The Audi RS Q e-tron: Second evolution of the technology laboratory

The first concept idea for the Audi RS Q e-tron was developed in 2020, a year later the prototype underwent intensive testing, and in January 2022 the baptism of fire at the Dakar Rally was on the agenda. After the first rally victory in March, Audi Sport presented the second evolutionary stage in September 2022. It is further optimized in many areas from weight to aerodynamics to efficiency.

Audi wants to be the first automobile manufacturer to fight for overall victory in the world’s toughest rally with an electrified drive in combination with an efficient energy converter against conventionally powered competitors. “The Audi RS Q e-tron points the way to the future,” says Head of Audi Motorsport Rolf Michl. “It competes in the T1 Ultimate category for low-emission vehicles. Its technology proves itself in an incredibly rough motorsport discipline. It’s hard to imagine a tougher testing ground for electromobility. The basic concept has proven itself so well that we have adopted it for the second evolutionary stage.”

Because there are no charging opportunities in the desert, Audi has chosen an innovative charging concept: On board of the Audi RS Q e-tron, there is the highly efficient TFSI engine from the DTM. It is part of an energy converter that charges the high-voltage battery while driving. Since the combustion engine is operated in the particularly efficient range of between 4,500 and 6,000 rpm, the specific consumption is well below 200 grams per kWh.

The drivetrain of the Audi RS Q e-tron is electric. The front and rear axles are both fitted with a motor-generator unit (MGU). A third MGU is part of the energy converter and serves to recharge the high-voltage battery while driving. In addition, energy is recuperated during braking. The battery weighs about 370 kilograms and has a capacity of 52 kWh.

“The battery is also a proprietary development that we have realized together with a partner,” says Stefan Dreyer, Head of Development at Audi Sport for motorsport projects. “As engineers, we basically see development potential in every component. But in terms of the drivetrain system, we have already achieved a system efficiency of over 97 percent in Formula E. There’s not much more room for improvement. The situation is quite different with the battery and energy management. This is where the greatest development potential lies in electromobility in general. What we learn from the extremely challenging Dakar project will flow into future production models. As always, we are also working closely with our colleagues from road car development on this project.”

The regulations have reduced the maximum drive power from the previous 288 kW to 263 kW from the 2023 season. The electric drivetain offers many advantages. The electric motors can be controlled extremely precisely and can thus ensure good drivability. In addition, braking energy can be recovered. One of the learning effects from the first season is an improved electronic control system. It proved its worth in the first rallies. Only in extreme cases did challenges arise. For example, Audi noted short-term power surpluses at the Dakar Rally in situations where the wheels had little contact with the ground when jumping or on uneven terrain. The officials of the FIA, the world automobile federation, already intervene at a threshold of 2 kilojoules of excess energy and hand out sporting penalties. “By way of comparison, more than one hundred times the amount of energy flows to the engines per second within the permissible limits,” says Florian Semlinger, development embedded software, application and test bench. “We could have made it easy on ourselves and set our threshold several kilowatts lower, but that would have meant performance disadvantages. Instead, we put a lot of fine-tuning into the power controllers.” Two individual limits – one for each machine – are now recalculated by the software in milliseconds. As a result, it operates exactly along the permissible limit.

The Audi RS Q e-tron only needs one forward gear. The front and rear axles are not mechanically connected, as is also common in electric vehicles. The software developed by Audi takes over the torque distribution between the axles and thus creates a virtual and freely configurable center differential, which has the positive side effect of being able to save the weight and space that woud have been required by propshafts and a mechanical differential.

The body is completely new and has not a single component in common with the first evolution stage. It offers two major advantages: It helps reduce weight by several dozen kilograms up to the raised minimum weight of 2,100 kilograms. At the same time, it is significantly more aerodynamic and reduces overall drag – i.e. the product of cW value and frontal area – by 15 percent. This does not change the top speed. It remains limited to 170 km/h in the regulations. Nevertheless, the improved air flow offers the advantage of further reducing the car’s electrical energy requirements.

Audi has also improved the RS Q e-tron in other areas for the 2023 season. Optimized control of the auxiliary consumers noticeably improves the energy balance. For example, the air conditioning system now only runs in intermittent mode. The operating strategy for the fans and the servo pump has also been optimized. The systems can now be regulated differently for the lower loads on the liaison stages than on the special stages.

In the cockpit, but also when changing wheels, Mattias Ekström/Emil Bergkvist, Stéphane Peterhansel/Edouard Boulanger and Carlos Sainz/Lucas Cruz benefit from improved ergonomics and a revised operating logic. For example, the engineers have restructured the central switch panel in the drivers’ and co-drivers’ field of vision with its 24 fields: The individual functions are grouped into four areas (Stage, Road, Error and Settings) to facilitate quick access. If sharp rocks destroy a tire on the stages, the wheel can be changed even faster. Easily removable body components help with stowage, while the new ten-spoke rims from partner Rotiform are much easier to grip and therefore make changing easier.

Finally, the RS Q e-tron sets a milestone in the area of emissions. In the future, Audi will use reFuel as fuel. To further reduce carbon dioxide emissions, Audi is relying on residue-based products that do not compete with food. Behind this is a process that converts biomass into ethanol in a first step. The final fuel is then produced in further process steps. The process is abbreviated to ethanol-to-gasoline (ETG). The process engineers use biogenic plant parts as the starting product.

The tank content of the RS Q e-tron consists of 80 percent sustainable components, including ETG and e-methanol. The energy converter uses this fuel to generate electricity for the electric drive. The combustion engine part operates with high compression and is therefore very efficient. So while the drive concept basically already requires less fuel than conventional systems, there is now a further optimization. “With this fuel mixture, the Audi RS Q e-tron saves more than 60 percent of carbon dioxide emissions,” says Dr. Fabian Titus, Development Application and Thermodynamics.

Initial tests of the new Evolution in Europe and Africa in mid-season 2022 were followed by the first start in October 2022. At the Morocco Rally, the Audi Sport driver pairings were able to get to know the innovations under competitive conditions before tackling the 2023 Dakar Rally with the innovative prototype.