Renault hopes to be close to top four

"It has been very tough to understand and unpick the details of winter testing and how we compare with the other teams because we don't know what approach they have taken," said Boullier ahead of this weekend's season-opening Bahrain Grand Prix.

"We took a decision to run with heavy fuel at every test because we believed this was the best way to understand and improve the car.

"In terms of outright performance, I hope we are close to the top four teams," added the Frenchman, who is now in charge of the team following the exit of Flavio Briatore.

Polish driver Robert Kubica agreed that it was very hard to tell how strong Renault will be, but he believes the French squad is at least working in the right direction.

"It's difficult to judge performance, but we're heading in the right direction," he said. "We also haven't run with all our new updates yet and there is another aero upgrade for Bahrain, which we hope will match the wind tunnel predictions and improve performance.

"Overall, it seems that all the top teams are quite close, but some have definitely hidden their full potential during testing and will also have more updates for Bahrain. So far, I think Ferrari and Mercedes look very strong."

Team-mate Vitaly Petrov, making his grand prix debut this weekend, admitted he was eager to go racing.

"People are asking me if I feel nervous, but I'm used to racing and I know what I need to do," the Russian said. "Of course things are different in F1 and I'm still learning about the car and how to work with the team. But I feel good and I can't wait to go racing in Bahrain."