hp per liter
(from Audi Press
Release) The Detroit showcar Audi e-tron shows another variant
of an electric vehicle developed by Audi
Audi is showing an uncompromising purist compact sports car with
all-electric drive at the first major auto show of 2010. The Detroit
showcar Audi e-tron is the name of this 3.93 meter (154.72 in) long
and 1.78 meter (70.08 in) wide but just 1.22 meter (48.03 in) tall
two-seater; just a few months after the debut of the Audi e-tron at
the 2009 Frankfurt Motor Show, this is now the second electric
concept vehicle from the brand with the four rings.
Coupled with the Detroit showcar Audi e-tron’s low gross weight of
around only 1,350 kilograms (2976.24 lb), high-torque power units
driving the rear wheels guarantee commensurate road performance. Two
electric motors with a combined output of 150 kW (204 hp) and 2,650
Nm (1954.54 lb-ft) accelerate the coupe with ASF-design aluminum
body from 0 to 100 km/h (62.14 mph) in just 5.9 seconds. The Audi e-tron
accomplishes the sprint from 60 to 120 km/h (37.28 - 74.56 mph) in a
mere 5.1 seconds.
The Detroit showcar Audi e-tron is able to distribute its electric
motors’ high torque between the wheels entirely as required. Its
“torque vectoring” is the key to a thrilling level of active
precision and excellent traction. Thanks also to its low weight,
short wheelbase and perfect weight distribution for dynamic
handling, the Audi e-tron has all the drivability of a go-kart –
agile, good on bends and neutral right up to the very high handling
Lithium-ion batteries, located for an optimal center of gravity
behind the passenger compartment and ahead of the rear axle, make an
effective energy content of 45 kilowatt-hours available. This makes
an operating range of up to 250 kilometers (155.34 miles)
As previously with the first e-tron concept car shown in Frankfurt,
Audi again bases all components in this electric vehicle on an
integral concept with many revolutionary details: a heat pump as an
efficient means of heating up and maintaining the interior
temperature. The drive system, power electronics and battery have
innovative thermal management – crucial for maintaining a high
operating range coupled with outstanding interior comfort.
Design and package
Audi is presenting a
further variant of an electric vehicle in the form of the Detroit
showcar Audi e-tron. The vehicle body has a powerful, wide and
muscular stance on the road, and looks extremely compact and
puristic not least thanks to the typically short sports car
wheelbase of just 2.43 meters (95.67 in) – a whole 22 centimeters
(8.66 in) shorter than the R8.
The sweeping line of the front end and the flat curved roof
immediately identify the two-seater as an Audi. The sides reveal
familiar contours: The way the dynamic line is tailored above the
sill and the prominent wheel arches, as is typical for an Audi R,
combine the front, side and rear into a monolithic entity and
strongly emphasize the typical Audi feature of round wheel arches
enclosing the large 19-inch wheels. The highly tapered front end
gives the Detroit showcar Audi e-tron distinctly wedge-shaped basic
1.78 meters (70.08 in) wide, just 3.93 meters (154.72 in) long and
1.22 meters (48.03 in) tall – those are the classic proportions of a
sports car. That leaves space ahead of the rear wheels for the 399
kilogram (879.64 lb) battery unit, with converter and power
The two electric motors, which have their own cooling system, are
mounted on the rear axle. This special package, featuring a 40:60
weight distribution, ensures perfect balance, which contributes to
the driving dynamics of the Audi e-tron.
The trapeze of the single-frame grille dominates the distinctly
wedge-shaped 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 headlight modules with their clear glass covers. All light
units use ultra-efficient LED technology.
The headlights are the core of a fully automatic light assistance
system that reacts flexibly to any situation. The new technology
recognizes weather conditions and adapts the illumination to rain or
fog. The technology at the heart of the light assistance system is a
camera that works together with a fast computer to detect oncoming
traffic, recognize lanes and measure visibilities, such as in the
event of fog.
If there is oncoming traffic, the high beams are turned off in the
corresponding section of the illumination field. The cornering light
system analyzes data from the navigation system and illuminates
corners before the driver steers into them. The Detroit showcar Audi
e-tron does not have conventional fog lamps that consume additional
power. It intelligently varies the low beams instead; in fog, for
example, it produces a wider, more horizontal illumination field,
thus significantly reducing the glare from the car’s own lights.
The variability of the headlights is also reflected in their design.
The LED elements change appearance and thus the character of the
front end of the vehicle depending on the speed driven and the
ambient conditions. The innovative lighting technology now offers
the Audi designers almost as much design freedom as the shape of the
One design element that is specific to electric vehicles developed
by Audi – such as the Audi e-tron – are the air intakes in the
single-frame grille and behind the side windows on the C-post. They
are closed flush under normal circumstances and opened by retracting
slats when additional cooling air is required. The slats above the
drive unit then also open to provide a better through-flow of air.
These measures, too, maximize efficiency – the concept car is
outstanding for an already low drag coefficient that is further
improved when the flaps are closed.
The ASF body
construction is an even more important prerequisite for efficiency
and range with electric vehicles than for conventionally powered
automobiles. Lightweight construction is moreover the key to
thrilling handling characteristics. Audi developers focused on a
core competence of the company when creating the Detroit showcar
Audi e-tron: The body structure is based on Audi Space Frame
technology (ASF), with a hybrid design approach adopted. All add-on
parts – doors, lids, sidewalls and roof – are made of a
The combination of aluminum and carbon fiber-reinforced composite
material guarantees supreme rigidity coupled with low weight. Audi
will soon use this technology in a similar form for future
production vehicles. Despite the complex drive system layout with
two electric motors and a high-capacity battery system, the total
weight of the Audi e-tron showcar on display in Detroit is only
around 1,350 kilograms (2,976.24 lb).
Interior and operating concept
Visual and functional
references to the new drive concept characterize the purist interior
design. They establish a connection between proven Audi genes and
new formal hallmarks. Typical for the Audi design idiom is the
reduction of the architecture, controls and information output to
the essentials in favor of visible lightweight construction and a
tidy overall impression.
The slim dash has a curve that extends laterally into the door
panels. With no need to allow for a transmission, shifter and cardan
tunnel, the designers took advantage of the opportunity to create a
particularly slim and lightweight center tunnel and convex, arching
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.
The Audi e-tron’s cockpit, which represents a further development in
an electric vehicle, is also oriented toward the driver – a further
characteristic Audi trait. Instead of the classic instrument
cluster, the concept car is the first Audi to be equipped with a
large built-in central display with integrated MMI functions. It is
flanked by two round dials.
The MMI is controlled via a scroll pad with a touch-sensitive
surface on the steering wheel (“MMI touch”) – an element inspired by
modern smartphones. The steering wheel itself is clearly flattened
off at both the top and bottom, in a clear reference to motor sport.
A smartphone that can be integrated into the front section of the
center console interfaces between the vehicle, the driver and
external information sources. The driver can use a suitably equipped
conventional smartphone as a car phone, address database, navigation
system and video player. At the same time they can also use it as an
operating unit for many specific on-board systems in the Audi e-tron.
Many phones that are suitable for these functions are already
available from various manufacturers.
The driver can then enter their route plan or adjust the sound
system to their individual preferences, all from the comfort of
their own home, for example. The Smartphone and vehicle communicate
via the mobile communications network, even over considerable
The system also provides a security function for the owner; within
the range of the WLAN it can constantly monitor the current status
of the vehicle, for instance whether all windows and doors are
closed. If the Audi e-tron showcar on display in Detroit is parked
at a charging station, for example, it also sends details of the
current charge status to the driver’s smartphone.
While an analog speedometer on the driver’s right provides speed
information, the instrument dial on their left tells them 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
Characteristic for the concept of the Audi e-tron – and therefore
also characteristic for a further development in an electric vehicle
– is the near total elimination of switches and small components
such as the ignition. The climate control unit is located to the
right above the steering wheel. The display provides temperature and
ventilation information. Again drawing inspiration from a smartphone,
the system is controlled by means of a touch-sensitive sliding
The equally racing-inspired lightweight bucket seats combine
excellent lateral support with comfort. Two contrasting colors
delineate the various zones of the interior. The colors and the
high-quality materials combine elegance and sportiness.
Drive system and energy supply
electric motors with a total output of 150 kilowatts (204 hp) give
the Detroit showcar Audi e-tron the performance of a genuine sports
car. The concept car can accelerate from 0 to 100 km/h (0 – 62.14
mph) in 5.9 seconds if necessary, and goes from 60 to 120 km/h
(37.28 – 74.56 mph) in 5.1 seconds. The torque is distributed
selectively to the wheels based on the driving situation and the
condition of the road surface, resulting in outstanding traction and
The top speed is limited to 200 km/h (124.27 mph), as the amount of
energy required by the electric motors increases disproportionately
to speed. The range in the NECD combined cycle is approximately 250
kilometers (155.34 miles).
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. The charging time when the battery is
empty is around 11 hours, but heavy current (400 volts, 32 amperes)
cuts this to around just two hours.
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 recharging of the battery is already available
on many Audi production models. During braking, the alternator
converts the kinetic energy into electrical energy, which it then
feeds into the on-board electrical system.
The Detroit showcar Audi e-tron in its further developed version
goes one decisive step further into the future; an
electro-mechanical brake system means the potential of electric
motors for energy recovery can now be exploited. 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.
By virtue of being isolated from the brake pedal, the Audi e-tron’s
electric motors can convert the entire deceleration energy into
electric current 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.
An automotive first: the heat pump
The heat pump, too –
which made its first appearance in an automobile on the Audi e-tron
concept car shown in Frankfurt – helps to boost efficiency and
range. Unlike a combustion engine, the electric drive system
generally does not produce enough waste heat 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. This is
because the battery, power electronics and electric motors must be
kept at their respective ideal operating temperatures to achieve
optimal performance and range.
As soon as the vehicle is connected to a charging station the
vehicle is preconditioned as appropriate by the thermal management
and other associated systems. In cold conditions the drive system is
preheated, and in hot conditions it is cooled. This preconditioning
can also be extended to the interior, if necessary, so that the
passengers can step into a cabin that has been heated or cooled as
appropriate for their comfort.
The drive system’s power
is transferred to the road by the rear wheels, reflecting the Audi
e-tron’s weight distribution of 40:60.
Both the individual motors, which are installed behind the wheels
close to the vehicle’s center line as wheel drives, also enable the
Detroit showcar Audi e-tron's lateral dynamics to be intelligently
controlled. This also boosts traction. Similar to what the sport
differential does in conventional Audi vehicles, torque vectoring –
the targeted acceleration of individual wheels – makes the newly
developed electric drive of the Detroit showcar Audi 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 proverbial rails.
The chassis has triangular double wishbones made of forged aluminum
components at the front and rear axles – a geometry that has proven
in motor sports 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.
The direct rack-and-pinion steering gives finely differentiated
feedback. Its electromechanical steering boost varies with speed, so
that the Detroit showcar Audi e-tron only has to provide energy
while steering, but not while driving straight ahead.
As befits its status, the Audi concept car rolls on 19-inch wheels
of 35-spoke design. 235/35 tires up front and 255/35 tires at the
rear provide excellent grip. Another special feature of the tires:
Audi designers created the profile specifically for the Detroit
showcar Audi e-tron.