Drag: essential on long
journeys
On long journeys where the Audi e-tron
prototype is perfectly at home, the drag
constitutes the key driving resistance – far
more important than the rolling resistance
and inertia.
The energy is lost which the car needs to
overcome this resistance.
That is why good aerodynamics are so
important. In urban traffic, however, other
factors come into play.
Here an electric car can recover a large part
of the used energy when braking, thereby
reducing the importance of its mass.
To achieve the drag coefficient of 0.28, the
Audi engineers developed a wide range of
aerodynamics measures in all body areas.
Some of these technical solutions are
evident at first glance, while others fulfill
their purpose hidden away from sight.
Thanks to these solutions, the drag
coefficient for the Audi e-tron prototype
is almost 0.07 less than for a comparable,
conventionally powered vehicle. With a
typical usage profile this set-up increases the
range by around 35 kilometers (21.7 mi) per
battery charge in the WLTP cycle.
Smart solutions: virtual
exterior mirrors and dimples
on the underbody
The optional virtual exterior mirrors will be
making their world premiere in the volume-
production version of the Audi e-tron
prototype.
They are much narrower than the standard
mirrors: They reduce the vehicle width by
15 centimeters (5.9 in) and, thanks to their
new shape, not only reduce drag, but also
noticeably cut the nonetheless low wind
noise.
Each of their flat supports integrates a small
camera.
The captured images appear on OLED
displays in the transition between the
instrument panel and door. The virtual
exterior mirrors can be adapted for
various driving situations, thus potentially
improving safety. Three views are available
in the MMI system – for highway driving,
turning and parking.
Another important factor is the standard
adaptive air suspension – a pneumatic
suspension with adjustable damping. At
speeds above 120 km/h (74.6 mph), it lowers
the body by up to 26 millimeters (1.0 in)
below the normal position, thus reducing
the drag.
The underbody of the all-electric SUV is fully
enclosed; the front and rear area are fully
paneled.
Underneath the passenger cell, an
aluminum plate protects the high-voltage
battery against damage from below, such as
stone chipping or curbs.
Its bolting points come with bowl-shaped
indentations, similar to the dimples on a golf
ball.
They make the air flow much better than a
totally flat surface.
Additional information about the
Audi e-tron prototype is available at
www.e-tron.audi
• Electric car with
sophisticated
aerodynamics concept:
drag coefficient of 0.28
• Important factor
particularly on long
journeys: drag
• For the first time in a
volume-production car:
virtual exterior mirrors as a
high-end option
Issue 33 PECM
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