With the two-liter four-cylinder version of the Audi RS 5 DTM, Audi has underscored its leading position in the field of highly efficient turbocharged engines. In its first season, the compact engine was the measure of all things.
The four-cylinder turbo of the Audi RS 5 DTM is the most efficient and powerful engine in the company’s DTM history. The Audi engineers extracted over 610 hp from the engine, which is only two liters in size, in its first year of operation. In terms of reliability, too, the new engine was exemplary from the outset: Audi was the only manufacturer to make do with the engine quota of 1.5 units per car allocated by the regulations. At the end of the season, one engine had a mileage of about 6,000 kilometers.
The DTM’s Class 1 regulations focus on maximum efficiency. High efficiency and low fuel consumption are decisive factors for success in DTM: Whoever has the more efficient engine can get more power out of the available fuel. Just like in road car production, the task is to get the maximum out of the available fuel with high compression and very good efficiency.
In the DTM 2020, the fuel quantity is limited to 90 kilograms per hour. “That sounds like a lot, but in view of the power output of about 580 hp it’s not really much,” says Stefan Dreyer, Head of Powertrain Development at Audi Motorsport. “The DTM engine has an extremely low specific fuel consumption, which is now moving into regions where it used to typically be for diesel engines. In terms of weight and lightweight construction – particularly with regard to CO2 avoidance – we’re showing ways that will hopefully find their way onto the road in the future – like the first TFSI for Le Mans and the TDI.”
The compact four-cylinder turbocharged engine with direct petrol injection (TFSI) weighs only 85 kilograms and thus almost half as much as the naturally aspirated V8 engine that was used in the DTM from 2000 to 2018. As a result, the dry weight of the Audi RS 5 DTM dropped to under 1,000 kilograms. The power-to-weight ratio is now around 1.7 kg per hp.
A DTM engine has to last for a complete season, just like before. Therefore, the mileage is designed for about 6,000 kilometers. “The DTM format is a major challenge,” says Dreyer. “The long mileage, spread over many events with short runs, is rock-hard. In addition, the four-cylinder engine has a completely different vibration behaviour than the V8. This was a huge challenge in the development of the engine, but also for our test beds.” More than 100 hp additional power and also the higher torque mean an additional load for the complete drive train.
Thanks to a so-called “Push-to-Pass” system, the driver can even call up additional engine power at short notice at the push of a button, for example for an overtaking maneuver. A bypass of the Fuel Flow Restrictor (FFR) provides an additional 10 kg of fuel per hour for a period of up to five seconds, resulting in an increase in output of approx. 60 hp.
The DTM is driven with standard filling station fuel (Aral Ultimate 102). This favors the technology transfer from motorsport to series production. In addition, the engine is ready for the use of alternative fuels as Audi has already successfully tested them during the 2019 DTM finale at Hockenheim. As a result, the CO2 emission of combustion engines can be further reduced significantly.
Audi has a lot of experience with turbo engines in motorsport from the legendary original quattro to the successful Le Mans prototypes. Each of the approximately 2,000 components of the DTM engine was redesigned on this basis. The compact four-cylinder in-line engine is installed longitudinally at the front in the Audi RS 5 DTM. The turbocharger, which operates with a maximum absolute boost pressure of 3.5 bar, is located on the right-hand side of the vehicle and is kept at speed by means of an anti-lag system (ALS) even when the driver is not on the gas. The red-hot manifold of the engine, which glows red under full load, protrudes artistically upwards in the engine compartment. The maximum permitted engine speed is 9,500 rpm.