The championship chief produced the products on his remaining lap to publish a 1m40.878s to grab pole by 0.165s from Prema team-mate Robert Shwartzman.
Piastri’s title rival Guanyu Zhou was sixth quickest, virtually half a second shy of the poleman, and consequently is now 40 factors behind within the championship race.
As drivers jostled for monitor place, the primary indicative occasions on the tremendous smooth tyres got here 5 minutes into the 30 minute session as Pourchaire shot to the highest.
Nonetheless, he was quickly pipped by Ralph Boschung, Piastri and follow pacesetter Shwartzman, who posted a 1m41.747s to move the timesheets by 0.064s after the primary flying laps.
Zhou might solely managed a time adequate for tenth, the reversed-grid pole, some 1.3s adrift of Shwartzman.
Rookie Clement Novalak made a powerful begin to his first F2 qualifying session to take a seat fifth behind Pourchaire after his first run.
Pourchaire made probably the most of his second flying lap to eclipse Shwartzman by three tenths, however the later issued a direct response to reclaim provisional pole on the midway mark, to pip the youngest ever F2 race winner by 0.029s.
The sphere all got here in for a second set of tremendous softs forward of their second and remaining runs with 10 minutes remaining.
Solely Zhou and Marcus Armstrong improved on their first flyers of the run because the title contender jumped to 3rd, whereas Armstrong climbed to eighth.
Hopes of a pole for Ticktum had been dented after struggling a proper rear puncture that required an unscheduled journey to the pits.
Zhou shaved much more time from his private greatest on his second flyer to preliminary slot into third.
Behind, nevertheless, his rivals had been additionally on scorching laps with Pourchaire subsequent to strike, shifting into provisional pole.
Theo Pourchaire, ART Grand Prix
Picture by: Components Motorsport Ltd
However the teenager’s pleasure was short-lived as Piastri denied him pole courtesy of a fast first sector in his remaining lap. Shwartzman threatened to knock the Australian off pole however fell quick as he crossed the road.
Christian Lundgaard ended the session fourth after a late effort noticed the dane leapfrog Drugovich and Zhou.
Boschung, Vips and Armstrong stuffed seventh by to ninth, whereas Liam Lawson rounded out the highest 10 and can earn the reverse grid pole for Saturday’s opening race.
Novalak emerged because the quickest of the 4 F2 debutants in twelfth place.
The opening dash race of the weekend is because of begin at 1530 native time, or 12:30pm GMT.