An overview of work relating to the investigation of direct injection gasoline engines is presented.Comparisons between conventional port-injected and two separate gasoline direct injection combustion systems are drawn. The comparison is between two of the main alternative GDI systems currently under consideration, reverse tumble charge motion with high-pressure swirl-type fuel injector (RTGDI) and low-pressure air-assist direct injection (AAGDI). This comparison was carried out using a 444cc single cylinder research engine of Cosworth Technology design. Included in the discussion are the influence of GDI systems on volumetric efficiency and performance at full load and fuel efficiency and emissions at part load.Techniques to aid the development and calibration of GDI systems are discussed, including Moving Geometry CFD analysis and Design of Experiments (DOE). The development and application of these techniques is considered key to the successful development of GDI combustion systems.Some design considerations for the practical implementation of direct injection gasoline concepts for inclusion in production programs are addressed.