Audi is poised to run with only one hybrid system in this year’s FIA World Endurance Championship after calling off plans to utilize an exhaust-based energy recovery system for its new LMP1 challenger.

Head of Audi Motorsport, Dr. Wolfgang Ullrich, told the Austin American-Statesman Tuesday that its ERS-H system, developed to capture and convert thermal energy from the exhaust into electric energy, will not be used in this year’s championship.

The German manufacturer is testing at Circuit of The Americas this week, following a six-day test alongside Porsche’s new LMP1 car at Sebring International Raceway earlier this month.

“We did quite some work on it, but… it does not bring what we expected on the real racetrack,” Ullrich told The American-Statesman. “The risk to use it without the benefit we wanted to have and the question mark of reliability, we didn’t want to go that route.”

Instead, Audi will rely on its kinetic energy recovery system (ERS-K) as the sole hybrid powertrain for the new R18 e-tron quattro. Up to two hybrid systems are allowed on LMP1 cars this year, with rivals Toyota and Porsche set to use dual systems.

Audi’s flywheel-based unit, an evolution of last year’s model, will again be used on the front wheels, but will be able to transmit significantly more power, thanks to the new-for-2014 rules.

Up to 8 MJ of energy will be permitted, although Audi has yet to officially reveal which level of ERS they will utilize. The new LMP1 rules permit 2MJ, 4MJ, 6MJ or 8MJ (per lap of Le Mans), each with varying levels of fuel flow allocation.

While Audi will unveil its diesel-powered prototype at Le Mans on March 25, Toyota is set take the wraps off the TS040 Hybrid two days later at Paul Ricard, site of the FIA WEC “The Prologue” official test, which will also see Porsche’s new 919 Hybrid in action.