Technologies for direct injection of fuel in compression ignition engines are in continuous development in order to get an increasingly high injection pressure. One of the most investigated component of this system is the injector; in particular, main attention is given to the nozzles characteristics as diameter, number, angle, internal shape. The reduction of nozzle hole diameter seems the simplest way to increase the fuel velocity and to promote the atomization process. On the other hand, the number of the holes must increase to keep the desired mass flow. On this basis, a new logic has been applied for the development of the next generation of injectors. The tendency to increase the nozzle number and to reduce the diameter has led to the replacement of the nozzle with a circular plate that moves vertically. The plate motion allows to obtain a cylindrical surface for the delivery of the fuel on 360° degrees; while the plate lift is calibrated to obtain the desired fuel mass flow. The injector has been tested in a single-cylinder metal engine in order to carry out data on its performance in terms of emissions, consumption and NVH. Then the behaviour of this new injector has been investigated in an optical single-cylinder diesel engine via high speed digital imaging in order to catch information on its operation. Tests in metal engine showed a good response of the injector in terms of fuel delivering control while, with respect to conventional multi-hole nozzles, penalties in terms of exhaust pollutant emissions and fuel efficiency were observed. Images of the injection process showed that the fuel assumed an asymmetric shape at the exit of the injector so affecting the mixing quality and, then, the combustion efficiency.