The complete numerical tool was the

The complete numerical tool was then validated through an extensive comparison with experimental data taken for different injector working conditions. Finally, the validated model was applied to help develop the direct-acting prototypal injector through a better understanding of the cause and effect relationships in the analysis of the performance of the injection system. An upgraded version of the injector has been set up on the basis of the indications of the model and tested on the hydraulic test rig. The hydraulic performance of the modified injector has proved satisfactory and to be in line with the model predictions.