Audi flies at Texas Motor Speedway

Third fastest was the number one Panoz LMP Roadster S of David Brabham and Jan Magnussen, while championship leaders Jorg Muller and JJ Lehto were fourth fastest in their BMW, a full second down on Pirro's time.

Pirro explained that he expected times to fall during Friday's practice and qualifying sessions on the brand new 2.3-mile circuit near Dallas-Fort Worth. "The grip level is really low," he said. "For sure, everyone is going to go quicker tomorrow."

The new infield road course inside the NASCAR Winston Cup oval got a tentative thumbs up from the drivers. McNish said: "It's always difficult to build a circuit inside an oval, but this isn't a bad attempt. I'd say it's better than Charlotte [which the ALMS visited in April], although not as exciting. "The infield section should produce some good racing. There are some wide overtaking areas."

The 30-year-old warned that one problem during Saturday evening's race could be the amount of dust thrown onto the circuit. "If a car goes off the track, it's going to bring a lot of sand and gravel back on. That could be a bit of a drama during a race lasting two hours and 45 minutes."