Williams became the latest team to try and find a straightline speed boost through stalling its rear wing after trying out engine cover modifications during final free practice at the Chinese Grand Prix on Saturday.
As teams scramble to try and copy the F-Duct system that was pioneered by McLaren, Williams evaluated its first version of the concept on Rubens Barrichello's car on Saturday morning in Shanghai.
The new parts, which only featured the engine cover vent that directs air onto the rear wing to stall it for a straightline speed advantage, were only fitted to the car on Saturday morning because they had been held up by Chinese customs.
Initial feedback from Barrichello about the wing did not indicate that the design was achieving the boost that the team hoped, and the team reverted to its more normal engine cover halfway through the session.
Williams' initial tests of the blown rear wing come after Ferrari tried out the engine cover parts of its F-duct system on Fernando Alonso's car during Friday free practice in Shanghai, with a vent situated behind the drivers' head.
Mercedes GP is also close to introducing its own version, after carrying out rear wing pressure analysis on both its car during practice on Friday too. McLaren and BMW Sauber are the only two teams that have so far successfully raced with the F-duct system that was the subject of a major controversy at the beginning of the season.