Friday, November 28, 2008

Honda Prelude 4 Wheel Steering (4WS)

The original Honda with four wheel steering

In the late 1980s and early 1990s, Japanese sports car engineers were crazy about four wheel steering. The Mitsubishi 3000GT, the Nissan 300ZX, and the Honda Prelude all had it but the respective systems were very different from each other.

Honda's first generation 4WS system debuted in the 1988-1991 Prelude. It was the first production car with the system. Moreover, this generation Prelude was unique in that the system was the only system that was truly mechanical (as opposed to hydraulic or electric) in operation.

This video from a Prelude enthusiast truly captures the essence of the Honda system:


By turning the steering wheel, the rear wheels turn in the same direction as the front ones, only to a lesser degree. When the front ones turn 9 degrees, the rear ones turn 2 degrees. This scenario (small steering input) is anticipated at high speed. The rear wheels turning in the same direction as the front ones improved stability.

With the steering wheel turned further, the rear wheels went back and pointed straight. Turn the wheel further still, and the rear wheels turn in the opposite direction.

At steering wheel lock, the rear wheels are pointed 6 degrees in the opposite direction. This happens most often when parking and making u-turns. The opposite directions of the wheels decrease the turning radius.

The Honda system never truly caught on because the complexity and weight of the extra hardware made any steering improvements from the system negligible.

Footnote 1: The HICAS and Super HICAS steering (Nissan) used hydraulics and electric actuators, respectively. The rear wheels turn in the same direction as the front wheels at medium to high speeds, no more than one degree.


Footnote 2: The 3000GT's system worked like Nissan's. The rear wheels turned at the most 1.5 degrees in the same direction as the front wheels at speeds in excess of 31 mph.

CKY

1 comment:

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