Jul.21 (GMM/Inautonews.com) Toro Rosso chief Franz Tost is hoping Renault can now add much-needed performance to its 2015 ‘power unit’.

As the season reaches its mid-point, experts increasingly agree that the James Key-designed STR10, despite the team’s modest budget, is one of the very best chassis on the grid this year.

However, the Red Bull junior team is currently just eighth in the constructors’ championship, ahead only of the struggling McLaren-Honda and Manor.

“There are still ten races on the calendar,” said Tost, referring to Toro Rosso’s stated goal of finishing fifth in the end, presumably behind Mercedes, Ferrari, Williams and Red Bull.

“The STR10 is a very good chassis,” he told Speed Week, “both our drivers are extremely talented and doing an excellent job, and the team’s working methods are slowly coming up to formula one standard.

“Lack of reliability is the cause of our currently-weak position,” Tost added. “When eight times out of nine races you don’t see the chequered flag, you cannot be in the top five of the world championship.

“This is the main reason, as well as accidents and errors of the team. But we need to solve this (reliability) vulnerability together with our partner as soon as possible.”

Toro Rosso’s ‘partner’ is Renault, the under-fire French supplier that is said to be close to changing tack and buying back Lotus to re-form a works team.

Tost acknowledges, however, that Renault has still been working hard on solving its problems in 2015.

“They have worked a lot on the reliability. I hope that is now under control, as the next thing that must be improved is the performance,” the Austrian said.