The gap to Mercedes is going to be "tough" for Lotus to close by Melbourne, according to technical director Nick Chester.

Lotus has been trying to play catch-up at the second test in Bahrain after skipping the first test, with the team setting the fastest Renault-powered time of the week on Saturday. However, Pastor Maldonado's time was still over five seconds slower than Nico Rosberg's best lap time even though Chester admitted Lotus had been able to run at full power on occasions during the day.

Asked by if Lotus feels it could realistically attain a similar lap time to Rosberg, Chester was confident that there is a lot of improvement to come from the E22.

"We weren't running qualy sims for a start so [Rosberg] was on softer tyres, lower fuel," Chester said. "And we know we haven't done any set-up with the car yet so we know the balance was not where we want it. It's the first time that Pastor has driven with the car at full power so trying to find the braking points is hard. So there is a lot of progression yet to come. Whether we can take all of that 5.2 seconds out I'd be brave to say 'Yes, for sure we can' straight away, but we know a lot of areas where we will make a lot of progress."

However, when then asked by if that gap to Mercedes was unclosable by Melbourne, Chester replied: "It is going to be tough by Melbourne, for sure.

"I think they've effectively had a couple of very good tests now and have got themselves to a good level. We have still got a lot of progression, so I don't imagine they are going to make so much more improvement before Melbourne and we've got a lot to make. But yeah, it is quite a big gap to close."

Although Mercedes appears to have a large advantage, Chester said he was pleased with the way Lotus had started to make progress following three tough opening days of testing.

"We had a much better day today. We'd had quite a slow start to the test with particular problems on the first and second day and then a few more drivetrain problems on the third day. But today we got a decent number of laps done; we're starting to learn more about how to use the energy recovery system and how we start tuning it to get the best out of it for some of the laps so we made decent progress today."