G90 CONCEPT CAR LEADS GM'S 'GREEN' DRIVE

R�sselsheim/Frankfurt. The "G90", an innovative, minimal-consumption concept car, will be one of the major attractions on the Opel stand at this year�s Frankfurt International Motor Show (IAA). With its 44 kW/60 hp, three-cylinder gasoline engine, the concept car produces only 90 grams (G=90) of CO₂ emissions per kilometer. This undercuts by more than a third the limit of 140 grams per km planned by the European Union to become the manufacturer's average fleet value in the year 2008. 90 grams of CO₂ per km represents MVEG-standard fuel consumption of 3.88 liters per 100 km.

This exceptionally low figure for a spacious four-seater in the Astra class was achieved by innovative weight-saving and a drag coefficient of cD = 0.22. At the same time the G90, which hints at the direction that Opel's body styling could take in the future, demonstrates new approaches in interior design.

"With its aerodynamic design and low curb weight of only 750 kilograms, the G90 concept car demonstrates an alternative approach to future mobility on the eve of the next millennium", says Hans Demant, Opel's Head of Development. "This new vehicle concept shows that - independent of the power train and without having to resort to exotic materials or detract from passenger comfort - it is possible to make a reasonably priced car with fuel consumption in the region of three liters per 100 kilometers - and one that is also great fun to drive!"

From the very start of the project, Opel�s engineers had a clear picture of the basic design of their concept study. As far back as 1997, during the forward engineering phase, two fundamental decisions were taken: the engine should not be a special design but a unit in the Opel production program. And it had to be a gasoline engine. Walter Treser, Opel's Director of Advanced Engineering says, "There were two reasons why we went for a gasoline engine: first, the direct-injection principle has a lot of potential, and second, it's cheaper to make a gasoline engine than a diesel. That clearly benefits the customer and is in keeping with our philosophy of offering top technology at reasonable prices."

Light and Efficient: Three-Cylinder ECOTEC Engine
As a consequence, the G90's power plant was chosen from Opel�s wide range of high-tech engines, "off the shelf" as it were. The final decision went in favor of the Corsa's extremely efficient three-cylinder ECOTEC unit. This has a displacement of 973 cc and advanced technological features such as hollow camshafts, a modern micro-hybrid engine-management control unit and sequential fuel injection. In the concept car, this 12-valve engine has an output of 44 kW (60 hp) and maximum torque of 85 Nm at 2,800 rpm. A genuine lightweight at only 80 kilograms, the engine drives the front wheels through a sequential-shift transmission, with its five speeds actuated either manually at a rocker on the steering column, or automatically if a button is pressed.

In the G90, the performance of this compact three-cylinder engine is truly astounding: it whisks the 750-kilogram car from zero to 100 km/h in only 14 seconds, accelerates from 80 to 120 km/h in 18 seconds and goes on to reach the impressive top speed of 180 km/h. Another well-suited engine for the "G90" study is the 1.2-liter, four-cylinder unit from the ECOTEC Compact engine series. With this lively 55 kW (75 hp) four-valve engine, the G90 would reach a top speed of 200 km/h.

Aerodynamic Design: Perfect Droplet Shape Cuts cD Value to 0.22
The G90�s high top speed is partially a by-product of the concept car�s excellent drag coefficient of 0.22 and a frontal-area index (cd x A) of only 0.45. These aerodynamic data were achieved although the Opel engineers and designers working on the G90 project were unable to achieve a streamlined shape by increasing the length. They had to get the same results from a short vehicle with an overall length of precisely 3996 millimeters (wheelbase: 2550 mm). Frank Leopold and Martin Gerspacher, engineers in Opel's advance development "think tank" at the International Development Center (ITDC) in R�sselsheim, recall the first tentative steps: "To find out exactly how a car with these dimensions and a drag co-efficient of under 0.25 ought to look we started off by building a model based solely on technical factors." They soon hit upon something that today represents the fundamental aerodynamic element in the Opel concept: a striking teardrop shape with a distinctly sloping roof and sharply cropped tail. The first draft designs, with their smooth, rounded surfaces, recalled the aerodynamic prototypes of the early 1970s; but the G90 as revealed in Frankfurt has a very individual character with typical Opel design cues such as the kink below the windows, the bold wheel-arches and the V-shaped radiator grill with its large Opel emblem.

With elements such as these the study's styling not only speaks the technically-oriented design language already expressed by the Astra and Zafira. It also establishes new trends and points the way to Opel's future styling intentions. This is exemplified in the "crease", designer jargon for the raised line running down the center of the engine hood but also in the styling and technology of the headlamps. Integrated at different levels in a single unit are the headlights, fog lights, and the indicator lights which use light-emitting diodes (LEDs).

Visuals: Technical Design with High Functionality
The lights also dominate the rear of the G90. The brake lights and indicators are incorporated in small plexi-glass housings and, when not activated, are seen as small white elements through the transparent cover. Stefan Arndt, head of the G90 design team, says, "Elements like these and the precisely defined aero-trailing-edge that passes through the glass of the tailgate and the rear lights, help to underline the functionality of the car." In conjunction with the dark smoked glass of the tailgate and the lights, the trailing edge emphasizes the horizontal plane and gives the four-door car a wider appearance.

The aerodynamic detailing is also easy to see at many points on the body - the partly concealed rear wheels, the smooth side panels or the two aerodynamic "humps" in the roof. These guarantee excellent headroom for all four occupants (980 mm at the front, 970 at the rear), while the recess between the domes also helps to reduce the total frontal area to only 2.05 square meters.

The most distinct feature of the 1650-mm-wide, 1477-mm-high car is the wind tunnel influenced teardrop-shape at the rear. To ensure that the G90 kept as closely as possible to this pure, natural shape with a narrow tail section, and to prevent the additional drag caused by turbulence, its rear-end dimensions were greatly reduced. At 1360 mm the rear tread is distinctly narrower than the front (1452 mm). As a result the G90 offers two individual seats instead of a conventional bench.

The concept car's comprehensive range of safety features includes seat belt tensioners, front and side airbags and Opel's Pedal Release System that reduces the risk of inury to the driver's legs in a frontal collision. Active Head Restraints on both front seats significantly reduce the risk of whiplash.

Plenty of Space for Four People and their Luggage
The G90's load compartment is spacious, and together with the added volume in a concealed storage space under the lid, has a volume of 350 liters (VDA standard test method. This volume can be increased to 980 liters if the rear seat backs, which split 50:50, are lowered. The front passenger seat can be folded down to provide a completely flat surface for loads up to 2.50 m in length. The maximum load-width between the wheelarches is 1.10 m.

Progress: Smooth Underfloor with Efficient Diffuser Effect
Like the rear-end design, the smooth, enclosed underbody, into which the entire exhaust system is integrated, contributes significantly to the G90's excellent aerodynamics. The undertray is formed from aluminum sheet designed specifically for the study. Says Uwe S�ss, one of the engineers in the advance development team: "It is only one millimeter thick and extremely light. Its stability comes from a special honeycomb structure with hexagonal domes. To retain the flat surface, we integrated the crossmembers - which are usually exposed beneath the vehicle - into the floor structure inside the car."

The greatest aerodynamic progress in the G90's underbody area, however, was obtained by allowing the floor to rise at the rear by an angle of six degrees. This results in a "diffuser effect", well known from racing car design. Together, the rearward sloping roof line and the low trailing edge on the tailgate combine to reduce the rear surface area. The airflow above and below the car passes the body faster, resulting in less turbulence and reduced drag.

Lightweight Construction: Systematic Use of Aluminum and Magnesium
The G90�s weight of only 750 kg complements the concept car�s excellent aerodynamics in reducing fuel consumption. The low weight was achieved by the strategic application of lightweight materials such as aluminum and magnesium. Thanks to the G90�s low fuel consumption, a lightweight fuel tank with a capacity of only 30 liters is enough to give the concept car a range of about 770 kilometers. Since the body weight is so low, lighter brakes could be fitted. Specific weight reductions were also achieved on all the chassis components, including highly stressed elements such as the steering knuckles and the aluminum suspension struts.

Novel Design: Entire Exhaust System Weighs Only 13 Kilograms
The lightweight stainless steel exhaust system was not designed in the usual way as a self-supporting element. It has five mounts instead of the typical three, allowing the sheet metal thickness to be reduced from 1.5 to 0.8 mm. The G90's exhaust system - including the catalytic converter and manifold - weighs only 13.1 kg, almost six kilograms less than a comparable conventional system. In addition to this the car's aluminum engine hood at 6.0 kg weighs between three and four kilograms less than equivalent steel versions.

Differences in weight are even more marked where G90 components are made of ultra-light magnesium. As well as the transmission housing, steering wheel and elements of the seats, they also include the roof, though the body is otherwise made entirely of aluminum. Superfluous weight is eliminated further and the reduced weight at this height on the body lowers the center of gravity, which improves road. The optimum weight distribution of the front-wheel drive G90 is also aided by the unusual low-slung battery position.

Road-holding: Lower Center of Gravity and Agile Handling
Apart from the weight reductions, a notable aspect of the concept car's chassis is the lightweight torsion-beam rear suspension. It is so compact that the strut turrets no longer protrude into the luggage compartment, which results in a generous load-width. The large 17-inch alloy wheels with low rolling-resistance 155/55 R17 tires are another striking feature. Their tread design is such that when driving straight ahead the tire's contact-patch area is relatively small, but increases significantly when braking or cornering. The result is a combination of low fuel consumption and high safety.

Interior: Ingenious Ideas for Greater Convenience
Innovative ideas also abound in the passenger compartment, where the designers and engineers have adhered as rigidly to the G90's guiding principle of "Less is More" as they did when creating its fuel-saving body concept. This is most evident in the prominent T-shaped technology carrier at the center of the cockpit. With a polished metallic finish, the carrier contains the audio and mobile phone module, the climate control system and the navigation system with display. The latter is only visible after the driver presses the button to start the ECOTEC-three-cylinder engine and the display cover opens automatically.

Fact-Finding: Information at the Touch of a Button
The ergonomically-placed 5-inch screen above the technology carrier is not only for displaying the chosen route. With the aid of only four buttons at the left and right respectively, it is possible to access menus for the radio/CD player, telephone, navigation system and electronic climate control. The individual functions are displayed graphically and can be adjusted or altered via two rotary/push buttons. A click as with a PC-mouse is enough to confirm the command. Designer Stefan Arndt: "This is part of the strategy behind the entire G90 project. The car not only weighs less and has lower fuel consumption than comparable cars, it also has distinctly fewer switches and buttons."

The chronometer-look instruments are reminiscent of a motorcycle cockpit and are placed in the driver's unobstructed field of vision. This is achieved by the perfect ergonomic positioning of the speedometer and rev counter behind the adjustable-angle steering wheel. Separate displays in the center ensure that additional information such as the trip-distance or the gear selected remains visible even when the steering-column angle is adjusted. Other clever ideas in the G90 passenger compartment include indirect lighting in the roof, footwells and doors (which makes driving at night more pleasant), as well as a draft-free ventilation system that has a broad outlet on the passenger's side to keep the airflow speed lower than from usual vent nozzles.

Robert W. Hendry, Chairman and Managing Director, Adam Opel AG, says: "The G90 incorporates such well-known Opel characteristics as excellent aerodynamics, attractive design and outstanding fuel economy. It therefore represents the essence of our company's 100 years of automobile manufacturing tradition and engineering skill. In addition, the concept study expresses the responsibility which we bear as a car maker for the environment and for future generations."

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