Lightweight design/construction is one of Audi’s core areas of expertise. As a pioneer in this field, Audi discontinued and then reversed the trend toward ever-heavier vehicles. Regarding the basic version of the new A3 Sedan with S tronic, the curb weight (without driver) is just 1,250 kilograms (2,755.78 lb), which sets a new standard in this class. Yet this four-door vehicle is stately, too: 4,456 millimeters in length (14.62 ft), wheelbase of 2,637 mm (8.65 ft), 1,796 mm in width (5.89 ft) and 1,416 mm (4.65 ft) in height.
Ultra-lightweight: multi-material body
Whether aluminum, steel or composites, developers of vehicle bodies at Audi possess a wealth of expertise. They do not limit themselves to any one material; on the contrary, they rely on any and all materials that result in a perfect blend of properties.
Form-hardened steels constitute 26 percent of the A3 Sedan’s body. Before deformation, they are heated in a continuous-flow furnace to nearly 1,000 degrees Celsius (1,832 degrees Fahrenheit) and are then cooled to about 200 °C (392 °F) in a water-cooled stamping press. This radical drop in temperature creates an iron-carbon structure of exceptional tensile strength. Components made of these high-end steels can exhibit relatively thin walls, making them lightweight.
Form-hardened components are used in the transition from the front of the vehicle to the occupant cell, in the A-pillars, roof arch, center tunnel, side sills and floor panels. The B-pillars also consist of this form-hardened steel. Their lower sections are more flexible than higher ones, as the energy of a side-impact collision must be absorbed here. Audi uses high-strength and ultra-high-strength steel grades in many other body areas, such as the longitudinal members and the C-pillars. Something known as a tailored rolled blank joins the floor with the rear body section. Such a blank has eleven individual segments of five different thicknesses.
Moreover, the hood, the front axle’s subframe, the energy-absorbing section behind the front bumper and the rear shelf are all made of aluminum. All in all, these light-alloy components save 12 kilograms (26.46 lb). This advancement benefits the distribution of axle loads. The front-end axle carrier is made of high-strength plastic and weighs three kilograms (6.61 lb) less than its predecessor.
The vehicle body of the A3 Sedan features a remarkable variety of joining techniques. In addition to classic resistance spot welding – which creates 5,467 weld spots – primary techniques include MIG/MAG welding, laser welding, stud welding, projection welding, clinching, seaming and semi-tubular punch riveting. Just one A3 Sedan body contains 54 meters (177.17 ft) of structural adhesive, five meters (16.40 ft) of retaining adhesive, 20 meters (65.62 ft) of seam adhesive and four meters (13.12 ft) of lining adhesive.
A laser-brazed seam serves as a high-precision joint between the vehicle’s side wall and roof. This seam is smoothed with brushes, resulting in a practically invisible zero-joint that demonstrates Audi’s commitment to precision. The seams around the tailgate’s water drains are executed via plasmatron brazing. The doors and window frames are pressed in one piece, which likewise reduces weight. Cutting-edge remote laser welding is used for the doors.
Benchmarks: rigidity, acoustics, safety and aerodynamics
Thanks to the extensive resources Audi commits to body manufacturing, the
A3 Sedan boasts excellent static and dynamic torsional rigidity. This contributes to the vehicle’s excellent precision of manufacture and quiet interior. A noise-insulating windshield is standard equipment, as are two wraparound soundproofing seals that minimize wind noise at doors and windows. The outside mirrors were designed to likewise reduce interior noise levels. Noise-insulating materials in the interior, especially the molded part between the floor and carpeting, are very lightweight yet highly effective.
The new Audi A3 Sedan is tops when it comes to passive safety. In a frontal collision, the front cross-member distributes the forces to the two side members, which undergo defined deformation to dissipate these forces. Additional crumple zones include the front axle’s subframe and sections in the upper part of fenders. In a side impact, hot-shaped steel components such as the sills and B-pillars offer occupants excellent protection. In a rear-end collision, the bumper's cross members transmit the stress to large longitudinal members.
In a vehicle/pedestrian collision above a certain speed, an active safety system is activated. The hood separates from its hinges at lightning speed, and it is pushed upward by gas-filled springs. This increases the distance between the engine hood and hard parts of the engine compartment, and the impact of the pedestrian is less severe.
The Audi A3 Sedan features a drag coefficient of just 0.29, thanks in part to finishing touches in concealed areas. Covers made of glass-reinforced plastic line the underbody up to the B-pillars. These covers protect the sheet metal and engine from salt, water and pebbles while absorbing vibrations. A small spoiler in front of every wheel helps minimize loss of airflow. The aerodynamic underbody of the new A3 reduces overall aerodynamic drag by about 12 percent.
The equipment and data specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.