IMSA has made adjustments to numerous WeatherTech SportsCar Championship models following the recent Roar Before the 24 test at Daytona International Speedway.
The Balance of Performance changes will have a direct influence on how various manufacturers fare in Prototype, GT Le Mans and GT Daytona during the Jan. 25-28 Rolex 24 at Daytona.
Of interest in Prototype, Acura’s brand-new ARX-05 DPi has received an increase in fuel capacity (+4L, 80L total) and will flow fuel faster during pit stops with a larger opening in the restrictor (+1.5mm).
Cadillac’s DPi-V.R, which dominated every session at the Roar, has lost power to its 5.5-liter V8 engine with smaller openings feeding air to the motor (-0.6mm, 31.6mm total opening size), and has received an increase in fuel capacity (+1L, 68L total) and will flow fuel faster during pit stops (+0.5mm).
Mazda’s RT24-P is the only DPi to receive a weight reduction (-15kg, 915kg total), has gained a rev limit increase for its 2.0-liter four-cylinder turbo engine (from 8300 to 8600), lost boost at the bottom and top of the rev range, and will flow fuel faster during pit stops (+0.5mm).
The Nissan Onroak DPi has received an increase in fuel capacity (+2L, 80L total) and will refuel faster during pit stops (+1.5mm). On the engine front, its 3.8-liter twin-turbo V6 will have a bump in boost as it reaches a peak RPM of 7100.
Aerodynamic changes have also been called for with most of the DPis. Taller Gurney flaps attached to the trailing edge of the Acura, Mazda, and Nissan engine covers are required; Mazda’s Gurney is the tallest at 20mm, and a high-downforce upper rear wing element must be used. Nissan’s rear wing main plane will run at a steeper angle. Of the four marques, only Cadillac, which set the fastest trap speeds on the banking, escaped Rolex 24 aero BoP changes, but the reduction in engine power could be the method chosen by IMSA to pull the DPi-V.Rs in line with Acura, Mazda and Nissan.
As IMSA previously told RACER, despite any change of plans within the ACO and FIA WEC to make BoP adjustments to the spec LMP2 cars on the grid, it has not and will not follow suit in the WeatherTech Championship.
In GTLM, BMW’s new M8 GTE is the only model to lose weight between the Roar and Rolex 24 (-10kg, 1240kg total). Boost increased throughout almost the entire 7000rpm rev range for the BMW’s twin-turbo V8 have has also been applied, and the M8 will have an increase in fuel capacity (+6L, 93L total), and will flow fuel faster during pit stops (+3.0mm).
Corvette’s C7.R (+1L, 91L total), Ford’s GT (+2L, 91L total, and +1.0mm), and Porsche’s 911 RSR (-3L, 92L total, -1.0mm) also have capacity or flow changes in store for their cars. Only Ferrari’s 488 GTE was left out of fuel-related adjustments.
On the aero front, Corvette will lose top speed with a taller minimum rear wing angle (up from 0deg to 2deg) and Ford has also been hit with the same change (up from 2deg to 5deg).
In GTD, two cars have weight changes to make with Acura’s NSX GT3 increasing (+10kg, 1310kg total) and Mercedes’ AMG GT3 decreasing (-15kg, 1375kg total) on the scale. Three engine power modifications have been called for, with Audi’s V10-powered R8 LMS GT3 going to air restrictors with smaller openings (-1.0mm, 39mm total) along with the Audi-based Lamborghini Huracan GT3 (-1.0mm, 38mm total), and BMW’s M6 GT3 has received more boost at every step of the rev range with its twin-turbo V8.
From the nine GTD models, five have fuel capacity and flow changes for the Rolex 24. Acura (+5L, 105L total, and +1.0mm), Audi (-3L, 91L total, and -1.0mm), BMW (+3L, 106L total, and +1.0mm), Ferrari’s 488 GT3 (+2L, 94L total, and +0.5mm), and Lamborghini (-3L, 92L total, and -1.0mm) complete the extensive BoP efforts.
Practice for the Rolex 24 starts next Thursday, Jan. 25.