Williams is convinced this year's car is a clear step forward compared to last year's challenger, with which the team struggled most of the season.
The British team endured its worst ever Formula 1 season last year, scoring just five points on its way to ninth place in the standings. Williams is hoping to revive its fortunes with the new FW34, with engineering chief Mark Gillan adamant that the car proved to be stronger in the first test at Jerez.
"It is a definite step forward," said Gillan. "It is definitely a very different car and there are a lot of things that we need to start investigating and unlock, because last year we could not go down those particular routes – we were prevented by the way the car behaved or the way it used its tires."
He added: "It is clear that the car is very different to last year. And there are certain areas where we need to improve. Setup tends to take a while to iterate, too, and certainly that is what we will be looking at in the next couple of tests.
"Sometimes, the car can not look good in certain areas but there is not much lap time by improving those specific things, but in areas such as the low speed, where you get most lap time to gain, those are areas to investigate to always try to improve."
Gillan also praised the Renault engine powering the car this year: "It's very good, very positive. It is a very impressive engine," he said.
He was also happy with the performance of Bruno Senna during the first test with the team. The Brazilian was the busiest man over the week, with 250 laps covered.
"I would say from our side, we were very pleased with his general consistency," Gillan said. "Obviously, he is learning the car. His feedback is excellent, very precise. It is good to get a new perspective on things and very, very useful, so the debrief went on twice as long as it normally does and it was very, very good at all."