By alley - Jun 2, 2017, 10:43 AM ET

Cadillacs lead IMSA Detroit FP1

IMSA's latest attempts to slow Cadillac's all-conquering DPi-V.R were shown to be successful Friday morning at Detroit's Belle Isle, but it wasn't enough to knock the fearsome prototypes from atop the field.

Practice results

Christian Fittipaldi went fastest in his No. 5 Action Express Racing Cadillac (1m23.750s) and put some distance between himself and Jordan Taylor in the No. 10 Wayne Taylor Racing Cadillac (+0.480s) to give the DPi-V.Rs a clean 1-2 in the opening session. The effects of the Balance of Performance penalties were revealed by the third-place car, JDC-Miller Motorsports' WEC-spec ORECA 07-Gibson, which came within one second (+1.058s, to be exact) with Misha Goikhberg behind the wheel.

GT Daytona's European supercar battles raged until the No. 16 Change Racing Lamborghini Huracan GT3 driven by Jeroen Mul came out on top (1m30.782s) on the final lap. Jeroen Bleekemolen's No. 33 Riley Motorsports Mercedes AMG GT3 (-0.107s) and the No. 57 Stevenson Motorsports Audi R8 LMS GT3 driven by Andrew Davis (-0.155s) completed the top three.

The slim three-car PC field was led by Performance Tech Motorsports' Pato O'Ward (1m27.851s) as the young ace cleared the second-place car of Bruno Junqueira by almost three seconds.

Three crashes slowed the 90-minute curtain raiser at Belle Isle. BAR1 Motorsport's No. 20 PC found the wall early in the session with Ryan Lewis behind the wheel and retired to the paddock for repairs, and Alegra Motorsport's No. 28 GTD Porsche clouted the Turn 1 wall with the rear of the 911 GT3 R. The German GT machine was driven back to the transporter by Daniel Morad, although it was crabbing a bit with the rear damage in mind.

A lengthy caution period to repair the Turn 1 barriers was followed by a brief return to green running before another yellow for a nearly identical rear impact was made in the same corner by Ozz Negri in the No. 86 Acura NSX GT3.

UP NEXT: FP2, 1 p.m. ET