(Reuters) - Struggling Red Bull had cause for optimism following day two of Formula One's final pre-season test in Bahrain on Friday, with Daniel Ricciardo recording the team's fastest lap in six days of testing in the Middle East.
Using modified 'emergency' vents on either side of the troublesome RB10 to avoid overheating, the car managed its longest stint on the track in pre-season following multiple problems with its Renault-powered engine in the previous tests in Jerez and Bahrain.
Australian Ricciardo managed 66 laps in total, including a 20-lap burst late on, and turned in the third fastest time of the day with one minute 35.743 seconds.
"This morning it was important to have the race crew here to do the pit stops, as they haven't had the chance to get to grips with the car yet, so we didn't do that many laps in the morning," Ricciardo told the Red Bull website (www.infiniti-redbullracing.com).
"However, in the afternoon we did some good stuff. We had a go on the soft tire, which was nice, to see how the car responds with a bit more grip. We also did one long run at the end, which was very important, just to see how the car is behaving with the tires," he added.
"A big improvement everywhere over yesterday and a much more optimistic outlook now I think. We still have a lot to learn and understand, but we're making progress and the past two days have been a big step in the right direction."
Ricciardo will be replaced by four-times world champion Sebastian Vettel for the final two days of testing.
Mexican Sergio Perez, in a Mercedes-powered Force India, topped the times for the second consecutive day with one minute 35.570 seconds, completing 108 laps in the process.
It was the Mexican's final outing ahead of the season-opening Australian Grand Prix on March 16, with Nico Hulkenberg taking the seat for the final two days.
"It has been another busy day with lots of miles completed and a great deal learned," technical director Andrew Green said.
"The program this morning involved assessing a different set-up direction compared to yesterday, which will help in our decision-making going into Melbourne. After lunch we switched to extended runs using several of the tires compounds available to us. It's been important for Sergio to have two solid days in the car to get him more comfortable with the VJM07 and race-ready for Melbourne."
Ferrari's Fernando Alonso was second behind Perez in a satisfactory day for the team after Kimi Raikkonen was cut short on Thursday after 54 laps due to an electrical problem.
Alonso managed 122 laps.
Lotus, another Renault-powered team that has struggled in pre-season, were forced into the garage two hours early after Pastor Maldonado suffered an engine fire after 31 laps, while Lewis Hamilton, in a works Mercedes, notched 89 laps before being hit by gearbox failure, the second day in a row the team were forced to end practice early.
"Like every team, we're encountering problems every day and we've still got some work to do in terms of both reliability and speed," the Briton told the BBC.
"There are no specific problem areas, just lots of different things we need to improve.
"It's important to get as much mileage under our belts as we can and just as important to discover any problems before we get to Melbourne.
"It might be frustrating at times but finding them at this stage is actually a positive."
(Reporting by Josh Reich, editing by Ed Osmond)