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The Place For A Diesel Is...On The Racetrack?

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Prof. Dr. Martin Winterkorn, Tom Kristensen, Dr. Wolfgang Ullrich at the unveiling in Paris

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By Carey Russ

I received an interesting notice in my email recently. Audi is going racing in the 2006 24 Hours of LeMans, the famous French endurance race. No surprise there, Audi prototype racers have dominated the classic event for the past six years. But 2006 will be different. Previous R8s have used engines based on Audi's 4.2-liter gasoline V8, and have been instrumental in the development of the company's FSI direct fuel injection for its gasoline engines. The R8 has been made obsolete by rule changes for this year's race, so it is time for something different. And the diesel-powered R10 is definitely something different.

There have been diesel-powered racing cars, but not many, and none have been notably successful. Volkswagen, Audi's corporate parent, has raced diesels in European Touring Car series. The most successful racing diesel was perhaps the Cummins Special that got the pole for the 1953 Indianapolis 500. Although a factor in the race, it didn't finish. Audi is breaking new ground.

Why a diesel? In Europe, 50 percent of Audi sales are diesels. In the U.S., zero, although Volkswagen does sell a few. Audi could be considered to have proven all that was necessary with gasoline engines in endurance racing with the success of the R8, and that has led to its latest 2.0-liter turbocharged and 3.2-liter naturally-aspirated FSI gasoline engines. Diesel development is a new challenge. Diesel engines are not as highly-developed as gasoline engines, and there are few ways better than endurance racing to quickly develop an engine.

Diesels are currently best-known for fuel economy and longevity, both attractive characteristics for endurance racing as well as everyday use. LeMans, best-known in the U.S. as the scene of Ford triumphs in the 1960s with the GT40s and the setting for a Steve McQueen movie soon after, can be a 24-hour flat-out race. Audi estimates that the R10 can do one or two laps more per tank of fuel than the R8, and so have fewer stops during the race, a significant advantage. As for reliability, there is an old saying that goes ``to finish first, first you must finish.''

The 24 Hours of LeMans is in June. As a shakedown, the R10 will first see competition at the 12 Hours of Sebring, in Florida in March. There are no current plans for its participation in the American LeMans Series.

More air plus more fuel equals more power, and that can be by a larger displacement or faster speeds. Competition gasoline engines are limited in displacement by regulations, and so consequently develop more power by higher engine speeds. Current Formula One engines are naturally-aspirated 3.0-liter V10s that rev above 18,000 rpm to develop over 750 horsepower. They only run a few hours between rebuilds; a LeMans engine needs to last 24 hours and so may rev to ``only'' 10 to 12,000 rpm or less. The outright record for specific power output - horsepower per unit of displacement - in gasoline engines belongs to the 1.5-liter turbocharged Formula One engines of the mid-1980s. In race trim, they developed over 750 horsepower from 1.5 liters, or 91 cubic inches. In qualifying trim, with more boost, and for only maybe 15 minutes, over 1000 horsepower was extracted from the same displacement by both BMW and Renault. Perhaps well over 1000 horsepower....

The R10's 5.5-liter V12 twin-turbo intercooled high-pressure direct-injection diesel breaks plenty of new ground for a diesel. It may have the highest specific power output of any diesel ever, with over 650 horsepower and 800 lb-ft of torque. It's high-revving for a diesel, with power from 3,000 to 5,000 rpm, and it's block and cylinder heads are made from aluminum for light weight. Most diesels are made from cast iron for strength, and are heavy. And 3,000 rpm is a high engine speed for an automotive-size diesel, which is small as such things go. Modern locomotive diesels rev to perhaps 1200 rpm, usually less, with upwards of 180 liters capacity for 4,000 horsepower. The largest marine diesel I know of dwarfs that - it's a Wartsila-Sulzer turbodiesel built to power container ships. With a 38-inch bore and 98-inch stroke, the 14-cylinder version displaces 25,480 liters and produces over 180,000 horsepower at 102 rpm, and over 5.6 million lb-ft of torque at that speed. It weighs 2300 tons and is nearly 90 feet long.

So Audi is pushing the envelope in diesel development with the R10. Why should you care? Europeans drive diesels, Americans don't. Yet. But consider that diesel engines can easily run on fuel made from renewable crop resources, and from recycled vegetable oil used in restaurants. Biodiesel is rare now, but will only increase in use in the future. Hydrogen has been widely touted as the fuel of the future, but there is currently it takes more energy to produce hydrogen fuel than can be gotten out of it. And much hydrogen is produced from natural gas, which may not be oil, but is still a non-renewable resource. Biodiesel is here, now, and works in any diesel engine with little modification. You may be driving a diesel-powered car long before one powered by a hydrogen fuel cell.

(c) 2005

Audi Press Release



PARIS - AUDI AG is once again one step ahead of the opposition: The inventor of ‘TDI’ will become the world’s first automobile manufacturer to fight for overall victory with a diesel engine at the famous 24 Hours of Le Mans. The all-new Audi R10, which was unveiled on Tuesday in Paris, is powered by a totally new 5.5-litre, twelve-cylinder bi-turbo TDI engine, which is extremely quiet and economical.
The Le Mans Prototype, with over 650 hp and more than 1,100 Newton metres torque, significantly exceeds the power produced by the majority of previous Audi racing cars – including that of its victorious R8 predecessor. Audi ventures into previously unexplored diesel-engine terrain with the V12 power plant manufactured completely from aluminium. As with the TFSI technology, which triumphed initially at Le Mans before being adopted for mass-production, Audi customers should benefit once again from the lessons learnt in motorsport.
"With the A8 4.2 TDI quattro, Audi already builds one of the most powerful diesel cars in the world,” explained Prof Dr Martin Winterkorn, Chairman of the Board of Management of AUDI AG, at the R10 presentation in Paris. "The Le Mans project will help our technicians to extract even more from TDI technology. Nowadays, every second Audi is delivered with a TDI engine. We expect that the percentage of diesel engines will be even larger in the future.”
The R10 prototype’s V12 power unit, which is equipped with two diesel particle filters, is hardly recognisable as a diesel thanks to the engine’s smooth running nature. The TDI engine’s specialities presented the Audi Sport engineers with a whole list of challenges. The injection pressure easily exceeds the 1,600 bar achieved in production cars. The usable power band lies between 3,000 and 5,000 revs per minute – an unusually low rev range for a racing engine. The driver must change gear in the R10 far less often than in the R8 because of the TDI engine’s favourable torque curve.
The enormous torque of over 1,100 Newton metres does not only make extreme demands of the R10 transmission system – even the latest generation of engine dynamometers at Audi Sport had to be re-equipped with special gearboxes capable of withstanding the unusual forces.
Additionally, radical changes to the chassis were also necessary. The Audi R10 has a significantly longer wheel base than the R8. The overly wide front tyres are, up until now, unique for a Le Mans Prototype. New technologies were also implemented during the development of the carbon-fibre monocoque. Chassis, engine and gearbox form an extremely rigid, fully stressed unit.
"The R10 project is the biggest challenge ever to have been handed to Audi Sport,” said Head of Audi Motorsport Dr Wolfgang Ullrich. "TDI technology has not been pushed to its limits in motorsport yet. We are the first to confront the challenge. The demands of such a project are accordingly high. Long-term technology partners such as Bosch, Michelin or Shell support us in our quest. Together we have the chance to write new chapters in the history books of motorsport and diesel technology.”
The new Audi R10 successfully completed its first test at the end of November. An extensive test programme, including the 12-hour race at Sebring (USA) on 18 March, is scheduled before the 24 Hours of Le Mans on 17/18 June 2006. The development team from Audi Sport is supported by Reinhold Joest’s squad, which also performed this task during the R8 project.