The management of multiple injections in compression ignition (CI) engines is one of the most common ways to increase engine performance by avoiding hardware modifications and after-treatment systems. Great attention is given to the profile of the injection rate since it controls the fuel delivery in the cylinder. The Injection Rate Shaping (IRS) is a technique that aims to manage the quantity of injected fuel during the injection process via a proper definition of the injection timing (injection duration and dwell time). In particular, it consists in closer and centered injection events and in a split main injection with a very small dwell time.From the experimental point of view, the performance of an IRS strategy has been studied in an optical CI engine. In particular, liquid and vapor phases of the injected fuel have been acquired via visible and infrared imaging, respectively. Injection parameters, like penetration and cone angle have been determined and analyzed. The data have been collected by running an engine condition of the homologation cycle New European Driving Cycle (NEDC) with two values of the swirl ratio.Computational activities, aiming at the simulation of the in-cylinder phenomena and specifically the injection process starting from experimental data, have been performed by adopting the 3D Ansys-Fluent solver.In particular, the fluid-dynamic calculations performed in a 3D domain, allowed to describe the spray evolution in the combustion chamber and carrying out the spray characteristics such as tip penetrations, Sauter mean diameters and droplets distributions. Besides, the spatial vapor distributions allowed detecting the mixing rate and the regions where the first flame spots should appear. After a proper identification of the parameters of the atomization model by a comparison with the experimental results, the CFD model potentialities for the prediction of the main features of new injection strategies should be verified.Such combined experimental and numerical activity would be able to point out the potential of IRS strategy with reduced nozzle diameter to improve the air/fuel mixing.