The engine from the Audi R8, a 3.6 litre turbocharged V8, was used as the initial powerplant in 2001. The six-speed gearbox was also not the typical Ricardo unit from the R8, but instead a custom unit developed by Xtrac. Bentley also chose to run on Dunlop tyres instead of the Michelins used by Audi.
Following its initial year of competition, the Audi-sourced V8 was modified to better suit the EXP Speed 8. This saw the engine expanded to 4.0 litres, producing approximately 600 hp. This would ultimately lead to Bentley redesigning the car for 2003, leading to the change of name to simply Speed 8. The flat front end was replaced with a raised crash box for a nose, while deep valleys ran between the nose and fenders. This required the addition of large horizontal bodywork between the nose and fenders to shroud the suspension arms of the Speed 8. The cockpit would also be tapered to allow for better airflow to the rear wing. Bentley also decided to switch to Michelin tires for their 2003 campaign.
In total two Bentley testbeds, four EXP Speed 8s, and five Speed 8s would be built, although some chassis would never race due to damage or being converted to display cars.
In 2001 Bentley returned to the famous 24 Hours of Le Mans race, after a gap of 73 years, for a planned three-year campaign with the EXP Speed 8 in the closed-cockpit LMGTP class. During its run, the Bentleys were the only cars to run in the LMGTP class. Two cars were entered, with one earning third place behind a pair of Audi R8s. The other car unfortunately retired after a strong run in the rain due to a fire which caused the driver to abandon the car. Bentley returned in 2002, using their new larger engine, now running a lone entry as a testbed for the evolved Speed 8 in 2003. The car managed fourth place, once again behind only R8s.
For 2003, Bentley decided that their new evolved Speed 8 would need competitive testing in order to prepare for an overall win at Le Mans. The pair of new cars were therefore entered in the American Le Mans Series 12 Hours of Sebring. Despite having to start at the back of the field due to a rules infraction in qualifying, the two cars quickly made their way through the field. The Bentleys were able to take third and fourth places, behind the factory and a privateer R8.
Returning to Le Mans and joined by Joest Racing, a Bentley started from pole position. With no works Audi team participating, the two cars were able to lead nearly the entire event, with the #7 entry ahead of the #8, which had some electrical problems during the race. After 377 laps, the #7 Bentley successfully took the chequered flag, followed by the sister car two laps behind. This helped give the Volkswagen Group their fourth straight victory at Le Mans, split between the Audi and Bentley brands.
Following Le Mans the Bentley program ended, and the Speed 8s were never raced again.