HEADLINES

1999 Acura NSX-- Chassis

OVERVIEW

Outstanding handling characteristics have been a hallmark of the NSX and NSX-T since their inception. A sophisticated all-aluminum double-wishbone suspension provides outstanding ride and handling, while large, four-wheel disc brakes and a four-channel Antilock Braking System (ABS) help ensure secure stops.

In addition, the NSX revolutionary variable, electric-power-assisted steering system provides excellent road feel and easy operation.

SUSPENSION

The desired goals for the NSX suspension went well beyond the typical goals of high lateral adhesion, transient response and linear response to control input. The engineers wanted a suspension that allowed the driver to easily control the car right to the limit, particularly with the more powerful 3.2-L V-6 engine.

The basic configuration is similar to that of a Formula One car in that it employs an upper and lower control (or double-wishbone) design with a coil-over shock absorber and stabilizer bar front and rear. The rear suspension has an additional transverse link for greater wheel control. All the suspension arms are made of extremely lightweight rigid and durable forged aluminum. The front steering and the rear hub carriers are also made from heat-treated aluminum castings. The springs are straight rate with an extended rubber bump stop mounted on the chassis, which acts as a progressive springing element at the limit of wheel travel.

The shock absorbers are nitrogen-filled and feature a unique progressive valve design. The progressive opening of this valve produces a more favorable damping profile, and more precise damping control, than a conventional valve system in which the fluid control orifices are either fully opened or closed.

The front and rear suspension components are mounted on separate aluminum subframes using rubber bushings designed to reduce vibration yet limit flex and shift of the suspension components relative to the mountings.

The suspension development program was far-ranging and took place at Honda's Tochigi Proving Grounds and the Suzuka Circuit in Japan, the 179-turn Nurburgring course in Germany, the Honda Proving Center of California (HPCC) and Honda's newest test track in Takasu, Hokkaido. In addition to the standard evaluations conducted in-house by the suspension engineers, the car was subjected to evaluation by top-rank drivers such as the late three-time Formula One World Champion Ayrton Sennaand and Formula One driver Satoru Nakajima.

BRAKES

The NSX is equipped with four-wheel ventilated disc brakes and dual-piston steel calipers. The diameter of the brake discs is 298 mm in the front and 303 mm in the rear. The combination of Iarge rotors and flex-resistant dual-piston calipers allows the engineers to achieve the ideal braking system balance. The braking targets were to provide outstanding braking performance, excellent pedal feel, linear braking response and low pedal effort. Splash guards with cutouts aid in air ventilation and enhance fade resistance.

FOUR-CHANNEL ANTILOCK BRAKING SYSTEM (ABS)

The 4-channel Antilock Braking System controls each wheel independently with a 16-bit microprocessor. This four-wheel independent capability allows finite control of the antilock function, especially when the car is braking on a surface with a split coefficient of friction- for instance, if the left side wheels are on snow, ice or standing water, and the right side wheels are on dry pavement.

The basic configuration uses independent, parallel hydraulic circuits. In addition to the primary, non-antilock braking circuit, the antilock system has its own hydraulic reservoir, pump, modulator unit, solenoids and control pistons. If a failure in the ABS hydraulic circuit should occur, normal braking force would be fully retained by the primary braking circuit.

ELECTRIC, VARIABLE, POWER-ASSISTED STEERING SYSTEM

This power-assisted steering system was the first of its kind in the American market. The system consists of a rack-and-pinion steering gear with an electric motor installed concentrically around the steering rack. The steering system is a direct design which functions with no assist at higher vehicle speeds. A speed sensor in the electronic control unit determines road speed and, coupled with a new torque-sensing system, feeds a signal to the motor. To ensure reliability, the electrical system for this unit features gold-plated connectors. All NSX models feature this electric, power-assisted steering system.

FORGED ALLOY

To reduce unsprung eight, and provide the highest strength possible, the engineers specified forged-aluminum alloy wheels. To enhance the look of the wheels, they have been machine-finished, then clear-coated. The result is a very light wheel with the strength and impact resistance of a much heavier steel wheel. The rear wheels are 8.5 x 17 in, and the front wheels are 7.0 x 16 in.

TIRES

The suspension engineers, working in conjunction with Yokohama Tire Company and Bridgestone Tire Company, sought to produce tires that would not only provide excellent traction and handling, but also allow the driver to "feel" the limits of the tires' performance.

The resulting NSX-specific tires were remarkable, meeting all the high-performance targets the engineers established early in the program.

The NSX is equipped with wide, low-aspect-ratio tires, front and rear, for more responsive handling and increased cornering capability. The tire sizes are 215/45 ZR16 front and 245/40 ZR1 rear. These tires provide excellent wet- and dry-weather traction, high-speed stability immediate and predictable reaction to steering input.

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