Renault rookie Heikki Kovalainen raised his spirits after a disappointing race debut in Australia with the fastest time in testing at Malaysia's Sepang circuit on Friday.

The Finn, who has replaced double world champion Fernando Alonso at the Formula One team, lapped in an unofficial time of 1:35.757 after a qualifying simulation.

Friday was the final day of testing before next week's Malaysian Grand Prix, the second round of the season, with heavy rain in the afternoon.

"We worked hard throughout the week and we seem to be moving in the right direction," Renault's chief test engineer Christian Silk said in a statement.

"We made a number of changes overnight and they seemed to work well out on track today. There is still a lot of progress to be made but we are moving in the right direction," he added.

"Heikki seems comfortable at this track, he learned it quickly and is in good shape going into next week's grand prix. That was another important objective for this session, that we have achieved successfully."

Kovalainen finished 10th in Melbourne after a performance that his own team boss, Flavio Briatore, later described as 'rubbish'.

"Because his performance was so bad, it was not him," the Italian declared. "Maybe it was his brother. We will try to get the real Heikki for the next race."

Ferrari's Felipe Massa was second quickest on Friday with Briton Anthony Davidson, still recovering from a back injury after a collision in the Melbourne race, third on the timesheets in a Super Aguri.