REIGNING V8 Supercars champion Jamie Whincup will drive a new Holden race car in Darwin this weekend as he strives to leapfrog Ford driver James Courtney at the top of the rankings.Whincup won the opening race in Darwin last year driving a Ford and switched manufacturers at the end of the season after winning his second consecutive drivers’ championship.The TeamVodafone driver said his new Triple Eight Commodore could prove decisive in ”clawing back the momentum” snatched by Courtney and his Jim Beam Racing team during rounds in New Zealand and at Queensland Raceway.On softer compound sprint tyres Courtney made it a clean sweep in Hamilton and Queensland and heading into this weekend at Hidden Valley leads the championship by 114 points.”Everyone thinks we’re in a bit of a slump, but we’re second in the championship and we’re going well, we’ve had a good start to the year,” Whincup said.”I’m really pleased there’s this massive expectation on us and [the belief] when we don’t win a race there must be something wrong – that’s a good thing and I want to be in that position.”After a winning start to this year in Abu Dhabi and Bahrain, Whincup said there had been ”a few little challenges with moving manufacturers”, such as a black flag and zero points at the Clipsal 500 in Adelaide and an engine failure in Queensland.”We’re not leading the championship, but we’ve had a very fast, competitive car and won 50 per cent of the races,” he said.”There’s 29 cars out there and one car has won 50 per cent of them, so we’ve had a fantastic start to the year and want to continue that here in Darwin.”Toll HRT drivers Garth Tander (fifth in the series) and Will Davison (15th) will also debut new cars in Darwin.Whincup’s TeamVodafone partner, Craig Lowndes, a former winner of the round, sits third in the championship. Lowndes is expected to unveil his new Commodore at Phillip Island in September.Qualifying for this weekend’s two races begins tomorrow. All teams will have one set of sprint tyres, which can be used only in Sunday’s 200km race.Round seven of the championship in Darwin will also be the first time all the V8 Supercars teams run the control camshaft, which has been designed to decrease costs and increase engine life.