2002 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, four-wheel disc brakes and a four-channel Anti-Lock Braking System (ABS) help ensure secure stops.
In addition, the NSX's revolutionary variable, electric-power-assisted steering system provides excellent road feel and easy operation. A firmer front suspension and a larger diameter rear stabilizer bar on the 2002 model enhance cornering performance and handling.
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 in that it employs 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. All 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.
For 2002, the front spring rate was increased from 3.2 kg/m to 3.5 kg/m while the diameter of the rear stabilizer bar increased from 17.5 mm to 19.1 mm with a 2.3 mm wall thickness. These refinements increase the car's roll rigidity and improve rear stability for an increase in overall cornering performance.
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 four-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 front dual-piston 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 with a 16-bit microprocessor. This four-wheel independent capability allows finite 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 SYSTEM
The NSX's 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 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
To reduce unsprung weight, and provide the highest strength possible, the engineers specified forged-aluminum alloy wheels. The result is a very light, seven-spoke wheel with the strength and impact resistance of a much heavier steel wheel. To enhance the look of the wheel for 2002, the NSX has a redesigned seven spoke design with a painted, then clear-coated finish. Wheel sizes have been increased from 7 x 16 to 7 x 17 in front and from 8_ x 17 to 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 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. For 2002 tire sizes were increased from 215/45 R16 to 215/40R17 in front and from 245/40 ZR17 to 255/40R17 in the rear. The increase in tire size results in a larger contact patch for even better handling.