ultra lightweight construction has long been a main pillar of the brand. Audi recorded a pioneering achievement in the use of aluminum as a body material back in 1994: The first A8 had a full-aluminum body in ASF (Audi Space Frame) technology.
ultra lightweight technology reduces the weight of the new Audi A3 Sportback by as much as 90 kilograms (199.42 lb) compared with the previous version. Equipped with the 1.4 TFSI engine, the compact five-door model has a curb weight (without driver) of just 1,205 kilograms (2,656.57 lb). Audi, worldwide pioneer in lightweight construction, has reversed the weight spiral and once again set a new record.
ultra lightweight construction in the body
The broad-based expertise of the Audi body development engineers is by no means restricted to a certain material, but rather encompasses all relevant materials. The multimaterial construction of the new Audi A3 Sportback is entirely in keeping with the motto “The right material at the right place for optimal function.”
High-end components of hot-shaped steel in the occupant cell form a strong, yet lightweight structure. Before deformation, they are heated in a continuous flow furnace to nearly 1,000 degrees Celsius and are then cooled to about 200 degrees in a water-cooled stamping press.
This extreme temperature jump creates an iron-carbon structure with extreme tensile strength. Hot shaped steels are able to perform with relatively thin walls, and this makes them lightweight.
Hot-shaped steels represent a roughly 25 percent share of body materials. They 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. What is known as a tailored rolled blank forms the transition from the floor to the rear body section – its eleven individual segments are rolled into five different thicknesses.
The B-pillars also consist of this high-end steel; their lower sections are more flexible than above, since the energy of a side-impact collision must be absorbed here. All together, the hot-shaped steels in the new Audi A3 Sportback reduce the weight of the vehicle by 37 kilograms (81.57 lb) compared with the previous model.
High-strength and ultra-high-strength steel grades are used in many other body areas such as in the side members and in the floor of the passenger cell. The engine hood, fenders, the subframe of the front axle and the sections mounted behind the front bumper as crash absorbers are made of aluminum. Together the aluminum components save around twelve kilograms (26.46 lb), thus improving axle load distribution.
Processing aluminum components in body construction and joining these components with steel components are challenging tasks. The same is true of welding hot-shaped components, which are coated with a corrosion-inhibiting aluminum-silicon alloy. Audi benefits here from its extensive know-how in ultra lightweight construction – the joining technologies have been practice-proven for years now in models such as the TT. A number of very different joining technologies are used to assemble the new A3 Sportback, including bonding, clinching and punch riveting.
Between the side wall and the roof, which are both made of steel, a Plasmatron brazed seam produces the joint, where the allowable tolerance is just a few tenths of a millimeter. The finished seam is smoothed with brushes – the practically invisible zero-joint that is produced is an expression of the stringent precision thinking at Audi.
Unlike the previous model, the doors and window frames are stamped in one piece, and this also saves weight. The door hinges integrate a convenient new type of clamping mechanism.
Rigidity and acoustics
The body of the new Audi A3 Sportback attains very good values in static and dynamic torsional rigidity – this creates the foundation for its high precision, e.g. in the fits of doors, hoods, trunk lids, in production and in the acoustic comfort inside the car. A noise-insulating windshield is standard equipment; despite the addition of an intermediate film layer, it is no heavier than the previous windshield.
New are two encircling sealing lines that reduce wind noise in the area of the doors and windows. They also keep the entry sills clean. The design of the exterior mirrors, which are mounted to the upper door panels, also contributes to the car’s acoustic comfort.
Many other measures have been implemented to reduce interior noise in the new A3 Sportback, including wheel housing shells made of an acoustically insulating fleece material – its weight impact is 0.5 kg (1.10 lb). The insulation used behind the pillar trim, behind the instrument panel and in the luggage compartment consists of the same lightweight material.
Safety and aerodynamics
The new Audi A3 Sportback 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. The structural members for the engine and front suspension, as well as the sections in the upper area of the fenders, act as additional load paths. If necessary, the pedals are decoupled from the firewall; the steering column absorbs energy and is not displaced into the occupant cell.
In a side impact, the occupant cell offers excellent protection with its hot-shaped steel components such as the sills and B-pillars. In a rear-end collision, the bumper’s cross members redirect loads to the large side members made of high-strength steel.
The new Audi A3 Sportback meets all legal requirements for the protection of pedestrians in the event of a collision. Starting at a specific collision speed, a new system is activated. Pyrotechnic elements at the back of the engine hood raise it upward. This increases the distance between the engine hood and the engine components, thus cushioning the impact with the pedestrian.
Minor collisions, such as the standardized low-speed collision, do not result in any major financial impact, which is also reflected in the car’s favorable type classification – the new Audi A3 Sportback is rated the best-in-class for its market segment. It also performs well in the RCAR bumper test, focused on the compatibility with the other party in the collision.
The new Audi A3 Sportback is planted firmly on the road – a strength attributable in large part to Audi’s aerodynamics specialists. The underbody back to the B-pillar is completely lined. The covering is made of glass fiber-reinforced polymer. It protects the sheet metal and engines from salt, water and stone impact and absorbs undesirable vibrations. Small spoilers in front of the wheels help to guide the air flow with low drag losses. The aerodynamic underbody of the new Audi A3 Sportback reduces aerodynamic drag by about ten percent. To take full advantage of the aerodynamic potential, a great deal of effort was also focused on the flow of air through the engine compartment.
Thanks in part to the aerodynamic fine tuning in such areas as the underbody and the engine compartment, the new Audi A3 Sportback has a coefficient of drag of just 0.31 with a frontal area of 2.13 m² (22.93 sq ft).
ultra lightweight construction in the interior
The Audi ultra lightweight principle is not limited to the body or to specific subassemblies and parts – developers always consider the vehicle as a whole, and in their work every gram counts. This is the only way the car’s curb weight could be reduced by up to 90 kg (198.42 lb) compared with the previous model.
The engineers have internalized the Audi ultra lightweight principle, and in the interior of the new Audi A3 Sportback they also succeeded in eliminating every superfluous gram. The redesigned seats contribute a one kilogram (2.20 lb) weight savings; lightweight plastic inserts replace the steel wire used previously in the frame of the rear bench seat.
A new control unit arrangement requires fewer wires, thus reducing the weight by 1.5 kilograms (3.31 lb). The blower motor requires fewer coils, and the air conditioning system shed four kilograms (8.82 lb) of weight. The housing of the passenger airbag is made of polymer; the mounting for the MMI monitor is made of magnesium. Together these two solutions save 640 grams (1.41 lb). In the previous model, many linings in the interior were fastened with steel screws. In the new Audi A3 Sportback, polymer expanding rivets were used here for a weight savings of four grams (0.01 lb) per fastening point. When it comes to the Audi ultra lightweight construction principle, every gram counts.
ultra lightweight construction in engines and chassis
The engines of the new Audi A3 Sportback have shed a significant amount of weight as well. The engines of the new A3 have shed a lot of weight as well. The 1.8 TFSI, for example, weighs just a little over 130 kilograms (286.60 lb), while the 1.4 TFSI weighs in at just 107 kilograms (235.89 lb) – 21 kilograms (46.30 lb) less than the previous engine. With a weight difference of 15 kilograms (33.07 lb), the aluminum crankcase accounts for the largest share of reductions, but progress has also been made in many small engine details – e.g. in the new aluminum pistons and the hollow-bored connecting rod pins.
In the 1.8 TFSI, the thin-wall technology of the crankcase reduces weight by 2.4 kilograms (5.29 lb). In the 2.0 TDI, the balance shafts are mounted in the engine block, which accounts for three kilograms (6.61 lb) of savings, while modified sound dampers in the exhaust system save an additional two kilograms (4.41 lb). Weight was trimmed from the exhaust system in all engine versions.
In the chassis, the new one-piece aluminum subframe and aluminum pivot bearings (depending on the engine) reduced the weight of the front suspension system by about six kilograms (13.23 lb). The optional 18-inch alloy wheels are no heavier than the 17-inch wheels; they are produced by a complex flow-forming technology. In this process, the rim well is rolled out over a cylinder under high pressure and at high temperature. The system shapes the wheel blank in a single work step, during which the material also becomes stronger. This permits thinner wall thicknesses so that the wheel is both lighter and stronger.
In developing the new A3, Audi conducted an environmental assessment of two of the engine versions. The 1.4 TFSI and the 2.0 TDI – both with a manual transmission – were subjected to a detailed analysis. Both versions offer clear benefits compared with their respective previous models. Greenhouse gas emissions, for example, are reduced by roughly two metric tons per model. This corresponds to roughly seven to nine percent of the greenhouse gas emissions over the entire life cycle. This is due in large part to the substantially lower fuel consumption and low weight of the new models. At the end of its life, about 95 percent of the new Audi A3 Sportback can be recycled.
The theme of sustainability is a high priority in production as well. The new hall, in which the bodies of the A3 Sportback are produced, has a photovoltaic system on its roof that covers 7,500 m2 (80,729.33 sq ft) of surface area. It generates about 460 MWh of electricity annually, which avoids 245 metric tons (270.07 US tons) of CO2 emissions. All production systems and their control units are networked into an intelligent shut-down strategy that saves a lot of electricity.
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.