Kimi Raikkonen has admitted that he was underwhelmed by the improvements Lotus's major upgrade package made to the E20 in Korean Grand Prix practice.
The Finn felt it was too early to make a definitive judgement about the new developments, which include the much-vaunted Coanda-effect exhaust.
Lotus had hoped that the upgrade would get it back into victory contention after its form tailed off in recent races.
When asked for his opinion on the new package, Raikkonen replied: "I think it's too early still. We'll look at all the data and see how it is.
"We probably expect a bit more than what we've seen so far, but it's too early to say."
He conceded the car had been tough to drive in practice, where he ended up 10th fastest.
"It's not very easy to get the car right," said Raikkonen. "Hopefully tomorrow will be better."
The 2007 world champion felt that as the Yeongam circuit has so little in common with Suzuka, the venue for last weekend's Japanese Grand Prix, making technical comparisons is even harder than usual.
"They're completely different places, you cannot compare," Raikkonen said when asked if the upgraded car felt better than it had in Japan.
He remains optimistic that Lotus will have a competitive weekend as it get to grips with the upgrade.
"I think we are more or less where we usually are on Fridays. Hopefully we can improve the car and be faster tomorrow," said Raikkonen.
"The car didn't feel good today and we were one second off the pace, so if we can it right we can get higher, but other people might improve."