BARCELONA, Spain -- Toro Rosso boss Franz Tost is sure early issues with its new Renault engines are "nothing major", despite losing an entire day of the first winter test due to reliability problems.
Toro Rosso ran a year-old Ferrari engine in 2016 and saw its performances tail off through the year as a result, securing a partnership for up-to-date Renault's -- the same as parent company Red Bull -- for the new campaign. Despite the new deal and a lot of excitement around the striking STR12, the team accumulated just 183 laps over the first week of testing -- the lowest number of any team.
Thursday was the worst day for mileage, as the team completed a single installation lap before detecting an Renault issue which required a power unit change. Tost has downplayed those issues and says he expects reliability will not be a factor when testing resumes on Tuesday (March 7).
When asked about if he was hoping for a new spec of engine from Renault before Australia's season opener, he replied: "No I'm convinced that Renault is around it, all these small problems is nothing major and I'm quite optimistic that we will be very well prepared for the second test and for the races.
"Fortunately the first two days we could do a number of laps, so we got many datas on the aerodynamic side as well as the mechanical side but we are still missing some information regarding the compounds, regarding the soft tyres."
Toro Rosso's technical chief, James Key, does not believe the issues are a consequence of installing a different engine in the 2017 car.
"I think the reasons for the issues need to come from Renault, we've had some dramas. I don't think it's installation-related, from what we can tell. Anything that's happened on the power unit side we've had discussions on that but they don't appear to be to do with anything specific on our car."
Toro Rosso worked with Renault in 2014 and 2015 at a time when the French manufacturer struggled with both performance and reliability. Key is delighted with the step forward Renault has made in the time since.
"I think the good thing with Renault is on the performance side, since we've been with them, they've 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 vast improvement from what we saw in the past.
"You can see that, that's real, it's not just a value coming out of a dyno, I think it's real. So from a performance point of view we're happy with what we're seeing so far."