Audi has disclosed some of the details of its forthcoming R18 e-tron quattro, revealing a turbodiesel, electric flywheel hybrid, all-wheel drive prototype, and ensuring that the 2012 Le Mans 24 Hour Race will be a battle of the hybrids.

Though Audi's long-time rival Peugeot will not contest the race, Toyota is entering two hybrid race cars in the prototype class, as will Audi, and with Audi's plans for hybrid and electric e-tron road vehicles, the battle for the title of the world's fastest racing hybrids is now on.

And as an added side-show, two TDI Audi R18 ultras will contest the event - the cars are identical to their hybrid brethren apart from the hybrid system itself - so we'll really be able to see how much difference a hybrid makes to performance, particularly as a four-wheel drive vehicle which should offer much superior roadholding when it rains.

Audi's impeccable record

Audi usually wins Le Mans - 10 of the last 12 races have gone to the German marque with the 2003 win to Bentley so close on the Volkswagen family tree to the Audi marque for it to have been something of a moral victory for Audi. The marque's IP/DNA was used extensively in the Bentley car and even regular drivers were co-opted into the team, indicating the priorities of the Volkswagen Group at that time.

Even Audi stalwart Tom Kristensen who had just equaled the record for consecutive victories at Le Mans with three straight wins in an Audi from 2000-2002, was slotted into the Bentley in 2003 for his fourth consecutive win, then he added a further two wins in 2004 and 2005 in the Audi R8.

So apart from the narrow Peugeot 908 HDi FAP win in 2009, the last time an unrelated marque greeted the chequered flag first at La Sarthe on the big day was the BMW V12 LMR in 1999.

That's quite some record considering that 24 hour races are so incredibly unforgiving - the slightest problem can turn a team with race-winning speed into also-rans. Toyota's last tilt at glory in the what many claim is the "world's most important race" saw it field a very fast and very unlucky car which lives in legend - the 1999 3.6L Turbo V8 Toyota GT-One - but it didn't win and that is all that counts to the manufacturers.

The automotive world is facing what Audi's Head of Motorsport Dr. Wolfgang Ullrich terms "the electrification of the drive". After a century of petroleum-based motoring, the world will be forced to be more responsible in its energy usage, and electricity will almost certainly power, either partially of fully, the automobiles of the not-too-distant future.

"It's an issue in which our colleagues from production are also totally absorbed. In this respect a new era has in fact started", says Ulrich.

Sales figures for pure electric cars suggest that the hybrid and TDI diesel are more accepted by the public at this point in time, so winning the "world's most important race" with a hybrid would be invaluable to the marketing of both companies. Only one of them however, can win.

The relentless march of motorsport progress

Compounding reliability issues even further for new entrants in recent years is the ongoing evolution of the Le Mans 24 Hour from a reliability trial, which it was when it began, into a 24 hour sprint, which it has been for the last few years.

The above image shows how speeds have risen in the race since it was first won in 1923 at an average speed less than most legal speed limits. When average speeds reached more than 200 km/h (125 mph) in the mid-sixties, the organisers began a series of course modifications and engine restrictions designed to slow the race down. Though long straights now often have slow speed chicanes in them, each year, the best minds in autosport conspire to continue to progress against these restrictions. The reliability of the cars is now so good, and they can run so hard for 24 hours, that simply maintaining position for a few hours is no longer a viable strategy for serious contenders - if you're not running flat out, you're going backwards.

While the average speed of the event may not show much improvement in the last forty years, the speeds through the corners are now horrendously fast, and average speeds have only been held down with capacity and induction restrictions and continued remodeling of the faster parts of the circuit .

Just the same, the V12, 5.5 liter 700 bhp Audi R10 TDi was clocked at 329 km/h (204 mph) during the 2006 race, and at 339 km/h (211 mph) in 2007, both on the Mulsanne Straight.

In 2010, with more inlet restrictions and lower turbo boosts, a direct development of the same car ran a record 4838.30 km at an average speed of 225 km/h - with a 3.7 liter V6.

The Toyota Challenge

In 2012, Audi will face a new rival - the biggest kid on the block - Toyota. Toyota will run a petrol electric TS030 HYBRID powered by a normally-aspirated 3400 cc V8 petrol engine and a supercapacitor energy storage system developed by Nisshinbo.

Conventional batteries can't store and discharge energy fast enough for a race car, and Toyota and Audi will be running the two main contenders for hybrid race car energy storage - the Williams Hybrid Power electric flywheel system and supercapacitors. Toyota is obviously developing expertise in the very important area of ultracapacitors, supercabatteries, bacitors or Asymmetric Double Layer Capacitors (ADLCs) - a coming industry that doesn't seem to have established standard nomenclature just yet.

Audi's WHP magnetically loaded composite flywheel (MLC)

Audi's hybrid energy storage system has a lineage that goes directly back to the original KERS introduction in F1. The R18 quattro will use a magnetically loaded composite flywheel (MLC) originally developed for F1 by Williams Hybrid Power, that has subsequently been used successfully in Porsche's GT3 R hybrid in 2010 and 2011.

Williams F1's original investment in Williams Hybrid Power dates back to March 2008 when the company bought the minority share in Automotive Hybrid Power (subsequently re-named to WHP), a Norfolk-based provider of composite flywheels, when kinetic energy recovery systems (KERS) were being introduced into Formula One.

Williams F1 subsequently increased its shareholding to 78% on the back of some very favourable results on the racetrack and ever growing confidence that the company's MLC technology will find wide application in hybrid passenger vehicles, buses, electric trains, diesel-electric ships and wind power generation.

The original 2010-model 911 GT3 R Hybrid used two electric front-wheel-drive motors developing 60 kW (82 hp) each, which supplemented the 480 bhp four-litre flat-six engine at the rear of the 911 GT3 R. The car held the lead in the Nürburgring 24 Hour race, for more than eight hours before problems unrelated to the hybrid system saw it relegated through the field.

For 2011, the organizer of the Nürburgring 24 Hour race thought the performance potential of the hybrid vehicle was so auspicious that it crippled the rear-mounted petrol engine's performance to just 448 bhp. So Porsche built a completely new vehicle to the same design around the new regulations, lowered the weight, upped the electrical drive to the front wheels to 200 bhp and set out to run the same lap times. It hit the lead of the event at the four hour mark but a series of non-hybrid-related problems saw it finish down the field.

From 2010 to 2011, the Williams Hybrid Power system shrank 20% in size and weight. The Audi system looks to have gone on an even more radical diet, though we have no specific details.

The car's kinetic energy is recovered on the front axle under braking. The energy is fed as electricity into a flywheel accumulator before being retrieved under acceleration again above a speed of 120 km/h.

When overtaking or accelerating out of a corner, the driver can manually override the controls by pressing the boost paddle on the steering wheel and sending energy from the charged flywheel generator to the front axle. This additional power of 120 kilowatts is available to the driver after each charge process for approximately six to eight seconds.

A diagram of the WHP system fitted to the R18 e-tron system provided at the press release shows a quite different solution has been created for the new car.

The system will provide 150 kW of power at a top rotor speed of 45,000 rpm. The main benefits of the WHP system in comparison to batteries, ultra-capacitors or mechanical flywheels are a high power density and correspondingly low mass, high efficiency energy transfer to and from the e-storage, the ability to continuously deep power cycle and an insusceptibility to performance or life degradation over a wide range of operating temperatures.

In short, the technology is perfectly suited to the high performance demands of endurance racing.

Remarkably for this late stage of the proceedings, Toyota is still evaluating whether the THS-R (Toyota Hybrid System - Racing) will use a front motor system from Aisin or a rear motor system from DENSO. We suspect the DENSO system might be ahead politically, but I cannot see Toyota missing the obvious opportunity (the same that Audi has taken) in the development of four wheel drive race and road cars.

Even back in 2007, the Toyota Supra HV-R Hybrid which won the first major race for a hybrid used electric power on all four wheels. The 1,080-kg Supra used an ultracapacitor storage system and captured energy from all four wheels during rapid deceleration, and returned it under acceleration. The system used 10 kW in-wheel motors in the front wheels in addition to one 150 kW rear-axle mounted electric motor, giving the car 700 horsepower in total, with 473 bhp coming from the 4,480-cc motor and a further 227 bhp from the electric motors. The drivetrain was so impressive that it was named Race Engine of The Year 2007 by the editors of Race Engine Technology magazine.

The potential of hybrid power

The importance in understanding the enormous potential of hybrid power is to appreciate the vast difference between an electric motor and an internal combustion engine.

An electric motor is far more of a precision instrument than an internal combustion engine - it can be switched on and off in microseconds and computers can calculate and deliver the exact amount of power to the steering wheels, to get a car through a corner on the limits of adhesion.

Ultimately, in my humble opinion, two wheel drive motorcycles will also be faster and safer, but for four wheels, it makes absolute sense that you're going to get more power on the ground using four contact patches instead of two.

Audi's Quattro race history, mainly its domination of WRC during the early eighties, has already proven that four-wheel-drive works brilliantly with mechanical linkages. In the public's view, Audi's most famous driver was probably Michèle Mouton, who took four WRC victories and finished runner-up in the drivers' world championship in 1982 - without doubt the closest yet that a woman has come to winning a sport traditionally associated with the male of the species. Audi's WRC quattro won the WRC in 1983 with Hannu Mikkola and 1984 with Stig Blomqvist.

The second coming of the quattro promises so much more - medieval technology will be replaced by a computer with a precision, independent power output to each front wheel. We are entering an entirely new era of four-wheel-drive, where cars will go around corners faster than you thought possible, thanks to the additional power, traction and balance achievable by using four powered wheels instead of two.

Audi and Toyota will stage the initial battle of the hybrids and I find it almost unthinkable that Toyota could go in any direction with hybrid power other than driving the front wheels and hence exploring an obvious competitive advantage in the development of 4WD if it succeeds. By comparison, adding all the extra horsepower to the rear wheels seems of little incremental value, with no potential upside other than more power.

The Toyota effort is nonetheless very serious. Though the car is being built in Germany by Toyota Motorsport GmbH in the former Toyota F1 race headquarters near the Nürburgring circuit, the engine will apparently be supplied directly from the factory. We suspect it will be a good one, as were the engines it supplied to Rebellion Racing team for its Lola LMP1 car in 2011.

But with the basic drive technology for the TS030 not yet chosen, it's hard to see Toyota being ready to rumble competitively when we see the teams side-by-side at the Spa Francorchamps 24 Hour race on May 4.

Audi noted during its press conference that the e-tron quattro project started in February 2010 - two years ago. It considers that the 18 months that passed between the initial conceptual ideas and the first shake-down test was "a relatively short cycle for a technology that has never been tested in motorsport and which still doesn't even exist in production," stresses Dr. Martin Mühlmeier, Head of Technology at Audi Sport. "The challenge is correspondingly big."

Toyota is eight weeks from its first competitive outing and we still don't know the drive configuration - we hope they do.

Audi's "two by two" car strategy

In a strategy probably formulated well before Peugeot quit the endurance scene in January, Audi has boldly decided to split its resources. In many ways it's a sign of a team on top of its game.

It has taken the car which won last year, and refined it in every respect, taking proven race-winning architecture and making each component incrementally lighter, stronger, more durable - from the carbon fiber composite monocoques that are significantly lighter than last year's cars, through to the TDI engine. Both cars from Audi will feature carbon fiber gearbox housings this year, with Audi building its lightest TDI race car yet.

Not a single one of Audi's race motors has suffered a failure in the Le Mans 24 hour race since before the start of the R10 era. Audi will field two such "Ultra" cars with conventional drive trains and when the clock ticks toward the 24 hour mark at La Sarthe this year, we can reasonably expect at least one of them to be in contention for the win.

After winning Le Mans five of the last six time with turbo diesel power, Audi is sold on the TDI engine. "The TDI was invented by Audi", says Dr. Ulrich, and "is still the most efficient drive in the world."

"We've also proved this at Le Mans since 2006. It's not a coincidence that turbo diesel engines are unbeaten there for six years now, even though the diesel cars were repeatedly limited. We are convinced that the TDI has even more potential. This is why Audi not only supports the hybrid in motorsport and production, but in parallel also the further development of the conventional drive. The combination of TDI and hybrid is, however, without doubt particularly interesting and very promising."

The insurance policy of having a bet each way is not new to Audi, which also split its initial 1999 Le Mans challenge with two different body types using the same chassis and twin-turbo 4.0 liter V8, albeit unsuccessfully. Two open cockpit Audi R8Rs finished third and fourth, while the enclosed R8C models finished nowhere.

Ironically, the race was Audi's initial foray into the sport and the spyder cars finished behind another relative newcomer - the aforementioned 3.6L Turbo V8 Toyota GT-One. Audi went on to learn the sport, while Toyota retired, and just 24 months later, Audi had learned enough to dominate the sport like no other marque in history. Now Toyota is returning, though not perhaps the novice it was in 1998-99. Toyota has been working on bleeding-edge hybrid motorsport for a long time. As far back as 2007, Toyota Motorsport won the Tokachi 24 Hour Race in Japan with a Toyota Supra HV-R Hybrid.

Hence Audi decided to build two cars based on proven technology to ensure victory should something go wrong with the two radical Quattro race cars. Though the original cars were no doubt designed to combat the Peugeot turbo diesel challenge (which failed by mere seconds to beat Audi last year), it will now ensure that the hybrid cars from its own team and that of Toyota, will need to prove their advantage over TDI if they are to challenge for the win. Motorsport provides an unrelenting, hypercritical review of new technologies and the 24 hour of Le Mans is the harshest critic of all.

When Peugeot left the sport, Toyota's job got both easier and harder. Peugeot's absence will make it easier to get to the front, but Audi's strategy with two sets of cars with different characteristics and only one serious competitor should make its job easier in managing to have one of its cars in the lead at the 24 hour mark.

Turbodiesel hybrids make a lot of sense - the excellent power spread and low emissions of a turbo diesel puts it ahead of a petrol engine for low-emissions road use (turbo or otherwise), and the broad power and remarkable economy available from a turbo diesel on the racetrack has translated into a winning advantage six from six at Le Mans.

Audi's choice of drivetrain layout is interesting in comparison to its cousin, Porsche which used the system in the last two years.

Porsche was very forthcoming with diagrams of the Williams Hybrid Electric Flywheel system it used in its GT3 car, and given that Porsche and Audi are quite closely related (Volkswagen owns 100% of Audi and 49.9% of Porsche), the Audi set-up could conceivably have looked a lot like the Porsche hybrid V2.0's config, yet it doesn't.

Four driving wheels will logically go around a corner faster than two driving wheels and by using the electrical power from two independent front motors to drive the front wheels, it has given itself the ability to dial in the exact amount of power at each wheel at every moment in time. Electric motors are far easier to control than petrol engines and with the advanced sensors and controllers now available, this exercise might yet give hybrid technology a demonstrable advantage at the racetrack.

"Audi has always consciously selected championships and categories in racing that have a close relationship to production and therefore have technical relevance for the Audi customers," said Ulrich.

"quattro, TFSI and TDI are three excellent examples of how motorsport has stimulated production development. A similar tendency is apparent with the e-tron quattro: we test a completely new technology on the race track before it's introduced to the Audi production line."

The Schedule

Audi Sport Team Joest will run the two R18 e-tron quattro and two R18 ultra prototypes which will debut at Spa-Francorchamps (Belgium) on May 5 in preparation for the Le Mans race in June, then Audi plans to enter one R18 e-tron quattro and one R18 ultra in the FIA World Endurance Championship (WEC) with André Lotterer and Allan McNish nominated as two of the drivers so far. The opening round of the World Championship in Sebring (USA) on March 17 will see Audi field three of last-year's R18 TDI driven by Marcel Fässler/André Lotterer/Benoît Tréluyer, Dindo Capello/Tom Kristensen/Allan McNish and Timo Bernhard/Romain Dumas/Loïc Duval.

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