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Three and a half decades ago, two young Mazda designers arrived at a far-sighted and well-calculated conclusion that was quite revolutionary for the time. In their technical presentation at the October 26, 1962 Japanese Automotive Engineers' Society Technical Conference, Dr Tadashi Okada and engineer Toshiaki summarised their arduous research concerning vehicle dynamics as follows. 23035
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1. The basic difference in the characteristics of oversteer and understeer lies in the magnitude of time delay and response.
2. a vehicle that is stable under high speed must possess understeer characteristics
3. the rear wheel tyre reflects heavily on the stability and
4. a major improvement on control and stability may be anticipated by means of the automatic rear wheel steering system.
The conclusions and formulations presented by these two engineers established the foundation for Mazda's present-day reputed suspension technology. Over years of dedicated research and development expertise, their original discoveries and theories have contributed to some of the most significant achievements within the recent history of automotive chassis engineering, incorporated by Mazda within its series production products. These developments include the twin trapezoidal link rear suspension, first employed in the original front-wheel drive Mazda 323 (1980) and the Mazda 626 (1982), and then perfected within the updated Mazda 626; the award winning Dynamic Tracking Suspension System of the second generation Mazda RX-7 (1985); and the elaborate E-link rear suspension of the new Mazda 929 (1987).
While various external forces and loads are exerted to the rear wheels of a vehicle as it combats the elements of the law of motion as defined by Sir Isaac Newton, these new suspension systems convert those forces into "4WS effects" which positively aid in vehicle stability and agility.
The Mazda designers' and engineers' ultimate goal was still a positive measure to generate forces for positive controls; a Four-Wheel Steering system.
In 1983, Mazda astonished the automotive world with the introduction of an engineering concept car, the MX-02, exhibited at the Tokyo Motor Show. This four-door Sedan, with generous passenger accommodation on an unusually long wheelbase, incorporated among its numerous advanced features a true 4WS system that aided high-speed stability as well as its low-speed manoeuvring. The degree of rear wheel steering was determined by the measurement of both front wheel steering angle and vehicle speed, by means of a central computer unit.
The MX-02 was followed by another exciting concept car; the MX-03, first exhibited at the Frankfurt Motor Show in September 1985. This sleek four seat futuristic coupe of the 1990s combined a refined electronically-controlled 4WS system with a continually varying torque-split, four-wheel drive system and a powerful three-rotary engine.
Mazda Electronically -Controlled Four-Wheel Steering System:
A Beneficial Technology
Mazda's electronically-controlled, vehicle-speed-sensing Four-Wheel Steering System (4WS) steers the rear wheels in a direction and to a degree most suited to a corresponding vehicle speed range. The system is mechanically and hydraulically actuated, producing greatly enhanced stability, and within certain parameters, agility.
The driver of a Mazda 4WS-equipped car derives five strategic benefits, over and above the conventional vehicle chassis.
1. Superior cornering stability
2. Improved steering responsiveness and precision
3. High-speed straightline stability
4. Notable improvement in rapid lane-changing manoeuvres
5. Smaller turning radius and tight-space manoeuvrability at low vehicle speed range
The most outstanding advantage of the Mazda 4WS is that it contributes to a notable reduction in driver fatigue over high-speed and extended travelling. This is achieved by optimally: