IMSA’s efforts to slow the Cadillac DPi-V.R Prototype through Balance of Performance changes have continued as the series readies to race this weekend in Detroit.

Set in front of General Motors’ global headquarters, the dominant Daytona Prototype international model will compete in Saturday’s GM-sponsored Chevy Sports Car Classic with three new attempts to bring the Cadillac down to a pace that matches its winless rivals.

Led by IMSA competition VP Simon Hodgson, the latest round of BoP penalties for the DPi-V.Rs used by Action Express Racing and Wayne Taylor Racing will see the trio of 6.2-liter V8-powered LMP2 cars lose a decent amount of power with air restrictors that allow less volume into the combustion chambers (-0.6mm total loss, now 30.4mm).

The Cadillacs will race with less fuel as well, down to 64 liters (-2.0 liters, now the smallest fuel cell in the class by 11 liters), which comes after IMSA cut the tanks to 66 liters for the April race at Long Beach. Hodgson also chose to reduce downforce for the DPi-V.Rs by limiting the maximum rear wing angle and Gurney flap heights. This decision should be impactful at a street course where teams rely on maximum downforce to compensate for the lack of grip.

The fourth wave of Cadillac BoP penalties since January also carry over the unprecedented mandate from Long Beach for tall first and second gears to be used, which eliminates the inherent torque benefits created by choosing a larger engine than Mazda and Nissan.

With the Cadillacs making less power, carrying less fuel, making less downforce and suitably delayed when accelerating out of corners through gears chosen by IMSA, a fifth consecutive win for the brand should be next to impossible at its home race.

Elsewhere in Prototype, Mazda and Nissan have been given one extra liter of fuel capacity (to 78 liters and 79 liters, respectively), Mazda’s 2.0-liter turbocharged four-cylinder engine has been given more midrange boost (from 5800-6250 rpms), and Nissan has lost some refueling speed through a new hose restrictor (-0.5mm).

No changes were made to any of the WEC-spec LMP2s, which have been incapable of challenging the better DPis for wins as the WeatherTech SportsCar Championship nears the halfway point in the season.

With GTLM off the Detroit schedule, GTD was the last recipient of BoP changes.

Audi’s R8 LMS GT3 will have more power through new air restrictors (an increase of 1.0mm total, now 40mm) along with one extra liter of fuel (to 94 liters) and slightly faster refueling (+0.5mm). Ferrari’s 488 GT3 and Lamborghini’s Huracan GT3 had fuel-related alternations made with the Prancing Horse losing refueling speed (-1.0mm) and the Bull getting more fuel (+2.0 liters) and faster refueling (+1.0mm).

The streaking Mercedes-AMG GT3 has, predictably, been penalized with weight (+20 kilos/44 pounds) and a loss of power (-0.5mm total, now 34.5mm). Porsche’s 911 GT3 R, which won the season opener in January before Mercedes-AMG went on to win three straight, has been handed extra weight for Detroit (+10kgs/22lbs).

Practice for the Chevy Sports Car Classic begins Friday morning.