An engine model developed earlier is validated through comparison between measurements and simulations of transient situations. In particular boost pressure build up is studied. The engine model is intended for use in computer simulation of transient behavior in drivetrain and vehicle systems.The model studied is semi-empiric. Some of the model properties are empiric: engine data in steady state operation and mappings of compressor and turbine performance. Others are physical properties, e.g. displacement and compression radio.The measurements have been carried out in a transient engine test bed. In the measurements the delivered fuel amount is measured, as opposed to pedal position, and thus the engine control system and fuel injection system are not included in the comparisons.The time constants of the measured and the simulated boost pressure buildups are compared for eleven different step changes in pedal position. All step changes go from lower to higher pedal position. The engine speed is held approximately constant.Despite the simplifications in the model studied, it shows good agreement with the measurements. It is concluded that the agreement can be improved further by introducing a time delay in the model.