Test drive unique Cw only 0,28 for Audi e-tron

The carrying capacity of the electric SUV model is an incredible achievement.

Exceptional aerodynamics for high efficiency and high mileage

With a consumption coefficient Cw of 0,28 Audi Peak e-tron in the SUV segment. Aerodynamics contributes significantly to increased mileage and is one of the most important factors in vehicle efficiency. Examples of the precision of every detail in the Audi e-tron are the contours of the battery attachment points in the floor structure and the virtual exterior mirrors with small cameras. This is the first of its kind in a production vehicle.

The road to electromobility

In the case of an electric vehicle, weight is less important in terms of energy consumption than in the case of a car with an internal combustion engine. In urban traffic, an electric vehicle can recover most of the energy consumed when accelerating while braking at the next traffic light. A completely different situation arises when driving at high speed outside the city, where the Audi e-tron is also in its waters: at speeds above 70 km / h, rolling resistance and other mechanical resistance forces gradually decrease in their relative proportion. accounting for air resistance. In this case, the expended energy is completely lost. For this reason, the designers of the Audi e-tron pay particular attention to aerodynamics. Thanks to the comprehensive aerodynamic optimization measures, the Audi e-tron also achieves high efficiency when driving at high speeds, thus increasing mileage. When measured in the WLTP cycle, the vehicle travels over 400 kilometers on a single charge.

Every hundredth counts: air resistance

The Audi e-tron is an electric SUV for sports, family and leisure. Like a typical high-end model, it has enough room for five passengers and a large luggage compartment. The wheelbase is 2.928 millimeters, the length is 4.901 millimeters, and the height is 1.616 millimeters. Although the Audi e-Tron has a relatively large frontal area (A) due to its width of 1.935 millimetres, its overall drag index (Cw x A) is only 0,74 m2 and is lower than that of the Audi Q3. .

The main contribution to achieving this is the low flow rate Cw of only 0,28. The benefits of low air resistance for customers are greater because air resistance plays a larger role in electric vehicles than in conventional vehicles. Every detail is important here: a thousandth reduction in the flow rate leads to an increase in mileage by half a kilometer.

Details about aerodynamic measures

Within the overall concept of the Audi e-tron, with its abundance of interior space, aerodynamic optimization has never been questioned. To achieve the aforementioned flow factor of 0,28, Audi engineers apply a wide range of aerodynamic measures in all areas of the body. Some of these solutions are visible at a glance, while others perform their tasks while remaining hidden. Thanks to them, the Audi e-tron saves about 70 Cw points or has a consumption value 0.07 lower than that of a comparable conventional vehicle. For a typical user profile, these designs help increase mileage by approximately 35 kilometers per battery charge per WLTP measurement cycle. To achieve such an increase in mileage by reducing weight, engineers must be able to reduce it by more than half a ton!

Brand new technology: standard exterior mirrors

The exterior mirrors create high air resistance. For this reason, their shape and flow are essential for the overall optimization of aerodynamics. For the Audi e-tron, engineers and designers have created new shapes that provide less resistance. The e-tron exterior mirrors literally "grow" out of the front windows: their bodies, which are differently shaped on the left and right sides, form small diffusers together with the side windows. Compared to conventional mirrors, this solution reduces the flow factor by 5 Cw points.

World premiere: virtual mirrors

For the first time in an Audi e-tron production vehicle, virtual exterior mirrors will be available on request. Compared to the standard exterior mirrors already optimized from an aerodynamic point of view, they reduce the flow factor by an additional 5 points clockwise and perform not only aerodynamic but also aesthetic function. Their flat bodies are joined by small chambers at the ends of their hexagonal shape. The heating function protects the latter from icing and fogging and ensures sufficient visibility in all weather conditions. In addition, each housing has an integrated LED direction indicator and optionally a Top-View camera. The new rear-view mirrors are much more compact than standard ones and reduce the vehicle width by 15 centimeters. As a result, the already low noise level is reduced even more. Inside the Audi e-tron, camera images are displayed on OLED screens located at the transition between the dashboard and the doors.

Fully Lined: Floor Construction

Many of the many technological measures to reduce resistance remain invisible. By itself, the flat, fully paneled floor structure provides a 17 Cw reduction compared to a conventional vehicle. The main element in it is an aluminum plate 3,5 mm thick. In addition to its aerodynamic role, it protects the underside of the battery from damage such as impacts, curbs and stones.

Both axle motors and suspension components are coated with extruded, thread-reinforced materials that also absorb sound. There are small spoilers in front of the front wheels, which, combined with narrow air vents, remove air from the wheels and reduce the vortex around them.

The wishbones at the rear of the Audi e-tron have separate roof elements that extract air. A stepped diffuser under the rear bumper ensures that the air accelerating under the vehicle reaches normal speed with a minimum of vortices. Aerodynamic precision is expressed in small, effective floor construction details such as the attachment points for the support elements of the high voltage battery. Similar to grooves on golf balls, these curved, spherical surfaces a few centimeters in diameter and depth provide better airflow than a flat surface.

Open or closed: front grilles on the front grill

Clockwise 15 dots help reduce air resistance thanks to adjustable louvers on the front grille. Between the front Singleframe and the cooling elements is an integrated module consisting of two louvers that open and close using small electric motors. Each of the blinds, in turn, includes three strips. Air guiding elements and foam insulated vents ensure optimal direction of incoming air without creating vortexes. In addition, the foam absorbs energy in the event of an impact at low speeds and thus contributes to the safety of pedestrians.

The control device takes care of the maximum efficiency of the blinds, and the control is carried out based on various parameters. If, for example, the Audi e-tron is traveling at a speed of 48 to 160 km / h, both louvers are closed whenever possible in order to maximize airflow efficiency. If the electrical components of the AC drive or condenser need cooling, first open the top and then the bottom curtain. Due to the high power of the energy recovery system, the hydraulic brakes of the Audi e-tron are rarely used. However, if they are heavier, for example when going downhill with a fully charged battery, the system opens two channels through which air is directed to the fenders and brake discs.

Standard: wheels and tires with optimized aerodynamics

Holes in the wheels and tires account for a third of the air resistance and are therefore extremely important in terms of aerodynamic optimization of the vehicle. The channels visible in the front of the Audi e-tron, integrated into the fenders, are designed to direct and remove air from the wheels. These additional vents and air ducts reduce air resistance by an additional 5 points clockwise.

The aerodynamically optimized 3-inch wheels fitted as standard in the Audi e-tron give an additional 19 Cw points. Buyers can also get 20- or 21-inch aluminum wheels. Their chic design features flatter elements than conventional wheels. The standard 255/55 R19 tires also offer particularly low rolling resistance. Even the sidewalls of the tires are aerodynamically shaped, without protruding lettering.

Lower over the road: adaptive air suspension

Another important factor related to aerodynamics is the adaptive air suspension, which includes air elements and shock absorbers with variable characteristics. With it, the clearance of the car above the road changes depending on the speed. This chassis helps reduce air resistance by 19 points clockwise compared to the steel-sprung model. At the lowest level, the body is lowered by 26 millimeters compared to the normal position. It also reduces the frontal area of the tires facing the airflow, as much of the latter is hidden from the body. It also reduces the gaps between the wheels and wing arches and improves handling.

Important details: Roof spoiler

Among the parts specially developed for the Audi e-tron, the vehicle also uses some of the solutions typical of conventional models. This is, for example, the long, three-dimensional spoiler on the roof, whose task is to clear the air flow from the end of the car. It interacts with the airbags on both sides of the rear window. The diffuser, just like in a racing car, is designed to cover the entire length of the car and provides additional compression force.

Aerodynamics Technical Dictionary

Aerodynamics

Aerodynamics is the science of the motion of bodies in gases and the effects and forces that arise in the process. This is important in automotive engineering. Air resistance increases in proportion to speed, and at speeds between 50 and 70 km/h – depending on the vehicle – it becomes greater than other drag forces such as rolling resistance and weight-handling force. At 130 km/h, the car uses two-thirds of the drive energy to overcome air resistance.

Flow coefficient Cw

The flow coefficient (Cw or Cx) is a dimensionless value that expresses the resistance of an object when moving through air. This gives a clear idea of how the air is flowing around the car. Audi is among the leaders in this indicator and has its own advanced models. The 100 Audi 1982 showed Cw 0,30 and the A2 1.2 TDI from 2001 Cw 0,25. However, nature itself offers the lowest value of the discharge coefficient: a drop of water, for example, has a coefficient of 0,05, while a penguin has only 0,03.

Frontal area

Frontal area (A) is the cross-sectional area of the vehicle. In a wind tunnel, it is calculated using a laser measurement. The Audi e-tron has a frontal area of 2,65 m2. For comparison: a motorcycle has a frontal area of 0,7 m2, a large truck has 10 m2. By multiplying the frontal surface area by the flow coefficient, the effective air resistance value (air resistance index) of a particular body can be obtained. .

Controlled blinds

The Controlled Air Vent (SKE) is a Singleframe grille with two electric dampers that open in sequence. At medium speeds, both stay closed as long as possible to reduce swirl and air resistance. In certain situations - for example, when certain units need cooling or the brakes of the Audi e-tron are heavily loaded - they open according to a certain algorithm. Audi uses similar solutions in other forms in its models with internal combustion engines.