Renault taking upgraded engine to U.S. Grand Prix

AUSTIN, Texas (Reuters) - Renault will be taking an upgraded, more powerful engine to Austin for this weekend's U.S. Formula One Grand Prix but Red Bull and Toro Rosso will have to accept grid penalties if they want to use it.

"We will have our new specification of power unit available to use in Austin," said Renault's director of operations Remi Taffin in a preview for Sunday's race.

"The principal changes involve the internals of the ICE (internal combustion engine) to give improved power and efficiency.

"We know that introducing the new PU (power unit) will incur a grid penalty (for exceeding the season's allocation) so the decision to use will be made in full consultation with the teams."

With four races remaining, and Mercedes already crowned champions, both Renault-powered teams still have points and championship position to fight for.

Red Bull are fourth and 71 points behind third-placed Williams and 57 ahead of Force India.

Toro Rosso are seventh and only 21 points behind Lotus, who will become the Renault works team next year if a takeover goes through.

Sauber, celebrating their 400th race this weekend, are 11 points behind Toro Rosso.

(Reporting by Alan Baldwin, editing by Peter Rutherford)