Audi will be switching from the two-megajoule to the four-megajoule sub-class this year within the LMP1 class in the World Endurance Championship. What does that mean? This year's Le Mans prototype racer gets more hybrid power, delivering more of electric boost for longer periods of time.

The R18 has been around for quite a while now, but the car has significant revisions over last year's version, the most visually noticeable being the huge air ducts below the lights in the front. The front end, sidepods and rear end have all been revised to allow for better airflow and reduce aerodynamic drag. Like many Formula One cars this year, the engine cover packaging is tighter and tapers off more behind the driver, again, for better aerodynamics.

The headlights are smaller this year to allow for that big air duct, so they have to make up for having less front-end real estate to work in. Audi is using their Laserlight system on the R18 in conjunction with their usual LEDs for better night vision.

As for the sidepod changes, the revised design of the sidepods and and radiator system allow for better engine and hybrid system cooling, which was needed with the bump up to the 4MJ system.

That hybrid system is the star of Audi's updates to the R18, as it's something they have been gradually working up to over the past year or so. According to , the system is an evolution of the 2MJ system they've been using, which has one kinetic energy recovery system on the front axle. Audi added a larger flywheel energy storage system this year, which can keep up to 700 kilojoules of energy on demand. In a on the new car, Audi states that the system can output 272 hp.

"The correct approach was to take it step by step to have a well-sorted 2MJ system for last year and a clear road map very early to upgrade this system in an evolutionary way to this year's 4MJ system," LMP1 technical project leader Christopher Reinke told . "It was the more efficient way to upgrade the existing system to 4MJ rather than introducing a second system."

So far, the drivers are also impressed by the extra boost. "You can really feel the benefit of the four-wheel-drive now, especially at somewhere like," Audi driver André Lotterer told . "Out of Turn 17, the rear of the car used to step out over the bumps: now you floor it, the car jumps and off you go."

Audi continues to test its LMP1-class R18 e-tron quattro at Sebring, where the surface is just old…

This new hybrid system is mated to yet another Audi V6 turbodiesel. This year's version is a four-liter engine that outputs 558 hp. Now that the car is under the 4MJ ruleset, Audi has had to optimize the engine and hybrid system to use 2.5 percent less diesel fuel per lap.

Surprisingly, Audi has kept to the minimum weight needed for the series despite upgrading the hybrid system. It weighs a mere 1,918 lbs. This also likely helps keep fuel consumption low.

Why all the changes? The new wild and wonderful era of increased manufacturer involvement in LMP1 is forcing even the dominant squad at Audi to step up their game.

"We expect that the technological progress resulting from the fierce competitive pressure exerted by four automobile manufacturers that are now involved will significantly improve lap times this season – while concurrently reducing fuel consumption," explained Audi Sport Head of Engineering Jörg Zander in aabout the 2015 car.

Even Audi's feelin' the heat. I love this season already.

Curious about the rump of the car? We were, too. Our friends at Autoblog have a whole gallery for the browsing of R18 pictures .