An innovative quasi-dimensional multizone combustion model for the spray formation, combustion and emission formation analysis in DI diesel engines was assessed and applied to an optical single cylinder engine.The model, which has been recently presented by the authors, integrates a predictive non stationary 1D spray model developed by the Sandia National Laboratory, with a diagnostic multizone thermodynamic model.The 1D spray model is capable of predicting the equivalence ratio of the fuel during the mixing process, as well as the spray penetration.The multizone approach is based on the application of the mass and energy conservation laws to several homogeneous zones identified in the combustion chamber. A specific submodel is also implemented to simulate the dilution of the burned gases.Soot formation is modeled by an expression which derives from Kitamura et al.'s results, in which an explicit dependence on the local equivalence ratio is considered.The model was used to analyze low load (BMEP = 2 bar at 1500 rpm) and medium load (BMEP = 5 bar at 2000 rpm) operating conditions in an optical single cylinder engine sharing the combustion system configuration of the 2.0L Euro5 GM diesel engine for passenger car application. The images obtained by a CCD camera were used to derive statistically averaged values of the spray tip penetration and of the dispersion angle. The soot concentration was also calculated by means of the two-colour pyrometry method. These experimental data were used for the multizone model assessment.