Sebastien Ogier has urged his Volkswagen team to keep pushing with the development ahead of the debut of its Polo R in next year's World Rally Championship.
The German squad completed 250 miles during a two-day test in Finland this week.
Ogier said he was pleased with the performance of the car, but he pointed out that there was still plenty for VW to do ahead of next January's Monte Carlo Rally.
"The test went well, we can be happy with the result," said the former Citroen driver. "The Polo already felt very good at high speed and when jumping although we weren't driving the final version yet."
"We've still got a lot of work to do during the time that's left before the debut in Monte Carlo. Next week we'll already be continuing in Portugal."
VW motorsport director Jost Capito added: "The rally tracks in Finland are famous for their fast pace and long jumps.
"Various components that have been developed based on simulations and wind tunnel tests were successfully tried out in these tests."
Volkswagen recently revealed that it would not be running the Polo R WRC on an event this season, following intervention from the series' other manufacturers who felt it was unfair for VW to contest an unhomologated car.
It had previously announced plans to debut the car in either Italy or Spain this year.