Mercedes: Renault behind Red Bull/Lotus surge

Mercedes motorsport boss Toto Wolff believes Renault could be behind Red Bull and Lotus's recent surge in performance.

The Austrian suspects that clever engine mapping, throttle control and exhaust flow could be the reason why the two outfits have made significant steps forward at such a late stage in the season.

Renault is engine supplier to both teams and could have found a clever engine map to give its customers an advantage, or so Wolff thinks.

"I think what you can see is that Red Bull from Singapore onwards looked like having made a big step forward, and then in Korea the Lotus made a big step forward of 0.2-0.4 seconds," he said.

"The question we need to look at is what they do in terms of engine mapping maybe.

"Is there something there? The blowing strategy maybe?

"In terms of development over the last races, we seem to be behind. Is it because there is something we don't understand in terms of mechanical set up?

"Or did first Red Bull and then Lotus do something which is related to engine strategy?"

Mercedes are pushing to finish second in the constructors' but lost ground to Ferrari after only Nico Rosberg scored in Japan and Lotus are beginning to catch up.

Wolff is hopeful they can recoup some lost ground, but doesn't want to compromise 2014 to do so.

"We need to balance the resources right in terms of 2014 versus 2013," he said. "Then we have to be looking at finishing second in the championship.

"That is our target and we can't let that go."