Audi continues to forge ahead as the pioneer of lightweight construction for enhanced performance and optimised efficiency with a new aluminium A5 Coupe prototype.
The new A5 prototype follows from the 550,000 cars with aluminium bodies Audi has built since 1994. It aids development of the Audi Space Frame (ASF) concept and points the way to new material and technology for the cars of tomorrow.
The prototype has jettisoned over 100kg by swapping steel for advanced aluminium and carbon fibre construction in the interest of fuel economy, emissions reduction and handling agility. The A5 project is the latest example of Audi’s pioneering work to extend efficiency optimisation measures well beyond the engine bay.
The ASF principle reduces the weight of a car body by at least 40 per cent compared with conventional steel construction; the kerb weight is 1,310kg for the aluminium A5 prototype, against 1,420kg for the equivalent steel-bodied series production model.
Thanks to the significant weight loss, achieved by mounting aluminium and carbon fibre-reinforced plastics onto the aluminium ASF, the A5 prototype is able to use a four-cylinder engine, giving economy and emissions advantages with the performance of a higher output V6.
With the acclaimed 2.0-litre, 211PS Turbo FSI engine, the A5 achieves a power-to-weight ratio of 161PS per tonne – a production A5 3.2 FSI V6 quattro with 265PS, tips the scales at 1,540kg, and shades it only by a fraction at 172PS per tonne.
The lightweight design has a knock-on effect on ancillaries such as the brakes and transmission, which can also be reduced in size and weight. It enables the car to change direction noticeably more nimbly and, thanks to the reduction in unsprung weight, to ride with even more refinement.
15 years of lightweight construction experienceOver the past 15 years, Audi has employed the ASF principle in two generations of A8 luxury saloon, in the hyper-efficient, ahead-of-its-time, A2 compact hatchback and in the celebrated R8 supercar. ASF has also been re-interpreted in the creation of the latest TT Coupe and Roadster, which feature advanced steel and aluminium ‘hybrid’ construction that allows for outstanding weight distribution.
“One of our most enduring aims for the future is to reverse the weight spiral,” says Michael Dick, Member of the Board of Management of AUDI AG responsible for Technical Development. “Lightweight design is the foundation of our entire approach to improving efficiency.”
The Aluminium and Lightweight Design Centre
Audi established a special Aluminium Centre in Neckarsulm for development, production planning and quality assurance in 1994. The Aluminium and Lightweight Design Centre experiments with high-strength steels, tailored blanks, fibre-reinforced plastics and magnesium.
Heinrich Timm, the Head of the Aluminium and Lightweight Design Centre, says: “Aluminium remains the primary material, but we are intensively investigating the other materials, with our primary focus on fibre-reinforced composites.”
The lessons learned at the Aluminium and Lightweight Design Centre innovation foundry, which employs 150 people, have already served as the basis for a three-digit number of patents in development and production. The European Patent Office named Audi “European Inventor of the Year 2008” for its achievements with the ASF technology.
Lightweight design in the rest of the vehicle
Audi also makes systematic use of lightweight design in the drivetrain and the chassis. Many engines use aluminium and vermicular graphite cast iron, which is the result of a high-tech production process, to reduce the weight of the crankcase. Many models have chassis with predominately aluminium parts.
Carbon fibre-ceramic brake discs are available as an option in the high-performance models. Other highlights of lightweight design include brake calipers, bonnets and boot lids, side panels or cover components made of aluminium and steering wheel rims or instrument panel mounts made of magnesium.
Experience from the world of motorsport flows back into the development work – the reduction and distribution of weight are extremely important for Audi’s pioneering diesel-engined Le Mans sports-prototypes and its DTM touring cars. The race cars provide the production development engineers with important information about carbon and its combination with metal.
Research continues into new materials and alloys, with the focus on minimal weight with maximum durability as well as design and fabrication compatible with the materials.
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