Valtteri Bottas certain Williams understands how to fix its issues

Williams will try some car tweaks during Friday's free practice session in China, with a major upgrade planned for next month's Spanish Grand Prix.

Bottas, who like team-mate Pastor Maldonado visited the Williams factory twice during the break between the Malaysian and Chinese Grands Prix for simulator sessions and meetings with engineers, also paid tribute to the troubleshooting effort put in by the team.

"That's the most important thing, to understand what the problem is," said Bottas when asked by AUTOSPORT whether the team has a good understanding of its issues.

"Now, we really clearly see it, much better than in the first two weekends as we have had more time now to look at things.

"For nearly three weeks, everyone was working as hard as possible to understand the problems and to fix the problems.

"It will not be an overnight fix, it will take some time, but it's nice to see we already have some new bits for this weekend."

The upgrade package for China will include a modified front wing.

But the team is sticking with the launch-specification exhaust even though technical director Mike Coughlan admitted in Malaysia that reverting to a late-2012 exhaust was an option.

Asked by AUTOSPORT which exhaust specification Williams would run, Maldonado replied: "We will have something similar to what we have in the previous races.

"There is a step on the aero side, we have a couple of new bits and we need to see if there is a clear improvement, even if it is small, just to keep that direction and to develop the car as soon as we can.

"The new parts we have got here are not mega-revolutionary for the car.

"It's the front wing and some other stuff.

"Hopefully the car should work a bit better but we still are far away from where we need and want to be.

"But the good thing is that we are working very hard in the factory."