DAYTONA BEACH, Fla. – One primary challenge is faced by all four manufacturers preparing cars for the new Grand Touring Prototype (GTP) class: How to match a spec hybrid system to each manufacturer’s engine.
Sounds basic, but it’s far from it. Each of the manufacturers set to join the new GTP class when the 2023 IMSA WeatherTech SportsCar Championship season opens in January has begun the complicated process of marrying their individual powerplants to the uniform hybrid system.
In doing so, Acura, BMW, Cadillac and Porsche (with Lamborghini to join in 2024) are sharing certain details of their systems with each other while keeping other aspects of the process to themselves.
“We are working together,” said Laura Wontrop Klauser, GM’s sports car racing program manager overseeing development of the Cadillac V-LMDh. “Not so much that we’re helping tune each other’s cars, but there is a lot of alignment for handling all the things that this post-pandemic world has thrown at us from parts supply shipping and other things. We are keeping dibs on each other in terms of ‘How are you doing? Can you make it to the test? Can we share resources? Can we talk to the supplier to send us whatever it is and see if they can bundle it?’ I have a good feel just from that open communication on how everyone is doing.”
The LMDh cars in the GTP class use two types of power – the traditional internal combustion engine (ICE) unique to each manufacturer and an electric motor generator unit (MGU) that’s the same for all competitors. The MGU system harvests and stores kinetic energy generated in the car’s braking and stores it to batteries. The stored energy is then deployed as propulsion energy during acceleration.
While they’re watching and sharing during early test sessions, engineers from manufacturers and teams are focused on refining their own engine-to-generator match while adapting to other elements, including braking systems.
“The way the regulations are set up, as long as each of us gets our cars right and fit into the rules that we’re supposed to be in, we’re inherently going to be very close from a performance perspective,” Klauser said. “It’s a bigger picture concern with what is going on with the competitors and mainly how we can help each other. I think it will be pretty wild when you see us start racing. It should be a great show.”
The first step toward that show belongs to the hybrid powertrain, which consists of a common Xtrac gearbox that utilizes a motor generator unit (MGU) and control electronics supplied by Bosch. The harvested energy is stored in a battery pack developed by Williams Advanced Engineering.
“It’s probably the most exciting part – all of the opportunities,” Klauser said. “We can drive the car in electric mode. We can launch it, so you can see the true hybrid coming out. Where we evolve and how that works from the fuel economy standpoint versus other usefulness of having an electric motor on the car is what is going to make the class interesting.”
The Xtrac gearbox casing houses the electric motor, which requires liquid cooling. It is designed to fit multiple chassis and interface with different ICE configurations.
For manufacturers, the early on-track testing is assisted by computer simulations and communication across company lines.
“There is a little freedom in how we’re integrating everything and when we want to use the power coming off the hybrid versus engine power, or both or mix that,” Klauser said. “That’s where a lot of the learning is happening and working through things well past January because there is a lot to look at. There is some opportunity to have some identity from each (manufacturer’s) perspective, but they’ve done a lot of work to make sure that they keep it parity as much as they can so that we don’t end up in a situation where one car is completely off in the weeds either positively or negatively and the rest are not.”
One thing they’d all like to see: a 24-hour test to confirm the new car is ready to get through its first race – the Rolex 24 At Daytona on Jan. 28-29.
“We’d love to have it as soon as we can so we can react to what we learn,” Wontrop Klauser said. “In my perfect world, we would have done the 24-hour test in September. It’s something that we definitely need to get done before we race in January.”
Private manufacturing testing continues this fall, with an IMSA-sanctioned test for all four manufacturers set for Dec. 6-7 at Daytona International Speedway.