As the world enters a new millennium, the spark ignition engine enters a new age of gasoline fuel injection technology – direct injection. Orbital Engine Company is at the forefront of this technology with a unique, air–assist direct injection (ADI) system, which utilises a low–pressure air pulse as fuel atomiser and carrier. Modelling of Orbital's ADI system was carried out using a Eulerian–Lagrangian formulation for two–phase flow with a commercially available CFD package called Star–CD. The research has been a large step forward towards an improved predictive injection model for use in engine development.A simple model for simulating spray parameters was developed. This model involved the specification of initial airflow and droplet conditions, as initial results indicated that spray characteristics are strongly dependent on these initial conditions. Accurate specification of initial droplet size distributions was also determined to be necessary. The study demonstrates the high practical potential of two–phase modelling of Orbital's ADI system. The final model accurately simulates spray parameters over a fairly wide range of injection conditions.