Daniel Ricciardo is confident Red Bull are beginning to resolve their issues after 91 laps in Bahrain on Tuesday.
The Aussie, who finished fourth in Sunday's Bahrain Grand Prix, returned to the cockpit of his RB10 on Day One of a two-day test at the Sakhir circuit.
Tuesday's running did not get off to a smooth with an issue in the morning, however, once underway Ricciardo covered 91 laps.
"We missed a little bit of time but we made up for it in the afternoon," he said. "I think I was in the car for a good few hours.
"We didn't get in any performance runs but we did some good long runs in the afternoon with three set-up changes and we got some good feedback from that.
"I think during last weekend we struggled a bit in P1 and P3, the daytime sessions in the heat, but the car felt a lot better today in those conditions, particularly on those long runs."
His best time for the day was a 1:38.326, which put him seventh on the timesheets, 2.4s adrift of Nico Rosberg's P1 time.
Ricciardo, though, is adamant Red Bull Racing and Renault are moving forward.
"We're still a little behind but we're chipping away and I'm sure over the course of this test and in China we'll get a little bit closer," he said.
"For the moment, though, we'll take every little bit we can get. We're learning and we're making progress."
Gallery: Sensor Centre In Sakhir