Injection rate shaping is a powerful tool to control the combustion process and pollutants emission in DI Diesel engine. Recently, new injection systems that allow a more complete rate control have been developed.This paper presents a model to simulate the hydrodynamics of these injection systems with two main objectives: To determine the influence of the different injection system geometrical parameters and to explore different configurations to optimise the injection rate shape. To determine the origin of the pressure perturbations that may appear in the system, due for example to interactions between injectors, and to quantify them. This model has been developed with a modular approach that allows the simulation of very different injection system arrangements: classical pump-line-injector systems, common-rail system, and others. The paper describes: The model structure and the physical hypotheses compared with those of the bibliography. The methodology to characterise experimentally the main elements of the system. The methodology to adjust and validate the model with experimental data.