Renault has turned "huge corner" with F1 2017 engine

Although he French car manufacturer faced some reliability dramas that meant Toro Rosso completed the fewest laps out of all teams at Barcelona, in power terms there has been good progress.

Sources suggest that Renault is on course to deliver the three tenths of a second improvement it has targeted for the Australian Grand Prix – and Toro Rosso is encouraged.

Speaking about the job Renault has done, Toro Rosso technical director James Key said: "The good thing with Renault on the performance side, since we've been working with them, they've definitely turned a huge corner. Our impressions are positive.

"Exactly where it stands in the order is impossible to say at this stage, but there's definitely a marked improvement from what we saw in the past, and last year as well.

"You can see that; it's real. It's not just a value coming out of a dyno. So from a performance point of view we're happy with what we're seeing so far."

Reliability woes

Toro Rosso would not reveal the causes of the Renault reliability problems it suffered this week, but was adamant they were not related to the way it had installed the power unit.

Key said: "I think the reasons for the issues clearly need to come from Renault. We've had some dramas and I don't think it is installation related from what we can tell.

"Obviously, anything that has happened on the power unit side we've had discussions about that, and it doesn't appear to be do with anything specific on our car."

Team boss Franz Tost said: "You know, it's a completely new car and it's a mix from everything. For example, [on Wednesday] with Daniil Kvyat, we had a problem with the clutch bearing, and then with Carlos Renault decided to change the engine because of some isolation issue.

"But I'm convinced that Renault will sort out all these small problems. It's nothing major. I'm quite optimistic that we will be very well prepared for the second test and for the races."