One factor believed to influence a customer's perception of vehicle performance is the powertrain sound. However, its influence relative to other factors, such as vehicle acceleration or transmission shift characteristics, remains largely unknown. Past studies of performance perception have either neglected the effect of powertrain sound, studied its effect independent of other factors (e.g., listening to powertrain sounds over headphones), or have confounded its effect with other factors. In this paper, we describe an in-vehicle system for methodically studying the influence of powertrain sound on a customer's perception of performance. The system is beneficial in that it allows the experimenter to electronically modify the sound associated with the powertrain while not affecting other possible performance factors. Results from a corresponding experiment are also presented, in which customers rated their perceived performance of the powertrain sounds. These results suggest that the synthesized powertrain sounds affect performance impressions, and can be used in a planned in-vehicle experiment.