Adrian Newey doesn't expect Red Bull RB11 F1 title bid in 2015

The design genius, who has stepped back from a full-time role at Red Bull's F1 team, is well aware that his squad's hopes of success depend on how Renault performs.

On the back of a disappointing 2014 campaign, Newey believes it unrealistic to expect the French car manufacturer to have fully closed the gap to F1 pace-setter Mercedes.

"I think we should be realistic about our expectations for this year," said Newey in a video interview published by Red Bull ahead of the first pre-season test at Jerez in Spain.

"Mercedes have a very strong power unit, we estimate [with] somewhere around 60 horsepower [advantage] at the end of last season.

"Renault are working away very hard at eliminating that deficit, but it does take time. Power units have a very long lead-time.

"The pace of development, just because of the technology, is slower than we're able to work at on the chassis side.

"They have a challenge ahead, which I'm confident they will meet, but they need time to achieve that.

"This year will really be about continuing to try to move forward and reduce the deficit that we suffered at times last year.

"If we can manage the odd win, as we did last year, then that would be fantastic.

"But we can't count on it. I think it's really a season that will be very much about trying to extract the most we can and build on it for the future."

NEW RED BULL APPROACH

As well as Renault having revamped its F1 programme to try to make progress, Red Bull has also changed how it deals with the French car manufacturer.

The team's chief designer Rob Marshall thinks that Red Bull has helped fast track improvements.

"The process of working with Renault has changed a little bit," he said.

"We've taken on more responsibility to help them with certain areas of the engine package.

"The demarcation zone between engine and chassis is not as clear as it used to be.

"Getting the most out of one of these modern power units requires a lot of integration between the chassis and engine side, so we're working with Renault much more closely.

"We hope to make significant gains. We know it's a bit on both sides - the engine was clearly struggling against the Mercedes.

"We hope to make a reasonable improvement, and close the gap by a tangible amount.

"If we can do enough on the car and get some benefit on the chassis side, then hopefully we can compete and win some more races."