Sauber's C33 has undergone an "extensive weight reduction" ahead of next weekend's Spanish Grand Prix.
Sauber is one of four outfits that have yet to get off the mark this season as the team has been hampered by an overweight car.
Although this year's minimum weight was increased to 690kgs, the C33 failed to come close to that costing the team valuable time.
As such, Sauber worked on new lighter parts during the break between China and Spain with Giampaolo Dall'Ara revealing they have achieved their aim.
Sauber's head of track engineering said: "At the Spanish Grand Prix both C33s will have essential revisions, following an extensive weight reduction and a significant aerodynamic update.
"This update consists of a modified front wing and a new engine cover, new side-pod fins and deflectors, as well as a number of other aerodynamic changes.
"Besides that, we will also have a software improvement which will enable us to use the potential of the power unit in a better way. We expect a busy Friday at the track while tuning the set-up to the new package.
""Making the best use of the tyre compounds will also be a challenge, as Pirelli's choice to allocate medium and hard tyres appears to be conservative. We very much look forward to converting everyones' efforts into improved lap times."
Dall'Ara, however, admits it won't be easy closing the gap as other teams will also improve as Spain often sees massive updates for all cars.
"We know that all the other teams are progressing as well, so it will be interesting to see where we stand," he added. "We will certainly do our best in order to race for points."
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