Team Lotus was left encouraged by the early performance of its updated T128 after Heikki Kovalainen split the two Force India drivers during Friday practice for the Spanish Grand Prix.
The team introduced a major upgrade package onto the car for the start of on track action at Catalunya, including revisions to the aero package and a new exhaust system.
Kovalainen responded by outpacing Adrian Sutil during the quicker second session while the Finn was less than half a second behind Paul di Resta.
"Overall we can be very happy about this Friday,” he said. “I think we've seen an improvement today on where we were and throughout the sessions we could see that we were getting more and more out of the new package. The gap to the cars ahead seems reasonably small so I think it's all positive.
“The key point is that there is a lot more to come out of it. Optimising the whole update will take time and even though the car felt good on both the options and the primes we know that after going through the data tonight we can make more improvements tomorrow, and in the coming races."
Although a steering issue meant a loss of track time for Jarno Trulli during the morning, he bounced back to end the afternoon session less than a tenth of a second behind Sutil.
"That was a very interesting and useful day, and good to put so many laps on the new package,” chief technical officer Mike Gascoyne said. “As we expected the behaviour of the car is now quite different to what we have been working with so far this season and it will take a lot of fine tuning to get the best out of all the improvements, but I think that on the soft tyre and the longer runs we could clearly see some of the improvements we were aiming for.
“There are obviously areas we need to focus on, but those can all be dialled out, so all in all this has been a good day with the new package, well done to the whole team for working hard to get it all working so well on the car on its debut and I am sure there is much more to come."