Flows in the induction systems of internal combustion engines are extremely complex being two phase, separated stream, multi-component, pulsating flows with interchange between the streams due to deposition, re-entrainment, evaporation and condensation. In addition, under normal operation, acceleration and deceleration transients are superimposed. This study examines a quasi-steady approach to the calculation of transient air/fuel ratio effects which is based on output from a steady state analysis of the manifold flow. By comparing the results with experiments, additional aspects of the flow can be inferred. In particular, some secondary atomization to a mean droplet size of 20 μm at the throttle plate is needed.