Feb.13 (GMM/Inautonews.com) Renault has confirmed reports it did not hit full throttle at the recent Jerez test.

Works team Red Bull evidently had a difficult start to the winter season, struggling for pace and laps with the new RB11 car.

Under its skin is a heavily-upgraded Renault ‘power unit’, the result of a sweeping restructuring at the French marque and the hefty exchange of so-called unfreeze performance ‘tokens’.

After Jerez, though, Red Bull’s Dr Helmut Marko played down rumours of technical trouble, insisting the RB11 was running “a mix of old and new parts” and a new engine running at “reduced power”.

Renault’s Remi Taffin confirmed to the French outlet F1i that, at Jerez, the new 2015 power unit was indeed only running at “80 or 90 per cent”.

He said Renault will now “gradually pick up the pace and gain momentum to reach 100 per cent by the season opener”.

“In Jerez, I think we were 1.5 seconds off our potential in terms of raw pace, but we had to preserve the power units in order to get mileage,” Taffin added.

“In Barcelona, we’ll move more to the performance aspect of the engine and explore its limits.”

Renault notably struggled at the start of the new V6 era, with Red Bull team boss Christian Horner last year revealing the deficit to Mercedes was as much as 75 horse power.

“We’ve definitely taken a step forward,” said Taffin, “but it remains difficult to know where we stand compared to our rivals who have also progressed, hopefully not as much as us.”

Adrian Newey, Red Bull’s car designer who is now taking a step back, is not sure the team’s 2015 package will be capable of beating Mercedes this year.

“When you’re at a disadvantage, it’s hard to catch that up,” he said, “as engine lead-times are very long; much longer than chassis lead-times.

“But Renault are working hard and we have to have faith in our partner.”

The team’s optimistic number 1 Daniel Ricciardo – the only non-Mercedes driver to win races in 2014 – is hoping to mount a full title challenge in 2015.

Newey is not sure that will be possible.

“I think it’s going to be extremely difficult,” he said. “The Mercedes engine power advantage last year, about 10 per cent, is not really something that we can close in the space of one season.

“In truth, we are still going to be on the back foot,” added Newey, “but we’ll keep pushing.”