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To realize high levels of handling, driving performance, and NVH characteristics for a sports car, it is important to develop a lightweight and high-stiffness vehicle body. For the new RX-7, weight saving and higher stiffness were pursued as top priorities from the very first stage of the program. We were able to achieve 20% higher bending stiffness and 15% higher torsional stiffness with vehicle weight reduced by 30 kg, compared with the former model. The development of the lightweight, high-stiffness body for the new RX-7 is discussed under three subjects: 1. Contributions of vehicle components to vehicle stiffness 2. Effective procedure for developing vehicle high stiffness and lightweight construction with emphasis on calculation analysis 3. New RX-7's body structure and accomplishment

It is well-known that decreasing idle speeds is one of the ways to reduce fuel consumption. On the other hand, it is also well-known that even slight fluctuations of the idle speed cause unpleasant vibrations of the vehicle when this speed is set at low values. Therefore, it is important to create idle-speed control (ISC) systems that undergo less idle-speed fluctuations with respect to various load disturbances, in order to reduce fuel consumption without giving rise to unpleasant vibrations. The first topic of this paper is a linearized model which derives a new feedforward compensation method for reducing idle-speed fluctuations caused by load distrubances for specific electric loads. The second concerns the control results of our ISC system using this feedforward compensation. The final topic is a discussion of the validity of the parameter values used in the feedforward compensation.

Equalizing phase lags of yaw rate and lateral acceleration while also minimizing both phase lag values in vehicle transient response has been found to improve vehicle maneuverability at low to high road speeds. To realize these operating characteristics, “SS 4WS” (Speed-Sensing Four-wheel Steering system) has been developed as a system to control optimally the steering ratio of rear to front wheels. Various tests have verified the effectiveness of this system.