Something that appeared to be all but impossible will become reality in 2023 when IMSA allows the FIA World Endurance Championship’s LMH prototypes to compete against its brand-new LMDh models in the WeatherTech SportsCar Championship.

The agreement, ratified on Thursday in Paris through the FIA’s World Motorsport Council, formalizes the behind-the-scenes work conducted by both sanctioning bodies and the ACO in recent months to create a Balance of Performance structure capable of corralling the high-tech LMH cars that made their debut in May.

“What we achieved as a group a few weeks ago in Paris has the potential to revolutionize prototype sports car racing all over the world,” said IMSA President John Doonan. “The stage is set for a highly competitive top category that will include many of the world’s greatest automotive manufacturers, showcasing relevant technology in the world’s most prestigious endurance races. Collectively, we have an opportunity to engage with the next generation of endurance sports car racing fans and elevate our sport to the highest levels. I cannot be prouder of the spirit of collaboration between our IMSA team, our colleagues at the ACO and FIA, and all of our automotive partners.”

Prior to the new accord, there was no expectation for the WEC’s costly LMH models made by Toyota, Peugeot (pictured, top), Ferrari, and Scuderia Cameron Glickenhaus to be given entry to the WeatherTech Championship prior to 2024 or 2025. With its new LMDhs in the pipeline for 2023, IMSA held firm to plans to develop its rear-wheel-drive prototypes featuring spec 40hp KERS units for a year or more before allowing the RWD and all-wheel-drive hybrid LMHs to intermingle in North America.

In the WEC, LMHs have exceptional freedom to use far more powerful KERS units, and to run with wider front tires to handle the output; in IMSA, its LMDhs must channel the modest KERS boost through the rear tires and use narrower fronts. Of the four current or future LMH models, three — excluding the SCG 007 — are committed to AWD and hybrid power. Acura, Audi, BMW, Cadillac, and Porsche are the five known LMDh manufacturers preparing LMDh models for 2023, with one or two more anticipated for 2023 or 2024.

The 2023 Rolex 24 At Daytona will mark a fresh start for IMSA and international sports car racing. Michael Levitt/Motorsport Images

Under the new pact, LMHs are welcome to compete against LMDhs from the opening WeatherTech Championship round in January of 2023, the Rolex 24 At Daytona, where a custom BoP will be applied to the WEC cars as LMH and LMDh vie for the overall win in the same class.

“This major announcement stems from our ambition to forge a common future for endurance racing,” said ACO President Pierre Fillon, whose organization runs the 24 Hours of Le Mans. “We have all worked together to achieve this landmark agreement and I would like to thank all the stakeholders very sincerely. It is wonderful news for teams and fans alike and maps out a bright future for endurance.”

The attempt to create parity will come from four directives, with one key BoP measure for LMH. The first will see all models restricted to reaching a high minimum speed before hybrid AWD power can be sent to the front tires. That minimum speed BoP number will be tailored to each circuit in an effort to prevent those LMH models from drastically outperforming the LMDhs under acceleration. Depending on the IMSA circuit, the anticipated range of LMH KERS activation is 74.6 to 99.4mph.

The second BoP measure is to uncouple the front differential linking the left and right KERS motor generator units under braking. Left connected, it would offer a notable deceleration advantage to the hybrid LMHs. Tire sizing and aerodynamic benchmarking were also outlined in the ratification of convergence.

RACER understands two technical working groups were formed to propose BoP concepts that would allow for convergence. Split into AWD and RWD teams, manufacturers submitted their collective suggestions from each group, with RWD’s ideas being chosen as the path to follow in the details represented below:

Acceleration

• As there are wide-ranging options for how much KERS powers AWD LMHs can generate, each model will have custom BoP settings that dictate the speeds where KERS power can be unleashed at each circuit. Two KERS BoP strategies will be created for LMHs at every track, with minimum activation speeds set for wet and dry conditions. The aforementioned estimation for those activation ranges fall between 120 and 160 kph (74.6-99.4mph).

• The only guideline for the RWD LMDh models is to use software to limit the MGUs from being acting as a form of traction control.

Aerodynamics

• A shared aero evaluation program was agreed upon that will see LMHs continue to be tested at Sauber’s wind tunnel in Switzerland. For LMHs that will be raced in IMSA, the same aero testing must be performed at North Carolina’s WindShear.

• The same process applies to all LMDhs, which must be benchmarked at WindShear to race in IMSA, and for LMDhs headed to the WEC, trips to Sauber for aero testing is a must.

Braking

• The plan is to equalize the function of differentials for AWD and RWD models while coasting, which speaks to the efforts to equalize braking capabilities, but also involves zeroing any advantages that might be had in turning while coasting.

• AWD LMHs with single or dual MGUs will function without locking while coasting and will be monitored by the sanctioning bodies to ensure compliance is being met.

Tires

• AWD LMHs cars will use four identical 31-centimeter-wide Michelin slicks. RWD LMHs and LMDhs will use slick 29-centimeter-wide fronts and 34-centimeter-wide rears from Michelin.