On the eve of the 2015 V8 Supercars tour, Jamie Whincup’s four straight championships count for nothing as he plots another title assault.

Australia’s touring car championship begins again this weekend with the Clipsal 500.

A raft of changes to drivers, teams and championship rules should invigorate the tour.

Whincup, who broke new ground with his sixth title last year, knows the score.

“We all start at zero points again,” he said.

The Red Bull Racing driver’s return to the number one car is a constant as the tour begins its 2015 season in South Australia.

The biggest off-season move is the injection of former Supercars champion Marcos Ambrose into the new Ford Falcon FG X with DJR Team Penske.

Dick Johnson’s partnership with American Roger Penske promises to shake up the sport, even if there are low early expectations for Ambrose, returning from a long stint driving in the NASCAR competition in the US.

Fellow Ford drivers Mark Winterbottom and Chaz Mostert will no longer drive for Ford Performance Racing after it was rebadged Prodrive Racing.

Lee Holdsworth makes the switch from a Mercedes to a Walkinshaw Holden, with Ash Walsh entering the field in his place.

There’s movement too in the Volvos, with David Wall joining rising star Scott McLaughlin after the departure of Swede Robert Dahlgren.

Despite the changes, Whincup justifiably starts as favourite to win an incredible seventh V8 Supercars crown.

While he endured a tough weekend at the Eastern Creek test event, Whincup said he was just “running through the motions”.

“We’ve prepared as well as we can but we’re not exactly sure where we’re at compared to our opposition,” he said.

“On the test day we ran on old tires in hot conditions.

“The only thing we could got out of it was me doing laps … there was no performance gain.

“Our first test will be in Friday qualifying.”

Whincup has more wins than anyone else in the Clipsal 500 but said he still got nervous at the start of the season.

“It’s a lot of expectation, mainly what we put on ourselves to perform well,” he said.

“It’s a big deal, every race meet’s a big deal and we want to be the best so of course we get a bit nervous.”

While each race meet from 2014 has been retained, the championship has been cut from 38 to 36 races.

Organisers have also cut the tyre allocation, hoping to tighten the 25-driver field further.