Audi has built a new Le Mans car – and this one’s a diesel. There have been diesel race cars before – and of course racing trucks are diesels – but no company has previously brought this level of technology to the task.
The heart of the Audi R10 is a completely new V12 TDI engine with a capacity of 5.5 litres – the maximum permitted at Le Mans. Power exceeds 650hp and a peak torque of more than 1100 Newton metres is available.
"This engine is the specifically most powerful diesel there is in the world and, up until now, the biggest challenge that Audi Sport has ever faced in its long history,” says Ulrich Baretzky, Head of Engine Technology at Audi Sport.
"There has never been anything remotely
comparable. We started development with a clean sheet of
Unfamiliar to the driver is the low noise level and, unique for a racing engine, the smooth running V12 TDI power unit. At high speeds the engine cannot be heard from the Audi R10 prototype’s open cockpit, while Audi claims there is also hardly any vibration.
For the 24 Hours of Le Mans, the V12 TDI is
equipped with a pair of diesel particle filters. Flashes of flame from the
exhaust, which are created by unburned petrol in spark-ignition engines, are not
seen coming from the R10.
ChassisOne of the most significant differences to its predecessor, the R8, is the integration of monocoque and bodywork. The R8 still had a traditional chassis clothed in synthetic bodywork, whereas the majority of the carbon-fibre parts belonging to the R10 monocoque are now suspended directly in the airflow and therefore require no additional fairings.
"The R8 originates from 1999 and we’ve gathered a
huge amount of know-how since then,” says Wolfgang Appel, Head of Vehicle
Technology at Audi Sport. "All this experience found its way into the new
Although the R10 prototype’s carbon-fibre monocoque is more waisted than that of the R8, the drivers can sit comfortably in the cockpit – a factor not to be underestimated in a 24-hour race like at Le Mans. The servo steering, which is now electric instead of hydraulic, also helps to increase comfort.
A similar direction to that taken in production cars was followed with the electronics. The number of electronic control units rose considerably when compared with the R8. A "network” system (CAN-Bus) runs through the entire R10; all important functions are controlled centrally by computers. Even the indicators and headlights are no longer directly activated by the driver, he simply makes a manual impulse – everything else is done by the on-board computers.
Together with electronic partner Bosch, a new vehicle data logging system (FDE) was developed for the R10. All data is transmitted by telemetry to the pits and shown in the cockpit on a steering wheel mounted display. The most important functions are controlled by buttons mounted on the steering wheel, which is equipped with a micro-processor and was developed together with the specialist company Megaline. The Megaline experts were also involved in the development of the electro-pneumatic shift mechanism, which is activated in the R10 by two steering-wheel mounted paddles. The gearbox itself originates from X-trac and, despite the enormous torque produced by the TDI engine, is lighter than that of the R8.
Thanks to the turbo-diesel engine’s characteristics, the number of gear changes made during a 24-hour race falls significantly – an important factor concerning durability, particularly as the transmission system is subject to extremely high loads.
Because of the high level of torque produced by the V12 TDI, the forces acting on the R10 transmission system are even greater than those experienced by a Formula 1 racing car. The gearbox was conceived to withstand these forces, as are the driveshafts which are thicker than the ones on the R8. The same is valid for the novel ceramic clutch that was developed together with ZF Sachs.
The greater thermal discharge and the corresponding increase in cooling requirements are also diesel-specific. Higher side pods, in which the larger coolers are fitted, are the result. The wider front tyres, which were commissioned by tyre partner Michelin, are completely new to the LM P1 class. The use of traction control reduces the high loads created by the torque fed to the rear tyres, and helps the driver to modulate the V12 TDI engine’s power delivery, particularly in wet conditions. The refuelling system, re-developed with specialist company Stäubli, allows a fast and virtual splash-free refuelling process. In contrast to petrol, spilled diesel does not evaporate. As was the case with the R8, various coloured LEDs located close to the refuelling inlet vent act as initial visual information indicating the diesel, engine oil and water levels to the mechanics during a pit stop.
Fans at Le Mans will no longer be able to see glowing brake discs on the Audi R10: the carbon-fibre brakes discs are fully enclosed in a cowling. Just like on Formula 1 cars, the brake discs are no longer fed with cooling air through pipes but are cooled by air channelled through carbon-fibre ducts mounted directly to the suspension.
The daytime low-beam lights use a row of white light-emitting diodes and the rear lights are also LEDs.
DevelopmentThe idea to develop a diesel sportscar for the 24 Hours of Le Mans had already emerged in 2002 but things became very serious in September 2003 when the concept guidelines for the new Audi R10 were determined.
"That was the most important stage,” says Ulrich
Baretzky, Head of Engine Technology at Audi Sport. "You have to define the
number of cylinders, the engine’s length, bore and stroke. Everything else
results from these basic dimensions. If you make a mistake at this stage, it is
almost impossible to correct later. That’s why we considered every facet very
carefully before we fixed the package.”
"Compared with the R8, the engine’s length has grown through the number of cylinders, and because of a diesel’s typical power and strength,” says Wolfgang Appel, Head of Vehicle Technology at Audi Sport.
"In this respect we had to react by making everything as light as possible on the chassis side.”
"It was incredibly interesting, because we really
have explored completely new territory with this engine,” says Ulrich Baretzky.
"Previously, together with our colleagues from the production car development,
we had made basic tests with modified production engines and a single-cylinder
model. That was all!”
90 degree V12 turbo-charged engine, 4 valves per
cylinder, DOHC, 2 Garrett-turbo chargers, 2 x 39.9 mm engine-air intake
restrictors (defined by regulations) and maximum turbo pressure of 2.94 bar
absolute, diesel direct injection TDI, stressed aluminium crankshaft