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  • 24 Hours Of Diesel Power at Le Mans

24 Hours Of Diesel Power at Le Mans

Imagine Driving From Los Angeles to New York at 120 mph—In One of These…

Rusty Rae
Dec 1, 2011
Photographers: Rusty Rae
Suppose you and your buddies decide to drive from Los Angles to New York City one afternoon. You plan to leave L.A. at 3 p.m. on Saturday and arrive in the Big Apple at 3 p.m. Sunday. Of course, you’d have to have a couple of good drivers to take turns at the wheel, and probably someone who could do a little wrenching for you on the way. Oh, and there would be one other thing: The diesel vehicle you drove better be able to average 120 mph for the entire trip.
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Sound like mission impossible? Well, this is the exact scenario the winning Audi Le Mans Prototype One (LMP1) team went through in early June at Circuit de la Sarthe in France. Audi conquered four other diesel- powered Peugeots and a host of gasoline-powered race cars in what many consider to be the most challenging motorsport event in the world—the 24 Hours of Le Mans. And it did it with a 3.7L V-6 diesel engine that was not only able to average more than 120 mph for the race but regularly topped 200 mph on the famous Mulsanne straight.
TDI Win On Sunday, TDI Sale On Monday
Audi believes in the old adage “What wins on Sunday, sells on Monday” and has carved out a niche market as a result of its wins in major races. Audi uses what it’s learned on the racecourse to improve the daily drivers of its fleet. But it has also borrowed from the production fleet to improve its race car, as is evident in the LED lights that illuminate the way for the vehicle.
We must remind you that in Europe, the price of fuel is around $7.00 a gallon, and TDI gives consumers the best value for transportation. Audi and Peugeot see diesel motorsports as a direct channel to market, and both have used racing to market their brands and improve their cars.
Diesel Is Changing the Rules
During the last five years, teams that have chosen to go with the diesel engines have experienced more and more restrictions from the Automobile Club de l’Ouest (ACO) sanctioning body. When Audi first came to Le Mans with a diesel in 2006, it was a 5.5L V-12. This year, the powers that be restricted engine displacement to 3.7L.
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The Peugeot team, which has challenged the dominance of Audi in endurance racing, won the Le Mans race in 2009. But the Teutonic Knights of Ingolstadt, Germany (Audi’s home base) are dominant in the crown jewel of endurance racing, winning the 24 Hours of Le Mans four of the last five years.
Tale of Two Engines
With just 3.7Ls to work with this year, each team had to come up with a new engine. Peugeot chose to build a 90-degree V-8, while the Audi team introduced a 120-degree V-6.
Photo 4/9   |   Audi’s aluminum V-6 isn’t based on any production engine, but it does use Bosch’s CP4-pump-based common-rail injection system. Like the new 6.7L Power Stroke, the exhaust manifolds are located in the lifter valley (close to the turbo), and the intake manifolds (the large cast-aluminum chambers) are mounted on both sides of the engine. Rumor has it these engines run steel pistons from Mahle.
Bruno Famin, Peugeot Sport’s Technical Director, noted Peugeot wanted to stay with technology it knew, and therefore simply reconstituted its 5.5L V-12 into a 3.7L V-8. “We tried to use our know-how in engine development. Basically, the engine’s block, pistons, and combustion chambers are an improved version of what was used in the V-12. We just reduced their size to comply with the 2011 rules. By keeping the engine architecture the same, it makes the new V-8 easier to work on,” he said. The Peugeot V-8 uses twin turbos as it did on the V-12, but the engine uses an updated Bosch injection system.
Audi’s 540hp V-6
Initially, Audi came to Le Mans with a 5.5L V-12 and twin turbochargers. Then, in 2009, it shrunk the outside of its engine by building a 5.5L V-10. But gasoline-burning teams whined about the advantages of the diesel, and the ACO, looking to ensure some semblance of competition, listened.
Photo 5/9   |   The Audi’s mid-mounted V-6 engine is packaged under a maze of carbon fiber, titanium, and German engineering. The new single exhaust is routed rearward, directly from the center-mounted VGT Garrett turbo. You’ll note there doesn’t appear to be any muffler on this car—just the diesel particulate filter. The exhaust exits the car from what looks like a carbon-fiber shark tail.
At the end of the 2009 season, Audi began designing its close- cockpit R18 TDI. No idea was left on the table as the team put the corporate motto, “Vorsprung durch Technik” (forward advancement through technology), to work.
When it came to the engine, Audi made a bold choice to go with a V-6, but not just any V-6 design. The engineers came up with a compact 120- degree cylinder-block-angle V-6, which allowed for a lower center of gravity as well as the opportunity for what it called “electrification” in the future.
First, rather than the twin turbochargers of past, the V-6 utilizes a single turbocharger that sits above the engine and draws its air directly through the air scoop mounted in the roof of the chassis. Developed with Garrett, the turbo utilizes variable-turbine geometry, just like the Le Mans-winning R15 V-10 TDI.
Ulrich Baretzky, Head of Engine Development for Audi, noted, “Without VTG, the response characteristics of one large turbocharger would just be too slow.” In the end, Audi was able to produce a 540hp V-6, and with the improvement in aerodynamics of the car, it kept the performance in the same realm of the 5.5L V-10 R15 TDI .
A couple of other differences between the V-6 Audi and your normal diesel include the fact that this diesel is whisper quiet. As Dr. Ullrich notes, “Noise is unused energy. A quiet engine is more efficient than a loud one. At the moment, being quiet sets us apart. Just as long as there are others that are loud, we make a lasting impression.”
This Audi is more efficient from a fuel economy perspective as well, getting 20 percent better fuel economy than the 3.6L direct-injection gasoline engine Audi raced with in 2000. Additionally, injection pressures have increased from 23,000 psi with the R10 to something approaching 36,000 psi in the R18.
Finally, Audi logs 1,005 channels of data from each vehicle. That information is recorded, monitored, and transmitted to the data center in the pits. At Le Mans, that amounts to 16 MB of data each lap for engineers to study.
Race Day
The technical differences in the cars notwithstanding, when it came to qualifying, there were six very fast diesels on the grid. Just 0.534 second separated the number one qualifier (the No. 2 Audi of Fässler/Tréluyer/Lotterer that would eventually go on to win the race) from the number six qualifier.
Photo 6/9   |   Audi’s diesel dominance began with its 700hp, twin-turbo, 60-degree, 5.5L V-12 (left) that was fitted to the R10. In 2009, Audi went with a 60-degree, 5.5L V-10 (center), which allowed the engine in the new R15 to be moved forward for better balance. For 2011, the rules limited diesels to just 3.7L, so Audi built an all-new 120-degree, single-turbo V-6 (right) that’s reported to be making 540 hp in the R18.
The Audis sprinted to the front and gave their French rivals the chance to assume the lead while they were in the pits. The game of high-speed leapfrog gave 250,000 fans in attendance a chance to see their favorites in the lead at one time or another. But before the first hour was complete, the No. 3 Audi went out of the race in a spectacular crash when Scotsman Allan McNish got tangled with a slower car in the fast downhill sweeper known as La Chappelle. The Audi went off the track and skipped over a gravel trap, impacting the track barrier at speed. The impact totally demolished the chassis, but McNish escaped with no serious injuries.
180-mph Crash
Then, just before midnight, the No. 1 Audi suffered a similar fate with Mike Rockenfeller at the wheel. Rockenfeller said he was “cruising” along at 180 mph in Second Place as darkness settled over the track. A GT car clipped his left rear wheel and caused the R18 TDI to turn left into a guardrail at more than 150 mph. Rockenfeller was able to climb out of what was left of the No. 1 chassis, but he spent the night in the hospital for observation. The impact of the Rockenfeller crash caused a two-hour yellow on the course, and according to one report, required more than 100 pieces of Armco barrier to repair.
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The Fox and the Hounds
Following that incident, the four Peugeots became the hounds and the remaining Audi the fox. With the odds stacked against Audi, Fässler, Tréluyer, and Lotterer had to drive a perfect race for the final 16 hours.
During the night, the pack of Peugeot 908s put continual pressure on the lone Audi, and when the sun rose, the battle for the lead came to a head with the No. 7 and No. 9 Peugeot 908s and the Audi No. 2 grouped together and locked in a battle royale. Slowly, however, the tide turned in favor of the Audi.
First, the No. 8 Peugeot was assessed a one-minute stop-and-go penalty. Then, Alexander Wurtz in the No. 7 Peugeot went off the track at Indianapolis and impacted the tire barrier when he misjudged braking. Wurtz limped back to the pits where his Peugeot team worked frantically to replace the right front axle—in nine minutes. By the time the car rejoined the fray, it was four laps down from the leaders.
As the race came down to is final climactic moments, it was Lotterer in the Audi and Simon Pagenaud in the No. 9 Peugeot 908 who were to do the final battle. Pagenaud crept within 30 seconds of the Audi with judicious tire management by his crew.
Fight to the Finish
With a little more than 14 minutes left in the race, both cars made their last stop. The Audi took on tires, while the Peugeot just took on fuel. When they exited the pits, the Audi had but a 10 second lead—but thanks to new tires, it was able to increase the lead to a final margin of more than 14 seconds. Earlier in the morning (on lap 229), Lotterer had in fact turned a 3:25.289, which was faster than the team’s qualifying time.
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In the end, it was speed and precision that won Audi its 10th 24 Hours of Le Mans. The No. 2 Audi completed 355 laps—just shy of 3,000 miles—and averaged around 124 mph for the race. Dr. Ulrich noted after the race, “2011 was no doubt the most difficult Le Mans race we’ve ever contested—but with the sweetest result we’ve ever had as well. From such a difficult situation, we managed to recover again on our own power in the end to defeat—albeit with a narrow margin—our really strong competitors from Peugeot.
“After eight hours, we’d lost two of our three cars and knew it would be extremely difficult with just one car. The entire squad gave everything to do the best for this car. Of course, the drivers had to drive it. And they did a really fantastic job—although it was the squad with the least experience at Le Mans. It’s extremely important that Allan (McNish) and Mike (Rockenfeller) came out of both accidents, which were really severe, without any injuries.
Why Le Mans is Such a Tough Race
For those of you not familiar with the race, it is run on an 8.4-mile-long track with 38 turns, which is mostly comprised of local public roads. The race cars spend more than 75 percent of their time at wide-open throttle. The first race was held in 1923, and with time off for WWII, this year was the 79th running of the race. With longevity has come stature, and with the management of the ACO, the race has grown into one of the premier racing events in the world, rivaling the Indy 500 and the Monaco F1 race. Perhaps the 1971 Steve McQueen movie Le Mans has done as much as anything to bring the race to the forefront of the public.
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