Bourdais lapped his #01 Chip Ganassi-run V-Series.R in 1m11.637s around the 1.9-mile temporary circuit in the 90-minute session.
Nick Tandy set the earlier pace in the #6 Porsche Penske Motorsport 963, lapping in 1m12.579s, a quarter of a second clear of Connor De Phillippi’s RLL BMW M Hybrid.
FP1 pacesetter Pipo Derani began chipping away in his #31 AXR Cadillac V-Series.R, getting within 0.237s of Tandy after 20 minutes of the session had run.
De Phillippi improved with 40 minutes on the clock, topping the times at 1m12.554s before team-mate Nick Yelloly took over the #25 and chipped another 0.002s off that, to pip Tandy by 0.027s.
Yelloly then went even quicker, recording a 1m12.121s, with Bourdais jumping to second in the Chip Ganassi-run Caddy, 0.28s in arrears. Derani retook P2 with 15 minutes to go, 0.097s off Yelloly.
Bourdais improved his time but stayed third on 1m12.359s, before spinning off at Turn 1. He recovered from his moment to set the fastest time of 1m11.637s on his final lap.
Behind Yelloly and Derani, Philipp Eng was fourth in the #24 BMW from the PPM Porsches of Tandy and Dane Cameron.
Richard Westbrook (JDC-Miller MotorSports Porsche 963) was seventh, ahead of the Wayne Taylor Racing with Andretti Acura ARX-06s of Jordan Taylor and Filipe Albuquerque (separated by 0.48s but almost a second off the pace), and Mike Rockenfeller, who has joined Gianmaria Bruni this weekend in Proton’s 963.
The GTP class is using Michelin’s soft-compound tire at Long Beach for the first time outside of Daytona night running, and an extra set has been made available for Saturday’s 100-minute race.
#66 Gradient Racing Acura NSX GT3: Sheena Monk, Stevan McAleer
Photo by: Josh Tons / Motorsport Images
Acura fastest in GTD
In GTD, Parker Thompson set the early pace at 1m18.838s in the #89 Lexus RC F, 0.012s ahead of Loris Spinelli’s #78 Forte Racing Lamborghini Huracan.
Danny Formal then put WTRA’s #45 Lamborghini on top of the pile, rattling off three consecutive improvements to work down to 1m18.361s. But behind him, it was insanely close.
Albert Costa moved up to second in the Conquest Racing Ferrari 296, 0.021s slower, ahead of Matt Bell (AWA Corvette C8.R), who was 0.07s in arrears, with Spinelli a further 0.006s back.
But then Steven McAleer vaulted the Gradient Racing Acura NSX from last to first in class, lapping in 1m18.259s in the seat he’s taken over from Katherine Legge.
Qualifying begins at 8:00pm ET, ahead of Saturday’s 100-minute race.