Cars

Dakar Rally: That’s how complex Audi’s Dakar-Mobil is

It is the mother of all desert rallies: the Dakar. Audi is now also looking for the challenge, and will be launching the Audi QS e-tron in Saudi Arabia in 2022.

“Never before have we at Audi Sport launched such a complex vehicle in such a short time,” says Julius Seebach, Managing Director of Audi Sport GmbH and responsible for motorsport at Audi. “Our first endurance test under competitive conditions is now the longest and most demanding rally in the world.” On the twelve stages of the desert rally in Saudi Arabia, the Ingolstadt-based company will meet 91 other participants in the automobile class.

The Audi highlight: the all-terrain all-wheel drive is powered by two electric motors with a total output of 680 hp. I’m sorry, what? With electric downforce on stages of up to 800 kilometers through the desert? Without a charging station and with a limited range of the batteries?
So it’s no wonder that all e-car projects in the Kox308; nigin of the desert rallies have so far failed. Audi now wants to change that – and use the Dakar Rally as a truly desolate test laboratory for its production vehicles.

A new era begins for Audi in marathon rallying.

There are twelve stages on the program. The total length of the rally is 8,099 kilometers, the sum of the timed off-road tests 4,252 kilometers. The starting and finishing point is Jeddah, on January 8th the Dakar in Riyadh will have a day of rest.

Mattias Ekström (43, with Audi twice DTM champion, once rallycross world champion), Carlos Sainz (59, three times Dakar winner) and the Dakar record winner Stéphane Peterhansel (55, 14 wins) are at the start.

Ekström on ABMS: “One of the coolest cars I’ve ever driven.” Carlos Sainz adds: “At the beginning, the only thing that was unusual was the internal combustion engine, which constantly works in my back, even when I’m not on the gas. You have to get used to it first. “

Technical specifications

Motor: Hybrid (electric drive, battery charged by turbo motor)
Turbo engine displacement: 2000 cm3
Maximum system output: 500 kW (680 PS)
Drive: electric all-wheel drive
L / W / H 4500/2300/1950 mm
Empty weight: 2000 kg
0–100 km / h: less than 4.5 s
Top speed: 170 km / h
Petrol consumption: 200 g / kWh
Battery: lithium-ion, 52 kWh, 370 kg
Tires: BF Goodrich front / rear 37×12.5R17g
Tank capacity: max. 295 liters

We explain the complex technology of the Audi RS Q e-tron:

drive

The heart of the RS Q e-tron is a hybrid system with a maximum of 680 PS (500 kW). The front and rear axles are each driven by a 250 kW (340 hp) electric motor from Formula E. There is also an internal combustion engine behind the driver. This in turn drives a generator that charges the battery for the drive motors.
The combustion engine is the two-liter, four-cylinder turbo that Audi used in the DTM until the end of 2020. Audi still has 30 of these units. The engine was revised for the Dakar use. Stefan Dreyer, Head of Development at Audi Sport: “We have reduced the output from 450 to 200 kW. It works best-point-optimized in a narrow speed range between 4500 and 6000 instead of 9000 tours. ”And it is extremely efficient: Its specific consumption is well below 200 grams per kilowatt hour.

“The car is the most complex I’ve ever seen,” says Sven Quandt, founder of Q Motorsport, the Audi team. He even compares the project with the first moon landing: “Back then, the engineers didn’t know what to expect. It’s similar with us. A finish at the first use would be a success. “

The lithium-ion battery

The high-voltage battery is literally in the middle of the Audi RS Q e-tron.

The high-voltage battery is literally in the middle of the Audi RS Q e-tron. Capacity (52 kWh) and weight (370 kg) are reminiscent of Formula E (54 kWh / 385 kg). Compared to the electric formula, the Dakar Rally is completely different: daily stages of many hundreds of kilometers, enormous driving resistance in the soft desert sand, plus high outside temperatures and a minimum vehicle weight set at two tons by the regulations – these are extreme values ​​in motorsport.

When the rally drivers leave the bivouac with a charged battery on the morning of each stage in electric drive, a highly complex control begins. The engineers have programmed algorithms so that energy consumption and recharging of the battery are always in balance over defined distances.

An example: If a difficult passage through the dunes requires maximum energy for a short time, the charge level drops. The reason: According to the regulations, the drive power of the motor-generator units on the front and rear axles is limited to a maximum of 288 kW. However, the energy converter can provide a maximum charging power of 220 kW. In extreme cases, the consumption is temporarily higher than the energy generation. “Something like this is possible for a limited time,” says battery engineer Lukas Folie. “But over a longer distance there is always a zero-sum game. The absolute amount of energy available on board must be sufficient to cope with the day’s stage. “

For maximum efficiency, the RS Q e-tron recovers energy on its journey through the desert. The MGU units on the front and rear axles can convert the rotational movement of the wheels into electrical energy. Result: Although it has to move a larger mass due to the regulations, the RS Q e-tron therefore uses less energy than the competition.

cooling

For battery cooling, Audi uses a coolant called Novec, which does not conduct any electrical currents.

“Audi has never been to the Dakar Rally. So the first thing we asked ourselves: How do we get the heat out of the car? ”Explains Sebastian Fröber, the engineer responsible for the cooling systems. Instead of aerodynamic efficiency, the desert prototype is about the best possible heat dissipation. This is ensured by several cooling circuits.

Low-temperature circuit for the high-voltage battery (HVB): Audi uses a coolant called Novec, which does not conduct electrical currents, to cool the battery. This low-temperature circuit has a cooler under the front hood.

Low-temperature circuit for the motor-generator units (MGU): The combustion engine is mechanically coupled to an MGU that generates the electricity for the high-voltage battery. It transfers its energy to two other electric motor-generator units: One drives the rear wheels, the other the front wheels. These three MGU modules are connected to one another via their own low-temperature circuit. It gives off its heat via the left radiator in the front of the car. The challenge compared to classic cooling systems: “40 degrees hot desert air cools 60 degrees warm cooling liquid only insignificantly because of the small temperature difference,” explains Fröber.

Two high-temperature circuits for coolant and charge air: the drive system of the Audi RS Q e-tron also includes an energy converter. The highly efficient turbo gasoline engine, which is arranged transversely behind the front passenger seat, has a fluid circuit with a cooler. The engine oil circuit is thermally connected to this system via a heat exchanger. Exhaust gas turbocharging requires a second cooling system: the compressed intake air flows through a charge air cooler into the engine. The liquid cooler and charge air cooler sit next to each other above the rear axle. The scoop on the roof divides the air flow between both radiators. “In difficult passages, for example when crossing dunes at slow speed, this air flow may not be sufficient,” says engineer Fröber. “For this reason, there is a fan behind each of the two radiators, which can extract the warm air if necessary.” It emerges from the rear of the Audi RS Q e-tron.

Well chilled, it’s off to the desert from January 1st. We will know by January 14th whether the highly complex technology will hold up.

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