Sauber used the first of their four curfew exemptions at Suzuka on Friday night as they needed extra time for aero work.
The team, who arrived in Japan this weekend with several big upgrades for their C30.
Speaking ahead of the race weekend, technical director James Key said: "We will bring a wide ranging aero package for the car, which includes a completely new front wing, new rear wings, new turning vanes and side pod deflectors, new brake ducts and modifications to the floor."
And with Sergio Perez and Kamui Kobayashi finished 13th and 16th on the timesheets on Friday, the team opted to work through curfew in order to better prepare for Saturday's practice and qualifying.
As of this season, a new rule in F1 states that no team personnel who are "associated in any way with the operation of the cars" are permitted within the confines of the circuit in a set period.
However, all teams were given four exemptions at the start of the season with Sauber using the first of their's on Friday night in Japan.