In Detail: Audi e-tron S and e-tron S Sportback
• Drive concept with three electric motors as a global innovation in mass automobile production
• New quattro generation with electric torque vectoring
• 370 kW of power and 973 Nm (717.6 lb-ft) of torque for high level of dynamic handling and agility
Ingolstadt/Neuburg a. d. Donau, February 21, 2019 – Audi is systematically moving forward with its e-offensive: The Audi e-tron and the Audi e-tron Sportback are becoming more agile, sharper and more dynamic as S models. The three electric motors, two of which are located on the rear axle, together offer 370 kW of boost power and a 973 Nm (717.6 lb-ft) of torque. This allows the two purely electrically driven models to accelerate to 100 km/h (62.1 mph) in 4.5 seconds. The intelligent drive control raises vehicle safety, and dynamic handling in particular, to a new level: In addition to the electric all-wheel drive, there is the electric torque vectoring with active and fully variable torque distribution on the rear axle.
Dynamism 2.0: the driving experience
The driving experience of the two Audi e-tron S models cannot fail to impress with its level of dynamism, agility and traction increased once more. In the S gear, both cars reach 100 km/h (62.1 mph) from a standstill in 4.5 seconds – smoothly and with almost no noise – propulsion is not electronically limited until 210 km/h (130.5 mph). Thanks to a powerful cooling system, the drive gives the full boost power of 370 kW and 973 Nm (717.6 lb-ft) of torque in reproducible form for eight seconds in each case. The nominal values in the D gear without boost are 320 kW and 808 Nm (596.0 lb-ft).
In terms of handling, the electric S models cannot fail to impress with their outstanding agility and traction: They can accelerate from a curve as dynamically as a sports car, their drive character is much more focused on the rear wheels and much sportier in nature. If the ESC stabilization control is set to “Sport” and the Audi drive select dynamic handling system is set to maximum performance with “Dynamic” mode, the drive layout facilitates a high level of transverse dynamics and, on 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 mass production
The new Audi e-tron S models are the first electric cars worldwide with three motors to be mass-produced. Their drive layout is based on the concept with two different asynchronous motors; the e-tron product line was designed in modular form in line with this from the start. The larger electric motor, which powers the rear axle in the 55 models, has now been installed on the front axle in an adapted design, and configured for 124 kW of power, or 150 kW in the boost. The smaller electric motor now works in a modified form in the rear, together with a counterpart that is identical in design; together, both offer 196 kW of power, or 264 kW in the boost.
Every electric motor is supplied with three-phase current by its own power electronics; planetary gear transmission with a fixed ratio transmit their forces onto the wheels. The front electric motor is installed parallel to the axles for packaging reasons. The two electric motors on the rear axle are installed coaxially, back to back. Force transmission onto the wheels is performed without a mechanical differential and thus makes electric torque vectoring possible. 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 both motors share.
The high-voltage battery system of the Audi e-tron S models is located beneath the passenger cell in the form of a long (2.28 m (7.5 ft)), wide (1.63 m (5.3 ft)) and flat (0.34 m (1.1 ft)) block. Each one of its 36 modules contains twelve cells. The modules are subdivided into two levels – a long one at the bottom and a short one at the top. They occupy the space beneath the back seat. The physically separated cooling system is installed beneath the cell room; it consists of flat aluminum extruded profiles that are subdivided into small chambers. The battery works with a nominal voltage of 397 V and can temporarily provide up to 430 kW of electrical peak power. It has a gross energy storage capacity of 95 kWh, of which the net amount of 91%, or 86.5 kWh, is available for use.
With the optional virtual exterior mirrors (cameras that send their pictures to high-contrast displays in the interior), the Audi e-tron S models achieve very good drag coefficients. Flow-optimized wheel arch extensions make a considerable contribution to resolving the conflict of interest between outstanding aerodynamics and a sporty look in the fully electric S models. Audi is incorporating this innovative solution into mass automobile production for the first time. This allows the Audi e-tron S Sportback to achieve a drag coefficient of only 0.26, despite the widening of its wheel arches by 23 mm (0.9 in); in the Audi e-tron S, the drag coefficient is 0.28. A second major element in the aerodynamics concept is the controllable cooling-air inlet with ducts to cool the front wheel brakes. It remains closed as often as possible so that the airstream flows over the front hood with almost no turbulence.
Innovation from the quattro pioneer: twin motor with electrical torque vectoring
The drive has been programmed for efficiency in everyday life; in normal driving mode, only the rear electric motors work. The front drive is unpowered but switches itself on – with the driver barely noticing – if the driver needs more power.
It also switches on predictively if the grip declines. It does so when friction values are low and during rapid cornering. The electric all-wheel drive is complemented by a further technical innovation in the form of electrical torque vectoring, which brings the advantages of the conventional sport differential into the electric era. Each one of the rear electric motors sends the drive forces directly to the wheel via a transmission; there is no longer a mechanical differential. 40 years following the launch of quattro technology, Audi is thus raising the principle of the four powered wheels to a completely new level of technology.
Electrical torque vectoring – distributing the drive forces between the rear wheels – takes place within milliseconds thanks to the spontaneity of the electric motors and can offer very high torques. If the driver accelerates out of a curve in a sporty manner, the electric motor gives the rear wheel on the outside of the curve up to 220 Nm (162.3 lb-ft) more torque than the wheel on the inside of the curve. The ratio results in a difference in drive torque of around 2,100 Nm (1,548.9 lb-ft) between the rear wheels. The latency, i.e. the time offset, is only around one fourth of that of a mechanical system, while the torques are considerably higher in electrical torque vectoring. Not only does the yaw moment that is generated support the steering characteristics, the curve radius can be retained with a smaller steering angle. The result: more agile driving and self-steering characteristics, and thus a higher cornering speed.
One further advantage is the traction. If, during acceleration, a rear wheel comes into contact with a road surface with a low friction value, i.e. if the road surface is covered in black ice or has a loose subsurface, the moment can be distributed precisely and quickly between the two motors. The full moment is gradually distributed to the wheel with powerful traction, while the wheel with low traction continues moving with almost no moment.
A pre-requisite for the precision with which the electrical all-wheel drive and the electrical torque vectoring work is the close linking of the control devices. This sees the electronic stabilization control (ESC), drive control unit, electronic chassis platform (ECP) and the power electronics functions all meshing together. All software functions, apart from the ESC, have been developed by Audi itself and benefit from around 40 years of quattro experience.
The mastermind in this combination is the electronic chassis platform – it makes a decisive contribution to managing the all-wheel drive and torque vectoring. It is informed at all times about the car’s driving status by means of sensor signals. On the basis of this data and the driver’s requirements, it calculates the ideal distribution of longitudinal and transverse torques. One of its tasks is wheel-selective torque control. At the dynamic limit, the front wheel on the inside of the curve with a lower load is decelerated slightly via the wheel brake. This small intervention, which the driver does not notice, prevents slippage and makes handling even more agile and neutral.
Closely linked: the suspension of the e-tron S models
In the suspension area, the EFP works closely together with the standard Audi drive select system. The driver can use it to vary the character of the two electric models in seven profiles: comfort, auto, dynamic, efficiency, individual, allroad and offroad – depending on the road state and personal preferences. In a similar way, stabilization control (ESC) provides four programs: Normal, Sport, Offroad and Off.
Audi drive select also incorporates the adaptive air suspension. Air suspension with adaptive damping (also standard) can vary the ride height by up to 76 mm (3.0 in). During rapid driving, it lowers the vehicle by up to 26 mm (1.02 in) compared to with the normal level, and the range benefits from the improved surround flow. The low center of gravity and the almost equal distribution of the axle loads are important factors for the dynamism of the electric S models.
If the driver selects Offroad mode, the e-tron S and the e-tron S Sportback offer increased ground clearance and an offroad-optimized setting of the powertrain. Electronic stabilization control automatically switches to a stability, traction and brake control that has been optimized for offroad use. The standard hill descent control system is also activated. It provides support by means of automatic brake applications when driving down a steep gradient that exceeds six percent.
A true high-tech element and unique selling feature of the Audi e-tron is the electrohydraulic by-wire brake system. A strong electric motor facilitates an extremely rapid pressure build-up, and this can shorten the braking distance. Depending on the driving situation, the brake control system decides whether the car decelerated with the electric motor, the wheel brake or a combination of both systems. Up to a deceleration of 0.3 g, i.e. most everyday situations, the electric motors (for efficiency reasons, primarily the two rear ones) perform most decelerations; it is only above a level of 0.3 g that the hydraulic wheel brakes come into play in a homogeneous transition. However, the electric motors remain active: if the car brakes from 100 km/h (62.1 mph), they can recover up to 270 kW of power, more than a formula E racing car, which only achieves around 250 kW.
The Audi e-tron S and the Audi e-tron S Sportback achieve high recuperation rates not just during braking but also in the boost, i.e. whenever the driver releases the right-hand pedal. During boost recuperation, they can choose between three levels. At the highest one, which reaches up to 0.13 g, they experience a distinctive one-pedal feeling.
The two e-tron S models drive on 20-inch alloy wheels in the 5-V-spoke S design as standard. Different wheels up to 22 inches in size are available on request. To achieve an S-typical transverse dynamism, the tire widths in the sizes 20 inches, 21 inches and 22 inches have all been enlarged to 285 mm (11.2 in). Black brake calipers with a red S rhombus, with six pistons at the front in each case, grip the large brake discs (front diameter: 400 mm (15.7 in)).
As an option, Audi will paint the calipers in the HV signal color dynamic orange. A further standard feature is the sporty progressive steering – its ratio becomes more and more direct, the more the driver sets the steering. The front and rear axles have been created as a five-link design. Harmonization of the elastokinematics and of the dampers has also been optimized for the S models. In order to even further reduce the rolling movements during cornering, the stabilizers on both axles have been enlarged.
Up to 150 kW: peak power, even during charging
When charging the car in their garage at home, the electric S model customers have different options at their disposal. The optional charging system compact can be used on a 400 V three-phase socket as well as on a 230 V socket. Using the myAudi app, customers can control all charging processes and timers as well as pre-entry climate control via their smartphone. In conjunction with a home energy management system, the optional charging system connect also offers smart charging functions, such as the cost-optimized charging with solar power if a PV system has been installed, or charging at inexpensive times when dynamic power rates are in place.
When the driver is on the road, the electric S models can be charged with up to 150 kW of direct current power (HPC), e.g. in the European Ionity network. This means that charging from 5 to 80% only takes around half an hour. An important factor for this is the elaborate thermal management system with a standard heat pump, which cools and heats the battery, the interior and the electric motors with four circuits. Naturally, the Audi models can also charge with alternating current (AC) – up to 11 kW as standard.
The Audi e-tron Charging Service guarantees convenient access to more than 140,000 public charging points in 24 European countries on request – with nothing more than a charging card. In the first year, Audi covers the basic fee for the transit rate, which also offers access to high power charging columns.
Optical statement: widening of the wheel arches
The powerful and sporty design of the e-tron S models features Audi’s progressive design vocabulary, which emphasizes the strong contours of the wheels. Details such as the octagonal Singleframe, which is for the most part sealed and painted bright gray, move the design into the electric era. At the lower edge of LED headlights, four struts create the e-tron-specific signature in the daytime running lights. The S models’ leading role can be seen straight away. The front and rear bumpers are heavily contoured, while the diffuser insert runs almost the full width of the vehicle. The bumper is flanked by bigger and more expressive air curtains, which improve air flow. They extend below the headlights, thereby creating a dynamic appearance even from a distance. On both sides, the wheel arches are a whopping 23 mm (0.9 in) wider. Silver-colored elements – from the lip of the front bumper, the Singleframe and the door inserts right up to the diffuser – emphasize the vehicle’s features. Audi will paint larger detachable parts in a contrasting color on request.
Both S models are available, on request, with the digital Matrix LED headlights, a global innovation in mass production. Their light is dispersed into small pixels and can be controlled with high precision, and this facilitates many new functions such as lane and orientation light. In narrow areas, for example, it shows the car’s position in the lane and thus helps the driver to remain in the center.
Progressive: the interior and equipment
The interior of the two S models has been kept in dark colors. A large arc connects the displays of the virtual external mirrors (option) with the hood above the Audi virtual cockpit. The instrument panel is driver-oriented, the middle tunnel’s console rests on open side walls. Electrically adjustable sports seats are a standard feature. Their leather/Alcantara covers and the gear selector lever feature a rhombus S embossing. The door sills and steering wheel feature S badges. On request, Audi can offer a super sport seat in leather with a rhombus pattern in black, rotor gray or Aras red, as well as an air-conditioned customized contour seat with perforated leather. The decorative panels consist of dark brushed aluminum or, as an option, open-pored carbon. The inlays in the door sills are made of aluminum. The contour/ambient lighting package adds progressive highlights in the dark.
Even at low speeds, the electric S models offer an impressive driving experience – an impression of peace, peace that is home to power. The body has been carefully dampened to prevent the transmission of structure-borne noise. When the vehicle is driving slowly, a loudspeaker in front of the right front wheel emits a synthetic driving sound in order to warn other road users. The wind noise level remains very low, even at high speed, as is typical of Audi.
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