The sanctioning body for the TUDOR United SportsCar Championship has made Balance of Performance alterations to three of its four classes ahead of next week’s race at Circuit of The Americas in Austin.

IMSA’s changes to the Prototype class include an increase in power and weight for the HPD ARX-03b P2 chassis, and the addition of BoP specifications for the new Ligier JS P2-Honda that will make its series debut with Oak Racing.

HPD’s P2 chassis, which is fielded by Extreme Speed Motorsports, will carry an extra 40 kilos (88 pounds), increasing from 900 to 940kg (2072 pounds). Its twin-turbo V6 engine will receive new air restrictors that are less constricting, moving from a pair of units with 31.3mm openings to two restrictors at 32.5mm apiece. The ARX-03b will also gain an additional liter of fuel capacity at 76L, up from 75L.

The Ligier coupe, which makes use of the same engine found in the ARX-03b, has received a baseline identical to the HPD with a minimum weight of 940kg, two 32.5mm restrictors and a 76L fuel capacity.

Fuel capacity changes were made for Daytona Prototypes, with the Corvette DPs and Honda DP seeing a reduction from 76L to 70L, and the Ford EcoBoost turbo DP dropping from 76L to 73L.

In GT Le Mans, the Corvette Racing team will lose some weight, reducing from 1270 to 1255kg (2767 pounds), and gain a small bump in power, moving from two 29.2mm restrictors to a pair of 29.5mm units.

Coming off its thrilling victory at VIR, Risi Competizione will lose a small amount of power, replacing its single 41.2mm restrictor for a more constrictive 40.9mm unit.

The BMW Team RLL outfit will gain weight and power with their Z4s starting at COTA. Both cars will be saddled with 25 extra kilos (55 pounds), bringing their minimum up from 1230 to 1255kg (2767 pounds). Their V8 engines will breathe easier though a pair of 30.2mm restrictors, replacing the 29.8mm units.

Four of the six models that race in the GT Daytona class have had weight adjustments made prior to COTA. Porsche’s GT America will lose 10 kilos (22 pounds), moving from 1200 to 1190kg, and will also have its refueling time slightly reduced with a change from a 28mm restrictor to a 29mm unit. The GT America is also “permitted maximum 50 mm front splitter, the addition of a single dive plane each side, maximum 25mm wheel arch extension, and removal of area behind the front wheel,” according to IMSA.

Ferrari’s F458 Italia is gaining what the Porsche’s losing, moving up 10 kilos from 1310 to 1320kg (2910 pounds), yet will have a few extra revs to use with an increase from 8000 to 8150rpm.

Turner Motorsport’s BMW Z4 will carry an extra 25 kilos, up from 1270 to 1295kg (2855 pounds), and Riley Technologies’ SRT Viper will also add 25 kilos, becoming the heaviest car in GTD as it increased from 1310 to 1335kg (2943 pounds).

The final BoP change should help Audi’s R8 to improve its top speed issues as the German V10 makes a sizeable jump from a pair of 40.0mm restrictors to more favorable 42.0mm units.​