The Grove-based outfit is currently fifth in the constructors' championship standings, but knows it needs to lift it game to ensure it can stay ahead of Toro Rosso, Haas and Renault.

With technical chief Paddy Lowe seeing areas for improvement since joining the outfit at the start of this year, sources have suggested that key areas of the car's philosophy will be evaluated with new parts this week.

Although Lowe has drawn short of calling the major changes – believed to be both aerodynamic and mechanical – a B-spec version of the car, he has confirmed the changes are important for working out what his team needs to do.

"There are some fairly significant bits that we're trying," said Lowe. "We're doing some interesting bits of R&D. Some are relevant for this year, but some are things we need to learn and understand for next year. There's some important work going on, actually.

"It's a set of experiments, that's the best way to put it, which is how we always conduct our testing. Where that leaves us in terms of what we take racing is a downstream consideration."

The Williams work comes after a disappointing weekend in Hungary, where it failed to score any points.

Even before Felipe Massa's illness threw a spanner in the works, it was clear that the team was not be competitive on the tight and twisty Budapest track.

Lowe said he hoped the difficulties would act as a spur for a bigger effort to turn things around.

"I just said to the guys that's a good weekend to motivate us to make a quicker car," said Lowe. "I think that's the best way to sum it up – we've got a lot of work to do, and we need to be better than that. And we can be better that. So that's what we'll go away and do.

"There's a pretty clear pattern, we're not performing as we should at what you would call the max downforce circuits, so those are Monaco, Hungary and Singapore. But I'm never one to give up before we've got there, so we'll see what we can do for Singapore. A lot of it is about fundamental design aspects that we'll have to wait for another year."

Lowe stressed that the team hasn't yet ruled out chasing Force India for fourth place in the world championship, despite a significant gap having opened up.

"We wouldn't give up on that. I think we can be very strong at some other races this year. Hopefully some of the ones coming up. And we'll aim to get better at exploiting the performance with points, which we've also not been great at doing in the first half.

"The first half term report is could do better – could do a lot better – and we'll go back to the second half with that mentality."

Lance Stroll has been drafted in to this week's Hungary test with Massa being forced to step down because of his illness.

The full line up of the test is as below

Team Tuesday Wednesday Mercedes Russell / Bottas* Russell Red Bull Verstappen Gasly Ferrari Leclerc Vettel / Raikkonen Force India Mazepin / Auer Auer / Mazepin Williams Stroll Ghiotto McLaren Vandoorne Norris Toro Rosso Gelael Sainz / Kvyat Haas Ferrucci Ferrucci Renault Latifi Kubica Sauber Malja Matsushita

* - tyre testing for Pirelli