With 24 hours of data to draw from after January’s season-opening TUDOR United SportsCar Championship race at Daytona International Speedway, IMSA has made some adjustments to the cars competing in its four classes ahead of next month’s 12-hour race at Sebring.

Starting with the Prototype class, gasoline-powered P2 cars have been given a slight increase in fuel capacity, moving from 72 liters to 75. Fuel flow rates from the pit lane refueling tanks hav?e also been slightly increased, moving from a 32mm restrictor to 33mm.

These changes, which affect the 2.8-liter twin-turbo V6-powered HPD ARX-03b, and 4.5-liter Nissan V8-powered ORECA and Morgan cars were made to address a disparity in how long P2s were able to go during a full stint compared to the Daytona Prototypes at the Rolex 24 at Daytona, and how long it took to refuel both types of car.  

Sonic air restrictor sizes for all of the DP cars is still being evaluated, as is the maximum turbo boost level for Ford’s 3.5-liter twin-turbo V6 EcoBoost DP powerplant.

In PC, the minimum rear wing angle that was mandated for Daytona—one that was made to decrease top speed to keep the cars from spending too much time on the rev limiter in sixth gear—has been removed.

Significant changes in fuel capacity throughout the GT Le Mans category for Sebring, starting with the Rolex 24 class-winning Porsche 911 RSRs.

10 liters of fuel capacity has been removed from the Porsches, down from 110L to 100, Ferrari F458s have lost 16 liters (110 to 94), Corvette’s C7.Rs gives up seven liters (110 to 103), BMW’s Z4 sacrifices 10 liters (110 to 100), Aston Martin sheds three liters from its Vantage V8 (90 to 87) and SRT Viper parts with the biggest reduction, parting with 15 liters (120 to 105).

GTLM BMWs will gain 15kgs (33lbs), a jump to a minimum weight of 1245kgs (2745lbs). The SRT Vipers, which received the biggest weight break of any GTLM car leading into the Rolex 24 (30kgs/66lbs), has had that break cut in half for Sebring. With the extra 15kgs (33lbs), the V10-powered cars have an increased minimum weight of 1250kgs (2756lbs). Aston Martin, at present, is the only GTLM marque to receive a well-deserved weight break for the 12 Hours.

20kgs (44lbs) will come off the V8 Vantage, bringing its minimum weight to 1205kgs (2657lbs).

IMSA’s views on which GTLM cars were most heavily advantaged and disadvantaged by Balance of Performance changes at Daytona is rather evident in the big fuel capacity reduction and weight increase for the pole-sitting SRT Viper, and in the weight break and comparatively small fuel capacity reduction made for Aston Martin.

The theme continues in sonic air restrictor sizes as well, with the Vantage V8 getting a mild bump in power from a .3mm increase in each restrictor (2X29.7 to 2X30), and a mild reduction in power for the Vipers, which lose .3mm in each restrictor (2X29.6 to 2X29.3).

GT Daytona has also seen numerous changes, beginning with fuel capacity reductions for every car.

Team’s using Porsche’s 911 GT America (-17 liters, from 85 to 68), Ferrari’s F458 (-11 liters, from 86 to 75), Audi’s R8 (-11 liters, from 86 to 75), BMW’s Z4 (-16 liters, from 100 to 84), Aston Martin’s V12 Vantage (-9, from 90 to 81) and SRT’s Viper (-10, from 95 to 85) will have an interesting time outfitting their cars with capacity-reducing devices in time to get accurate fuel consumption and stint length information during the February 20-21 series test at Sebring.

Weight has been added to two models, with Ferrari’s Rolex 24 class-winning F458 gaining 20kgs (44lbs), moving to a new minimum weight of 1300kgs (2866lbs), making it equal with the SRT Viper for the heaviest GTD car in the class. Audi’s R8 also gets an extra 20kgs (44lbs), landing at 1290kgs (2844lbs) for its Rolex 24 runner-up.

IMSA’s efforts to slow the GTD Ferraris and Audis continues in the sonic air restrictor department, with the Prancing Horses getting a notable drop of 5mm with each restrictor (from 2X50.5 to 2X45.5), and a loss of 2mm for each restrictor (from 2X42mm to 2X40mm) for the Four Rings.

As promised, IMSA has also reset rear wing locations for GTD cars, requiring each team to affix the spec wing element within the same vertical and fore/aft location relative to its body. Only one rear wing wicker BoP change was made, adding 10mm to the GTD SRT Viper (an increase from 10mm to 20).