Di Resta hopes for Force India progress

"It's been difficult and I must say the days that we've had some things that definitely haven't run quite as smoothly as possible, but I think it is definitely better to get it out of the way at this point of the year, as opposed to coming at Bahrain," said di Resta at the end of the second day of testing at Barcelona.

"We are improving. Realistically, we know where we kind of are. We're not looking at timesheets as of yet because we've had so limited running on this car that it's just about gathering the data and sending it back for the guys to analyse.

"Day by day it is getting better and the improvement we made from doing the short blasts we did in the last hour yesterday to this morning was quite big and I'm sure you could make that step easily again.

"Certainly, even at the end of the day, the improvement we made from just before lunch to the beginning of the afternoon session was big again.

"We're on the up and I think that's the important thing. I'm sure Adrian [Sutil] will then take over and you will see the performance certainly rise from there again," added the Scot, whose team introduced its new car in the second test of the winter at Jerez.

Di Resta had another difficult day today, with his car's throttle getting stuck and forcing him to go into the gravel to stop it.

He still managed 80 laps on his way to the ninth fastest time.

"We were having quite a reasonable day until about three o'clock when a throttle sensor failed, which unfortunately stopped it early, but I think certainly there was points today I think we can reference off other teams and I think we were quite reasonable," he said.

Like the majority of his rivals, the Scot said it was very hard to get a clear picture of the field's pecking order at the moment.

"It's difficult to predict," he added. "I mean, I did a long run behind the Red Bull in the afternoon and it was quite comparable and I know where we were and you can only gauge where you think they are. It's all on tyre age. We can certainly sit down and look.

"Jenson [Button] also did a run at the same time so there was three of us on track that you could gauge. It was all pretty nip and tuck, but definitely Red Bull seem in good shape. There are some teams that are showing well but it's difficult - you can't get too carried away until you get to Bahrain because you just have no idea of your true performance until that point."

And he admitted Force India still has some work to do with in the set-up area.

"Definitely we need to get into the finer details. It's not necessarily always going forward as well, you need to try things that might take a step back just to understand a bit more. We did that today.

"The fine-tuning I'm sure will come at the next test and that's what you do over the grand prix weekend. We need to get the big stuff and the reliability of the car running first before you can do that, and also understanding the tyre a bit more."