Under pressure

It’s minus 18 degrees Celsius and a layer of ice obscures the front windscreen of an Audi SQ8 Sportback e-tron sitting in the conditioning box of Audi’s climatic wind tunnel. Water has been sprayed onto the front windscreen in advance to create the legally required layer of ice and an employee sits in the Audi SQ8 Sportback e-tron and to hit the ‘Defrost High’ control – the air conditioning system’s maximum blower level on the front windscreen.

After three minutes, the first holes start to clear in the layer of ice on the front windscreen. Jürgen Ehemann, head of wind tunnels at Audi, who is monitoring the test on the bench, appears satisfied: 

“This is typical behaviour for an electric car. It provides heat from the first second the air conditioning is activated. On a petrol vehicle, the first holes start to clear after around five minutes, while diesel vehicles usually take seven minutes,” he says.

Welcome to Audi’s climatic wind tunnel at the heart of the Audi Technical Development division in Ingolstadt. The air humidity here can be regulated on various test benches, as can the wind and temperature – from minus 25 to plus 50 degrees Celsius.

The windscreen defrosting test is just one of many undertaken in the wind tunnel and is a requirement for approval in Europe and elsewhere. For this test, every vehicle type, whether combustion or electric, must have cleared a minimum field of vision on the front windscreen within a set period of time. As head of Audi’s Wind Tunnel Centre, Michael Zalud is the most senior figure on the test bench: 

“We make no distinction as to whether we are testing a vehicle with an electric motor or combustion engine. An Audi is an Audi.”Sophisticated thermal management of the entire operating system is even more important for an electric vehicle than for a vehicle with a combustion engine. If too much energy is lost by heating or cooling the interior, this energy is inevitably taken from the traction battery, which immediately reduces range. Intelligent thermal management, by contrast, that consumes minimal energy and uses as much air circulating around and flowing through the engine compartment as possible, permits a longer range.
So after the ice conditioning box, it’s time to move on to Audi’s next test – in the heat of the climatic wind tunnel. That’s where the Audi Q8 Sportback e-tron undergoes what is known as the Großglockner test. 

This involves simulating the route profile of the famous Alpine pass using the resistance of the rollers on the test benches. A tremendously scenic and engaging drive for any driver and a steep and taxing one for any vehicle.
“The temperature of the battery must be optimally regulated on electric vehicles,” says Jürgen Ehemann.

“We can simulate what would happen if the Audi Q8 Sportback e-tron were to drive along the Großglockner pass with or without a trailer. If the air conditioning of the interior is also turned up while under load on the mountain, a lot of power is also drawn from the battery. The software developed by Audi then decides whether heat dissipation from the battery is more important than maximum air conditioning. The Audi engineers can test all of these things here.”

In this case, this means that after a five-minute warm-up period, the Audi Q8 Sportback e-tron is put through its paces at 30 degrees Celsius with the resistance on the roller test bench simulating the real gradient of the Großglockner pass. In addition, the airstream can be simulated in the climatic wind tunnel, corresponding to the driving situation and the resulting cooling. 

The Audi Q8 Sportback e-tron must then maintain a speed of 30 km/h with a simulated trailer or 55 km/h without a simulated trailer.

“This test simulates extreme conditions – a relatively high load at low speed. We check whether the Audi Q8 Sportback e-tron maintains full functionality when subjected to such a load,” says Ehemann.
Yet the testing is far from over for the Audi Q8 Sportback e-tron. The electric vehicle still has to cope with a straight American pass at a temperature of 50 degrees Celsius – a different profile at higher speed than the meandering Großglockner pass.

And for another extreme test, Audi’s climatic wind tunnel is heated to 35 degrees Celsius while the vehicle travels 60 kilometres at top speed. This doesn’t reflect the everyday use of an electric vehicle, of course, but the Audi Q8 Sportback e-tron is being tested to see how it can cope with maximum loads – just like any other Audi. And not just on a test drive anywhere in the world, but on test benches in Audi’s climatic wind tunnel.

In fact you name it and the scenario can be reproduced in Audi’s climatic wind tunnel at any time, irrespective of the location, weather and season. Audi engineers working on the interior air conditioning, drive system development and overall vehicle development use it to conduct various tests. To this end, different speed and temperature curves as well as load scenarios are simulated on different test benches using various resistance settings, in line with the specifications defined by the relevant Audi departments.

Homologation tests that are required for approval purposes are generally conducted in the presence of independent technical services, who monitor the processes at Audi’s Wind Tunnel Centre and to this end, the test laboratory at the Wind Tunnel Centre must meet stringent government requirements.

The end result is that regardless of where an Audi ultimately ends up spending its ‘working’ life, the conditions will be of little consequence. From the baking heat of the Mojave Desert to the arctic conditions in far northern Europe, the vehicle has already been subjected to the harshest climactic conditions and everything else is just another day in the life.