"The equipment was for testing purposes only," said the British team.
Jenson Button smiled: "Unfortunately it's not a new trick that's going to make us faster."
There are grave concerns about McLaren's readiness for the looming 2011 season, with BBC commentator and former team driver Martin Brundle describing the car as "a mess".
"It didn't slow down," he told the Telegraph after seeing the car in action on the Spanish track recently. "It didn't turn in. It couldn't get the power down. Clearly they have a fundamental issue."
Officially, Button hailed the team's "progress" on Tuesday, but he then told reporters that he is not expecting to win a third consecutive Australian grand prix.
"I would be surprised if we can match the Red Bull and the Ferrari when we get to Melbourne," he admitted.
He is quoted by Finland's Turun Sanomat: "If we have the third fastest car at the opening race, it will be a good start to the season."