Audi presents the highlight of the 2011 Australian International Motor Show: the e-tron, a high-performance sports car concept with a purely electric drive system.

Embodying Progressive Performance, the Audi e-tron is poised to become a synonym for advanced electric mobility and Audi’s commitment to an electrified future. Combining Audi’s core brand pillars of efficiency and performance with breathtaking design and next-generation technology, the Audi e-tron is the future.

Four motors – two each at the front and rear axles – drive the wheels, making the concept car a true quattro. Producing 230 kW, the two-seater accelerates from 0 to 100 km/h in 4.8 seconds, and from 60 to 120 km/h in 4.1 seconds. The lithium-ion battery provides a truly useable energy content of 42.4 kilowatt hours to enable a range of approximately 248 kilometres.

The Audi e-tron first stunned the world when it was revealed at the IAA in Frankfurt in 2009 and highlighted Audi’s future-thinking in electro-mobility.

Those impressive performance figures are by no means the only evidence of the consistent and holistic strategy. The design makes it clear that the e-tron belongs in the major leagues of sports cars, and the package takes into account the specific realities of an electric vehicle. The battery is directly behind the passenger cabin for an optimal center of gravity and axle load distribution.

The e-tron is able to freely distribute the powerful torque of its four electric motors to the wheels as required. This so-called torque vectoring allows for dazzling dynamics and an incredible agility and precision when cornering.

Audi has taken a new and in some cases revolutionary approach to many of the technical modules. A heat pump is used to efficiently warm up and heat the interior. The drive system, the power electronics and the battery are controlled by an innovative thermal management system that is a crucial component for achieving the car’s range without compromising its high level of interior comfort. Networking the vehicle electronics with the surroundings, which is referred to as car-to-x communication, opens new dimensions for the optimisation of efficiency, safety and convenience.

The Concept

Electric driving offers numerous advantages. Electric cars reduce the dependence of transportation and the economy on the raw material petroleum. They produce no direct exhaust emissions and thus ease the local burden on the environment. Electric drive systems are also significantly more efficient than combustion engines, consequently making them easier on the customers’ wallets.

There is still a lot of work to do before electric cars are ready for volume production, but Audi is meeting those challenges and the e-tron forms the basis for the Audi R8 e-tron – a fully electric supercar that goes into production late in 2012.

Audi e-tron – The Holistic Approach

The most important development related to batteries for electric drives are lithium-ion cells. Numerous experts throughout the world are working on their further development for use in cars, with the primary objectives being to reduce weight and increase capacity and performance.

The requirement specification for the concept vehicle goes far beyond battery technology and the replacement of the combustion engine with an electric drive system, however. The Audi development engineers decided back in the concept phase to design practically every component and technology based on the new requirements of electric mobility. The interaction of all elements has a decisive influence on the factors efficiency, range and practicality.

Design and Package

The caliber of the car is apparent to the observer at first glance. The Audi e-tron has a wide, powerful stance on the road. The trapeze of the single-frame grille dominates the front end and is flanked by two large air intakes. The top of the grille merges into the flat strips of the adaptive matrix beam headlamp modules with their clear glass covers. High-efficiency LED technology is used for all lighting units – a matter of honour for Audi as the worldwide pioneer in this field.

A new design element unique to the e-tron are the air intakes in the single-frame grille and in front of the rear wheel arches. They are closed flush under normal circumstances and opened by means of flaps when additional cooling air is required. Maximum efficiency is also the reason behind this measure. The concept car has a remarkably low drag coefficient, which gets even better when the flaps are closed.
The vehicle body is compact. The sweeping line of the front end and the flat curved roof immediately identify the two-seater as an Audi. The contours of the flanks are familiar. The tapering of the dynamic line above the sill and the shoulder line tie together the front end, the side and the rear, lend a plastic quality to the doors and the transition to the side air intake and sharply emphasize the Audi-typical round wheel wells with the large, 19-inch tyres.

1.90 metres wide, just 4.26 metres long and 1.23 metres tall – these are the proportions of a supercar. The wheelbase of 2.60 metres leaves plenty of room between the axles for people and technology. Like with a mid-engined sports car, the cabin of the e-tron is shifted far forward toward the front axle, leaving room in front of the rear axle for the roughly 470 kilogram battery unit, the inverter and the power electronics.

The two electric motors, which have their own cooling system, are mounted behind the rear axle. The front electric motors are mounted on the front axle, with their cooling system arranged in front of them. This special package, which features a 42:58 weight distribution, ensures perfect balance, which contributes to the driving dynamics of the e-tron.

Systematic lightweight construction is an even more important prerequisite for efficiency and range with electric vehicles than for conventionally powered automobiles. The Audi development engineers drew on the core competence of the company for the e-tron. The body structure is based on Audi Space Frame (ASF) technology and was realized as a hybrid construction. All add-on parts – doors, covers, sidewalls and roof – are made of a fiber-reinforced plastic.

The combination of aluminium and carbon fibre-reinforced composite material guarantees supreme rigidity coupled with low weight. Audi will soon use this technology in a similar form for production vehicles. Despite the complex drive system layout with four electric motors and a high-capacity battery system, the total weight of the Audi e-tron is only around 1,600 kilograms.

Interior and Control Concept

Optical and functional references to the new drive concept characterise the interior design. They establish an advanced connection between proven Audi genes and new hallmarks. Typical for the Audi design language is the reduction of the architecture, controls and flow of information to the essential in favour of visible lightweight construction and a tidy overall impression.

The dash appears to float and has a curve that extends laterally into the door panels. With no need to allow for a transmission or gear lever, the designers took advantage of the opportunity to create a particularly slim and lightweight center tunnel and center console. The flush gear selector, with which the driver chooses between the modes forward, reverse and neutral, emerges from the tunnel when the vehicle is started.

While an analog speedometer on the right provides speed information, the instrument on the left tells the driver how much power is being drawn. The central display shows the range in the status bar and presents all key information from the infotainment and navigation systems. It also provides the driver with relevant data from the vehicle’s communication with its surroundings. The instruments combine the analog and the digital worlds into a single unit.

Characteristic for the concept of the Audi e-tron is the near total elimination of switches and small components such as the ignition.

The racing-inspired lightweight bucket seats combine excellent lateral support with comfort. To contrasting colors – snow white and cognac – delineate the various zones of the interior. The colors and the high-quality materials combine elegance and sportiness.

Drive System and Energy Supply

Four asynchronous motors with a total output of 230 kilowatts give the Audi e-tron the performance of a high-output sports car. The concept car can accelerate from 0 to 100 km/h in 4.8 seconds if necessary, and goes from 60 to 120 km/h in 4.1 seconds. The torque flows selectively to the wheels based on the driving situation and the condition of the road surface, resulting in outstanding traction and handling.

The top speed is limited to 200 km/h, as the amount of energy required by the electric motors increases disproportionately to speed. The range in the NECD combined cycle is approximately 248 kilometres. This good value is made possible by the integrated concept: technology specially configured for the electric drive system combined with state-of-the-art battery technology. The battery block has a total energy content of roughly 53 kilowatt hours, with the usable portion thereof restricted to 42.4 kWh in the interest of service life. Audi uses liquid cooling for the batteries.

The energy storage unit is charged with household current (230 volts, 16 amperes) via a cable and a plug. The socket is behind a cover at the back of the car. With the battery fully discharged, the charging time is between 6 and 8 hours. A high voltage (400 volts, 63 amperes) reduces this to just around 2.5 hours. The Audi engineers are working on a wireless solution to make charging more convenient. The inductive charging station, which can be placed in the garage at home or also in special parking garages, is activated automatically when the vehicle is docked. Such technology is already used today in a similar form to charge electric toothbrushes.

The battery is charged not only when the car is stationary, but also when it is in motion. The keyword here is recuperation. This form of energy recovery and return to the battery is already available today in a number of Audi production models. During braking, the alternator converts the kinetic energy into electrical energy, which it then feeds into the onboard electrical system.

The Audi e-tron, which is equipped with lightweight ceramic brake discs, takes the next large step into the future. An electronic brake system makes it possible to tap into the recuperation potential of the electric motors. A hydraulic fixed-caliper brake is mounted on the front axle, with two novel electrically-actuated floating-caliper brakes mounted on the rear axle. These floating calipers are actuated not by any mechanical or hydraulic transfer elements, but rather by wire (“brake by wire”). In addition, this eliminates frictional losses due to residual slip when the brakes are not being applied.

This decoupling of the brake pedal enables the e-tron’s electric motors to convert all of the braking energy into electricity and recover it. The electromechanical brake system is only activated if greater deceleration is required. These control actions are unnoticeable to the driver, who feels only a predictable and constant pedal feel as with a hydraulic brake system.

Making its Automotive Debut: The Heat Pump

The heat pump – used here for the first time ever in an automobile – also serves to increase efficiency and range. Unlike a combustion engine, the electric drive system may not produce enough waste heat under all operating conditions to effectively heat the interior. Other electric vehicles are equipped with electric supplemental heaters, which consume a relatively large amount of energy. The heat pump used by Audi – and commonly used in buildings – is a highly efficient machine that uses mechanical work to provide heat with a minimum input of energy.

A high-efficiency climate control system is used to cool the interior. It works together with the thermal management system to also control the temperature of the high-voltage battery. The battery, the power electronics and the electric motors must be kept at their respective ideal operating temperatures to achieve optimal performance and range.

Driving Dynamics

The normal distribution of the tractive power is clearly biased toward the rear axle in accordance with the weight distribution of the e-tron. Similarly to a mid-engined sports car, roughly 70 percent of the power goes the rear and 30 percent to the front. If an axle slips, this balance can be varied by means of the four centrally controlled electric motors. The electric vehicle from Audi thus enjoys all of the advantages of quattro technology.

The four individual motors, which in the interest of greater traction are installed behind the wheels as wheel drives, also enable the e-tron’s lateral dynamics to be intelligently controlled. Similar to what the sport differential does in conventional quattro vehicles, torque vectoring – the targeted acceleration of individual wheels – makes the e-tron even more dynamic while simultaneously enhancing driving safety. Understeer and oversteer can be corrected by not only targeted activation of the brakes, but also by precise increases in power lasting just a few milliseconds. The concept car remains extremely neutral even under great lateral acceleration and hustles through corners as if on the rails.

The chassis has triangular double wishbones at the front axle and trapezoidal wishbones made of forged aluminium components at the rear axle – a geometry that has proven in motorsports to be the optimal prerequisite for high agility, uncompromising precision and precisely defined self-steering behavior. A taut setup was chosen for the springs and shock absorbers, but it is still very comfortable.

As befitting its status, the Audi concept car rolls on 19-inch tyres with a new blade design. 235/35 tires up front and 295/30 tires in the rear provide the necessary grip.

Audi R8 e-tron to hit the streets in 2012

Audi has an unmatched history in taking concept cars to reality and the e-tron is no exception. The e-tron first showed what was possible for Audi in electro-mobility and now engineers are making that a reality with the R8 e-tron going into series production in 2012.

A small production run of the R8 e-tron sports car, the first all-electric Audi, will hit the roads in late 2012. quattro GmbH is currently building the first technology platform for the electric model at the Neckarsulm plant’s satellite site in Heilbronn-Biberach. Specially qualified employees are borrowing from the series production of the successful Audi R8 mid-engine sports car as they assemble the R8 e-tron at the development workshop.

“With the R8 e-tron, we are showing how inspiring electric mobility can be. Every system in this car has been tuned for maximum performance and range,” says Franciscus van Meel, Head of Electric Mobility Strategy at AUDI AG. “The R8 e-tron is a very important project for Audi because the competence and experience we glean from it will later flow into the large volume production of electric automobiles.” The expectation is that e-tron will become a synonym for advanced electric mobility, just as the term “quattro” today stands for pioneering all-wheel drive. “We want to be the leading premium manufacturer of electric vehicles by 2020,” says van Meel.

Systematic lightweight construction is one of the key preconditions for efficiency and range in electric vehicles. The Audi development engineers are therefore drawing on one of the company’s core competences for the R8 e-tron: The body is two-thirds aluminum; thanks to Audi Space Frame technology (ASF), it weighs barely more than 200 kg. The lightweight body is an important reason why the R8 e-tron weighs in at just 1,600 kg.

AUDI AG is investing more than €5 billion in the two German sites at Ingolstadt and Neckarsulm between 2011 and 2015. A majority of this investment will flow into the development of new products and into future technologies such as electric and hybrid drive systems.

 

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