Renault engine technical director Remi Taffin says it is hard to compare with Mercedes because the team has been hiding performance.
Ferrari set the fastest time on five of the eight days of pre-season testing in Barcelona, with Mercedes only doing so once courtesy of a soft-tyre lap from Nico Rosberg. While Renault enjoyed a solid pre-season following its takeover of the Lotus team, Taffin says he is unsure how far away from the strongest power unit it will be this year.
"To be fair it's difficult to compare to Mercedes," Taffin said. "They are hiding their game and going to raise it when we get to Q3… in Silverstone!
"I guess we should be closer to them – but the gap will still be there. Depending on how we assess this season and the steps we can fit in, I think the aim is still, starting 2017, to be fighting with them if we are to produce overall a good car."
From Renault's own point of view, Taffin says the power unit development is set for 2016, with the French manufacturer knowing it can make sweeping changes next season when the restrictions from the token system are lifted.
"The programme is settled, we know when we wish to introduce new specification. Then, we are looking into 2017 as well. There are plenty of things that we are carrying from last year that we would like to change, we will try to change everything in one go."
ANALYSIS: The two F1 pre-season tests in numbers
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