Having put in the laps on Day One in Bahrian, Adrian Sutil says Sauber now need to focus on performance.
The German driver covered 89 laps of the Sakhir circuit on Thursday with a best time of 1:37.700.
His time put him fifth on the day's timesheets, 2.410s behind pace-setter Sergio Perez, however, it was 4.417 short of Nico Rosberg's best from last week.
"We did a lot of mileage," said Sutil, "however, we have to work on our performance. We still had a few issues.
"Nevertheless, we were able to do qualifying runs and almost a complete race simulation.
"We have collected a lot of valuable information, and we know we still have to make further progress. Also I was able to gain experience on all dry tyre compounds.
"Generally they are all a bit harder than last year, but I have no concern about them as they should last well over the race distance."