It has been five years since Audi's Frank Biela raced on a street circuit in the American Le Mans Series. Coincidentally, his return to the Series next week in the Acura Sports Car Challenge of St. Petersburg presented by XM Satellite Radio takes place in the same state as his last street race (Miami in 2003). Biela's history of street races in the Series is admirable: two victories, five podiums, two pole positions and two fastest race laps in six starts.

"I'm very happy to be back," Biela said earlier this week from Road Atlanta where Audi Sport North America was testing its two diesel-powered Audi R10 TDIs. "Last year I only had two races: Sebring and Le Mans. I haven't seen the (St. Petersburg) circuit before so I have two new circuits out of three at the beginning of the season. This is a nice challenge. After being around for a very long time, it's nice to experience some new things. St. Petersburg will be one of those new things."

The American Le Mans Series last saw Biela at Sebring in 2007, an overall victory with Emanuele Pirro and Marco Werner that preceded their second straight triumph at the 24 Hours of Le Mans. Biela and Pirro will reunite for this season's remaining 10 Series events. They teamed for seven races in 2006 - with two victories - in the R10 TDI and shared the LMP1 championship in 2005 driving the legendary Audi R8.

It was Biela who drove the first laps in the R10 TDI during its shakedown in November of 2005.

"The car was really good right from the beginning. There were some things we couldn't fix with the R8 because there was a given monocoque and given circumstances," he said. "Some things you can change and some things you cannot. The things we wanted to improve went into the R10. Even now we always are trying to make the car a little bit better. Definitely compared to what I had at the very beginning, the car is very different. I went out at Atlanta on Tuesday and after three or four months not being in the car, again the car had improved by using different settings and dampers. So it does feel better and the package is a lot stronger than three years ago."

The R10 TDI also serves as a forerunner to Audi's diesel offensive in the passenger car market. Audi will launch its Q7 3.0 TDI in January and hopes diesel technology will be accepted in the US as well as it has been in Europe. By the way, Biela is a diesel convert, having given up a petrol-powered car in lieu of TDI.

"I was one of the people who was against it for a very long time at first," he admitted. "I didn't like it; it was smelly, it was dirty, it was slow. But I know now that it is different. When we started to develop TDI technology it was a massive change in power, drivability and comfort. It is really nice to drive. It's hard for people in the US to believe that diesel can be strong, can be fast, can be sporty and be clean. We try to prove that a diesel can be. By doing this project, maybe we can accelerate the minds of people. We'll see when the road cars come here how people react."