Jean Eric Vergne says he is pleasantly surprised by the pace of the STR8 ahead of this weekend's British Grand Prix.
Vergne was seventh fastest in second practice, one place behind team-mate Daniel Ricciardo.
"This afternoon, as soon as I left the garage, I could tell the car felt very good. It was easy to push and my lap times were good," said Vergne.
"That doesn’t mean we’re going to relax, far from it and we will be working hard tonight to look at all the data to see how we can improve. I feel we have a chance here to do well over the rest of the weekend. Coming to this track which is so different to the last two ones we have raced on, I would say today’s performance has been a pleasant surprise".
Ricciardo was quickest in a rain affected first practice session, Toro Rosso's first session topping time since 2010.
The Australian conceded that long run pace requires improvement but that Toro Rosso can be pleased with the start to their weekend.
"I decided to do quite a few laps in the rain this morning, as I felt the track was safe enough and you can always learn something in those tricky conditions and I think it pleased the fans as well!"
"This afternoon, we were pretty good in the dry, getting a good run on the Hard compound and improved further on the Medium. However, I had hoped our long run would be better, so we definitely have more work to do overnight, but generally a positive day