Red Bull and the FIA have dismissed suggestions it is illegal, and Vettel said on Thursday: "We are pretty proud of the system.
"The others have to figure out how we have done it," the German is quoted by the Associated Press.
The other big talking point is suggestions Davide Valsecchi has been briefed to be ready to step into the Lotus, should Kimi Raikkonen's back problems worsen in Friday practice.
The Finn was playing down the situation on Thursday.
"It would be a bit pointless to come here if I didn't think that I would race," he told reporters.
"Right now it's ok. Obviously tomorrow we'll see."