Marcos Ambrose asked to temporarily be replaced as driver in the V8 Supercars Series, Roger Penske said Tuesday.
The former NASCAR driver made the request so he can familiarize himself with the cars following his return this year to the series, Penske said. Ambrose won the V8 Supercars championship in 2003 and 2004.
He spent six years in NASCAR's Sprint Cup Series but returned to Australia at the end of 2014 to drive for DJR Team Penske.
Ambrose's top finish in two races is 12th, and he'll be replaced in his hometown event in Tasmania by Scott Pye.
''Although this is a decision which has been hard to make, it has become clear to me over the first two events of the season that I need more experience in these cars to do what is required of the lead driver and to be competitive for the team and our partners,'' Ambrose said. ''Scott is a great driver, has already worked with the team and has more experience in these cars, which will give the team the best chance to be successful right now. This decision to step aside from the lead driver role at DJR Team Penske is completely my decision.''
Penske said in a statement that Ambrose ''understood that the competition in this series is at a very high level and now realizes that more time is required for this transition.''
Ambrose came to the U.S. in 2006 in pursuit of a NASCAR career, but never found regular success driving stock cars. He won just two races for Richard Petty Motorsports, both on the Watkins Glen road course.
He returned to Australia so his children could attend school in their native country.
Ambrose expected to return to the car this year, including serving as co-driver in the 2015 Endurance Series races for the team.
Pye will drive the No. 17 Wurth Ford Falcon FG X at the next V8 Supercars Championship event, the Tyrepower Tasmania SuperSprint later this month. He joined the team last season and posted nine top-10 finishes with two top-five finishes.