Diesel-powered combustion engines offer environmental benefits in the form of increased fuel economy and decreased carbon monoxide emissions. However, they also generate greater emissions of particulate matter and nitrogen oxides than traditional gasoline-powered engines. The European Commission is addressing this issue by implementing stricter EURO emission standards for diesel engines, spurred on by increasing evidence of health impacts from particle inhalation. Aiming to assist European auto manufacturers meet the more stringent emissions standards, Centro Ricerche Fiat (CRF) employed Computational Fluid Dynamics (CFD) modelling. Using the STAR CFD package created by CD-adapco, CRF simulated the physical and chemical processes occurring in the combustion chamber of a diesel engine. CRF applied STAR to successfully reproduce the evolution of the flow and temperature fields inside the combustion chamber. The model results compared well against measurements made in the laboratory by CRF's partners in the PARTSIZE project. Another key contribution was the incorporation of a new model for soot particle formation into STAR that was developed by another member of the PARTSIZE consortium. This added feature provides valuable output such as the total mass and particle size distribution of the soot. European automobile manufacturers will be able to exploit these new software tools to design better diesel engines that produce fewer particles. This will not only ensure conformance with emissions legislation but also competitiveness in the international marketplace.