Drive system and suspension
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Efficiency, performance and quiet tranquility – the Audi e-tron offers the driving experience of a new technological era. Two electric motors drive the electric SUV powerfully, free of emissions, and almost silently, with a system output of up to 300 kW. Its high-voltage battery stores 95 kWh of energy to provide a range of over 400 kilometers (248.5 mi) in the WLTP cycle. The Audi e-tron is thus predestined for long distances. The new electric all-wheel drive system combined with cutting-edge suspension solutions provide for optimal traction and handling in all driving situations and any weather.
Powerful performance: the electric motors
The Audi e-tron offers driving pleasure in a new dimension. With 265 kW and 561 Nm (413.8 lb-ft) of torque, the two electric motors accelerate the electric SUV from zero to 100 km/h (62.1 mph) in 6.6 seconds – with no hesitation and virtually silently. The asynchronous motors can deliver this peak performance for up to 60 seconds. This way, they allow the vehicle to accelerate from a standstill to the electronically limited top speed of 200 km/h (124.3 mph) several times consecutively without output losses.
The start-off performance, for example at a traffic light, is comparable to that of a sports car. The maximum drive torque is available within fractions of a second and provides enormous pulling power. The front electric motor, which is positioned parallel to the axle for the purpose of optimum packaging, achieves a peak output of 125 kW at 247 Nm (182.2 lb-ft) of torque. The rear, coaxially positioned motor reaches an output of 140 kW with a torque of 314 Nm (231.6 lb-ft). Two-stage planetary gearboxes with one gear range transfer the forces to the axles via the differentials.
Asynchronous motors can increase their output for a short period of time. By shifting from drive range D to S and fully depressing the right-hand pedal, the driver can activate boost mode. It is available for eight seconds. Here, the drive produces 300 kW of system output and 664 Nm (489.7 lb-ft) of torque. The Audi e-tron then sprints from 0 to 100 km/h (62.1 mph) in 5.7 seconds. The forces are distributed as follows between the electric motor at the front axle and the one at the rear axle: 135 kW of boost output with 309 Nm (227.9 lb-ft) of torque at the front, 165 kW with 355 Nm (261.8 lb-ft) at the rear.
The two asynchronous machines of the Audi e-tron offer major design advantages. They do not produce any electrically induced drag losses in the deenergized condition, which makes them highly efficient. Not only are they lightweight due to the aluminum rotor, they require little maintenance and are particularly robust.
Transformers: the power electronics
Every motor in the Audi e-tron is supplied and controlled by its own power electronics module, which works together closely and extremely dynamically with the drive control unit. All requests come together in the drive control unit – from the accelerator pedal, the brakes, or the electric all-wheel drive. The power electronics modules read in sensor data 10,000 times per second and output current values for the electric motors. This results in the optimum use of output during dynamic vehicle operation in particular. Some functions, such as vibration damping and the slip control functions, are integrated into the power electronics directly. This enables the deceleration-free translation of interventions and improves, for example, the vehicle’s ability to accelerate on icy roads significantly.
The two structurally identical power electronics modules are positioned on the housings of the electric motors and are integrated into the thermal management system of the drive system. They take up little space, and each weighs only eight kilograms (17.6 lb); this is also thanks to their aluminum housing. The pulse width modulating inverter, its central component, converts the direct current from the battery into three-phase current. When the electric motors operate as a generator during recuperation, the pulse width modulating inverter converts the generated three-phase current into direct current and feeds it back to the battery.
High traction in any terrain: electric all-wheel drive
In the Audi e-tron, the brand with the four rings introduces a new quattro generation as standard: electric all-wheel drive. It ensures the continuous and fully variable regulation of the ideal distribution of drive torque between the two axles – within a fraction of a second. The electric SUV thus offers optimum traction in all weather conditions and on any type of surface. Its talents really shine on low-friction surfaces such as a snow.
In most cases, the Audi e-tron mainly uses its rear electric motor in order to achieve the highest efficiency. For reasons of efficiency, the drive torque is generally distributed with a rear-axle bias. If the driver demands more power than the rear electric motor can supply, the electric all-wheel drive redistributes torque as required to the front axle. This also happens predictively even before slip occurs in icy conditions or when cornering fast, or if the car understeers or oversteers. It takes just around 30 milliseconds from the system detecting the driving situation and the torque from the electric motors kicking in – much faster than with conventional quattro technology. The reason is that with the electric all-wheel drive a mechanical clutch is not engaged but electricity is simply distributed. And that is almost instantaneous with absolute precision. So even with sudden changes in the coefficients of friction and extreme driving situations the full quattro performance is guaranteed.
The key to the electric all-wheel drive is the intelligent networking of numerous control systems. The central control unit for the chassis integrates both the handling controller of the quattro drive and the wheel-selective torque control for the first time. If understeer is detected during sporty driving, it gently brakes the inside wheels, which are under a reduced load, thus directing the drive force to the outside. The car turns into the curve and precisely follows the steering angle. Furthermore, an innovative traction control provides high traction and stability. Wheel slip is controlled directly at the power electronics of the electric motors, 50 times faster than before and even more precisely matched to the driving situation. For the driver, this is particularly noticeable in combination with the four-stage Electronic Stabilization Control (ESC). It offers a sport and offroad program in addition to normal mode, and can also be switched off entirely. The driver can thus increase performance in certain situations and choose to extent to which the ESC helps to stabilize the vehicle.
Standard: Audi drive select and air suspension
In addition, the characteristics of the Audi e-tron can also be adapted to various types of terrain using the standard dynamic handling system. Whether relaxed cruising, dynamic cornering or excursions off the beaten track, the driver can choose between seven profiles depending on the driving situation, road conditions or personal requirements: auto, comfort, dynamic, efficiency, individual, allroad and offroad.
Besides the drive system characteristic and steering boost, Audi drive select also influences the standard adaptive air suspension with controlled dampers. As a result, there is a vast difference between smooth rolling comfort and sporty, stable handling. The air suspension with damper control is integrated into the electronic chassis platform and Audi drive select management. The central control unit for the chassis individually controls the shock absorbers at each wheel at millisecond intervals – according to the road condition, driving style and the mode set by the driver in the Audi drive select dynamic handling system. In auto mode this is very balanced. With the comfort setting, the shock absorbers are controlled so that they provide relaxed motoring even on poor roads.
The pneumatic springs adjust individually to the road conditions depending on the speed and the driver’s preferences, varying the ride height by as much as 76 millimeters (3.0 in) starting from the basic setting of 172 millimeters (6.8 in). On the highway, the body is lowered by as much as 26 millimeters (1.0 in), which improves stability and the aerodynamics, thus facilitating a long range. In offroad mode, it increases ground clearance by 35 millimeters (1.4 in). If the driver also activates the “Lift” function in Audi drive select, the body is raised an additional 15 millimeters (0.6 in). In conjunction with the front angle of approach of 18.2 degrees and the rear angle of approach of 24.4 degrees with the offroad setting, the Audi e-tron is well prepared to tackle gentle offroad terrain. The ramp angle of the electric SUV is 16.8 degrees in this configuration.
Sporty, precise handling: transverse dynamics, axles, steering
A key factor for the sporty character and outstanding transverse dynamics is the low and central position at which the drive components are installed. The high-voltage battery system is optimally matched to the dimensions of the Audi e-tron and is located between the axles in the form of a flat, broad block beneath the passenger compartment. The center of gravity of the Audi e-tron is thus on a level similar to that of a sedan. Axle load distribution is perfectly balanced at almost 50:50.
The front and rear suspensions of the electric SUV are five-link designs. This axle principle enables optimal absorption of transverse and longitudinal forces. Its mounts are sportily rigid in a transverse direction and supple and soft longitudinally. All of which substantially improves comfort coupled with enhanced driving dynamics. Audi wraps the aerodynamically optimized 19-inch wheels with 255/55 tires that boast low rolling resistance without compromising handling or braking performance. As an option, Audi also supplies aerodynamically optimized 20-inch wheels with 255/50 tires and 21-inch wheels with 265/45 tires.
The standard progressive steering adjusts its generally directly configured ratio to the steering angle. It becomes more direct with increasing steering angle, which provides handling advantages when maneuvering and in tight curves. The car can be moved agilely and precisely with little steering effort. The Audi e-tron steers into the bend spontaneously without understeer and remains neutral for a long time even at high speeds. All the while it feels astonishingly light-footed. Steering boost is increased at low speeds for easier maneuverability.
From freewheeling to a one-pedal feeling: electric deceleration
The intelligent recuperation concept is also tightly integrated into the Audi e-tron’s electronic management system. It is the most innovative system on the market and accounts for up to 30 percent of the range. The electric SUV can recover energy in two ways: by means of coasting recuperation when the driver releases the accelerator, or by means of braking recuperation when the brake pedal is depressed. In both cases, the electric motors function as a generator and convert the kinetic energy of the Audi e-tron into electric energy. Up to 0.3 g, the SUV recuperates energy solely via the electric motors, without using the conventional brake – that covers well over 90 percent of all deceleration. So, energy is returned to the battery in practically all normal braking maneuvers.
The internally ventilated, 18-inch wheel brakes do not come into play until the driver uses the brake pedal to decelerate with more than 0.3 g. The electric SUV decides whether to decelerate using the electric motor, the wheel brake, or a combination of the two depending on the driving situation – with this taking place individually at each axle. In case of a brake application at a speed of 100 km/h (62.1 mph), for example, the Audi e-tron can recuperate with a maximum of 220 kW of electric power; that corresponds to more than 70 percent of its operating energy input. No other series production model can achieve such a value.
The driver can select the degree of energy recovery in three stages using paddles on the steering wheel. In the lowest setting, the Audi e-tron coasts with no additional drag torque when the driver releases the accelerator pedal. The Audi e-tron continues to roll forward. No electricity flows to or from the electric motor while the vehicle is moving. In level 1 (balanced – minimal deceleration) and level 2 (strong – high deceleration), the electric motors generate regenerative brake torque and produce electricity. The electric SUV reduces the speed noticeably – the driver can decelerate and accelerate using just the accelerator pedal. This creates the one-pedal feeling. There is no need to use the brake pedal in this case.
In addition to manually adjusting the recuperation level with the steering wheel paddles, the driver can also select automatic mode in the MMI. The predictive efficiency assist then regulates the deceleration as needed and predictively, for example in relation to the route or vehicles in front. The driver can adapt the deceleration effect by selecting the desired recuperation level via the shift paddles. It remains active until the driver operates the accelerator pedal again
Instant pressure buildup: the electrohydraulic brake system
Audi is the first manufacturer worldwide to use the electrohydraulically integrated brake control system technology in a series production vehicle with electric drive. The compact module weighs less than six kilograms (13.2 lb) and is thus 30 percent lighter than a conventional brake system.
Powerful 18-inch brakes work on the large wheels – with six-piston fixed calipers at the front and single-piston floating calipers at the rear. Optionally they stand out brightly with their e-tron-specific finish in the high-voltage signal color orange. At the front the internally ventilated disks have a diameter of 375 millimeters (14.8 in) and 350 millimeters (13.8 in) at the rear. They are used when the driver presses the brake pedal so hard that deceleration exceeds 0.3 g; otherwise, the Audi e-tron decelerates through recuperation via the two electric motors. The controller computes the required amount of braking power within milliseconds. If the recuperation torque is not sufficient, a displacement piston in the brake hydraulics generates additional pressure. Put into motion by an electric spindle drive, it pushes brake fluid into the brake lines and generates brake force through the conventional friction brake in addition.
The transition between electric and hydraulic braking is smooth and homogeneous, so the driver does not even notice it; the brake forces remain constant. Using a pressure-resistant element, a second piston generates the familiar pedal feeling for the driver’s foot. Thanks to this brake pedal simulator, the driver is not affected by what is happening in the hydraulics. In the case of ABS braking, pressure buildup and reduction are not noticeable in the pedal in the form of irritating hard pulsations. Even at a very slow speed, such as during maneuvering, the Audi e-tron decelerates via the wheel brakes because this is more efficient than electric braking in this case. Otherwise, the electric motor would have to use valuable battery current to decelerate actively at low rotational speeds.
The new electrohydraulic actuation allows the brake control system to build up brake pressure for the wheel brakes with great precision and roughly twice as fast as a conventional system. This enables a larger air gap, i.e. a greater distance between the brake pad and brake disk, to be set. This minimizes possible friction and heat generation and contributes actively to the long range of the Audi e-tron. When automated emergency braking is performed, there are only 150 milliseconds – ever so slightly more than a blink of the eye – between the initiation of the brake application and the presence of maximum brake pressure between the pads and disks. Thanks to this rapid pressure buildup, the electrohydraulically integrated brake control system shortens the braking distance by up to 20 percent compared with a conventional brake system.
The wheel brakes are seldom needed in normal operation, which has a positive effect on wear. The Audi e-tron is equipped with a brake cleaning function that helps the steel disks to remain free of oxidation as far as possible. During deceleration, it automatically uses the friction brake instead of recuperation at specific intervals. This way, the system is always in optimum operating condition.
Improving perception: technologically futuristic sound
The Audi e-tron with its electric drive lends a whole new feeling to mobility. Especially when driving in the city, it radiates an almost perfect sense of calm. The only sounds are from its tires and the gentle hum of the electric motors. In certain countries in North America and Asia, an artificial driving sound is superimposed on electric cars at low speed to satisfy legal requirements. Depending on the country, it must be clearly audible up to 32 or 20 km/h (19.9/12.4 mph) and gradually fades as speed increases. In the Audi e-tron, a small controller generates a technically futuristic sound that is played back through a loudspeaker in the right wheel arch to alert others to the car’s presence. When the car reverses, the sound level increases so it is clearly perceptible at the rear.
The equipment, data and prices specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.