Merc uses old piston design

The team's Martin Whitmarsh, who now heads up both the chassis and engine sides of the company, explained that although the reversion has been made, it was forced on the team by time pressures and he does not believe that the new piston design tried in Germany was a direct cause of the problem.

"Further analysis has shown that the failed pistons came from two batches of material, so we think we know why we had the problem," he explained in Canada. "We had a slightly different design of piston at Nurburgring, so inevitably when you have piston failures and you've just changed the design, you focus on the design issue.

"But, in the light of the analysis that we've done, we've now tracked it down to two batches of material. In the meanwhile we had to build engines for Canada and so we reverted back to the old specification of piston for this race so that we could build those engines before we completed the material analysis."

McLaren's fortunes received a boost on Friday when Kimi Raikkonen set the fourth fastest time, despite losing time while a damaged floor was repaired. Team-mate David Coulthard was also in the top 10.