Following the successive exits of Audi and Porsche from the FIA World Endurance Championship at the end of the 2016 and 2017 seasons — triggered by the Volkswagen emissions scandal affecting the Volkswagen Group, parent company of both manufacturers — and spiralling costs in the LMP1 Hybrid sub-category, the ACO began discussions aimed at reducing competition costs for the next generation of LMP1 rules.
Initial plans involved a single, low-power hybrid system and a shared platform with IMSA. A customer hybrid powertrain was considered for small-volume manufacturers and privateers, potentially replacing the Daytona prototype International (DPi) at the top of the WeatherTech SportsCar Championship in 2022. This would have enabled unified competition in the "triple crown" of endurance racing — the 24 Hours of Daytona, the 24 Hours of Le Mans, and the 12 Hours of Sebring. A renaming of the category was later suggested by FIA President Jean Todt.
In June 2018, ahead of the 2018 24 Hours of Le Mans, the FIA confirmed that the new top-level prototype regulations would feature design concepts based on hypercars. A summary was presented to the FIA World Motor Sport Council in Manila. Toyota, Ford, McLaren, Aston Martin, and Ferrari were revealed to have participated in roundtable meetings, with a targeted full-season budget of around 25 million euros — 75% lower than existing LMP1 manufacturer budgets.
At the 2018 24 Hours of Le Mans, initial details were announced at the ACO's annual press conference, with regulations set to be active for five seasons. Engine architecture would be free — turbocharged or naturally aspirated, any number of cylinders. Cars would weigh 980 kg with controlled weight distribution and a defined maximum fuel flow. A fixed 200 kW (270 hp) electric motor mounted on the front axle would provide four-wheel drive, with the combustion engine targeting 520 kW (700 hp). Each car would have two seats, a larger cockpit than contemporary LMP1 cars, a wider windscreen, and a roofline more consistent with road cars. A target lap time of 3:20 was set.
Scuderia Cameron Glickenhaus became the first manufacturer to officially indicate participation, on 25 July 2018, releasing images of a prototype planned for Le Mans and offering a limited run of 25 road-legal versions to fund the programme. By the end of 2018, Glickenhaus remained the only committed manufacturer. McLaren announced on 21 October 2018 that it would not participate in the first year, citing tight timelines and the fluid state of the regulations.
On 5 December 2018, the FIA published the technical rulebook, mandating production-based powertrains. Manufacturers were required to produce a minimum of 25 road cars fitted with the combustion engine and energy recovery system (ERS) of the race car by the end of their first season, rising to 100 by the end of their second. Non-OEM constructors such as Oreca, Onroak Automotive, and Dallara were therefore not permitted to build hypercars. The regulations called for a total maximum power output of 785 hp (585 kW), with the electric component limited to 200 kW. Diesel power was banned. A 3 million euro ($3.4 million US) cost cap was set on ERS supply to customer teams, and an ERS manufacturer was prohibited from supplying more than three competitors without FIA approval. Minimum weight was raised to 1,040 kg (2,290 lb); maximum length was set at 5,000 mm (200 in).
On 7 March 2019, the FIA adjusted the criteria to permit race cars derived from road-going hypercars, after manufacturers cited budgetary and platform availability concerns. The target lap time was increased from 3:20 to 3:30, and movable aerodynamic devices were removed due to cost concerns.
At the press conference held the Friday before the 2019 24 Hours of Le Mans (14 June 2019), the full technical regulations were unveiled alongside confirmation that Toyota Gazoo Racing and Aston Martin Racing had committed to the inaugural season. Aston Martin confirmed the use of the Valkyrie road car as the basis for its hypercar; Toyota hinted at the GR Super Sport concept. Both would join Glickenhaus and ByKolles Racing for the opening races.
On 19 February 2020, Aston Martin announced it was postponing its LMH project following the announcement of the joint ACO-IMSA Le Mans Daytona h (LMDh) rules and the company's plan to re-join Formula One in 2021.
On 11 May 2020, the FIA approved changes reducing the maximum power output from 585 kW (784 hp) to 500 kW (670 hp) and minimum weight from 1,100 kg to 1,030 kg (2,270 lb).
In 2021, just days after Peugeot revealed the 9X8 Hypercar, IMSA and the ACO announced a convergence of their respective sports prototype rulesets into a single unified class. The class is named Hypercar in the FIA World Endurance Championship and Grand Touring Prototype (GTP) in the IMSA SportsCar Championship. From 2023, LMH and LMDh cars have been able to compete in both North American and world championships simultaneously — a level of commonality between Europe and America not seen in top-level sportscar racing for several decades.
In 2025, it was announced that the Hypercar class would be permitted to participate in the Asian Le Mans Series with customer teams and Pro/Am lineups, beginning from the 2026/27 season.
The frontal surface area of an LMH car may not be below 1.6 m². Bodywork must not reveal mechanical components unless explicitly authorised by the regulations or if consistent with the original car design. Movable aerodynamic elements are prohibited.
Only four-stroke petrol engines are permitted. For production-based engines, the block and head castings must come from the base engine (though they may be slightly altered via machining or addition of material); the crankshaft may be a maximum of 10% lighter; valve angles, number of camshafts, and location of camshafts must remain as on the original engine.
For cars using an energy recovery hybrid system, deployment speed is set in the Balance of Performance table. The electrical DC power of the motor-generator unit (MGU-K) must not exceed 200 kW. Outside the pit lane, the MGU-K may only apply positive torque to the front wheels when the car reaches or exceeds the speed threshold set in the BoP table, or when it falls and remains below that threshold until reaching the pits.
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