Audi RS 5 DTM: Detailed work within narrow limits

The engineers at Audi Sport developed the Audi RS 5 DTM for the DTM Technical Regulations which have been in effect since 2012. The regulations particularly emphasize three aspects: maximum safety, maximum equality of opportunity and maximum cost efficiency.

Therefore, the organizers of the internationally popular touring car series have been relying on a concept that was originally unique in the world and that has since been largely adopted by the Japanese Super-GT Championship as well. Numerous components such as the carbon monocoque, safety elements, the six-speed transmission, the clutch, the carbon brakes and the DRS rear wing are identical on all DTM race cars.

The organizers differentiate between specification, standard and listed components. Specification components are purchased by the automobile manufacturers from the DTM’s central suppliers. Standard components may be produced by the manufacturers themselves based on clearly defined requirements. In addition, there is a list of optional components.

In spite of the restrictions, there is still enough room for the automobile manufacturers’ own developments, particularly in the areas of aerodynamics, suspension and powertrain. “The RS 5 DTM consists of some 4,000 parts,” says Dieter Gass, Head of DTM at Audi Sport. “Less than 100 of them are specification, standard or listed components.”

The pioneering Technical Regulations have reduced the costs of a DTM race car by about 40 percent – while simultaneously increasing the safety and spectacular look of the cars.  

In terms of technology, the Audi RS 5 DTM with which Audi Sport is chasing the title in 2015 corresponds to the model – internally designated as ‘RC3’ – that the company won the DTM manufacturers’ title with last year. To relieve the manufacturers’ budgets, the DTM organizers imposed a freeze on the technology by homologation after the third race in 2014 until the end of 2016. Therefore, the next major development step will only be possible for the 2017 season when the new regulations are introduced.

In winter, the engineers at Audi fully concentrated on localizing untapped potential and on further optimizations of the existing package. The result is a new, even more efficient basic set-up for the 2015 season.

In addition, all eight race cars were completely dismantled and carefully reassembled at the new Competence Center Motorsport by the Audi Sport Teams Abt Sportsline, Phoenix and Rosberg based on last year’s monocoques and components. The teams need nearly two weeks for this work for each RS 5 DTM.

The chassis underneath the full-carbon body which, at first glance, reveals the close kinship to the production RS 5, features a hybrid design weighing a little less than 160 kilograms. The combination of the carbon fiber monocoque and steel cage with front, rear and side crash elements sets standards for a race touring car in terms of safety.

“With the cell, we’ve set new standards,” says Stefan Aicher, Head of Vehicle Engineering Design at Audi Sport. “The monocoque weighs only 126 kilogram and the roll cage 32.5 kilograms. At the same time, the safety standards have massively increased when the current regulations were introduced. The construction is extremely strong not only in longitudinal crashes but particularly in side impacts. The entire side panel has to resist a force of 360 kN in a side impact crash test, which equates to about 36 tons.”

The RS 5 DTM is 5.01 meters long, 1.95 meters wide and 1.15 meters high. The identical wheelbase of all DTM vehicles is 2,750 millimeters. As in the production model, the V8 engine that delivers about 340 kW (460 hp) is at the front. In a parallel project, Audi Sport is currently developing a four-cylinder TFSI engine for the new Class 1 regulations that will become effective in 2017.

DTM race cars have rear-wheel drive. quattro drive is not permitted. The semi-automatic six-speed transmission of the RS 5 DTM is pneumatically operated via paddle shifters on the steering wheel. The shifting events, which are more precise compared with conventional manual gearshifts, make it possible for the transmission to achieve a mileage of up to 24,000 kilometers. The engine electronics (Bosch MS 5.1), which do not use fuses, and the central display that provides the driver with all the relevant information – such as key tire parameters – feature state-of-the-art technology as well. Data transmission by radio to the pits (telemetry) is not permitted in the DTM.

A large safety fuel tank with a capacity of 120 liters that allows the drivers to complete the full distance without refueling stops even in the longer DTM race on Sunday is integrated into the safety cell of the Audi RS 5 DTM.

As specification components on the suspension, only the engine sub-frame at the front and the transmission at the rear limit the freedom of the engineers. The suspension has to be mounted on these specification elements. In addition, for the wishbones, the use of steel as the material and the tube dimensions are specified. Numerous dimensions are defined by the regulations – for instance the wheels. The tires of all DTM race cars are exclusively supplied by Hankook.

With respect to aerodynamics, the possibilities are not unlimited either. The driver can flatten the rear wing angle by 18 degrees by means of the drag reduction system (DRS) as needed. Underneath the imaginary horizontal line between the wheel hubs, the engineers have extensive freedom – albeit only with each new homologation. During the season and the homologation period, modifications to homologated components are not permitted.

The regulations permit and promote a close visual reference to the production car, for instance in the form of the single-frame honeycomb grill that is typical for the RS 5 and that contains the airflow ducts to the engine and the brakes on the race car. “The regulations in the DTM are generally very strict,” says Stefan Aicher. “Therefore, we are challenged to fine-tune details within narrow limits.”