The research and development activities on diesel injection systems have focused some key-factors that improve the solenoid actuated injector performance, especially in the frame of the multi-event injection strategies. This paper deals with a 3-D numerical investigation that highlights the nozzle flow features of different injector layouts. A comparison between a last generation standard injector and an optimized unit characterized by an improved dynamics, different number of holes and reduced maximum lift is performed. By means of transient numerical simulations, the behavior of the fuel flows, the tendency to cavitation development and the response to the deviation from the standard operating conditions (highlighted by introducing a radial perturbation on the lift motion) are investigated.