Pipo Derani led the way in opening practice for Saturday’s Chevrolet Detroit Grand Prix at Belle Isle, in a storming lap for the Whelen Engineering Racing driver.

The Brazilian reeled off a 1:20.538 in the No. 31 Cadillac DPi-V.R to go quickest of the DPi cars, and nearly three-tenths clear of the competition.

Helio Castroneves posted the second quickest time in the No. 7 Team Penske Acura ARX-05, followed by the No. 5 Mustang Sampling Racing Cadillac DPi of Filipe Albuquerque in third.

Both of the Team Joest Mazda RT24-Ps encountered problems in the session, with the No. 55 car of Harry Tincknell completing just three in-and-out laps and the No. 77 car not even taking to the track.

Both cars made trips to the garage, with the teams not commenting to IMSA Radio on the extent of the issues.

Legge, MSR Acura Quickest in GT Daytona

Katherine Legge got her quest for a three-peat at Detroit off to the best possible start in topping the time charts in GT Daytona.

Legge reeled off a 1:30.304 lap in the No. 57 Meyer Shank Racing Acura NSX GT3 Evo, outpacing the Bryan Sellers-driven No. 48 Paul Miller Racing Lamborghini Huracan GT3 by 0.243 seconds.

Zach Robichon, who is in the No. 73 Park Place Motorsports Porsche 911 GT3 R this weekend, was third on the time sheets.

The session was halted twice, involving both of the JDC-Miller Motorsports Cadillac DPis.

First, Simon Trummer came to a halt on track early in the 90-minute session to bring out an initial red, while teammate Misha Goikhberg made heavy contact with the Turn 2 wall, in an accident that also collected the No. 76 Compass Racing McLaren 720S GT3 of Matt Plumb.

The accident resulted in a lengthy red flag to put the damaged Cadillac DPi on the flatbed tow truck, while the McLaren drove back to the pits but did not take any further part in the session.

Practice 2 gets underway at 12:40 p.m. EDT.

RESULTS: Practice 1