Kiwi ace Earl Bamber unleashed the best speed to date from the #911 Walkinshaw Racing-run factory Porsche to be third quickest in 2:03.40s.
With a further qualifying session to come which is reserved for Class A runners that will set the Top 10 Shootout, the opening session determined the grid for the lower classes.
The KTM X-Bow GT4 of Glen Wood led the way in Class C.
The Class I pole was taken out by the #65 Daytona Sportscars-entered Viper driven by Dean Lillie.
Earlier Tim Slade arrowed down the escape road at Turn 1 in the Objective Racing McLaren 650S before the car became stuck with 35 minutes remaining which triggered a red flag.
In the opening 15 minutes, the session was stopped when the #18 Porsche Cayman GT4 of Charles Putman found the fence exiting Turn 1.
Officials later issued a notice that the #18 and its PROsport Performance stablemate, the #19 Cayman, would take no further part in qualifying after breaching the rules by refuelling during the session.
Ben Barnicoat then suffered a heavy hit in the #59 Tekno McLaren when the machine slammed into the left-side fence exiting the Chase inside the final 15 minutes.
As Barnicoat managed to move the stricken McLaren out of harms way, the #23 Nissan made a return to the track with Alex Buncombe at the wheel after being repaired from its Practice 5 shunt.
Buncombe managed a 2:05.39s best as the team evaluated the Nissan ahead of the Class A-only qualifying run.
A third red flag was called with just under six minutes remaining when Ricky Collard (#99 Walkenhorst BMW M6) appeared to be hit by the Hallmarc Audi of Lee Holdsworth, forcing the former into the fence at the Dipper.