Guy Smith claimed a surprise American Le Mans Series pole position for the Dyson Racing team at Virginia, while BMW's Maxime Martin headed a truncated GT qualifying session.
Smith's effort denied champion Pickett Racing a sixth straight pole position, as Klaus Graf tried in vain to get his HPD ahead of the Lola-Mazda at the top of the times.
But Briton Smith's benchmark, a 1m35.965s, proved too much for Graf, who returned to the pits with more than a minute on the clock after a big moment on his final flying lap trying to overturn the 0.20s deficit.
In the fight for LMP2 pole, Ryan Briscoe headed a Level 5 one-two, with points leader Marino Franchitti half a second slower in the second HPD.
Title challenger Scott Sharp's weekend start with difficulty, as he made an error on his out-lap, nerfing the tyre wall on the exit of the Hog Pen and requiring repairs to his Extreme Speed machine. He was able to get back out, but could only manage 10th.
LMPC title rivals Michael Guasch and Jonathan Bennett left it to their out-of-the-picture team-mates to scrap it out in qualifying.
Guasch's PR1/Mathiasen co-driver Dane Cameron edged CORE's Tom Kimber-Smith after an epic fight for the class pole that had both drivers take turns at the head of the field.
BMW ON TOP IN GT
Martin claimed the second pole of his debut ALMS season in the lead Rahal Letterman Lanigan-run BMW Z4.
He usurped Matteo Malucelli's Risi Ferrari 458 at the head of the times with his fourth lap, and was the only driver to get below 1m46s.
It was a strong session for BMW, with Dirk Muller third fastest, while Chevrolet's joint-points leader Jan Magnussen could only manage eighth.
Any chance of the #3 Corvette making a late improvement was ended when Malucelli caused the session to be cut short with a few minutes remaining.
His 458 dropped fluid at the Hog Pen, causing Tommy Milner to crash in the #4 Corvette and also Kuno Wittmer to spin his SRT Viper. That led to the Ferrari's best time being deleted, though Malucelli's second-best effort was still good enough to split the two BMWs.
TRG's Damien Faulkner was quickest of the GTC runners, ending the session 0.40s clear despite an off-track excursion just after posting his fastest time. Jeroen Bleekemolen pipped Spencer Pumpelly to second.
Pos Cl Drivers Team/Car Time Cl Gap
1. P1 Smith/Mowlem Dyson Lola-Mazda 1m35.965s
2. P1 Graf/Luhr Pickett HPD 1m36.169s +0.204s
3. P2 Tucker/Briscoe Level 5 HPD 1m39.796s
4. P2 Franchitti/Cosmo/Johansson Level 5 HPD 1m40.307s +0.511s
5. P2 Brown/van Overbeek Extreme Speed HPD 1m40.743s +0.947s
6. PC Guasch/Cameron PR1 Mathiasen FLM 1m41.854s
7. PC Bennett/Kimber-Smith CORE FLM 1m42.105s +0.251s
8. PC Marcelli/Cumming BAR1 FLM 1m42.419s +0.565s
9. P2 Sharp/Lazzaro Extreme Speed HPD 1m42.497s +2.701s
10. PC Nunez/Booth Performance Tech FLM 1m42.574s +0.720s
11. PC Schultis/van der Zande DragonSpeed FLM 1m42.869s +1.015s
12. PC Mitchell/French BAR1 FLM 1m43.406s +1.552s
13. P1 Meyrick/Legge DeltaWing 1m43.724s +7.759s
14. GT Auberlen/Martin RLL BMW 1m45.978s
15. GT Beretta/Malucelli Risi Ferrari 1m46.113s +0.135s
16. GT Muller/Hand RLL BMW 1m46.174s +0.196s
17. GT Miller/Holzer Miller Porsche 1m46.211s +0.233s
18. GT Bomarito/Wittmer SRT Viper 1m46.528s +0.550s
19. GT Farnbacher/Goossens SRT Viper 1m46.568s +0.590s
20. GT Long/Braun CORE Porsche 1m46.673s +0.695s
21. GT Magnussen/Garcia Corvette 1m46.923s +0.945s
22. GT Gavin/Milner Corvette 1m47.038s +1.06 s
23. GT Henzler/Sellers Falken Porsche 1m47.730s +1.752s
24. GT Sweedler/Bell AJR/West Ferrari 1m47.761s +1.783s
25. GTC Keating/Faulkner TRG Porsche 1m52.213s
26. GTC MacNeil/Bleekemolen Alex Job Porsche 1m52.610s +0.397s
27. GTC Canache/Pumpelly Flying Lizard Porsche 1m52.621s +0.408s
28. GTC Cisneros/Edwards NGT Porsche 1m52.927s +0.714s
29. GTC Cisneros/Giermaziak NGTC Porsche 1m53.286s +1.073s
30. GTC Hedlund/Heylen JDX Porsche 1m53.425s +1.212s
31. GTC Neiman/von Moltke Flying Lizard Porsche 1m53.507s +1.294s
32. GTC Dempsey/Lally Dempsey Del Piero Porsche 1m53.571s +1.358s