Di Grassi gets revised Virgin for Turkey

The Brazilian rookie has been left with the original design as transport delays caused by last month's volcanic ash crisis left Virgin unable to prepare two of its new cars for Spain, where Timo Glock gave the upgraded chassis its debut.

The revised car has a wheelbase 135mm longer than the original, and addresses the fuel tank size issue that hampered Virgin in the early races.

"We were really pleased with its debut," Wirth told AUTOSPORT. "Obviously very, very disappointed for Lucas that events conspired to prevent us getting that car done, but it was down to timing and we were about two or three days out when the freight came back so we couldn't do it.

"I'm glad that this weekend is going to be the last race with the old spec."

Wirth believes the team has not yet shown the full potential of its new car.

"The new car in Barcelona spec was about half a second quicker than the old car, and there are a few issues we were having with the new car there," he said.

"One was that it was slightly overweight, which we've addressed somewhat here. The other thing was that we had some specific issues with the braking system on that car, so I don't think we really saw in qualifying what the car was capable of doing, but I think we saw it in the race.

"I was pleasantly surprised at the race-long battle that we had with the much-vaunted Lotus upgrade."