RALLY DAKAR 2022

Audi develops an advanced cooling system for the RS Q e-tron that will compete in the famous rally

The futuristic exterior design of the Audi RS Q e-tron perfectly reflects its advanced concept, with electric four-wheel drive and an energy converter. In order to moderate the temperature of complex components that, in many cases, are subjected to great stress, Audi has developed an advanced cooling system for the vehicle.

“Audi has never participated in the Dakar Rally before. The first question we asked was: how to take the heat generated by the car and send it outside”, explains Sebastian Fröber, the engineer responsible for the vehicle's cooling systems, referring to this crucial task. "We started working using CFD (Computational Fluid Dynamics) simulations for aerodynamics and then designing the individual cooling systems." Audi's experience with complex cooling needs, such as with the Audi R18 e-tron quattro hybrid, a three-time Le Mans 24 Hour winner, and in Formula E, was a big help in the process. However, this time the objective was clearly different: while in the cars for Le Mans maximum aerodynamic efficiency was a priority, in the prototype that will compete in the desert the key is to dissipate the heat. The various refrigeration circuits that the vehicle counts are responsible for ensuring the correct temperature at all times.

Low Temperature Circuit for High Voltage Battery (HVB)...The heart of the electric drive is the high voltage battery system. To keep it at the right temperature, Audi uses a coolant called Novec, which does not conduct electrical current. This low temperature circuit has a radiator under the hood at the front.

Low Temperature Circuit for Motor-Generator Units (MGU)...The combustion engine is connected to an MGU which generates electricity to recharge the high voltage battery. This later transfers the energy to two other MGU units: one moves the rear wheels and the other the front wheels. When the power flow is reversed, that is, during braking, both units recover energy and return it to the battery. These three MGUs are connected through their own low temperature circuit, which dissipates heat through the radiator located on the front left of the vehicle. Low temperature circuits pose a special challenge for engineers. Even with an extremely hot environment, the high temperature circuit makes the refrigerant not reach its boiling point, making the job for low temperature systems much more difficult. “This is due to the fact that desert air, at 40 degrees centigrade, only allows the refrigerant to go down to 60 degrees centigrade, due to the small temperature difference,” says Fröber.

Power steering cooling circuits and lift jacks...There is also an oil cooling circuit located in the left front air duct, in front of the low temperature radiator. This circulates hydraulic fluid for power steering, which is subjected to heavy workloads during off-road driving. The system also feeds the two lift jacks located on the right and left side of the vehicle through valves, in case a hole forces the pilots and co-pilots to change a wheel.

The air conditioning refrigeration circuit...In the right front air duct there is also the condenser of the air conditioning system. Inside the cabin, a fan allows air to circulate. The two high temperature circuits for the refrigerant and the charging air...The propulsion system of the Audi RS Q e-tron also includes an energy converter. The highly efficient TFSI engine, located transversely behind the copilot's seat, has a cooling circuit with a radiator. The engine oil lubrication circuit is thermally connected to this system through a heat exchanger. Exhaust turbo compression requires a second cooling system: compressed intake air flows to the engine through an intercooler located above the rear axle. The air intake located on the roof divides the air flow between the two radiators. “On difficult stretches, for example, when crossing dunes at low speed, this airflow may not be sufficient”, comments Sebastian Fröber. “For this reason, behind each of the two radiators there is a fan that can extract hot air if necessary”. Air exits through the rear of the Audi RS Q e-tron.

Designed for big challenges...The Audi RS Q e-tron's cooling system is designed for big challenges. “The last time we worked with temperatures was in Morocco, in November”, adds Sebastian Fröber. “Carlos Sainz crossed the soft sand of a dry river bed with the cooling inlets covered to do the endurance test. All systems worked perfectly”. Despite the losses associated with power unit cooling requirements, Audi built a highly efficient rally prototype. Within motor sport, this vehicle is a landmark in long-distance racing, thanks to its electric propulsion system and its energy converter. The TFSI engine, which runs on about 200 kW of power, is extremely efficient when operating between 4,500 and 6,000 rpm. Its specific consumption is far below 200 g/kWh. As a result, Carlos Sainz/Lucas Cruz, Mattias Ekström/Emil Bergkvist and Stéphane Peterhansel/Edouard Boulanger, along with the Audi RS Q e-tron, are not only ready to cross the desert in the Dakar Rally with a good temperature, but also with good temperature. a high efficiency.

Autonews