The additional car Audi has entered for the Le Mans test day in June will be used to gather data to help Michelin develop tires for the next generation of LMP1 prototype.
The fourth Audi R18 e-tron quattro, which is not participating in the 24 Hours two weeks after the test on June 9, will be set up to simulate the aerodynamic and axle loads of an LMP1 car built to the 2014 rulebook.
The Audi will be equipped with measuring equipment to provide data for the development of the 2014 Michelins, which will be two inches narrower and slightly smaller in diameter than the current tires by regulation.
"Our objective is to generate a database for handling the future tires that is as versatile and reliable as possible," Audi Sport boss Wolfgang Ullrich explained. "The impending technological change is fundamental. Therefore, we are providing all the data being gathered to our long-standing partner Michelin as well."
The 2014 rules will allow energy-retrieval on both front and rear axles, rather than one or either at present, and will also mandate a five percent or 100mm overall width reduction of the cars.
The fourth R18 will be driven by test and reserve driver Marco Bonanomi and run by Audi Sport's test team.
This year's test day offers the only opportunity to test a car on the high-speed 8.47-mile Circuit de la Sarthe, of which more than two thirds is made up of public roads, ahead of the start of the 2014 World Endurance Championship. The additional Audi is one of five cars that will take part in the test day that do not have firm entries for the race:
The Signatech Alpine LMP2 team, which has one entry and one spot on the reserve list, will run both its ORECA-Nissan 03s LMP2s at the test. Ex-Formula Renault driver Paul-Loup Chatin, who is Alpine's test and reserve driver, will get his first experience of Le Mans in the additional entry.
America's Level 5 Motorsports squad will again field its second HPD ARX-03b in order to maximize team owner Scott Tucker's driving time over the eight hours of the test.
The ORECA-run Team Endurance Challenge, which is running three of its Chevrolet-engined LMPC one-make prototypes in the 2013 European Le Mans Series, has entered two of those cars for unspecified drivers.
The Gulf Racing Middle East squad, which missed the opening round of the World Endurance Championship at Silverstone last weekend, has withdrawn one of its Lola-Nissan B12/80s from the 24 Hours.
Its second entry been replaced by Luxembourg squad DKR Engineering, which is contesting the ELMS with its Lola-Judd/BMW B11/40.
The solo Gulf Lola will be driven at the next round of the WEC at Spa on May 4 by team boss Fabien Giroix, Frederic Fatien and Keiko Ihara.
Audi runs its third car at Spa ahead of Le Mans as expected, while Aston Martin Racing fields its extra GTE Pro entry. AF Corse is taking an additional GTE Am class Ferrari 458 Italia.