IMSA has released the Balance of Performance tables for the Mobil 1 Twelve Hours of Sebring, and compared to the configurations for the Rolex 24 at Daytona, the tables for Sebring include changes to every car in the GTP and GTD fields. The Sebring BoP tables are the result of a revised process after a new method of determining BoP for the GTD PRO and GTD classes was attempted at Daytona.
To better adjust new cars, and also to have a better Balance of Performance as the GTD cars switched to a new Michelin tire, IMSA conducted tests following the IMSA-sanctioned test at Daytona International Speedway in December. Working with the manufacturers, a representative car from each OEM was observed in a set of specific exercises to determine the BoP for the Rolex 24 at Daytona. However, Daytona being a unique circuit among IMSA WeatherTech SportsCar Championship tracks, and without the opportunity to conduct a similar test at Sebring or elsewhere, the decision was made for IMSA to take more control of the BoP process going forward.
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“We’ve looked at some of what happened in the race, we looked at some of the data on the new tires from the race, and we’ve then worked with the OEMs on further evolution of the Balance of Performance process going into Sebring,” explained Matt Kurdock, IMSA’s senior technical director. “So we were able to leverage not only data from some select events in 2023, on cars that have returning year over year, but really have relied on data from the 24 hours of racing on the new Pilot Sport Pro tire, and particularly with the three new car models – the Corvette, the Mustang, and the Aston Martin Evo.
“We concluded a technical working group yesterday with the OEMs, discussing the process, discussing the performance targets for Sebring, and the OEMs felt that carrying on in a manner where working towards the common performance targets would prove to be difficult, particularly as there is no opportunity to conduct a Sebring sanctioned test. So what we’ve done is IMSA has taken some of the 2023 data in combination with some of the Rolex 24 data, and has since devised a BoP solution for Sebring that basically is a combination of those sources of data available with trying to hit a common performance target for the GTD and GTD PRO classes for the Sebring event.”
Although the Daytona process seemed to work to a degree, IMSA issued penalties to two manufacturers, Ferrari and BMW, for exceeding the performance targets during the race. That included loss of all manufacturer points and $25,000 fines. Both the BMW M4 GT3 and Ferrari 296 GT3 see a reduction in boost and power for Sebring, as well as additional weight.
Kurdock noted that no additional tests like the one conducted at Daytona are planned, although the series may consider a post-season test at a track more representative of the majority of the circuits on the calendar. Absent such tests, the series will continue to rely on data from prior events to continue refining the BoP process.
“The message I’ve tried to reinforce the manufacturers is, five years ago, I was on their side of the table,” said IMSA President John Doonan, who came to IMSA after a long stint running Mazda Motorsports. “I haven’t forgotten what it was like from my perspective. and I’ve also learned a tremendous amount internally at IMSA, since arriving, of how truly challenging the BoP process is. We’ve learned a lot and starting last August, led by Simon Hodgson, Matt Kurdock, Bill Pearson, John Strudel, we embarked on a new journey with the manufacturers of a more collaborative, transparent and open BoP process. And that’s where we landed going into Daytona. But things evolve and continue to evolve in a positive way. And I think, based on the feedback since Daytona, from the OEM technical working group, our learnings, our data analysis… Sebring perhaps opens up Chapter 2, for lack of a better term.”
Most of the GT3 cars receive a bump in power from Daytona, the exception being the Lexus RC F GT3, although it also receives a weight reduction. The Ford Mustang GT3 also receives a weight break, but no change in engine air intake restrictor size. The biggest change for the GT cars is for the Porsche 911 GT3 R, which gets 3.5mm larger restrictors for about a 19kW boost in power, but the car will also carry 35kg more weight.
The weight variance in GTP cars is greatly reduced from Daytona, with a 30kg swing from lightest (BMW M Hybrid V8) to heaviest (Cadillac V-Series.R). Maximum power ranges from 506kW for the BMW to 520 for the Cadillac. The new Lamborghini SC63 is set at 1044kg and 513kW maximum power.