Timo Glock has revealed that some of Virgin's much-needed car upgrade has not worked as expected.
At the wheel of the MVR-02 not featuring the bulk of the upgrade, teammate Jerome d'Ambrosio has been quicker all weekend in Turkey than the new car steered by German Glock.
"Some of the updates worked, some didn't," Glock told the German broadcaster Sky.
"The parts that would have brought most of the (lap) time didn't (work)."
He said the biggest innovation was the blown exhaust, but like many other teams have also suffered, it initially caused overheating problems.
"We tried it yesterday," said Glock on Saturday, "and it didn't work as it should have. There were some things becoming too hot, so we've had to go back a bit."