Having a reliable Honda power unit for pre-season testing matters to Toro Rosso “a great deal,” according to technical director James Key.

Honda has often struggled during pre-season testing since returning to Formula 1, with new power unit concepts in 2015 and ’17 proving particularly unreliable and limiting mileage. This season will see a new partnership between Toro Rosso and Honda, while the power unit is an evolution of last year’s new design.

Asked if his biggest desire was to have a reliable power unit during pre-season, Key told RACER: “Yes, I think it makes a huge difference.

“It works both for us and Honda as a team together, it’s important for both of us to have that situation. When we ran the 2015 Ferrari engine in 2016, that was a very well-established engine. It had done an entire season; all of its issues had been ironed out and as a result we got an extremely reliable unit and we were able to do absolutely tons of winter testing. That was extremely useful for the team and for the drivers. So it does make a difference.”

Key’s opinion stems from having suffered with reliability in the past when a Renault customer, meaning Toro Rosso is aware of how damaging it can be to miss out on significant running during pre-season testing.

“We have had different experiences! Last year I think we did half the amount of mileage and in 2014 we did a tiny amount of mileage and that was all power unit-related, so I think it matters a great deal.

“Let’s see where we are – it matters of course very much to Honda too, so hopefully at that point it will be OK. There could be teething problems with certain things but that’s what testing is for. You never know, but that is the target for both sides.”

The Toro Rosso Honda will be unveiled on the morning of the first pre-season test in Barcelona on February 26, with the second four-day test getting underway on March 6.