Cadillac's Imaj concept car features a host of high-tech features including front and rear Night Vision, ForeWarn collision-avoidance, aluminum spaceframe body construction, Goodyear 20-inch EMT run-flat tires, supercharged Northstar V8 engine, and next-generation StabiliTrak chassis control. GM worked with Delphi Delco Electronics and IBM to develop Imaj's electronics. A Communiport interface delivers cellular phone, fax, and e-mail, as well as navigation and local information. The Imaj's seats are fully reconfigurable, and each features individual climate, sound, and video controls with headsets and cellphone ports.

Underneath its hood is an updated version of the supercharged Northstar V8 engine from the Evoq. Featuring a liquid-to-air intercooler and continuously variable valve timing, the enhanced engine delivers 317 kW (425 hp), which is fed to all four wheels through a new five-speed automatic transmission. The car has a front and rear Night Vision system, along with obstacle-alert sensors and rear-vision cameras that replace exterior mirrors. Other details include aluminum spaceframe body construction, Goodyear EMT run-flat tires on 20-inch wheels, Delco ABS and traction control, Brembo 380-mm (15.0-in) diameter ventilated-disc brakes, and a next-generation StabiliTrak chassis control system.

Work began in mid-1999 to develop the four-door, four-passenger sedan to complement the Evoq two-seater. The initial Imaj concept was conceived in Detroit, and the design was carried out in England with support from Detroit. Cadillac used elements from GM's global resources and re-engineered them to fit the package and to save weight.

The resulting 5.1-m (16.7-ft) long vehicle has a 3085-mm (121.5-in) wheelbase with short front and rear overhangs. Active front and rear aero panels provide downforce, while a smooth underbody improves drag. The roof is made almost entirely of electrochromatic glass that can be varied from opaque to clear, while each passenger can control roof louvers above their seat to let in fresh air. Imaj's large trunk has an extendable floor that powers out over the bodywork for ease of loading and unloading. The trunk lid is power-operated as are the rear doors, which are rear-hinged to the bodywork. All doors lock and unlock using the e-lock fingertip system.

The car's seats are fully reconfigurable, and each features individual climate, sound, and video controls with headsets and cellphone ports. Each seat is also heated and ventilated. Pedals and steering column are driver-adjustable. Italian luxury-goods maker Bulgari provided a special set of modular aluminum luggage, in addition to a clock and IP instrumentation.

GM worked with Delphi Delco Electronics and IBM to develop the car's electronics. The Communiport interface is the "mainframe" of the system, and at its core are three IBM 10-GB Thinkpad 600Es linked by a 10/100 Mbps ethernet LAN. This system provides the infrastructure for delivery of cellular phone, fax, and e-mail, as well as navigation information. The car's mobile Internet browsing capability, with e-mail and text downloading, uses the new wireless application protocol (WAP) and wireless mark-up language (WML). Since typical Internet HTML language is not convenient for use with "thin client" wireless mobile applications, a WAP browser with WML is used for telematics applications.

Menu navigation for all of the system's features is voice-activated. E-mail can be read to the car's occupants through a text-to-speech feature. A voice memo device allows voice messages to be recorded, stored, and played back later. An infrared port function allows handheld devices such as portable phones and personal digital assistants to exchange information. The CD/CD-ROM drive plays music CDs and reads CD-ROM databases such as maps. The system's compact flash slot allows for expanded memory and software upgrades. There is a central Communiport unit and monitor in the IP, but all passengers have their own individual monitor, the two for the rear passengers mounted on the backs of the front seats.

The car's audio system was provided by Bose. It offers personal surround sound for each listener and includes two Bose technologies implemented for the first time in the Imaj. Digital signal processing technology allows each listener to enjoy five-speaker surround sound in addition to enabling the small, closely spaced speakers to generate a wide, large, realistic sound. Bose's latest Jewel Cube speaker design is said to deliver rich sound from 50-mm (2-in) speakers. The 17-speaker system includes three wide-range speakers in the IP, two woofers in the front doors, two wide-range speakers in the B-pillars, and one wide-range speaker in the rear seat console.

Imaj's Night Vision system uses an infrared camera developed by Raytheon. Mounted at the front and rear of the car, its sensors help drivers see objects at night that are out of visible range. Images are based on the heat energy emitted by objects that are presented in monochromatic form on the windshield head-up display (HUD). The images switch from front to rear views as the car is shifted from forward to reverse.

Imaj's front and rear obstacle sensors use radar to alert the driver of nearby objects when parking in close quarters. In addition, Delphi's Forewarn collision-avoidance system is used to provide an "electronic cocoon" around the vehicle's perimeter. It includes forward-looking, blind-spot-warning, and back-up-aiding systems. The latter uses radar and ultrasonic sensors mounted in the rear bumper and senses objects within 6 m (20 ft).

Imaj also includes the latest version of GM's OnStar service, the 2.6 Virtual Advisor. It automatically calls for help in case of airbag deployment and notifies authorities if the car is stolen, tracking the car's location. It can also summon for routine or emergency assistance and gets routing assistance for a variety of concierge services.

The Imaj's 4.2-L supercharged V8, known as the SC4200, produces 317 kW (425 hp) at 6400 rpm and 542 N•m (400 lb•ft) of torque at 4000 rpm. Compared with the Evoq's engine, improvements were made to the supercharger and its air induction system to increase power. Further developments of GM's patented supercharger/intercooler system, coupled with refinements to the inlet and exhaust ports, provide improved airflow and power. The all-aluminum engine has four camshafts with continuously variable valve timing, low-friction roller-cam followers, and four valves per cylinder. The powerplant features closed-loop fuel control via mass airflow and four oxygen sensors, individual ignition coils, and four catalytic converters.

The engine is mounted longitudinally to accommodate the all-wheel-drive system. Power is fed to wheels through a low-mass five-speed automatic transmission with Performance Algorithm Shifting. Special effort was made to mount the engine and gearbox as low as possible to reduce the center of gravity. This is done by positioning the front axle cross shaft between the engine and gearbox instead of under the engine crankshaft as on most all-wheel-drive vehicles.

The front suspension features modular subframe-mounted units with double unequal-length lightweight aluminum arms, a high-mounted top arm for better geometry control, and a long monotube damper with a co-axial coil spring and lower yoke to straddle the front halfshaft. At the rear are modular rubber-mounted subframes that carry the suspension and differential for reduced road noise, multi-link aluminum lightweight arms with an adjustable toe control link, and a compact coil spring and monotube damper—all designed for minimal intrusion into the cabin and luggage space. Steering is a ZF Servotronic power-assisted speed-variable rack-and-pinion unit.

Chassis dynamics, of course, are managed electronically by the next evolution of StabiliTrak. The new system features active steering-effort compensation, which temporarily raises steering effort in low-traction or emergency-maneuver situations, and side-slip rate control, which improves stability and lateral traction if significant side slip is detected by the lateral-acceleration sensor.

The Imaj also makes use of Delphi's MagneRide semi-active suspension system. It uses Delphi-developed magnetorheological (MR) fluid, which enables fast response for better performance, virtually silent operation, and the elimination of electromechanical valves. The system's electronic control unit sends electrical current to electromagnetic coils housed in the dampers. The current alters the MR fluid's yield stress and, therefore, damping resistance. The damping struts and shock absorbers are gas-charged, monotube designs without valves or other small moving parts. Current applied to an electromagnetic coil inside the damper's piston controls the flow of MR fluid in the damper. Damping levels can be changed as much as 1000 times per second with no lag, and they are said to be extremely stable and insensitive to contamination. Linked to the StabiliTrak system, MagneRide is said to provide Imaj with high levels of vehicle stability control and active safety.

Kevin Jost

AEI May 2000