The computational code KIVA-3V has been used as the modeling platform for Gasoline Direct Injection engine simulations. Improved models for fuel injection, wall impingement and stratified combustion have been implemented. To complement the modeling effort, experimental data of an optical engine has provided extensive data for validating the new models. The experimental data include Planar Laser Induced Fluorescence measurements, of the injection, mixing and combustion events in an optical engine. In this work, focus is given on fuel injection, wall impingement and air-fuel mixing.