The aim of this research is to develop the diesel combustion simulation (UniDES: Universal Diesel Engine Simulator) that incorporates multiple-injection strategies and in-cylinder composition changes due to exhaust gas recirculation (EGR), and that is capable of high speed calculation. The model is based on a zero-dimensional (0D) cycle simulation, and represents a multiple-injection strategy using a multi-zone model and inhomogeneity using a probability density function (PDF) model. Therefore, the 0D cycle simulation also enables both high accuracy and high speed.This research considers application to actual development. To expand the applicability of the simulation, a model that accurately estimates nozzle sac pressure with various injection quantities and common rail pressures, a model that accounts for the effects of adjacent spray interaction, and a model that considers the NOx reduction phenomenon under high load conditions were added. In addition, engine, vehicle, and driver models using the commercial GT-Power code, and an electronic control unit (ECU) model were combined to predict transient phenomena.These models were used to make transient predictions for the New European Driving Cycle (NEDC). The results were sufficiently accurate for practical use. Further, as detailed analysis of transient phenomena is also possible, UniDES can help to make the development easy.