In the automotive field, the aim of these days is to reduce CO2 emissions of vehicles: the most promising solution for what concerns Internal Combustion Engines (ICE) and in particular Spark Ignition (SI) engines is the adoption of downsized turbocharged petrol engines. However this technology together with the continuously increasing levels of boost to achieve the desired performance requires a precise description of the combustion pro- cess so that the effects of parameters such as spark timing, EGR rate, compression ratio changes or knock level can be well evaluated. The development and the validation of reliable methods able to describethe condition inside the cylinders and the evolution of the combustion process have therefore acquired great importance in the most recent times.