This year's 24 hours of Le Mans, which takes place this weekend, will see some new faces among the familiar front runners, but one of the primary players from recent years will be missing.
Audi, which won the big endurance race last year, as it has done for six of the past seven years, will be back with no fewer than four factory entries in the top LMP1 racing category – two ' conventional' diesel-powered R18 Audi Ultra racers and two R18 e-tron quattro diesel hybrids.
Audi has already won the 12 hour endurance race at Sebring, this year, as well as finishing 1-2-3-4 at the 6 hours of Spa, in Belgium.
Peugeot, which won Le Mans in 2009 and has provided tough competition for Audi for several years – often outpacing if not outrunning the German marque – will be absent from this year's starting field.
The French automaker is facing some difficult economic challenges in its troubled European home market and cut its racing program earlier this year as part of an austerity program to address those problems.
Taking up the challenge to provide what will probably be Audi's major opposition is Toyota, which is entering two LMP1 cars, both with gasoline-hybrid powertrains.
The wild card among the big factory entries is Nissan, which is backing and providing engines for the controversial DeltaWing experimental entry.
The R18 Audi Ultra LMP1 race car is an evolutionary development of the R18 that won at Le Mans last year. It is powered by a 3.7-litre V-6 TDI engine, driving the rear wheels.
The engine features a single variable-geometry turbocharger mounted topside in the engine's vee.
A sleek enclosed-cockpit car, the R18 Ultra is brimming with technology, including a novel "digital mirror" system to improve the driver's visibility of what's behind. It also features a host of lightweight materials and applications, including a composite transmission case.
The two Ultras will be driven by Romain Dumas/ Loïc Duval/ Marc Gené (car #3) and Marco Bonanomi /Oliver Jarvis (car#4).
In addition to the two "conventional" diesel-powered rear-wheel-drive Ultras – powered by 3.7-litre V-6 TDI engines with single variable-geometry turbochargers – Audi will field two e-tron quattro diesel hybrids. As their name implies, they combine a diesel engine with a hybrid-electric all-wheel-drive system.
Similar in concept to the Porsche 911 GT3 R Hybrid, the R18 e-Tron stores kinetic energy from braking in a flywheel system that converts it to electricity that is then fed back through electric motors to the front wheels to provide extra driving force.
The rear wheels are driven only by the diesel engine.
The two quattro hybrids will be driven by last year's winners, Marcel Fässler/André Lotterer/Benoît Tréluyer (car #1) and Audi's veteran team of Dindo Capello/Tom Kristensen/Allan McNish (car #2).
McNish was fastest of all cars in the Le Mans test day, two weeks before the race.
Toyota's two gasoline-electric TS030 sports racers, which will compete in the same the LMP1 prototype class as the Audi's use both gasoline and electric power to drive the rear wheels.
A 3.4-liter V-8 engine is supplemented by a gearbox-mounted Denso electric motor.
Le Mans will be the first competitive outing for Toyota TS030 LMP1 race car, although it has undergone extensive testing and development at Paul Ricard, Magny Cours, Motorland Aragon and, during test day, at Le Mans itself.
A testing crash that destroyed one of the prototype racers forced cancellation of Toyota's plans to enter the 6-hour race at Spa.
The TS030's chassis was designed and developed by nearby Toyota Motorsport GmbH in Germany. It is powered by a 3.4-litre V-8 engine, supplemented by a gearbox mounted Denso hybrid electric motor.
Energy from regenerative-braking is stored in super-capacitors and released , potentially several times a lap, to boost the gasoline engine's performance.
Toyota's driver teams include Alex Wurtz/Nicolas /Kazuki Nakajima (car #7) and Stephane Sarrazin/ Anthony Davidsion / Sebastien Buemi (car # 8).
The team demonstrated competitive speed at the test day, with one car fourth fastest behind three Audis, but Toyota is treating this as a learning year.
Nevertheless, according to Team President Yoshiaki Kinoshita, "We set ourselves high standards, so we want to prove the performance potential of the (hybrid system]) ... but the ultimate medium target for this project is to win Le Mans, so we aim to take a big step in this direction in 2012."
Nissan's DeltaWing racer uses conventional gasoline-engine technology – a Nissan 1.6-litre DIG-Turbo gasoline engine – but that's about the only thing about it that is conventional.
Originally conceived as a candidate for the all-new 2012 IndyCar design, it not only incorporates a delta-wing body shape, it tucks two tiny front tires closely together within the front body-work.
After IndyCar chose a more conventional Dallara design to become its spec chassis, the DeltaWing's backers turned their attention to endurance racing and received permission from the ACO, the Le Mans organizing body, to race there as an experimental entry.
It will wear the number ‘0' and run from "Garage 56", reserved exclusively for experimental racers.
Everything about the DeltaWing is designed with efficiency in mind. Its unique shape has half the aerodynamic drag of a conventional racer, while all components are smaller and weigh much less than traditional Le Mans machines. Its goal is to complete the 24-hour race using half the fuel and half the tire material of a conventional LMP racer.
Just how it will perform remains to be seen, as it defies much of racing's conventional wisdom.
Paul Willcox, senior vice-president of Nissan in Europe, describes the experimental concept as harking back to the original motor racing trailblazers of the 1920s, who first set out just to go as fast as possible for as long as possible.
"While we can't win with the Nissan DeltaWing, because it sits outside the regulations, we can't lose either," he said.
But, as past races have proven, anything can happen at Le Mans.