McLaren on Top at Paul Ricard

After McLaren made modifications to their MP4-20 at Barcelona in Spain last week in a bid to help generate more heat in their tyres and therefore extract more speed over a single lap, de la Rosa showed the progress made when he ended Wednesday four tenths of a second faster than Giancarlo Fisichella.

But it was not a completely straightforward day for de la Rosa, whose long runs for tyre and engine work were affected by electrical problems.

All the teams present were working on finalising the choice of tyres for the San Marino Grand Prix, which meant the day was dominated by long runs as the teams tried to evaluate the endurance capability of the latest rubber.

The long runs clearly took their toll with a host of mechanical problems hitting the field. Nick Heidfeld suffered a gearbox problem at 12.17pm, while William team-mate Antonio Pizzonia stopped with suspected transmission problems at 3pm. Toyota's Ricardo Zonta and Renault's Franck Montagny also brought out red flags later in the day.

Zonta's main focus on the day was a new suspension system designed to help the team overcome the previous weakness their chassis have had in dealing with kerbs - which are a key component of the Imola circuit. The Brazilian believed the new suspension may be slightly too stiff to be suitable for Imola, but work will continue on Thursday.

Crucially the team are now getting input into the suspension dynamics from former Michelin engineer Pascal Vasselon.

At BAR, Takuma Sato was getting his first running with the new BAR007 aerodynamic package that showed immense promise at Barcelona in Spain last week.

The team are also awaiting the arrival of new sporting director Gil de Ferran at Paul Ricard on Thursday for his first day on track duty with the outfit. He has been present at high level meetings between Honda and BAR at their Brackley factory today.

The teams will continue using the 3.818km-long 3E track configuration for the remainder of the three-day test, although there is a possibility some outfits may end their running earlier if threatened rain showers arrive on Friday.

Today's times:

Pos  Driver        Team-Engine         Tyres  Time     Laps
 1. de la Rosa     McLaren-Mercedes     (M)  1:03.481  163
 2. Fisichella     Renault              (M)  1:03.843  171
 3. Montagny       Renault              (M)  1:03.901  159
 4. Panis          Toyota               (M)  1:03.916  120
 5. Bernoldi       BAR-Honda            (M)  1:03.958  182
 6. Zonta          Toyota               (M)  1:04.216   99
 7. Sato           BAR-Honda            (M)  1:04.320  137
 8. Wurz           McLaren-Mercedes     (M)  1:04.338  102
 9. Pizzonia       Williams-BMW         (M)  1:04.942  119
10. Heidfeld       Williams-BMW         (M)  1:06.086  109
11. Karthikeyan    Jordan-Toyota        (B)  1:07.413   40

All Timing Unofficial