Developmental History
On July 2, 2015, IMSA announced the base regulations for the new Prototype class, intended to succeed both the Gen 3 Daytona Prototypes and the Le Mans Prototype LMP2 class. These regulations restricted areas where custom manufacturer bodywork was permitted, requiring the use of base prototype parts. Specifically, restrictions were placed on the rear wing, rear wing mounts, engine cover fin, the underside of the car (splitter, floor, and diffuser), and the area directly behind the front tyres. Development of wing profiles was also prohibited.
The regulations called for the use of production-based engines, with targeted engine weights and maximum displacements. Turbocharging was permitted for 4 and 6-cylinder engines, while naturally aspirated engines would utilize sonic air restrictors. Turbocharged engines would operate without restrictors, with boost levels RPM-based to balance performance.
On October 1, 2015, IMSA confirmed engine and bodywork guidelines and announced the class name – Daytona Prototype International. Homologation was initially planned for a minimum of four years, from 2017 through 2020, to allow competitors to maximize their investments. To ensure performance parity, IMSA announced a Balance of Performance (BoP) system for both DPi and LMP2 specifications.
IMSA Director of Racing Platforms, Mark Raffauf, confirmed on January 11, 2016, that each manufacturer would be required to commit to both an engine and bodywork package, forming an alliance with a selected chassis manufacturer. This differed from the previous DP formula, which allowed bodywork interchangeability. Manufacturers were permitted to make changes to bodywork appearance or debut new engines and branding, subject to IMSA approval and homologation. Factory teams were allowed, and manufacturers were not required to sell chassis to customers.
The homologation periods for DPi, LMP2, and GTE-spec machinery were extended by a year on January 24, 2018, due to changes to the FIA World Endurance Championship calendar. This extended DPi eligibility through at least the end of the 2021 season, originally scheduled for 2020. Further extension in 2020 allowed DPi cars to compete until the end of 2022, due to delays in the development of LMDh cars caused by the COVID pandemic.
Competition at Le Mans
Initial plans considered allowing DPi cars to compete at Le Mans in the LMP2 class, outfitted with standard LMP2 bodywork and balanced via the ACO’s Balance of Performance process, controlled through the Engine Control Unit (ECU). However, changes to IMSA regulations, including the removal of the spec Cosworth ECU and other data logging systems, led to disapproval from ACO President Pierre Fillon. Consequently, DPi cars became ineligible for LMP2 competition at Le Mans, and attempts to place them in the LMP1 Privateer class were unsuccessful.