LMDh Tutorial: Entering IMSA’s Platinum Era


A new era of concept sports car racing will grace the high banks of Daytona International Speedway in Florida January 28-29 during the 61st Circuit of the Rolex 24 in Daytona.

America’s premier endurance race would see the return of the GTP class to the IMSA ranks, and the name was a throwback to the prototype heyday of the late 1980s and early 1990s when Porsche, Nissan, Jaguar and Toyota competed with some of the most advanced sports cars of the day.

With Porsche, Cadillac, Acura and BMW taking on each other in this year’s WeatherTech SportsCar Championship, and Lamborghini joining the GTP field in 2024, let’s dive into the new generation of IMSA’s sports concept car.

#02: Cadillac Racing, Cadillac V-LMDh, GTP: Earl Bamber, Alex Lynn, Richard Westbrook, #25: BMW M Team RLL, BMW M Hybrid V8, GTP: Jesse Krohn, Augusto Farfus, Connor De Phillippi
Chip Ganassi Racing Cadillac GTP machine in action at Daytona. (imsa photo)

Announced at Rolex 24 2020 as LMDh (Le Mans, Daytona and h not defined), the latest prototype specification aims to converge with the new LMH (Le Mans Hypercar) rules already submitted by the FIA ​​for the World Endurance Championship.

The goal is to have prototypes built to LMH’s American specifications competing on the same track against cars built to LMH’s rules.

LMDH cars will gain eligibility to race in the 24 Hours of Le Mans and the rest of FIAWEC while LMH cars can race in IMSA competition. Toyota, Ferrari, Peugeot and other LMH manufacturers will now be able to race their machines against the best cars that US regulations can provide.

In January 2022, IMSA announced that the prototype class would be renamed GTP, retaining LMDh as the name of the vehicle’s building rules for the new class, which replaces Daytona Prototype International.

LMDh regulations call for the manufacturer to design a car around a tub designed for the LMP2 class. For reference, the LMP2 class is a fixed-cost prototype class with a PRO/AM driver package. There is a single engine resource and several homogeneous chassis designs.

For LMDh, the manufacturer must design the car’s body, engine and transmission around a tub made by Oreca (partnership with Acura), Dallara (BMW and Cadillac), Multimatic (Porsche) or Ligier (Lamborghini).

While it looks very similar to the DPi, there are some changes under the surface as explained by IMSA President John Donnan.

“The intent from day one was to take what we did in the DPi and open up the airbox, if you will, from a design standpoint,” said Donnan. So allow more design in the side capsules and the tail and give the manufacturers a chance to take it to the next level with their design teams so that when you look at any of these cars, you see the brand that it represents. That’s the heart of it, that’s what it all stands for. I think in addition, the hybrid powertrain integration is something the manufacturers wanted, since we’re still a marketing platform for them, and we still need those kinds of stories to represent what they’re doing in their road car collections. A story of sustainability, and a real story at that.”

The cars will use a specific hybrid system with parts sourced from Bosch, Xtrac and Williams Advanced Engineering that will provide extra power under acceleration. While secrecy between competing manufacturers is usually at a premium, each manufacturer has been open with IMSA about hybrid system issues that emerged during testing.

#25 BMW M Team RLL, BMW M Hybrid V8 and GTP: Jesse Krohn, Augusto Farfus and Connor De Phillippi
The BMW GTP entry runs through the indoor road course at Daytona International Speedway. (imsa photo)

To prevent any type of testing from being stopped due to a problem with the hybrid system, IMSA wanted manufacturers to work together to make sure testing wasn’t interrupted due to parts shortages or reliability concerns. Manufacturers have responded to IMSA’s wishes and cooperated with each other.

“Some OEMs didn’t have a battery or an electric motor and there was a lot of involvement involved in making sure people could go out and hit the mileage on their car and install this system in their car,” said Donnan. “So you probably have one of the most historic collaborations to get the program to the right place.

“Porsche was beyond that in terms of getting the car on track, so they became your test customer, if you will. And so they had the opportunity to go outside, test any problems they had. They eventually reported to Bosch and to the other OEMs and then when it went Other OEMs are on the right track, same system, because it’s the same for everyone, it needs to work properly.”

All new mechanical systems require many miles of on-track testing to sort out any reliability concerns and every manufacturer has worked hard to get their cars as close to bulletproof as possible.

Porsche was the first manufacturer to test its new car in January 2022 at its factory test track in Weissach, Germany. Named as the successor to the highly successful 962, the 963 completed numerous test sessions at numerous tracks around the world, culminating in a 36-hour marathon test at Sebring (Fla.) Int’l Raceway. During this test, the 963 completed more than 4,500 miles on one of the most rugged circuits in sports car racing.

Porsche will have Team Penske as a factory team. The two companies notably worked together on the RS Spyder program in the American Le Mans Series. Team Penske will compete with two cars in IMSA. Porsche will also have two customer teams competing in IMSA in 2023 with JDC-Miller Motorsports and Proton Competition each having one car.

Cadillac was the most successful manufacturer during the DPi era, with three championships and dozens of endurance victories. Two teams will race the new V-LMDh machine, with Action Express Racing entering one car, and Chip Ganassi Racing entering two cars. Cadillac completed several tests with the car, including a 24-hour run at Sebring.

BMW has completed several tests in America and Europe as Rahal Letterman Lanigan Racing continues its relationship with the German brand with two BMW M Hybrid V-8s based in Zionsville, Indiana.

Acura tested its new ARX-06 in France before shipping the first car to the United States. Wayne Taylor Racing and Meyer Shank Racing would each run one car this season, but the teams had a unique situation in that they initially had to share one car for testing. Each team now has its own cars.

It is worth noting that Alpine is building a car according to LMDh regulations with the Oreca basin, but it will compete in FIAWEC. This does not mean that the car cannot appear in IMSA competition as soon as Alpine feels it is ready to compete.

Fans and manufacturers alike had hoped for years that a convergence in typical sports car regulations would allow one car to compete globally across different rule books, as it was during the ’80s and ’90s in the old GTP era.

“I think we’re giving the fans; we’re giving the automakers what they wanted and asked,” Doonan said. “And if the ’80s and early ’90s were the golden age, I think we’re entering the platinum era.”

This story appeared in the January 18th edition of SPEED SPORT Insider.

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