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  • 2012 24 Hours of Le Mans: Diesel Vs. Gas

2012 24 Hours of Le Mans: Diesel Vs. Gas

Racing with Hybrid Technology

Rusty Rae
Nov 1, 2012
Photographers: Rusty Rae
If you liked the 2010 movie Clash of the Titans, the mythical adventure about Perseus and his quest to battle the Kraken monster in order to save the princess Andromeda, then you’ll love the 2012 version of the 24 Hours of Le Mans. Le Mans is an automotive endurance race, and at this year’s event, two titans of the automobile industry—number one Toyota, and number three Volkswagen (the owner of Audi)—locked horns in a battle that is ultimately for world supremacy in automotive sales.
Photo 2/13   |   diesel Vs Gas audi Diesel Race Car On Track
Defending Le Mans champion Audi brought its 3.7L V-6 diesel- powered, carbon-fiber race cars to the party but this year upped the ante with the addition of a nifty flywheel-electric hybrid system (called E-Tron) and the return of its Quattro all-wheel drive. Not to be outdone, the Toyota brain trust, in a return to Le Mans after a 13-year hiatus, brought a 3.4L, 90-degree V-8 gas car, also with a hybrid system.
Diesel’s World Domination
The story begins in mid-January, when Audi’s archrival, the very successful diesel-powered Peugeot team, announced it was dropping out of the World Endurance Championship (WEC) series that had been developed by The Automobile Club de l’Ouest (ACO), leaving Audi holding the proverbial bag. Without another manufacturer in the series, no World Championship could be awarded, throwing a very wet rag on Audi’s aspirations of promoting its foray into the hybridization of its brand through racing. That’s when Toyota stepped in to replace Peugeot and give the LMP1 class the competitive life it required.
Photo 3/13   |   The Audi R18 race cars are all about power and efficiency. These ultra-light road-racing cars feature carbon-fiber unibodies, a diesel-electric-hybrid all-wheel-drive system, LED headlights, 540 hp, and the durability to run nearly nonstop for 24 hours—at speeds of more than 140 mph.
Toyota’s 3.4L V-8 Super Capacitor Hybrid
Toyota had not planned for the 2012 season to be a racing year, and according to Rob Leupen, Director of Business Operations Toyota Motorsport BmbH, it was to be a testing year, with a debut as a race team in 2013.
Indeed, Toyota missed the first two races of the series, at Sebring and at Spa. It had planned to bring its TSO30 Hybrid to Spa, but a crash during practice prior to Spa kept the team away from the race. While the Toyota team understood it faced an uphill battle against the experienced Audi team, it was not as if they were bringing a knife to a gunfight. As the world leader in hybridization of automobiles, Toyota had been working on the integration of its technology into a race car since 2006. Indeed, Toyota used the super capacitor system for regeneration on a Supra HV-R hybrid race car that won the Tokachi 24-Hour endurance race in July 2007. This Supra became the first hybrid car in the history of motorsport to win such a race.
Additionally, Toyota hired drivers from the Peugeot Le Mans team. This trio, Alexander Wurz (a two-time 24 Hours of Le Mans winner), Stephane Sarrazin, and Anthony Davidson brought an immediate infusion of knowledge and focus to the Toyota team.
Diesel Hybrid vs. Gasoline Hybrid
In this East-meets-West battle, the two teams used two different solutions to hybridization for a race car. The first challenge for each team is that batteries simply aren’t able to charge and discharge fast enough to be of any significant use in a racing scenario. Innovation is the name of the game at Le Mans, and each team brought its own vision of the future to the race track.
Photo 4/13   |   The Audi R18 also features all the things you’d expect from a state-of-the-art race car: 15¾-inch-wide tires, forged-magnesium 18-inch wheels, and a six-speed, electronically shifted manual transmission (with a carbon-fiber housing)—and the whole car weighs less than 2,000 pounds.
Audi chose a flywheel-based, power storage system, which it dubbed E-Tron and reintroduced its famous Quattro all-wheel drive with the car. Toyota took advantage of a super capacitor it believed gave it a better power-to-weight advantage. Toyota also toyed with an all-wheel-drive car, but when all was said and done, the decision was to go with a rear-wheel-drive car.
How Audi’s Diesel-Electric Hybrid Works
Audi’s E-Tron hybrid uses the concept of a kinetic energy recovery system (KERS), a concept that was actually formulated by the Nobel Prize-winning physicist Richard Feynman in the 1950s. Essentially, the idea is to accumulate energy during the braking of the car, and then use this energy either for additional acceleration out of the corner, or to improve fuel efficiency.
Photo 5/13   |   diesel Vs Gas audi R18 Leading Porsche
Audi has already showed the world the benefit of a clean-burning diesel engine, and now it’s looking for the most efficient method to harness regenerative braking energy. Its solution was to add what it calls a motor generator unit (MGU) to the front wheels of the car and mate it with an electronic flywheel accumulator to store this energy. It sounds challenging (and to a certain extent it is), but it’s a very elegant solution that allowed Audi the ability to take advantage of Feynman’s idea and stay within the limitations of the rules currently placed on hybrid cars.
Photo 6/13   |   Toyota’s TS030 carbon-fiber race car (right) is similar to the Audi R18 (left) in many ways. It too is a hybrid, features a carbon-fiber chassis, a six-speed transmission, and was built to showcase new technologies. Unlike the Audi, however, its V-8 engine is naturally aspirated—and burns gasoline.
Audi reengineered its R18’s Le Mans-winning design in an effort to save weight to make up for the extra weight of the hybrid system. For example, it reduced the mass of the 3.7L V-6 diesel to the point that it now weighs less than the 3.6L gasoline engine of a decade ago, yet it has about the same horsepower, more torque, and better fuel economy.
Special Rules For Hybrids
In an effort to keep the playing field somewhat level, while allowing all-wheel drive for hybrid cars, the use of the hybrid power was limited to speeds in excess of 70 mph. Having reduced the power of the diesel engine by 7 percent and further reducing the size of the fuel tanks for diesel-powered cars, it seemed to many as if Audi was being asked to fight the battle of Le Mans with one arm tied behind its back. The ACO also stipulated braking zones where the Audi and Toyota could use their recuperative power. On the Circuit du la Sarthe, there were seven zones, whereas at the shorter Spa track there were only five. In addition, the ACO required that the maximum amount of energy that could be transferred in one of these zones is 500 kilojoules.
Photo 7/13   |   Toyota’s TS030 carbon-fiber race car (right) is similar to the Audi R18 (left) in many ways. It too is a hybrid, features a carbon-fiber chassis, a six-speed transmission, and was built to showcase new technologies. Unlike the Audi, however, its V-8 engine is naturally aspirated—and burns gasoline.
Inside E-Tron
Here is how Audi solved the problem: The front wheels of the R18 E-Tron have two halfshafts, which are driven by the MGU. The MGUs were developed in partnership between Audi and Bosch. These units are water-cooled and have all electronics integrated into them. Each unit can generate about 100 hp. What is most amazing is that the total weight for the MGUs is less than 50 pounds. Under braking, the MGUs are driven by the wheels of the car to recuperate energy. The MGUs use electricity to accelerate a carbon-fiber flywheel (developed by Williams WHP), which is sealed in a vacuum enclosure next to the driver. This flywheel (or technically speaking, accumulator) will reach 60,000 rpm, so obviously there is a concern about safety with this mass holding so much energy and sitting next to the driver. However, the enclosure has a Plexiglas floor, and in the event of a major failure, the carbon flywheel will disintegrate and exit out this sacrificial floor.
Photo 8/13   |   You’re looking at the baddest V-6 four-valve-per-cylinder diesel race engine ever made. This 3.7L engine produces 540 hp and 664 lb-ft using a single variable-geometry Garrett turbo making 43 psi of boost. The block itself uses a radical 120-degree-cylinder-bank angle, which helps to lower the car’s center of gravity. Like the 6.7L Power Stroke, the engine’s exhaust is routed through the heads into the V of the engine, and the intake manifolds are where the exhaust manifolds are on a typical V-configuration diesel. And, like the Audi race engines of the past, this diesel uses a Bosch Motorsports common-rail diesel fuel system that’s run via a Bosch Motorsports MS 14 ECU.
Planetary gears adapt the transmission ratio during acceleration and braking. Each of the independently powered axles on the E-Tron Quattro (that drive the MGUs) are synchronized via electronic control strategies, which replaces the traditional center differential in previous versions of Quattro all-wheel drive. This control occurs automatically without driver intervention. The entire charging process (recuperation) is controlled by two parameters: the braking process, and the accumulator’s state of charge. The energy emission process (boost) is defined by the minimum speed of 75 mph stipulated by the regulations, the race strategy selected, the throttle pedal movement, and acceleration of the car.
Photo 9/13   |   From the side, you can see the 3.7L’s turbo mounted in the lifter valley, and you’ll also notice the driver-side intake plenum that’s made from carbon fiber. The carbon-fiber tank in front of the engine is the oil tank for the engine’s dry-sump lubrication system. If you look closely, you can just make out the two Bosch CP4 injection pumps that are driven off the back of the engine.
Audi’s Hybrid on the Track
Of course, all this techno-geek physics and applied math doesn’t mean a thing if it doesn’t convert to performance on the racetrack. For Audi, the results were no less than astounding: qualifying First, Second, and Fourth, with car No. 1 posting the top time with a lap of 3:23.787. The No. 3 Audi R18 Ultra was second fastest, and surprisingly the No. 7 Toyota 030 hybrid was Third. The No. 2 Audi E-Tron Quattro was Fourth, but the veteran driving team of Alan McNish, Dindo Capello, and Tom Kristensen are notorious for spending time in finding the best setup for the race, rather than for qualifying.
Photo 10/13   |   diesel Vs Gas audi Pit Stop
Race Day
From the start of the race, the No. 1 Audi was able to extend its top qualifying position, and it seemed as if it was a foregone conclusion that the defending champs Andre Lotterer, Marcel Fassler, and Benoit Treluyer would simply cruise to the checkered flag.
Photo 11/13   |   diesel Vs Gas race Track Staring Line
Early on, the Toyotas were slightly off the pace of the leading Audis. At one time, the No. 8 Toyota TS030 hybrid fell a lap off the pace of the leader, and the No. 7 car saw nearly a 2½ minute gap with the leader in the fourth hour. But then a funny thing happened on the way to the winner’s circle. The No. 7 Toyota started to reel in the leaders. In fact, at the end of the fourth hour, the Toyotas were running Second and Third behind the No. 1 Audi E-Tron, with the remaining R18s running Fourth, Fifth, and Sixth. Slowly, the No. 7 Toyota put the No. 1 Audi directly in its sights for the lead of the race. Stalking the No. 1 Audi, Toyota took a solid run at the Audi coming into the tight Mulsanne turn. Audi was able to sweep through the turn on the outside to remain in the lead. The two raced into the Indianapolis turn, where the Toyota took a divot out of the grass and snuck past the Audi, which was blocked by slower traffic.
The Toyota went by the Audi and this time made the lead stick. Audi countered, but it was the moment in the sun for the Toyota team, as it kept the number one spot on the course. Moments later, however, any joy the Toyota team might have enjoyed was over, as Davidson in the No. 7 Toyota was hit by a slower Ferrari car as he entered the Mulsanne turn.
This is one of the fastest sections on the race course, and the collision first spun the Toyota and then the car went airborne, completing a loop-the-loop before slamming into the tire barrier on the far outside of the course. The Ferrari also wound up impacting this same segment of the Armco barrier. Neither driver was seriously injured, though Davidson spent the night in the hospital with two broken vertebrae and was out of commission for 60 days.
Gasoline Strikes Back!
The No. 8 Toyota led for three laps, as the safety car was brought onto the track for more than 30 minutes while course workers feverishly labored to repair the barrier and reset the protective tire bales. Meanwhile, Lapierre pitted for a driver change and Kazuki Nakajima took control of the car. A rookie at Le Mans, Nakajima was able to keep the Audi within striking distance. With the racing going green again, the cars were bunched together and Nakijima lost track awareness, as his focus was on racing with the Audi. He moved right to stay with the lead Audi and inadvertently punted the Nissan DeltaWing car off the track. It was the beginning of the end for the remaining Toyota.
Photo 12/13   |   diesel Vs Gas race Steering Wheel And Dash
The Toyota crew had to replace the bodywork of the car as well as do a complete inspection. An hour later, at the end of the eighth hour of racing, the No. 7 Toyota was 25 laps behind the Audi after alternator problems besieged the car, and it withdrew from the race with undisclosed engine problems.
From then on, it was an Audi-only party and the only thing that really remained was which of the Audis was going to take the checkered flag. The youngsters of the Audi Team, driving the No. 1 E-Tron car, had little trouble running out front. But the No. 2 Audi E-Tron, with veterans Dindo Capello, Alan McNish, and Tom Kristensen, made a valiant attempt to reel their teammates in. To Audi’s credit, team management let the Audis race, unfettered by any team rules.
The No. 1 Audi cruised to the checkered flag, leading for the last 42 laps of the race and 333 laps of the 378 laps. In winning, the team of Treluyer, Fassler, and Lotterer became the first to win the 24 Hours of Le Mans with a car using hybrid power. The No. 2 Audi finished Second, a lap down to the winners and the No. 4 Audi Ultra was Third, three laps off the winning pace, giving Audi a sweep of the top three places.
Diesel-Electric Hybrid vs. Plain-Old Diesel
Audi officials indicated the 2012 winning Audi E-Tron was 6.4 percent faster and burned less fuel, getting the consumption down to 8.77 gallons per 62 miles, or 7.07 mpg.
Photo 13/13   |   The Audi R18 E-Tron Quattro’s front wheels are driven by an electric motor generator unit (MGU) that powers the front wheels via two halfshafts.
The victory is simply the next step in a journey that has no end. Audi has used its success at Le Mans and other venues to drive sales, understanding the old adage “What wins on Sunday, sells on Monday.” Since 2006, the diesel engine has reigned king of Le Mans. In these six years, the ACO has placed more and more restrictions on the diesel powerplant, and still it continues to go faster. And indeed, Audi has taken the diesel engine from the red-headed stepchild and turned it into a quiet, fuel-efficient, clean source of power for a daily driver.
The ACO has recognized what Audi has accomplished, and seeking to drive other manufacturers in the same direction announced a new set of rules for 2014, which essentially take the gloves off the hybrid formula. The new rules only limit the amount of fuel a team may use during the course of the race—but all other technical elements of the engine remain open. This means that for 2014, all entries will have to build new cars and it is expected that in addition to the Audi and the Toyota there will be additional factory entries, perhaps with the return of the Peugeot. It is the challenge for which Audi lives.


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