Infiniti Takes The Road With A Heritage Of
Innovative Q45 Suspension Systems

The original Q45 may best be remembered for its engine, a knock-you-back-in-the-seat 278-horsepower 32-valve, variable valve timing, fuel-injected DOHC V8. But if the engine was the heart of its performance, its suspension was its soul, with the two systems working in tandem to make power and put it smoothly to the road.

The first Q45 suspension took its cue from another legendary performance machine, the Nissan 300ZX. Adapting the Z's 4-wheel independent suspension to the larger, heavier Q45 meant months of computer work and miles of testing on handling courses, high-speed banking and real-world roads. The Q45 suspension utilized MacPherson struts in front and in the rear, three links at each comer (instead of the traditional two), helping keep more tire surface contact with the road at all times, resulting in precise, stable handling and reduced body movement during cornering, braking and hard acceleration.

The initial Q45 lineup also offered a Q45t model, featuring Super HICAS- (High Capacity Actively Controlled Steering), which provided an extra level of stability in highspeed lane changes and sudden cross-wind situations. Unlike other 4-wheel steering systems, which were developed primarily for low-speed parking maneuverability, the Super HICAS system was a high-performance system which steered the rear wheels in either phase (same direction) or counterphase (opposite direction) as needed (to a maximum of one degree) to enhance steering response and cornering power of the rear tires.

Taking the Active Route

In April 1990, Infiniti introduced a new model, the Q45a, with the world's first production full-active suspension system. Named one of Road & Track magazine's "10 Best Cars in the World," the Q45a looked like an ordinary Q45 except for the subtle "a" badging on the trunk. Yet it certainly didn't drive like anything ever on the road before or since.

The Infiniti Full-Active Suspension- retained the Q45's basic multi-link layout but replaced the shock absorbers with hydraulic actuators at each wheel (the coil springs were retained solely to help support vehicle weight). Rather than attempting to merely control the forces acting on a vehicle during driving, the Full-Active system was designed to neutralize those forces by actively generating precise counter-forces of its own.

The result was a remarkably flat and smooth car body positioning, much like the legs of a skier absorbing all the surface shocks and keeping the skier's body controlled. In the Q45's case, the actuators at each wheel, acting on input from a series of sensors monitored by a pair of advanced 16-bit microprocessor units, extended or contracted, able to change from full pressure (fully extended) to no pressure (fully contracted) in just one tenth of a second.

New For 1999: Electronic Modulation

Also new for 1999 is an Active Damper Suspension, available as standard equipment on the Q45t. This system offers electronically modulated shock valuing control with SPORT and AUTO driver selectable settings.

The system uses real-time, independent 4-wheel shock absorber damping force regulation in response to input from vertical G-sensors and steering angle sensors. Signals from these sensors are sent to the system's computer control unit, then matched with vehicle speed. "Instruction" data is then sent back to actuators above each individual shock absorber, which immediately adjust shock absorber damping force.

The system helps eliminate excessive body movement, such as in hard cornering, braking or acceleration. It also helps improve tire-to-road surface contact for greater stability and enhanced handling control.

With the two adjustable settings, drivers can chose between a softer, more comfortable ride or a firmer ride with more road feel, depending on road surface, traffic and climate conditions or personal preferences.

Advanced Braking and Steering

Along with its advanced suspension system, every 1999 Q45 also features a refined 266-horsepower 4.1 -liter DOHC 32-valve V8, producing a strong 278 ft-lbs. of torque.

Braking is provided by power-assisted 4-wheel vented disc brakes with standard 3-channel/4-sensor Anti-lock Braking System (AS). Smooth, responsive steering with excellent driver feedback comes from standard vehicle-speed-sensitive power-assisted rack-and-pinion steering.