Romain Grosjean believes that Lotus is making progress with their E22, ahead of this weekend's Spanish Grand Prix.
Grosjean has yet to finish in the points so far in 2014 but was running in the top 10 until a gearbox problem truncated his race in China.
"On paper we made a big relative improvement in China but it wasn’t just one thing," he said.
"We took the Renault updates and our own updates as well and moved forward. Altogether we made a big step, even though there were no massive changes on the car - we’re just trying to make everything work together better. There is more to come for Barcelona.
"I think it [the E22] is getting there. It is still not as good as we believe it can be. The aim in Barcelona is to keep improving, but we know we have a decent platform to work from and solve the remaining issues. Of course power unit wise we are not yet equal to the best and from our side we are still behind the top Renault team."
Technical director Nick Chester believes that Lotus has the potential to make massive gains in Spain.
"We’ve got further improvements on engine mapping, which should give us another step forward," he said.
"We’ve got a new cooling and bodywork package coming - quite a big upgrade - plus some updates to the rear wing and various other bodywork parts. All of the developments that we’ve brought for the car so far have been an improvement, which is highly satisfying and validates the hard work being done back at the factory. We also received more horsepower from Renault in China and I hope we’ll get a further step-up in Barcelona, which will make a massive difference."