This project has the aim of refining an existing zero-dimensional diagnostic tool developed in Matlab environment in order to analyse the combustion process of a compression ignition engine. The engine under exam is the F1A engine (FPT Industrial), a turbocharged diesel engine with a displacement of 2.3 litres. In addition to the common diesel fuel, a renewable fuel was also used (HVO) in order to evaluate what benefits could be achieved using this type of new fuel. Two models were used inside the tool: a complete one zone model and a three zone model, that is also used in order to evaluate the evolution of particulate matter (PM) and nitrogen oxides (NOx) emissions as function of the crank angle.