"There is a saying among actors that light entertainment is the hardest of all. The same principle applies in automotive engineering: treat the matter of vehicle weight too lightly and you will ultimately find it all the more difficult to achieve your objectives." The words of Dr. Franz-Josef Paefgen, Chairman of the Board of Management of Audi AG, echo the guiding principles of auto industry specialists across the world. And Audi has been treating the subject lightly: literally. For Audi is the company that in 1994 took the technology plunge by starting production of the all-aluminum luxury A8 sedan. The company is now embarking on manufacture of the high-volume aluminum A2 with a production target of at least 50,000 a year.
The guiding principle of the significant A2 project is efficiency. That covers everything from aerodynamics — the most aerodynamically efficient version has a remarkably low Cd of 0.25, with standard versions recording 0.28 — to powertrain and production. The range includes the introduction of a "three-liter" version that is claimed to achieve an average fuel consumption of 3.0 liters/100 km (78 mpg), joining sister company Volkswagen's similarly capable Lupo.
The A2 was unveiled at the Frankfurt Motor Show in September and will be in production shortly. AEI was among the first international media to visit the company's new Neckarsulm facility where the A2 will be built. At least one additional aluminum Audi is expected to be built in the near future. But for the moment, Audi is fully focused on getting the A2 into production.
"The A2 model series is our vision of progressive mobility in the 21st century. The A2 combines innovative technology with distinctive design, and its light weight opens up new horizons in terms of both dynamic performance and economy," said Paefgen. Audi has invested more than DM 300 million in plant and buildings for the A2, providing maximum capacity for a 60,000-a-year build. The A2 marks major innovations for Audi, with the necessity of developing what it describes as entirely new or modified techniques, procedures, tools, and production methods for the world's first volume-built aluminum body.
Development of the A2 body was carried out at Audi's Neckarsulm Aluminum Center based on experience gained via the Audi Space Frame (ASF) technology applied to the A8. However, the A2, which represents the second-generation ASF, comprises fewer but larger components, explained the company. It consists predominately of profiles and multifunctional large castings. A single-section side panel frame made from aluminum is also used for the first time in the car industry, according to Audi. Also novel are joining techniques for aluminum that involve a high degree of automation in volume production, with more than 30 m (98 ft) of seams being laser welded. Modular techniques are used in the car's assembly (the dashboard is a significant element of this), and Audi has simplified production line logistics by placing body production and final assembly in one building.
Audi's motto at Neckarsulm is "think light." It has been 15 years since the company started work seriously on aluminum with an eye to use it for production cars. Plant Manager Otto Lindner said it takes "immense technical expertise" and a comprehensive training program to build an aluminum car on an industrial scale. Audi has also made a major investment in automation, which accounts for a modest 25% of the A8's build but for more than 80% for the A2 — said to be necessary to achieve consistently precise dimensional accuracy in high-volume production.
Said Lindner, "This requirement went hand-in-hand with the need for similarly high dimensional accuracy of the body's component parts. Unconventional approaches had to be adopted in the technical development process in order to satisfy this requirement."
The production flow of the A2 starts with panel sections produced in-plant arriving from the press shop, the body components given a pretreatment before being transferred to the upper floor of the A2 production hall. Once assembled, the bodies are transferred to the paint shop via a conveying bridge. They are painted together with the A8 and steel bodies for the Audi A6. Once painted, the bodies are moved back across the bridge to the ground floor of the production hall for final assembly.
Lindner singled out several elements of the A2 build and production process for particular mention: "The single section aluminum side panel is of particular interest. This proved a notable challenge. It is manufactured at our press shop via a four stage drawing process." Automation includes metal inert gas (MIG) welding and punch-riveting. MIG welding allows Audi to produce nodes via butt-welded joins to reduce production time. Punch riveting also allows higher joining speeds and is already used on the A8. "Five years ago, no one would have thought we would be able to weld aluminum automatically by means of a laser, but there are 30 m (98 ft) of laser-welded seams on the production A2; this is certainly unique within the car industry," said Lindner.
Other novel aspects of the A2 include multifunctional large castings such as a single-section B-pillar that previously would have comprised six parts. The A2's extruded sections see the use of a "hydroforming method for calibrating extruded sections," production of the entire section achieved in a single pass with close tolerances, including punching and stamping processes.
Lindner underlined the importance of workforce training. Production workers are involved in technology development processes at an early stage of the planning and implementation phase and "cross-divisional" teams have been formed to optimize processes before production start-up. He added that a comprehensive "launch-flanking" program is used to inform and motivate all workers who will be dealing with the product. The workforce will be about 1500 by 2001, with 500 in body production, 800 in assembly, and the remainder in the paint shop.
The five-door A2 will go on sale this summer with gasoline and turbodiesel (TDI) power units of 1.4-L capacity, each producing 55 kW (75 hp). Later there will also be an ultra-economy version capable of achieving 2.99 L/100 km (79 mpg) fuel consumption using the 1.2-L three-cylinder TDI engine already available on the Lupo. It produces 45 kW (61 aerodyForged aluminum wheels are fitted. Rear bench seat weight was cut by the use of "special materials and a sandwich principle." saving 19 kg (42 lb). The three-liter A2's suspension is some 80 kg (176 lb) lighter than that of the regular car.
The engine fitted to the A2 three-liter has an aluminum crankcase and a mass of 100 kg (220 lb). The A2's 0-100 km/h (0-62 mph) acceleration in 14.8 s and its top speed is 168 km/h (104 mph). It has an automatic stop-start function as a fuel economy aid, the engine restarting as the accelerator pedal is depressed. The car has an intelligent electrohydraulic gearchange mechanism, providing fully automatic or clutchless manual changes. In terms of smoothness of operation, it is the least successful aspect of the three-liter Lupo; it will be interesting to see if the A2 application is better. There is no torque converter. In automatic mode, the driver can select "Eco" for improved fuel consumption with earlier upshift points. The engine complies with EU III emissions regulations and the stricter German D4 regulations. Fuel consumption and emissions performance qualifies the A2 three-liter for tax concessions in Germany.
