When Audi makes final preparations for the Dakar Rally next month, it has already listed the details of the RS Q e-tron cooling system, which handles the electric and IC powertrain components and allows the driver and co-pilot to Maintain (relative) comfort.
"Audi has never participated in the Dakar Rally before. The first question we asked ourselves was: How do we dissipate heat from the car?" Sebastian Fröber, the engineer in charge of the cooling system, summed up the core questions about cooling. "We first performed CFD simulations on the aerodynamics of the entire vehicle. Then we designed a separate cooling system."
Audi’s experience with complex cooling requirements, such as its experience in the three-time Le Mans champion R18 hybrid, and its Formula E program, is clearly in a good position in the Dakar challenge. However, Dakar’s goal is clearly different: although maximum aerodynamic efficiency is the top priority of a Le Mans sports car, the desert prototype is the best possible heat dissipation. Achieving this goal requires the use of multiple cooling circuits.
Starting from the core of the electric drive and the high-voltage battery system, Audi uses a liquid cooling system and a dielectric coolant called Novec, and the low-temperature circuit uses a radiator under the front cover.
At the same time, the three MGUs (motor generator sets) of the car are connected through their respective low-temperature cooling circuits, and the heat is dissipated through the left radiator at the front of the car. Audi said that this low-temperature circuit posed a special challenge to its engineers due to the high temperature of the Dakar circuit and the low temperature increase between the ambient air and the coolant.
“This is because the 40° desert air can only slightly cool the 60° coolant due to the small temperature difference,” Fröber said. Since the electric motor must operate at a much lower temperature than the internal combustion engine, the cooling system must be very efficient to protect the electric motor.
Audi RS Q e-tron, cooling concept
The oil cooling circuit is also located in the left front air duct in front of the low-temperature radiator. This will circulate the hydraulic oil used for power steering, which is subjected to high loads during off-road driving. The system also supplies power to the two jacks on the right and left of the vehicle through valves to force the crew to change wheels with run-flat tires. There is also a condenser for the air conditioning system in the right front air duct. Another fan in the car circulates the air in the cabin.
Finally, the IC engine placed laterally behind the passenger seat has its own fluid circuit with a radiator. The engine oil circuit is thermally connected to the system through an oil-water heat exchanger. There is also an intake air cooling circuit, which relies on the heat exchanger above the rear axle and next to the oil cooler. A fairing on the roof separates the airflow between the two radiators.
“In difficult passages, such as when crossing sand dunes at low speeds, this airflow may be insufficient,” Fröber said. "For this reason, there is a fan behind each of the two radiators, which can draw out hot air if necessary." It is located at the rear of the Audi RS Q e-tron.
“The last time we got hot air in Morocco was in November,” Fröber points out. "During a long test, Carlos Sainz walked through the soft sand of a dry river bed and deliberately fixed the cooling air inlet with tape. All systems were flawless."
Since 2007, Lawrence has been researching engineering disciplines-with a focus on racing technology-and editing and contributing to various international publications. Currently, he is responsible for the content of the UKI Media & Events website portfolio and also writes for the company's print publications.
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