Following their recent experiences in the fields of experimental analysis and numerical simulation of turbocharged engines, the authors present, in this paper, an integrated procedure for studying the behaviour of a light-duty turbocharged D.I. diesel engine, equipped with a variable geometry turbine, an intercooler and an EGR system for NOx control.Experimental activities consist of a complete investigation of the engine operating conditions under different rotational speeds and fuel deliveries. Experimental data provide the basis for numerical investigations.Numerical simulation is carried out through different level of approach, characterised by an increasing level of complexity. A simplified approach of the filling and emptying type is employed for a preliminary determination of matching conditions among the components. Next, a 1-D flow model allows a more correct evaluation of wave propagation phenomena through external ducts.A more detailed insight of the in-cylinder phenomena is obtained by employing a multidimensional model (i.e., the well known KIVA II code) for examining the closed-valve period. The authors employ a recently proposed methodology for matching the results of 0-D and multidimensional simulation as to improve the predictive level of both types of approach.