The high-pressure Common Rail (HPCR) injection system was originally introduced for diesel engines to both reduce pollutant emissions and enhancement of performance. HPCR separates fuel pressurization and injection processes from each other. The high injection pressure generated by the common rail system provides better atomisation and evaporation of fuel spray, resulting in improved air inlet and fuel jet mixing, which is advantageous for lowering soot emission. In this paper, a mathematical common rail injection system model has been presented. A Simulink/Matlab code was developed to execute this simulation. This work does not only seek to validate the presented numerical model but to
have more insight for understanding the overall common rail injection system diesel engine performance under different operating conditions. Some simulation results are illustrated to highlight modelling capability.The engine used is an HCCI turbocharged diesel engine, 2776 cc, 4-stroke, and 4-cylinder, water-cooled with overhead valve mechanism. The common rail pressure, fuel consumption, start and duration of each injection through one engine cycle are measured at various engine speed and loads. The measured common rail fuel pressure and consumption are used to validate the simulation results. The findings of the simulation show good consistency with the experimental results. At last, some simulation results, which highlight the modelling capability, are illustrated at certain values of engine speed and load.