Kyle Marcelli ended the second Pirelli World Challenge GTS SprintX practice session on top, with the Canadian setting the pace at Circuit of The Americas.
Marcelli took his No. 13 Pfaff Motorsports Porsche Cayman GT4 Clubsport MR to a fast lap of 2:18.625, early in the 50-minute session, outpacing the No. 06 Rearden Racing Audi R8 LMS GT4 by 0.468 seconds.
His time, however, was some four-tenth slower than Colin Braun, who led the way in the morning session in his No. 04 GMG Racing Audi GT4.
The No. 14 GMG Audi GT4 of James Sofronas was third quickest overall in the second session, followed by the No. 8 GMG McLaren 570S GT4 in fourth.
Mike Hedlund completed the top-five in the No. 45 Flying Lizard Motorsports Audi GT4.
The session was brought to an early end following a red flag for the No. 45 Racers Edge Motorsports SIN R1 GT4, which suffered damage after hitting a curb.
Qualifying gets underway at 9 a.m. CT on Saturday.
RESULTS: Practice 2