2004 Acura NSX -- Chassis
Outstanding handling characteristics have been a hallmark of the NSX since its inception. A sophisticated all-aluminum double-wishbone suspension provides outstanding ride and handling, while large, 4-wheel disc brakes and a 4-channel anti-lock braking system (ABS) help to ensure secure stops.
In addition, the NSX's revolutionary variable, electric-power-assisted steering system provides excellent road feel and easy operation.
The goals for the NSX suspension system went well beyond the typical goals of high lateral adhesion, transient response and linear response to control input. The engineers wanted a system that allowed the driver to easily control the car right to the limit, particularly with the more powerful 3.2-liter V-6 engine.
The basic configuration is similar to that of a Formula One car, employing an upper and lower control arm (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. The suspension arms are made of extremely lightweight, rigid and durable forged aluminum. The front and 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.
From the beginning, the suspension development program has been far-ranging, taking 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 Senna and Formula One driver Satoru Nakajima.
The braking targets were to provide outstanding braking performance, excellent pedal feel, linear braking response and low pedal effort. To reach these targets, the NSX is equipped with 4-wheel ventilated disc brakes, dual-piston steel calipers in front and single-piston calipers in the rear. The diameter of the brake discs is 298 mm in the front and 303 mm in the rear. The combination of large rotors and flex-resistant calipers achieves the ideal braking system balance. Splashguards with cutouts aid in ventilation and enhance fade resistance.
4-CHANNEL ANTI-LOCK BRAKING SYSTEM (ABS)
The 4-channel Anti-Lock Braking System controls each wheel independently using a 16-bit microprocessor. This four-wheel independent capability allows precise control of the anti-lock 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-anti-lock braking circuit, the anti-lock 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
The NSX's power-assisted steering system was the first of its kind on 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 torque-sensing system, feeds a signal to the motor. To ensure reliability, the electrical system for this unit features gold-plated connectors.
FORGED ALLOY WHEELS
Forged-aluminum alloy wheels reduce unsprung weight, and provide the highest strength possible. The result is a very light, seven-spoke wheel with the strength and impact resistance of a much heavier steel wheel. The NSX has seven- spoke wheels with a painted, then clear-coated finish. Wheel sizes are 7 x 17 in front and 9 x 17 in the rear.
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 would also allow the driver to "feel" the limits of the tires' performance.
The resulting NSX-specific tires are 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. Tire sizes are 215/40ZR17 front and 255/40ZR17 rear, resulting in a large contact patch for even superior handling.