Following the FIA World Endurance Championship's transition to a winter calendar in 2018, IMSA announced it would extend the homologation periods for LMP2, DPi, and GTE-spec machinery in the WeatherTech SportsCar Championship by an additional year, making DPi and LMP2 cars eligible until at least the end of 2021. Despite manufacturer calls to retain the DPi platform, IMSA president Scott Atherton announced that IMSA was looking beyond a further extension.
On May 6, 2019, IMSA announced DPi 2.0 — a next-generation DPi ruleset built on the existing LMP2-based platform and featuring hybrid technology from a single supplier. IMSA's VP of Competition Simon Hodgson stated that the regulations would allow manufacturers more scope to add styling cues, potentially with minimum styling requirements. Discussions with manufacturers revealed differing opinions over electrification levels; a 400-volt system providing 70–90 kW (90–120 hp) of electric power emerged as the leading option, though no consensus was reached.
Following the 2019 "Super Sebring" weekend — where the 2019 12 Hours of Sebring and the inaugural 1000 Miles of Sebring were held on the same weekend — WEC CEO Gerard Neveu revealed the possibility of DPi integration into the Hypercar regulations. Active efforts were undertaken between the ACO and IMSA technical departments to align performance targets between Hypercar and DPi 2.0.
Toyota stated it would be open to DPi integration into the WEC top class, provided it did not hinder display of their hybrid technology. McLaren Racing CEO Zak Brown stated that a LMH programme was unviable for McLaren and called for DPi to be brought into the WEC. Ford and Porsche expressed similar views. Toyota Racing Development president David Wilson stated in January 2020 that convergence would serve as a compelling reason for Lexus to launch a DPi programme.
On January 24, 2020, at a joint ACO and IMSA press conference at Daytona International Speedway, LMDh was announced as the set of regulations intended to supersede the existing DPi class in IMSA and converge with the incoming Le Mans Hypercar regulations, allowing both LMH and LMDh entries to compete in the top class in both the WEC and IMSA.
Initial plans for manufacturers to build their own hybrid systems were scrapped in favour of a spec 50 kW (67 hp) system. The draft regulations specified: car weight of 1,030 kg (2,270 lb); peak combined power of 500 kW (670 hp) from engine and hybrid system; a single bodywork package; a single tyre supplier; and a global Balance of Performance system to equalize LMDh and LMH cars. The gearbox hybrid system is supplied by Xtrac, with an integrated motor generator unit from Bosch and batteries from Williams Advanced Engineering. Chassis suppliers are Dallara, Ligier, Multimatic, and Oreca.
In January 2022, IMSA confirmed the class name would be GTP, in reference to the 1980s category of the same name.
The class debuted in IMSA at the 2023 24 Hours of Daytona. LMDh entries comprised the entirety of the GTP class in 2023 and 2024, racing alongside an LMH entry for the first time only with the introduction of the Aston Martin Valkyrie AMR-LMH for the 12 Hours of Sebring in 2025.
The FIA WEC introduced the Hypercar class in 2021; LMDh cars first competed there in 2023, joining LMH cars from Toyota, Glickenhaus, and latterly Peugeot, alongside an Oreca-built LMP1 car operated by Alpine in its first two WEC seasons.
In 2025 it was announced that the Hypercar class would be allowed to participate in the Asian Le Mans Series with customer teams and Pro/Am lineups, making LMDh vehicles eligible for the AsLMS starting from the 2026/27 season.
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