Kubica encouraged by Friday form

The Pole was third quickest overall in the afternoon session at Istanbul and told reporters that he believed it would be possible to break into Q3 in qualifying on Saturday.

"So far I am more happy with the overall car," said Kubica. "I cannot say I am just happy about the diffuser; the diffuser doesn't make it go fast or slow.

"I think it is all the package. I think the afternoon looks better, much better than in the morning - in the morning we were struggling.

"But the afternoon looks better, I think better than expected. Tomorrow I hope we can fight for Q3, but still it will be very difficult."

Kubica was adamant that due to the different track characteristics and weather conditions he could not measure whether a new slot diffuser the team has fitted to the car this weekend has improved BMW's performance: "I think it is impossible to say because of the different factors - different track, different tyres, different weather conditions, different characteristics of the corners here in Istanbul compared to Monaco. So it's very difficult to judge.

"I think we are a bit better than we were lately, but of course it is very difficult to say," he added. "And additionally the whole pack is very close together, so every hundredth, every tenth can make a big difference."

Kubica also admitted that he was frustrated not to have been able to capitalise on the moments when his car has been competitive so far this season.

"I think overall the start of the season was a bit unlucky and not as we were expecting, for different reasons," he said. "First of all in the first race where I could have scored many points I had an accident with [Sebastian] Vettel.

"Then in Malaysia where the car still was performing reasonably - I think top six - we had an engine failure before the start of the race. So when the car was good I had problems.

"Also in Barcelona, the car was performing well but we had two problems in the two most important moments of the weekend. So overall it's difficult because of the performance of the car and additionally because of the problems that we had.

"Let's hope that we will fix them and become better."