Part 1 describes a gas dynamic model to represent a pulse converter. In this model the pulse converter is represented by a three-way branch with pressure losses. Pressure loss coefficients are determined from steady flow tests and included in the boundary conditions for non-steady flow. Non-steady tests on pulse converters fitted in a four cylinder turbocharged engine showed that using the model, predictions of the influence of pulse converter area ratio on wave form and amplitude give good agreement with experiment.Part 2 gives results of a comprehensive investigation on the application of pulse converters to a four stroke automotive engine. It is shown that using the gas dynamic model presented in Part 1 of the paper in a simulation program the optimum combination of pulse converter and turbocharger size may be determined. This combination was confirmed in the experimental programme. The experiments and predictions showed an improvement in turbocharging efficiency with the optimum combination with a resultant increase in engine power. The combination enabled an improvement in engine back-up torque characteristics to be achieved.