/SUMMARYA detailed simulation of a turbocharged spark-ignition engine is presented. The model is based on the “control volume” concept. Yet includes pressure wave action effects in manifold pipes. Each cylinder is considered as a thermodynamic control volume. Manifolds are considered as pipes bounded by volumes (which may be small enough to represent pipe Junctions). The program is of modular form, hence any number of cylinders may be specified, along with pipes, turbocharger, waste-gate. EGR system and throttle in almost any arrangement. Energy mass flow and gas dynamic equations are solved in a quasi-steady manner at 1° crank angle steps.The accuracy of the simulation is illustrated over a wide range of speed and load, by comparison with detailed test results, from an Audi 200T engine. The utility of the model is shown by predicting the effect of design changes aimed at improving low engine speed boost pressure and turbocharger response, plus boost control at higher speeds.