Renault says there is more to come from its Formula One power unit after it confirmed it did not hit full throttle in the recent Jerez test.
Red Bull had a somewhat difficult start to the winter season, struggling for pace and laps with the new RB11 car during the four days of running at the Spanish track.
Under the car's 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 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 French outlet F1i that, at Jerez, the new 2015 power unit was only running at "80 or 90 per cent".
Gaining speed into Australia
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 75bhp.
"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."
Able to beat Mercedes?
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 number one 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."