Many technologies are being developed to solve the trouble of the urban pollution. Among other solutions (improvements in engine control and combustion, electrical propulsion) one of the foreseen ways is the employment of low or zero carbon content fuels, such as hydrogen. In fact a nearly zero emission vehicle may be obtained through the hydrogen propulsion; in this case the only polluting agents are nitrogen oxides if an internal combustion engine is used. Though fuel cells are considered as the most promising solution in the long term, they are still in their prototypical phase and the use of the internal combustion engine use remains until today a relevant topic.It has been evident since the 80s that direct injection is the only method to get a high specific power without pre-ignition and backfire phenomena. However this technique shows a higher difficulty in getting a well-mixed charge. The process of mixing between air and fuel obviously depends upon many parameters, such as the injection pressure and timing, the location of the injectors and so on. In this study the effects of the injection parameters on combustion, engine performances, emissions and efficiency were analyzed.Commercial electro-injectors were considered in this paper, and one of the main issues of the described work was the analysis of the engine performances and emissions as a function of the engine rotating speed and load. This paper shows the realization of a directly injected, hydrogen-fuelled prototype and the results of its experimental testing. Performances, consumption and NOx emissions are discussed as well as the influence of the injection parameters on the heat release rate.