At the January NAIAS in Detroit, Audi continued the e-tron all-electric sports car theme it launched at the 2009 Frankfurt Motor Show with a smaller concept version. The car signals that the company has big plans for an electric car range.
“E-tron for Audi will be our own product line,” Michael Dick, Member of the Board of Management for Technical Development at Audi AG, told AEI, though “no decision has been made on production [of the latest e-tron concept]; this is only a study at this time.”
Dick said that the Audi Space Frame (ASF) for the Detroit e-tron coupe is “totally unique from anything else Audi produces. The construction is similar to the e-tron from Frankfurt, but this one has only two ‘engines’ with rear-wheel drive. The Frankfurt car had Quattro and four electrical engines with more power.”
The two electric motors are mounted on the rear axle. The result of the electric drive system location is an “ideal” 40:60 vehicle weight distribution.
If Audi decides to produce a smaller e-tron, it probably would be cheaper than the R8 and the larger e-tron shown in Frankfurt; the latter car “will surely have a price over €100,000, with 100 cars being made in 2012,” said Dick.
The e-tron total vehicle concept is “not to fit an electric engine into a car we have; we wanted to make a completely unique concept, which is optimized in terms of energy consumption,” added Dick. “Each kW we can spare for comfort system we can use for [vehicle] range.”
The challenges in taking a concept like the Detroit e-tron to production (if Audi decides to make it) are similar to those for the e-tron from Frankfurt, said Dick. "It is a little easier in this car from the packaging side because it has only two electric engines, a little bit smaller battery block, but all other things are similar.” It uses the same energy- and thermal-management systems, for instance. “Our philosophy is to start top down, to test all the possibilities we have, and to use this to socialize this technique for smaller cars,” said Dick.
The Detroit show car’s low gross vehicle mass of 1350 kg (2976 lb), combined with two electric motors driving the rear wheels with combined output of 150 kW and 2650 N·m (1954 lb·ft), result in acceleration from 0 to 100 km/h (62 mph) in just 5.9 s; 60 to 120 km/h (37 to 75 mph) takes 5.1 s. Top speed is limited to 200 km/h (124 mph). The electric motors’ high torque is distributed independently between the rear wheels via torque vectoring.
The car’s 399-kg (880-lb) lithium-ion battery pack, along with converter and power electronics, is located for optimal center of gravity and moment of inertia behind the passenger compartment and ahead of the rear axle. The battery pack’s effective energy content of 45 kW·h makes for an operating range of up to 250 km (155 mi). A full battery charge can take as long as 11 h (at 230 V, 16 A), but heavy current (400 V, 32 A) can cut this to around 2 h.
“At this time we have a range of 155 mi, [but] we are working hard to increase it,” said Dick. “We are looking for more battery systems to find the optimized version.” The company is working with battery partner Sanyo on the e-tron and the Q5 hybrid that launches at the end of 2010.
The familiar contours of the Detroit e-tron echo those of the R8 and Frankfurt e-tron. The car has a short wheelbase at 2.43 m (95.7 in), which is 22 cm (8.7 in) less than an R8’s. Other vital stats include a 1.78-m (70.1-in) width, 3.93-m (154.7-in) length, and 1.22-m (48.0-in) height.
The e-tron’s ASF body structure is a hybrid design consisting primarily of aluminum with many of the add-on body parts (doors, lids, sidewalls, and roof) made of a fiber-reinforced plastic—a combination Audi says it will use more on future production vehicles. The advanced body construction offsets the heavy electric components for a total vehicle mass of around 1350 kg (2976 lb).
Air intakes in the grille and behind the side windows are closed under normal circumstances for low drag, but their slats open to direct air when additional cooling is required.
The car’s adaptive matrix beam headlight modules use LED technology, with a camera and controller detecting oncoming traffic, recognizing lanes, and measuring visibilities. A cornering light system uses navigation system data to direct light where it is needed. Instead of conventional fog lamps, which consume additional power, the headlight beams are intelligently varied to provide the same function.
An electromechanical brake system better exploits the potential of electric motors for energy recovery. A hydraulic fixed-caliper brake on the front axle is supplemented by two floating-caliper by-wire brakes on the rear axle. In normal operation, the system’s electric motors can recover nearly all deceleration energy, but the mechanical system comes into play only if greater deceleration is required.
Inside the car, a flush gear selector emerges from the center tunnel when the vehicle is started. Instead of a traditional instrument cluster, the car is the first Audi to be equipped with a large built-in central display with integrated MMI (multimedia interface) functions. Flanked by two round dials, the MMI is controlled via a scroll pad with a touch-sensitive surface on the steering wheel called MMI touch. It can be linked to a smartphone for data and connectivity functions.
Unlike other electric vehicles equipped with electric supplemental heaters that consume a relatively large amount of energy, according to Audi, the e-tron uses a heat pump that uses mechanical work to provide heat with a minimum input of energy. The high-efficiency climate control system also is used to cool the battery, power electronics, and electric motors.