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While hybrid-electric drivesystems have the potential to substantially improve fuel economy without sacrificing performance, the extent of the fuel savings is highly dependent on component optimization within the system. Effectively optimized components require the drivesystem designer to understand component trade-offs and to supply the component developers with sufficient information to optimize their designs. Without a systems approach to all levels of drivesystem design-and, clearly, of vehicle design as well-components will tend to either be substantially oversized and inefficient or provide compromised vehicle performance. Component specifications typically include power requirements, such as would be needed to provide adequate starting torque, gradability, acceleration, and braking.

A host of important and interactive factors contribute to the successful design of any production vehicle. However, the combination of hybrid-electric drive and low-drag platform design, with emphasis on vehicle mass and drag coefficient reductions, appears prerequisite to the simultaneous optimization of efficiency, emissions, performance, and cost. This paper examines the fundamental relationships between these and other design elements, such as series vs. parallel hybrid configurations, energy-storage mass, and safety. The intent is to present an approach to vehicle design that can yield marketable, production-worthy, high-performance automobiles while meeting or exceeding goals set by the Partnership for a New Generation of Vehicles (PNGV). Rather than attempting to push the envelope of maximum efficiency, this paper explores technologies and design strategies for baseline and further optimized design scenarios within the PNGV timeframe and design criteria.