HOCKENHEIM - Formula One champion Sebastian Vettel's Red Bull team have been referred to Formula One stewards for a possible breach of the technical regulations ahead of his home German Grand Prix.
The governing International Automobile Federation (FIA) raised concerns on Sunday, only hours before the 10th race of the season, about the engine torque mapping on the cars of Vettel and his Australian team mate Mark Webber.
Vettel is due to start on the front row.
"It became apparent that the maximum torque output of both engines is significantly less in the mid rpm range than previously seen at other events," said FIA technical delegate Jo Bauer in a statement.
"In my opinion this is therefore in breach....of Formula One technical regulations as the engines are able to deliver more torque at a given engine speed in the mid rpm range.
"Furthermore this new torque map will artificially alter the aerodynamic characteristics of both cars which is also in contravention of (technical directive) 036-11. I am referring this matter to the stewards."
Double world champion Vettel, third in the overall standings, has never won a Grand Prix in his country Germany.
Webber is second in the overall standings behind Ferrari's Fernando Alonso, who starts Sunday's race on pole position.
The FIA clamped down on the use of engine electronics and exhaust gases for performance gain last year after teams were found to be using what technical director Charlie Whiting called "extremely extreme" engine maps.
Red Bull still won both of last year's championships but have been less dominant this season even if their car is widely held to be the fastest.
The team's 2011 car was designed heavily around the exhaust system and now-illegal 'blown diffuser' and Red Bull have had to try and recover some of that lost performance.
It was not immediately clear what penalties the team might face if stewards ruled a breach had occurred.