Spa Francorchamps, the notorious circuit both loved and hated (or perhaps feared) by racers the world around, will play host to the first racing laps of the Audi R18 e-tron quattro this weekend. The hybrid, all-wheel drive, diesel prototype racer is the first of its kind.

The debut at Spa is also a first for Audi, which has previously debuted its direct-injection gasoline and diesel race cars at Le Mans in 2001 and 2006.

Though it's brand new, Audi says it has had the idea for a diesel hybrid quattro racer for years now. "We started to think about the hybridization of a Le Mans sports car relatively soon after the first TDI successes," said Audi Motorsport head Dr. Wolfgang Ullrich. "A concrete opportunity for this materialized when it became clear that the regulations would be permitting such an option."

The R18 e-tron quattro pairs a V6 TDI diesel engine driving the rear axle, and a flywheel-storage hybrid system on the front axle that powers the front wheels under acceleration. Unlike conventional all-wheel drive systems, there's no link between the front and rear wheels.

2012 Audi R18 e-tron quattro LMP1 race car

2012 Audi R18 e-tron quattro LMP1 race car

Audi chose the flywheel energy storage system because a battery wouldn't suit the racing environment--too heavy, too unreliable, and too complicated in comparison to the flywheel.

Ullrich also revealed that all of the development work for the R18 e-tron quattro was done on an R8 GT test mule--the whole flywheel hybrid system was mounted and tested on the front end of the R8. After testing, it was adapted to work with the R18 chassis.