Defending champion Jamie Whincup described his Holden Commodore as a rocket ship today as he continued his dominance of the V8 Supercar motor racing series by completing the double in the Hamilton 400.

The Team Vodafone driver won race two of the meeting to add to his victory on the 3.4km street circuit yesterday, with Toll Holden Racing's Garth Tander the runner-up on both occasions.

Whincup had had issues with his car in race one, but he said it was close to perfect this afternoon.

"We made some changes and adapted to the changing conditions," he said.

"She was a rocket ship and we were able to control from the front."

Whincup has now won the last four races in the New Zealand round of the championship.

After crashing out in practice when Hamilton made its debut in 2008, he was victorious in both contests 12 months ago in a Ford.

His team's change to Holden this year has clearly not affected his superiority in the Waikato.

Whincup has also taken the chequered flag in six of this season's eight races, with only Tander's two successes in Adelaide last month breaking the sequence.

Third today was Fujitsu Racing's Michael Caruso to give Holden a one-two-three.

"We don't have any huge strengths," Whincup said of his team.

"It's just there aren't many weaknesses. The pitstops were fantastic all week . The car was extremely quick. The reliability was there."

Tander, who won all three races in Hamilton two years ago, had qualified in pole ahead of Whincup and he made a clean start to go around turn one in front.

However, his lead lasted just over nine of the 59 laps before Whincup overtook him on an inside line with superior braking and quickly pulled away.

After only a lap, the Victorian's margin had already climbed to almost a second. By the end it was more than 6sec.

Tander stayed in second position, unable to close on Whincup, but also comfortably ahead of the rest of the field.

The West Australian did cause a mild scare when he hit a tyre bundle on the back chicane in lap 30, but he went on to finish 13sec ahead of Caruso.

He said he could probably match Whincup in speed over a single lap.

"But his car has better longevity, and the way Jamie drives the car, he clearly makes the tyre live longer than anyone else at the moment," he said.

"We need to continue to work on that."

A disappointing weekend for home fans largely continued today, although Shane van Gisbergen was able to improve his Ford from 12th on the grid to eighth at the finish after crashing out in the opening lap yesterday.

Three other New Zealanders finished in the top 20 -- Holden drivers Jason Richards in 12th, Steven Richards in 15th and Greg Murphy in 18th.