Valtteri Bottas is confident that Williams' latest updates are a step forward having run them at the Hungaroring.
The Finnish racer, who is seeking his fourth successive podium this Sunday in Hungary, put an updated FW36 through its paces on Friday.
Bottas finished the day eighth quickest, 1.517s down on pace-setter Lewis Hamilton, while Felipe Massa was a further 0.4s off the pace.
"We made steps forward so that's really nice to see," Bottas told Crash.net. "We went through all the updates and were trying all the bit.
"I'm really happy that everything we put on the car - that was planned - made the car better. So that was good to see, but obviously I think it's going to be really tight this weekend."
The Finn, though, conceded that even with the updates, the Hungaroring was never going to be a favourite for the Williams team given the high-downforce nature of the track.
"I think it was really expected that could be the case," he said.
"It's pretty difficult to predict where we will be tomorrow because from Friday practice to qualifying a lot of things can change.
"I know we can still improve everything for tomorrow. I can probably get a better lap in and we as a team can get the set-up better, so it's going to be close.
"All the bits that we put on the car which were new made the car better, so that was really good to see. I think there is still a lot of room - certainly in lap time - to go down tomorrow. From Friday to Saturday we can make some good steps."