Adrian Sutil admits that Force India faces a challenge to get up to speed with its updated VJM04 after a below par start to the Spanish Grand Prix weekend.

The German was outpaced by the Lotus of Heikki Kovalainen as he worked through a programme focused on set-up development with the new aerodynamic components being introduced for the first time this weekend.

Admitting that the team hasn't found the sweet spot with the parts, Sutil said it was going to be difficult to get all the updates working and was partly the reason why he was languishing down the times.

"I ran with all our new aero parts this morning and in the afternoon, but to be honest we haven't managed to find the sweet spot yet," he said. "The guys did a great job to get everything on the car, but it's never easy to introduce so many new things during a weekend and to test them properly.

"Getting this new package to work is probably going to be more difficult than we thought and that's why we didn't look that competitive today. So we have work to do this evening to see if we can improve things for tomorrow."

Team-mate Paul di Resta, who only ran during the afternoon to allow test driver Nico Hulkenberg to compete in FP1, agreed that there was a lot of work to be done on the upgraded package.

"I missed the morning session so there was a big workload to get through in the afternoon," the Scot said after posting the 17th quickest time. "It was the first time I'd been in the car with the entire new package and we always knew it would be a big change compared to what we were used to.

"The car feels very different and it's clear we have lots of work to do to understand the new parts and get the most from them. By the end of the afternoon we had definitely improved the car quite a bit, but we need to sit down tonight and think about how we should approach tomorrow."