Engineers developing powertrain control strategies are increasingly expected to build controls with greater functionality. At the same time pressures on unit costs are increasing, development schedules are tightening and higher results ratios are expected.Rapid prototyping Software tools are now available which help accelerate the development process. One such tool for engine control system design is CPower, (a numerical integration of GT-Power and Simulink). CPower allows prototypes to be developed and tested “on a desk” using a transient engine model which, unlike cycle-averaged engine models, reliably reproduces the engine operating characteristics, such as gas dynamics and complex combustion process. (Stobart et al,1998 )To demonstrate this tool Arthur D. Little have developed a simple idle-speed control system for a light duty truck engine. Idle speed control is a well known problem although it often represents a significant development cost.