Advanced research work has lead to the development of a new simulation program and the thermodynamic parameters at engine inlet and exhaust of an engine-mounted variable-geometry turbine can thus be evaluated. The machine is divided into characteristic sub-blocks and resolution of thermomechanical flow equations is carried out using the necessary geometrical parameters. A detailed study of losses is conducted experimentally and numerically into the scroll, the vaned nozzle and the rotor in relation to nozzle opening angles. Simulation results made on the variable geometry turbine are analyzed in relation to main flow entry parameters and are compared systematically with experimental data gathered on turbocharger test equipment, and on a Diesel engine used for industrial applications.