Buemi paces wet Portimao.

Sebastien Buemi posted the quickest time at Portimao as the first F1 test of 2009 kicked off in wet weather conditions at the Portuguese circuit.

The test marked the first time Buemi has hit the track following confirmation of his move into an F1 race seat with Toro Rosso for the coming season, and he proved to be comfortably quickest on the first day of the test.

Running in the only 2008-spec car on track, Buemi had been due to work on validating the 2009 engine specification, checking cooling configurations and general reliability. However, with circuit conditions requiring extreme rain tyres for the entire day, Buemi instead worked on electronics and also practiced his race starts on the wet circuit.

His best time during the day of 1min 41.528secs put him a full five seconds clear of the McLaren test driver Pedro de la Rosa in the new MP4-24. Rather than risk damaging the car, the team elected to send the Spaniard out with a 2008-spec rear wing to increase downforce and he was still able to complete a series of system checks on the car from his 28 laps.

After the car made its first appearance at the circuit during the morning, Nico Hulkenberg was third quickest for Williams in the new FW31 as the car hit the track in its interim testing livery while the other new car launched at the Portuguese circuit, Renault's new R29, was fourth quickest in the hands of Nelson Piquet.

Toyota test driver Kamui Kobayashi was fifth quickest on his first proper run in the TF109, working on the KERS system which is debuting on track in the car for the first time this week

"It is always a very exciting moment to see your new car begin pre-season testing and that is especially true this year after such a significant regulation change," senior general chassis manager Pascal Vasselon said. "Overall I am very pleased with the initial results from the TF109 and I believe we have good reason for optimism.

"Of course, it is very difficult to make comparisons to the other teams in the winter, and that is particularly true when the weather is not very good. In addition to the usual challenges of testing a new car, we worked with the KERS system again today. This is a new technology to Formula 1 so there is a huge amount to learn but our hard work in the factory meant we were quite well prepared for this first test and we have collected a lot of important information."

Testing continues tomorrow.