What is the difference between LMH and LMDh?

What an LMH car is

LMH is the FIA and ACO regulation set introduced for 2021. A manufacturer building an LMH car can design the monocoque, the engine, the front-axle hybrid system and the aerodynamic package itself. Most LMH manufacturers choose to do all of those things themselves: the Ferrari 499P, the Toyota GR010 Hybrid, the Peugeot 9X8 and the Aston Martin Valkyrie are all designed end to end inside the manufacturer.

LMH allows a hybrid system on the front axle of up to 200 kW, which the regulations cut in at speeds above 190 km/h on the way out of pit lane and again from a lower speed in race conditions. The engine architecture is free, subject to a power cap. Ferrari runs a 3.0-litre twin-turbo V6, Toyota a 3.5-litre twin-turbo V6, Peugeot a 2.6-litre twin-turbo V6, Aston Martin a 6.5-litre naturally aspirated V12, BMW a 4.0-litre twin-turbo V8.

What an LMDh car is

LMDh is a joint regulation set developed by the FIA, ACO and IMSA, introduced for 2023. An LMDh car must use one of four homologated LMP2 chassis suppliers, and must use a single common hybrid system: a Bosch motor-generator unit mated to a Williams Advanced Engineering battery and an Xtrac gearbox. The manufacturer provides the engine and the bodywork on top.

The four LMDh suppliers split the field. Porsche works with Multimatic on the 963. Cadillac and Alpine use Dallara. BMW uses Dallara. Acura uses Oreca. The Lamborghini SC63, the Genesis programme due to debut in 2026 and the Ford Mustang programme due to debut in 2027 all use a Multimatic chassis.

LMDh's main appeal is cost. A manufacturer can build a competitive Hypercar without the chassis and tub development bill that an LMH programme carries.

How they race against each other

The FIA and ACO use a calculation called Equivalence of Technology to make LMH and LMDh lap at the same pace. EoT works alongside the in-season Balance of Performance system that applies inside each platform.

EoT covers the things that the two platform regulations differ on: the maximum total energy a car can deploy across a stint, the weight floor, the power-to-weight ratio and the aerodynamic windows. Once EoT is set for an event, BoP makes the per-car adjustments inside each platform.

This system has been controversial. Critics point out that two different platform philosophies, designed years apart, are being balanced down to a fraction of a percent. The defenders of the system note that the Hypercar grid has eight manufacturers as of 2025, where the LMP1 era had two by 2018 and one by 2019.

Which has won more

Ferrari (LMH) has won every Le Mans since 2023. Toyota (LMH) won the first two Hypercar Le Mans in 2021 and 2022. No LMDh car has won Le Mans overall yet, although Porsche, Cadillac and BMW have all scored Hypercar-class race wins in the WEC season events outside Le Mans.

In the WEC manufacturers' championship the gap is closer. Toyota won the title in 2021, 2022 and 2024. Ferrari won in 2023 and 2025. Porsche, Cadillac and BMW have all scored race wins on the way through. The LMH-LMDh balance is most visible at Le Mans, where the LMH-built cars have so far had the strongest reach.

What it tells us about the future

The LMH and LMDh regulations are both signed off through 2032. That means the platform mix on the Hypercar grid is locked in for the rest of the decade, and the EoT calculation is the load-bearing piece of the WEC technical regulation. Every new manufacturer joining the class is choosing one platform or the other based on the cost-versus-flexibility trade and on the in-house engineering they want to put on the line. Genesis chose LMDh. Ford chose LMDh. McLaren has yet to announce.