Great article from Wolfgang Appel, head of vehicle development for Audi Sport. If you’ve wanted to know a bit more about the R10 TDI and its history and future, read on.
With most of the attention on the Audi R10 TDI focused on its revolutionary 5.5-liter turbocharged V12 diesel engine, it’s easy to forget there’s a whole lot of car – and performance – beyond the confines of the engine bay. That’s where Wolfgang Appel, head of vehicle development for Audi Sport comes in. Appel and his group are responsible for just about everything about the R10 except for the TDI engine itself.
“Vehicle development means aerodynamics, suspension, all the drivetrain except the engine itself which is under the direction of Mr. (Ulrich) Baretzky,” says the amiable Appel. “All the other stuff is our responsibility.”
And while Baretzky’s group faced one set of challenges in designing and developing the TDI V12, Appel’s group had its own challenges in creating a car capable of taking advantage of the diesel’s performance – if not the very first “modern” diesel race car then surely the most ambitious.
“In the past we did the very successful R8 with the TFSI engine in the middle,” he says. “But a race car is a race car. All the things around have to work together.
“The diesel was a great challenge. It was not easy to make a diesel car very quick and rigid and also reliable. If you remember, diesel engines in light trucks and so on are mounted on big rubber blocks so they can be free to vibrate. We can’t do that in a race car. It had to be rigidly mounted, that’s clear. In the beginning we did not know how to make it work and we could ask nobody, because nobody knew how it worked. It was an adventure!”
The R10 TDI, of course, made its competitive debut in the 2006 Twelve Hours of Sebring with Allan McNish, Dindo Capello and Tom Kristensen taking LMP1 class honors as well as winning race overall. Three months later, Emanuele Pirro, Frank Biela and Marco Werner scored the very first victory for a diesel-powered car at Le Mans and the R10 TDI has since amassed an impressive record of 21 class and 12 overall wins in American Le Mans Series competition.
“In the end the R10 was successful,” says Appel. “In the end we learned a lot because also in the beginning of the project we did not really know how competitive such a diesel-driven car would be. There was the weight, the big block, the vibrations and all the things around. But now the package is quite good.”
Good enough to earn a second straight Le Mans victory last year, along with the American Le Mans Series LMP1 title and – now – two LMP1 wins to start the 2008 season. Of course, it’s not quite as simple as all that, particularly on the American Le Mans Series side of the ledger where the R10 TDI has all it can handle with the (theoretically) slower LMP2 prototypes. The LMP2 Porsches took overall honors in eight of 12 races last year and opened the ’08 season with an outright win at the 12 Hours of Sebring before Audi bounced back with a win on the streets of St. Petersburg last week – but only after Lucas Luhr used the R10′s prodigious torque to pounce on Romain Dumas’ Porsche on a late restart.
The ongoing battle (on and off the track) between Audi’s LMP1 R10 TDIs and the LMP2s is an ongoing feature of Series competition, particularly given the fact that the R10 TDI was – ultimately – designed with the endless straightaways and quick corners of Le Mans in mind.
“At first (the R10) was not really designed for street circuits,” says Appel. “Street circuits … I think that’s the worst thing for the competition of our car. For Le Mans with the long straights a car with really a lot of weight in the rear is OK because you have many straights, less cornering and you have to have a big view of the drag coefficient so that’s what it’s made for.
“On the other hand to do these street circuits you have to adapt something on the car. We have done it and in the end we are working on the rear wheel loads – that’s our real problem at the moment and with Michelin and our tire partnership we try to develop the car to the circuit.”
Early indications are the R10 TDI circa ’08 is an overall improvement on its predecessors. Although a heavy crash involving the Mazda LMP2 entry led to the cancellation of qualifying at Sebring, the Audi R10 TDI of Capello, Kristensen and McNish started on pole based on the fact McNish turned the fastest time in the pre-race practice sessions (1:43.195) – one that was more than a second and a half faster than last year’s pole-winning time (1:44.974) recorded by Werner’s R10 TDI. And more importantly, it bested Peugeot’s diesel entry.
Similarly, Werner got around the 1.8-mile St. Petersburg street circuit in 1:02.825 to take this year’s pole, a time that was (again) more than a second and a half quicker than the best the R10 could do last year (1:04.415). And on race day this year, the R10 TDIs were the only cars to break the 1:04 mark.
“We are really faster for sure,” says Appel. “Not as fast as when we (will) develop the complete new car; that is not the case at the moment. At the moment we did a rework of the aerodynamic and small things in the weight distribution; we work with smaller batteries, we work with moving some parts that were mounted in the rear to the front, and on the drivability of the engine, because there is such a steep torque (curve) coming from low revs. The driver has to adjust to it and it’s not easy.
“The ASR (traction control) function, it helps a lot to make the car more driveable. It’s allowed in the regulations but also nobody has experience with a diesel car how to manage the system. So it’s always a new field, a big adventure for us.”
The future of the R10 TDI and Audi? A new open-cockpit car will succeed the R10 although it’s not clear when Audi would unveil a new design.
Did Mr. Appel utter the phrase “when we (will) develop a new car?”
The all-conquering Audi R8 saw some seven-and-a-half years of competition and was still winning races when it was supplanted by the R10 TDI midway through the ’06 campaign. Is Audi ready to pull the trigger on a successor to the R10 already?
That depends.
“That’s a matter of the regulations,” says Appel, “because the ACO (Automobile Club de l’Ouest) said in the past they had a draft of the new regulations and now they have changed it again, so for the designers it’s very difficult.
“At the moment we are focused on the current regulations and what we do in the wind tunnel for our investigations, we do it for the current regulations. That’s what we make proposals and we are in the wind tunnel for other concepts for sure, now we must be. And in the end of the year a new car should run. That must be the target if we are to make it completely new. Maybe the decision will be made in the Le Mans time.”
Of one thing Appel is confident: the future will not see Audi forsake the open cockpit concept of the R8 and R10 TDI. Initially, the ACO talked of making all LMP1 cars closed cockpits by 2010. Recently, however, they have revisited the idea and it appears future regulations will permit both open and closed cockpit prototype designs.
“Coming to Le Mans while the rules are stable,” says Appel, “they promised us with the new rules and the new safety regulations would stay for a long time. Now after two years they started a discussion for the new regulations and we were unhappy with it; and not only us but the other manufacturers. So the ACO is now in a direction of ‘OK, don’t make it mandatory to have a closed car; it should be the choice of the companies what to do.’
“Open, closed it makes the field more colorful. We saw it at first when we came with the diesel car, everybody noticed all the other cars are very, very loud and the Audi is very quiet. But if ALL the cars were very quiet, nobody would come because it would be like going on the Autobahn or the highway. To make the difference, to make the contrast, that is important.”
Apart from rules and regulations, one of the primary motivations for Audi either doing a redesign or a complete new car is the presence of Peugeot. While Audi was first to the turbo-diesel table with its R10 TDI – and got the glory of the first diesel victory at Le Mans in the bargain – Peugeot had the opportunity to go to school on Audi’s pathfinding effort in the process of designing and developing its 908 HDi which (if Sebring was any barometer) is quicker than the Audi.
Thus the engineer in Appel would love to start with a clean sheet of paper in formulating a successor to the R10 TDI.
“The dream of every engineer is to have a white sheet of paper and start again, because now we have so much more knowledge,” he smiles. “But that’s typical of any new project. If I had a wish I will do a new car, and we make proposals for that at the moment; how to go forward, how to make a new chassis or stay with the main structure of the car and make small adaptations. From my point of view we could make it new.
“If you are the first you didn’t know something. But if you look at Peugeot, they had our car in their view and what makes me feel great is they take a lot of things from you project to theirs. But they also take steps forward to make it in a second step – and now we should make it another, third step!”
In the meantime, however, Audi has embarked on an ambitious two-pronged program, running a pair of R10 TDIs in the American Le Mans Series in partnership with Champion Racing, while also competing in the European Le Mans Series. Apart from the challenge of two separate programs, the plan requires Audi to continue to develop the R10 TDI with the American schedule in mind, complete with its street circuits and LMP2-friendly Mid-Ohio and Lime Rock, at the same time the R10s compete on the more wide-open European road courses … all the while keeping their eye on sports car racing’s ultimate prize at Le Mans.
“From the engineering side we should develop the R10 for both the American Le Mans Series and the European series … and make a third car for Le Mans!” Appel laughs. “But our finance department doesn’t like that.
“Le Mans is so special that normally you need a third car. But in any case we must make a compromise and that’s also at the moment why the LMP2 cars are so quick, because they are more made for short circuits.
“But, in the end if they are very, very strong we have to think more about the street circuit and adapt or adjust the car. And if you think in the past, the Porsche 917 had a short tail and a long tail that was also made, one was for Le Mans and one was for the others. At the moment we try to do all the races with one concept.”
- ALMS
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