When the regulations for the new top-tier LMDh / GTP class cars were announced, they were confirmed to be for a new generation of hybrid car. After the eye-watering budgets of hybrid LMP1 cars, LMDh was designed to provide manufacturers with a low-cost alternative, while still meeting their requirement for a hybrid prototype.
The cars are based on what governing bodies hope will become the new LMP2 chassis. The hybrid system is spec across all cars, comprising an Xtrac gearbox, Bosch MGU and WAE-supplied battery.
However, while the cars are homologated for five years, drastically reducing the need for hardware development, there is complexity for the LMDh manufacturers in that the choice of electronic software that manages the power delivery is open, and less regulated than other comparable racing series. In short, this is the single biggest area of development for the category, and California-based HPD, which also designed and built a brand new, 2.4-litre, twin-turbo, V6 engine for the new era, has hit the ground running.
Development path
With the choice and programming of the engine control unit left up to the manufacturers, HPD made the decision to select the McLaren TAG-320 ECU, similar to that used as a spec controller in Formula 1 (the hardware is the same across both categories, though the software is unique to sportscar racing). Getting that coding right can mean the difference between the entire system working or failing, as well as providing scope for performance gains.
Having finished first and second at the 2023 Daytona 24 hours, it’s clear HPD had got it right, particularly given the amount of development needed since the test at the Florida circuit just over a month before the race itself. In this article, HPD’s head of vehicle dynamics, Benjamin Schmitt, runs through the trials and tribulations of developing the system, what it is capable of, and how much more there is still to come.
The LMDh hybrid system has been described in some media as low power, as it can only provide a maximum of 200kW by regulation. It is not used to increase the overall power, which is defined by regulation, so instead it replaces
