Handling 2.0: the driving experience

The driving experience that the two electric S models offer impresses with the kind of fascinating dynamism that only a superior electric drive can provide. If the driver selects the S gear and fully depresses the right-hand pedal, both cars accelerate from a standstill to 100 km/h (62.1 mph) in 4.5 seconds with almost no sound and great smoothness, as the full tractive power is available immediately. Top speed is electronically governed at 210 km/h (130.5 mph). The drive delivers its full boost performance for eight seconds at a time, even multiple times in a row, delivering an output of 370 kW and 973 Nm (717.6 lb-ft) of torque. The nominal values in the D gear, i.e. without boost, are 320 kW and 808 Nm (596.0 lb-ft).

In terms of handling, the electric S models impress with their excellent agility and traction and their extremely spontaneous response to the accelerator pedal. Their drive character has an even greater rear bias and is even sportier than that of the technical basis. If the ESC stabilization control is set to “sport” and the Audi drive select dynamic handling system is set to “dynamic” the drive layout facilitates a high level of transverse dynamics and, upon request, controlled drifts as well. The driving behavior is predictable at all times, and is characterized by an ultra-high level of safety and reliability.

The drive layout: three electric motors in volume production for the first time

Audi already used the concept with the two asynchronous machines (ASM) as a modular system with the e-tron and e-tron Sportback models. A third drive motor is now being added: The new e-tron S models are the first volume-produced electric cars in the world to have three motors. 

An adapted design of the electric motor that powers rear axle on the e-tron 55 is installed here on the front axle. It is designed for an output of 124 kW or 150 kW with boost. The smaller front electric motor from the e-tron 55 with adapted design now operates at the rear together with a structurally identical counterpart. The tandem achieves an output of 196 kW and 264 kW with boost. Planetary transmissions with one stage transfer the power to the wheels.

Each electric motor is supplied by its own power electronics that converts the battery’s direct current into three-phase current. The asynchronous motors can be overloaded and are extremely robust, and they do not produce any drag losses when they run along while deenergized, which is an advantage in terms of efficiency. The front electric motor is installed parallel to the axles for packaging reasons, while the electric motors at the rear axle are installed back to back coaxially. The rotor plate packages have been cast with light aluminum. Coolant flows through the rotor shafts; this coolant comes from a common coolant circuit that the electric motors share. The sophisticated cooling concept enables powerful performance even with high requirements.

95 kWh energy content: the battery system

The high-voltage battery system stores 95 kWh of energy, of which 91 percent (i.e. 86 kWh) is available for use. It operates with a nominal voltage of 397 volts. In the realistic WLTP cycle, the electric power consumption is 28.4–26.8 kWh per 100 kilometers (62.1 mi) for the Audi e-tron S and 28.1–26,4 kWh for the e-tron S Sportback. This allows for a range of up to 364 (226.2 mi) and 370 (229.9 mi) kilometers respectively. The battery is a flat block measuring 2.28 meters (7.5 ft) in length, 1.63 meters (5.3 ft) in width and 0.34 meters (1.1 ft) in height and is located beneath the passenger compartment. Its 36 modules are subdivided into two levels – a long one at the bottom and a short one at the top that occupies the space beneath the back seat. Each module integrates 12 cells.

The cooling system is made of flat, extruded aluminum sections that are divided into small chambers. It is installed beneath the cell space and maintains an even temperature of all modules, ensuring that they always remain in their optimum temperature window of between 25 and 35 degrees Celsius. The framework structure in the battery system’s interior ensures that it is particularly rigid. Its housing consists of 98 percent aluminum, and a strong frame protects it from becoming damaged. 35 bolting points integrate it into the body in such a way that its already high level of rigidity is increased by another 27 percent.

New level of technology: 40 years of quattro competence from Audi

40 years ago, the brand with the four rings presented the Audi quattro at the Geneva Motor Show – it was the pioneer of a huge success story. With the e-tron S and the e-tron S Sportback, Audi is now raising the principle of four-wheel drive again to a whole new level of technology: In addition to electric all-wheel drive, cars are equipped with electric torque vectoring:

For reasons relating to efficiency, the rear electric motors in the Audi e-tron S and e-tron S Sportback provide propulsion when driving normally. The front electric motor is deenergized, but flashes into action when the driver demands more output, or predictively before slip occurs when driving on slippery roads or cornering at high speed. This electric all-wheel drive is now being enhanced with electric torque vectoring at the rear axle: Each of the two electric motors send their torques directly to the wheel via a transmission; there is no longer a mechanical differential.

Thanks to the spontaneity of the electric motors, electric torque vectoring, that is the distribution of the torque between the rear wheels, takes place within milliseconds. The time offset as compared to a mechanical system is shorter by a factor of four. It can also manage considerably higher torque: When the driver accelerates out of a corner at a sporty speed, the outside rear wheel is subject to 220 Nm (162.3 lb-ft) more than the inside wheel. Due to the gear ratio, the difference at the wheels is around 2,100 Nm (1,548.9 lb-ft). The yaw moment that is generated supports the steering characteristics and the curve radius can be retained with a smaller steering angle. Electric torque vectoring also offers great strengths in terms of pure traction: If one of the rear wheels is on very slippery ground during acceleration, e.g. a patch of ice or gravel, it receives no torque. Almost all of the torque is transferred to the wheel that has stronger traction.

A prerequisite for the high speed and precision with which the electric all-wheel drive and the electric torque vectoring work is the close linking of the following control units: the Electronic Stabilization Control (ESC), the drive control unit (ASG), the electronic chassis platform (ECP), and the control units of the performance electronics, which output voltage pulses up to 10,000 times per second. All software functions, apart from the ESC, are Audi in-house developments that benefit from the brand’s roughly 40 years of quattro experience.

The ECP is the mastermind among the control units: It makes the crucial contribution to the management of the all-wheel drive and electric torque vectoring. It calculates the ideal distribution of longitudinal and transverse torque on the basis of the data from the sensors that continuously inform it on the car’s driving condition and the driver’s request. One of its tasks is wheel-selective torque control: At the dynamic limit, the unloaded front wheel on the inside of the curve is braked slightly via the wheel brake. This minor, almost unnoticeable intervention prevents slip and makes handling even more agile and neutral.

Highly efficient: recuperation

The recuperation system contributes roughly 30 percent to the range of the electric S models. It achieves high levels of efficiency, both when the driver releases the accelerator pedal and when they depress the brake pedal. The degree of recuperation can be selected in three levels via rocker switches on the steering wheel. At level 0, the car continues to roll free (coasting), and at the highest level, it decelerates with up to 0.13 g, which is accompanied by a noticeable one-pedal feeling. In the MMI control system, the driver can use the efficiency assist to set fully automatic recuperation.

Up to 0.3 g, i.e. in most everyday situations, the Audi e-tron S and the Audi e-tron S Sportback use the electric motors alone to decelerate. The electric motors even remain active in the case of heavier deceleration where the wheel brakes are involved. When braking from 100 km/h (62.1 mph), they can convert up to 270 kW of peak power, more than a formula E racing car, which achieves only around 250 kW. Depending on the driving situation, the brake control system decides – individually for each axle – whether the car decelerates only with the electric motors, only with the wheel brakes (in rare cases), or with a combination of both systems.

Fast and powerful: the brakes

When the electrohydraulic wheel brake system assists with electric brake recuperation, the transition is smooth and homogeneous, and the pedal forces remain constant. Actuation and regulation are performed via a compact module that controls the pressure build-up electronically (by wire), reinforces it electrically, and actuates the brakes hydraulically. An electric motor with a spindle drive actuates the displacing piston, which presses the hydraulic fluid into the line, extremely quickly. The brake pads are in full-pressure contact with the disks after just 150 milliseconds, barely more than a blink of the eye. This can reduce the braking distance considerably as compared to a conventional system.

The fast pressure build-up allowed the developers to slightly increase the air gap between the brake disk and pads. This reduces the losses resulting from short-term unintentional contact between the pads and disks. The wheel brakes are powerful and durable: Six-piston calipers painted black with a red S rhombus and large disks with a diameter of 400 millimeters (15.7 in) are installed at the front axle. Audi delivers orange brake calipers with e-tron logos upon request.

Ideal conditions for dynamism: the suspension

All aspects of the suspension of the Audi e-tron S and the Audi e-tron S Sportback are state-of-the-art, and the same applies to the five-link suspensions all around. Their elasto-kinematics and damping rates are tuned specifically for the S models, with stronger stabilizers reducing rolling when cornering at high speed. The ratio of the progressive steering, which is already sporty, becomes increasingly direct as the steering movement increases. The drive layout also promotes dynamism: All the heavy components, in particular the high-voltage battery, are concentrated at a low level between the axles, bringing the axle load distribution close to the ideal value of 50:50.

The driver can exert major influence on the car’s character at their own discretion. One of the instruments the driver can use for this is the Electronic Stabilization Control (ESC), which offers the “normal,” “sport,” and “offroad” programs as well as an off position. The Audi drive select dynamic handling system offers seven profiles: comfort, auto, dynamic, efficiency, individual, allroad, and offroad. It also incorporates the adaptive air suspension sport – the air suspension with adaptive damping can vary the level of the body by up to 76 millimeters (3.0 in).

When driving at high speed, it lowers the vehicle by up to 26 mm (1.02 in) compared to the normal level, and the range benefits from the improved surround flow.

If the driver selects offroad mode, the air suspension raises the body of the Audi e-tron S and the e-tron S Sportback by 35 millimeters (1.4 in). The ESC switches to a stability, traction, and brake regulation that is tailored to use on dirt roads. The standard hill descent control is also activated. It assists the driver by means of automatic brake interventions when driving down a steep gradient that exceeds six percent.

The S models are provided with 20-inch wheels as standard, and 21-inch wheels are available upon request. The even sportier 22-inch wheels will follow at a later time. The tire width is 285 millimeters (11.2 in) for all rims. This also contributes to the high transverse dynamics that are typical for the S models from Audi. While the e-tron S and the e-tron S Sportback are driving around the city, almost all the driver and passengers hear is the rolling noise of the tires. The body is carefully insulated to prevent the transmission of structure-borne sound. At low speed, a loudspeaker located in front of the right front wheel outputs a synthetic and legally prescribed driving sound to warn other road users. The wind noise level remains very low, even at higher speeds, as is typical of Audi. 

Versatile: the charging offering

Audi offers its customers two systems for charging their electric car in their own garage. The standard charging system compact can be used preferably with a 400-volt three-phase current socket, where it enables charging with an output of up to 11 kW. It is also possible to charge the car using a 230-volt socket. The optional charging system connect, which will be released shortly after the market launch, offers smart charging functions in interaction with a home energy management system, for example charging at times when electricity is less expensive or with solar power, provided that a photovoltaic system is installed. Audi customers can control the charging processes and timers as well as pre-entry climate control via their smartphone with the myAudi app.

On the road, customers can access more than 150,000 public charging points in Europe with the Audi e-tron Charging Service. All they need is a single card. There is a choice of two tariffs: The city tariff for occasional use in urban areas and the transit tariff for long-distance drivers. With the latter, Audi pays the base fee for the customers of its e-tron models for the first year. Customers also pay just 31 cents per kilowatt hour of direct current in the Europe-wide Ionity network – comparable to what they pay for charging their car at home.

The Audi e-tron S and the e-tron S Sportback can charge with up to 150 kW direct current at the HPC fast-charging stations (High Power Charging) that Ionity and other providers have installed. Here, their battery can charge from 5 to 80 percent in around half an hour under ideal conditions, with the charging process operating near the threshold to maximum performance up to this mark.

One important factor in this context is the thermal management of the electric S models, which cools and heats the battery, the electric motors, and the interior. It is comprised of four sub-circuits that can be connected in different ways as needed. During DC charging, it cools the high-voltage battery. The thermal management also enables the battery to have a reproducible drive performance and long life cycle. One of its functions is the heat pump that maintains the temperature of the interior in a highly efficient manner. It can draw up to 3 kW of heat power from the waste heat of the high-voltage components, thereby increasing the range by up to 10 percent depending on the outside temperature.

All terms in blue in the text are explained in detail in the technology lexicon at www.audi-mediacenter.com/en/technology-lexicon.

The equipment, data and prices stated here refer to the model range offered for sale in Germany. Subject to change without notice; errors and omissions excepted.