Formula One champion Sebastian Vettel dismissed the prospect of running away with a third straight driver's title, predicting a more competitive season because of rule changes that have cost Red Bull a precious advantage.

Vettel dominated the 2011 championship, winning the title by 122 points and finishing on the podium in all but two races. However, without the aerodynamic advantages from its pioneering exhaust-blown diffusers, which are now banned, it promises to be a very different year for Red Bull, which rolled out its 2012 car at its factory in north London on Monday.

"Looking at the cars, there's not much room left for the designers to play with, to find something extra," Vettel said. "The last two years we have had two big things taken away, the double diffusers, and for this year the system around the blown exhaust. We are missing that and so it's difficult to really create a difference. We'll see."

Replacing the RB7 car that won 12 of 19 grand prix races last season, the RB8 designed by technical director Adrian Newey has a different exhaust to accommodate the rule changes and also features a new nose to fit revised height regulations. Australian driver Mark Webber, who finished third in the drivers' standings in 2011, will be the first to test the new car at a track in Jerez, Spain.

"The team's goals are quite simple - it's to try and defend both titles in the manner in which we achieved them," said Red Bull principal Christian Horner, whose team is looking to capture the constructors' title for the third straight year. "Of course, when you've achieved what we have, particularly in 2011, we've set a very high standard for ourselves. But we're always looking to improve, we're always looking, in all areas, to try and do better."

The excitement factor was missing last year as Vettel clinched back-to-back titles with four races to spare, winning 11 races and setting a record for pole positions in a season - 15.

"I think it will be very, very tight this year. Anything else would be a surprise," Vettel said. "For us, it all starts from zero again; zero points, where everyone has the same chance and we are all building our new cars."