Carlos Sainz says he is excited by the potential of the Toro Rosso STR11 package this year as he continued to savour the power gains from his new Ferrari engine.

Getting his second day in the car this week having debuted the STR11 on Monday, though mechanical gremlins limited him to 55 laps on that occasion, the Spaniard recovered mileage by completing a mammoth 161 laps around the Circuit de Catalunya today.

A better opportunity for him to trial the Ferrari power unit, Sainz says the step up in performance is immediately noticeable despite it being a year-old compared with what Sauber and Haas will use this season.

"It's a step forward for sure, no doubt," he said. "As expected we have a bit more power everywhere, we have more top speed, we have easy handling of the battery and we have the same drivability - maybe a bit better - but that was not the biggest change, the biggest change is the power that is exactly what we needed and for the moment reliability also looks promising."

Indeed, though Toro Rosso will be bringing a updated version of the chassis to the next test, Sainz says he feels the team is already making good progress compared with last year.

"It means we are in the right way, we are progressing, we are doing more mileage every day and this was the target when we came here and we put a car together that was a mix of last year, some parts from this year. So we didn't really look at performance, we don't look at anything other than reliability.

"That was our weakest point last year and at the moment I'm confident that the car is lapping and lapping and lapping and not giving big issues. We are having small issues - very, very small issues that have to be addressed - but apart from that there is progress and confidence that we could have better reliability this year."

Sainz also took time to praise the Toro Rosso team for the mighty job of getting the car ready for the first test following the late decision on what engine it would be using in 2016.

"This is exactly what impresses me from the team and for sure it something to congratulate them for the amazing job they have done over the last two weeks to put a car together. How they could, I don't know! But they did it and it's working well. It's doing laps, it's doing mileage and we're covering all the areas well."