The Red Bull-owned Italian outfit has used engines by Cosworth, Ferrari and Renault since its arrival in grand prix racing, before joining Honda on a three-year deal starting from 2018.

Ahead of the team's first race with the Japanese manufacturer, Tost has explained why Toro Rosso's new partnership has so far been unlike the relationships with its previous suppliers.

“It is a big difference, believe me,” Tost told Motorsport.com. “This starts already with a design of the car. In the past, we just got a power unit and suppliers said: 'Look, this is the power unit, with the pipes, with all the aggregates, just put it into your car.'

“And now our designers are sitting together with the Honda engineers, they think 'OK, how can we create the oil tank, for example, in front of the engine, how to put it in a best possible way into the chassis'.

“Or the exhaust system. This is a big impact to the aerodynamics on the side of the car. Also, when you get the hot air from radiators to the back, how, where do you get it out?

“In former times, we just had to find the way from our side, and now we are discussing it together with Honda.”

There was acrimony between Toro Rosso and its previous partner Renault towards the end of their final season together, as the team and the supplier found themselves at odds over the causes of poor late-campaign engine reliability.

Tost reckoned the new Honda partnership was “the first time” that his team had this much input on the engine side, and said Toro Rosso engineers relished the freedoms they had in setting up the power unit.

“You should have seen the smiling faces of the engineers when they came back from dyno run with the gearbox and the power unit,” Tost said. “They said: 'Hey, we could change the mappings during the running'.

“You know before we just got it, we got the mappings and everything was in a black box and we couldn’t do anything. Even if we said 'well, maybe this is better” or 'this is better', they said 'take it and that's it'.

“And now we have an impact. And we can say 'look, let's try this and this way, maybe we can get a performance advantage'.

“And this helped a lot both sides, and therefore for Toro Rosso it was absolutely the best to decide [on] this cooperation with Honda.”

While Honda has had a rough time in F1 since its 2015 return, Toro Rosso's new Honda-powered STR13 car has enjoyed a smooth run in pre-season testing.

But Tost says it's the car the team will prepare for 2019 that he has particularly high hopes for.

“I am expecting a lot from next year’s car,” he said. “Since nearly one month we are working on next year’s car, and we get more and more better ideas how to place the different parts of the power unit in the best possible way for the chassis.

“From the placement side, from the thermic side, from the aerodynamic side, from the weight distribution. These are important factors for the performance of the car.”

Interview by Oleg Karpov and Roberto Chinchero