimating a turbine inlet pressure and a turbine outlet pressure, estimating a turbine speed, and estimating the maximum boost pressure.