Valtteri Bottas has insisted that Williams still have improvements to make ahead of qualifying at the Abu Dhabi Grand Prix.
The Finn suffered reliability problems in the morning session, mustering only eight laps of the Yas Marina Circuit.
However, Bottas believes that Williams performed better in the afternoon session after finishing fifth in FP2, and the 25-year-old has suggested that there is more to come from the Oxfordshire-based team.
He told reporters: "In the second session everything worked well, but there is still some work to do tomorrow with regards to the balance of the car. In some corners I lose the front and in others, the rear, so I want to get that sorted early.
"There is time, so we are under no pressure, and we still have some tuning to go which will add performance.
"We knew that by changing some bits it would be OK. We tried something different with it. I think the main thing was how it was connected and a different sidepod, which we have not run at as quick track as this before."
Bottas trails fifth-placed Fernando Alonso in the drivers' standings by one point.
