The aim of this work was to obtain a reduction in pollutant emissions, in particular for NOx and Soot, in an “Off-Road” DI Diesel Engine, equipped with a common rail injection system, by means of exhaust gas recirculation (EGR). First, an engine simulation was performed using a one-dimensional code, and the model was then calibrated with experimental results obtained from a previous research work conducted on bench tests.Thanks to the engine model, specific emissions were then determined in all conditions, that is, in “eight modes” pertaining to engine loads and speeds. Both the injection advance and EGR amount were changed for all of these conditions in order to obtain the best compromise between fuel consumption and emissions and to respect standard regulations. The investigation was performed using both the Wiebe and a more complex combustion models; this latter allows in fact to determine the soot emission through the Nagle-Strickland model. As the standard emission limits were not respected, in spite of the presence of EGR at partload, a pilot injection was also introduced into the simulation at full load, for maximum torque and power conditions, in order to reduce soot emissions. The presence of the pilot injection at full load allowed satisfactory results to be obtained for the emission limits and for fuel consumption, as some experimental tests have shown.