Panasonic Toyota Racing's Ricardo Zonta set the fastest time in the opening day of free practice for Sunday's Malaysian Grand Prix, round 2 of the 2005 Formula 1 World Championship.

The Malaysian race, held in furnace-like conditions at Sepang, is one of the most testing of the year for both drivers and teams. Already, the drivers have had to cope with track temperatures in excess of 55 degrees C, with strength-sapping levels of humidity. In an average race, a driver can lose up to a litre of body fluid through sweating, but in Malaysia it can be four times as much. And, bear in mind that just a three 3% loss in body fluid can reduce muscle strength by 10%. When physical performance becomes tougher, concentration levels fall too.

The heat exerts huge demands on engines, tyres and all car components too. Zonta, who will not of course be in action on Sunday, was nevertheless delighted to have got the weekend off to such a strong start for the team: "Despite the heat I like driving this circuit a lot," the Brazilian said. "I set the quickest time in the morning session and I'm confident I would have repeated that in the afternoon had it not been for a yellow flag in the final sector when one of the Red Bulls stopped. The car and the tyres felt good."

Zonta's 1m34.092s best lap was fully a second faster than West McLaren Mercedes test driver Pedro de la Rosa (1m35.144s), with Sauber Petronas' Felipe Massa (1m35.608s) third fastest. Juan Pablo Montoya was fourth quickest (1m35.620s) ahead of Red Bull test driver Vitantonio Liuzzi's 1m35.691s morning time, Kimi Raikkonen (1m35.719s) and Ralf Schumacher (1m35.838s) with the second of the TF105s. Jarno Trulli set a 1m36.841s best, 15th fastest, after limiting his laps.

"The car felt good and Ricardo, with more sets of tyres, has had the opportunity to show our pace," Schumacher said, "I just hope that there is no rain to conspire against us in qualifying as happened in Australia!"

Trulli added: "In the morning session I only completed a few laps so that I could conserve my engine. I did quite a lot of mileage in Melbourne and, remembering that engines have to last two races this year, we thought it was the sensible approach. In the second session I had some electronic problems but looking at times set by Ralf and Ricardo puts us in a good frame of mind for the rest of the weekend."

Techical Director Chassis, Mike Gascoyne, was even more optimistic about the team's chances in the Far East: "From what we saw from Ricardo it's a pretty clear tyre choice for us. The car balance is pretty good and all the drivers are reasonably happy. Jarno had an electrical problem with the engine at the end but we're looking pretty competitive. I think we can be pleased with where we are."

In the season-opening race in Australia, Trulli ran second but suffered from a tyre problem. Gascoyne, however, is more confident about the position in Malaysia: "The balance was obviously pretty good for the first 16 laps in Melbourne but I think our competitiveness was masked by Jarno's tyre problem but here I think we can see where we really are. In Melbourne the track was too cool and we didn't have the temperatures, but here it's hot, the tyres are working properly and we seem to be in good shape."