The quiet evolution

Audi’s new R15 turbodiesel has already taken up the R10’s winning ways, but is it enough to beat Peugeot at Le Mans?
By Gordon Kirby

Audi’s debut win at Sebring in March with its all-new R15 Le Mans contender showed the company’s mastery of sports car racing. Despite minimal pre-race testing, Allan McNish, Tom Kristensen and Dindo Capello scored a great victory aboard one of the two new R15s raced in the 12 Hours. The Peugeot team gave Audi a serious run for its money in Florida and appears to have made as much progress with its 908 as Audi has with the R15, ensuring that the 77th Le Mans 24 Hours, in June, is sure to feature another epic battle between these two excellent factory teams.

“It’s really extraordinary,” said Kristensen about the R15’s successful debut. “It shows the know-how Audi has taken from the previous cars, the R8 and R10.”

The R15 handles and brakes much better than the R10, but McNish believes the Peugeots will still be very hard to beat at Le Mans where the 908’s superior top speed will be more useful. “Peugeot’s reliability was pretty good today,” said McNish after the Sebring win. “They had a problem with one car right from the start, but they were reliable, they were fast, they were always there and they didn’t make any team mistakes like they’ve done in the past. Their pitstops were more efficient. I think they’ve learned a lot of lessons.

“They’re going to be very quick at Le Mans. To say that we’re favourites just because we’ve got a new car is very presumptuous. We’re going to have to do a very good job to try and beat them. Remember, they were five seconds a lap faster than us last year at Le Mans. We’ve got to bridge that gap.

“I think at Sebring we had a slightly quicker car over the distance in all conditions. They’re a bit quicker on top speed and we’re probably a wee bit quicker in high-speed corners. We’re probably very similar in the medium and low-speed corners.”

McNish’s race engineer Howden Haynes agrees with his driver’s assessment. “At Sebring the Peugeots upped their game,” says Haynes. “Their car is fast and they’ve upped all their pitstop strategies where they were lacking before. They’re still quick in a straight line. If anything I would say we’re quicker through some of the high-speed corners, which is good for Le Mans, but we need to find some more top speed and hopefully that’s what the new aero package will bring us.”

Audi Sport’s technical director Wolfgang Appel says the R15 is a product of optimising the lessons learned from the R10. “We started with the diesel engine three years ago and a lot of work has gone into this car,” he says. “We could not have ended up with such a nice car if we hadn’t had all the experience and knowledge we gained from the R10.

“The goal was efficiency, and there were three main areas to improve – aerodynamics, weight distribution and mechanical grip. And, for sure, a well-performing, clean and efficient engine.”

Dr Martin Mühlmeier, Audi Sport’s head of technology, adds: “Aerodynamic efficiency aims to reduce drag and increase downforce. Therefore we have larger front openings to reduce the virtual frontal area, giving increased airflow through the car, and also through the side and out the rear end. This is a whole new approach.”

The first sketches of the R15 were made in January 2008. “The R10 was the first car in racing with a completely new turbodiesel engine and we had to accept some compromises,” says Dr Wolfgang Ullrich, Audi motor sport boss. “But with the R15 we used what we had learned through three years of running the R10. We decided to start from zero with a new car and engine to try to make an optimised package for a diesel sports-prototype.

“One of the key factors was to improve engine efficiency. Efficiency always means a reduction in CO2 emissions. As you have already seen from the R10, the noise level is important to being green. Some race fans don’t like it but I think we started a new area with the R10. The R15 sounds a little bit different but is still very silent.

“The R10 was a more difficult challenge because we had nothing to direct us on how to do it. Nobody had done anything similar. It’s important to have a clear plan for development. But it’s also important to learn what not to do.

“When Peugeot came with their new car last year we suffered the whole season. In the end we made good results, but it was clear a new car must be designed.

“The R15 was the chance to make a proper LMP1 car for a diesel engine following the ACO rulebook and concentrating on a good compromise for the overall package. The engine people were pushed to go in the direction the car designers wanted, and the designers knew they had to be careful with a diesel engine in mind. We merged the whole design process in a better way than with the R10.”

The R15 is very clean without any of the aerodynamic kick-ups and bits we’ve seen in recent years on Formula 1 cars and most sports cars. The nose also presents an identifiable Audi look. “This was one of the things we tried to achieve,” admits Ullrich. “An Audi should always have top technology, but it should also have an Audi look and therefore we tried to give it that look. One does not automatically exclude the other. If you gave the car just to the designers it would look different, and if you gave it just to the aerodynamicists it would look different again. So, once again, we had to find a good compromise.”

A slightly different aero package has been developed specifically for Le Mans. “Sebring is a race track with a different characteristic from Le Mans, so we will make some changes to optimise the car for that track,” says Ullrich. “But the main parts of the cars will remain as they were at Sebring.”

The V10 engine is a lighter variant of the R10’s V12. “The architecture of the engine is very similar to the R10,” says Audi’s chief engine man Ulrich Baretzky. “There was no reason to change that because the system was working quite successfully.

“Our focus on the engine was to increase the efficiency, which means improving the combustion system. The other thing was to make the car aerodynamically more efficient and to improve the handling. So we cut two cylinders and made a V10, which is about 100mm shorter and nearly 10 per cent lighter. This helps make it a good-handling car with good power and response.”

Like the V12, the V10’s cylinder banks are inclined at a 90-degree angle. “There is no real argument for making a narrower angle engine,” says Baretzky. “It’s a diesel, so it isn’t revving very high.”

Work on the V10 started in September 2007 and the engine ran for the first time 12 months later, just six months before Sebring. “We’ve stayed pretty conservative this year because we wanted to avoid additional risk as it’s a new car, new engine and new gearbox,” says Baretzky. “Everything is new, so we should be careful not to override it. But we are working on further technologies for next year. This is all on its way now. We have done some substantial work on turbocharging. I don’t want to go into details. We’ll let Peugeot find out what it is. When they find it out they will find other things. They cannot copy it. It will be a new experience for them.”

Baretzky admits that aerodynamics played a primary role in designing the R15. “We have made many more compromises in favour of the aerodynamics than we did with the R10. This concept is quite radical with the airflow through the car, and this dominated everything.

“With the arrangement of the turbocharger and the exhaust it was really tight packaging. We tried to make it very compact, moving the engine forward and making it as low and as light as possible. There is some more to come which we can do when we have more experience with the existing engine to balance the risk.”

The engine chief could not be more pleased with the working relationship between Audi’s aerodynamicists, chassis and engine people. “There was a permanent exchange of opinions,” he says. “When I say we made more compromises than with the R10, I don’t say somebody squeezed us in a box. No, not at all. We said what we would be able to do on the engine side, what we needed for a cooling requirement. It was their problem to decide on the size of the intercoolers or heat exchangers. They asked us to make the engine in the rear as small as we could, and that’s what we did.”

Baretzky is delighted with this year’s Sebring win: “For me, it was beyond expectations, because we went there with a car which was not really tested. My big fear was we would see a problem running in the hot weather, and we didn’t. That shows our people work well together to make a car that works, just like that.”

McNish is a huge fan of the R15. “This car is very agile, very responsive to the steering, the throttle and the driver,” he says. “The information you get is immediate. I would say the R10 had a lot of potential but in comparison to the R15 it felt a bit lazy. The R15 is definitely a big improvement. You can place the car much better and turn in on the inside line when
you’re overtaking people. It’s got better front grip so your lines in traffic are better. That was something we couldn’t do with the R10. We could adapt, but we had limitations that we don’t have with the new car. There’s a different engine note and the throttle response is a bit better. It’s also lighter and has better weight distribution so you can put the power down better.
“The torque itself is down,” adds McNish. “But overall you use that to your benefit. You can be more aggressive on the throttle, and because we can turn the car in a bit better we can be more aggressive in the middle of the corner. So our exit speeds can be a bit better.

“In hairpins it’s not much different. With the old car we could get on the gas quite well when it was straight. But when it was a rolling type of corner we had to be more careful.”

The Scot says the R15 requires a different approach to its predecessor: “You really had to grab hold of the R10 and throw it around, tell it what you wanted it to do. There was a lot of physical effort the whole time you were in the car. The R15 does it much more gently, but the forces are higher because you’re going through the corners faster.”

The final word goes to McNish’s engineer, Haynes: “It looks like in terms of outright performance the Peugeots have still got the legs on us a bit. We’ve got to address that. The Le Mans package will be lower drag and will address any of the problems we saw at Sebring. Michelin will also have new tyres for Le Mans, and with no test day this year we’ll go straight to the race with no chance to change anything. We’ll have to wait and see what happens at Le Mans, but the R15 is certainly a huge step in the right direction for us.”