Inside the spec hybrid spine of LMDh cars

BMW will race its M Hybrid V8 in the IMSA SportsCar Championship next year and the World Endurance Championship from 2024. Project leader Maurizio Leschiutta shares the workings of the spec, rear-axle-mounted LMDh hybrid kit

Inside the spec hybrid spine of LMDh cars

Cars built to the LMDh ruleset that replaces the IMSA SportsCar Championship’s Daytona Prototype international class next year will be eligible to race in the World Endurance Championship’s Hypercar class against bespoke Le Mans Hypercars (LMH).

LMDh manufacturers must incorporate a spec hybrid system that produces 50kW (67 horsepower) into their powertrain package, which can produce a maximum power output between 480 and 520kW. This forms a core part of the car’s so-called spine – all LMDh cars are based on LMP2 chassis.

BMW will race in IMSA’s GTP class next year, where it will go up against Acura, Cadillac and Porsche, before the Munich manufacturer’s Dallara-based M Hybrid V8 makes its WEC debut in 2024. It will be joined by Alpine and Lamborghini, with Cadillac and Porsche taking the plunge on the world stage from next season.

PLUS: The long road to convergence for sportscar racing's new golden age

Speaking to Autosport, BMW’s LMDh project leader Maurizio Leschiutta shares the workings of the rear-axle-mounted kit.

Battery

Williams Advanced Engineering supplies the battery, which can provide up to 50kW (67 horsepower) of continuous power and has a regen capacity of 170kW. As this contributes towards only a modest element of the drivetrain’s maximum power output, which must fall within the range of 480 and 520kW, Leschiutta says it is “a moderate hybrid” but believes it has been pitched right for the class’s low-cost and performance-balanced mantra.

“The requirements are modest and the battery can be reasonably small, also because it has to be packaged within an LMP2 cockpit and there’s not a lot of space,” he says. “It’s an excellent compromise and from this point of view I think the Williams battery gets the job done.”

Connor De Phillippi, Marco Wittmann, BMW M Team RLL BMW M Hybrid V8

Connor De Phillippi, Marco Wittmann, BMW M Team RLL BMW M Hybrid V8

Photo by: Andreas Beil

Gearbox

Xtrac’s P1359 gearbox is a seven-speed transverse arrangement that counts the MGU as a fully integrated component and has a maximum power capability of 585kW.

Manufacturer-specific gear clusters, hybrid drive gears and ratios have to be homologated to accommodate the many different approaches to engine architecture taken by manufacturers, and the varying power displacement and torque curves that entails.

It may have been specially developed for the LMDh class, but the ’box uses Xtrac’s P1254 integrated valve actuator (IVA) gearchange system, which Leschiutta says is “a fairly conventional and known technology”. The British company has previously collaborated with BMW on its DTM title-winning M4 GT3.

“We work with them well,” Leschiutta says. Excluding the MGU, the package weighs 78kg.

Electric Motor

Bosch supplies the motor generator unit, inverter and is also the integration manager for the entire hybrid system. This includes the brake-by-wire, which cannot be overlooked as manufacturers work out how to deploy the hybrid energy most effectively. Control will be shared by the ECU, developed by the manufacturers, and Bosch’s vehicle control unit – whose configuration, software and settings are not accessible by teams.

Insight: What the brave new world of LMDh really looks like on track

“The electronic braking system is a contribution of the hybrid system to the rear-axle braking, [allowing drivers] to move the brake-bias migration,” says Leschiutta, “so there are a lot of things that you can develop. The key is to integrate these two systems. You have a purely hydraulic system that controls the front brakes and partially controls rear brakes, coupled with an electric motor which is contributing to the rear brake torque, so you want the driver to have a very linear feeling of what’s going on.”

The MGU drives through a gear train homologated for each engine and will perform the same regardless of engine type. To Leschiutta, this baked-in parity is “a key attraction of a spec system for this category”.

Andreas Roos, Head of BMW Motorsport M, Maurizio Leschiutta, Poject manager BMW M Hybrid V8

Andreas Roos, Head of BMW Motorsport M, Maurizio Leschiutta, Poject manager BMW M Hybrid V8

Photo by: BMW

Packaging, reliability and supply

The uniformity of the hybrid system means all LMDh manufacturers start from the same point on packaging, but their cooling requirements will differ depending on styling priorities. BMW has expertise in fully electric powertrains from racing in Formula E, but Leschiutta says applying this to a system linked to an internal combustion engine “was partially new to us”. However, he says “we haven’t had any major setbacks” in its software development.

The hybrid kit has been running since the start of the year with Porsche, the most advanced of the LMDh manufacturers in its development path. But this was “a mixed blessing” for the Weissach marque, says Leschiutta, as Porsche “went through all the difficult part of getting things sorted”. BMW has experienced “a few niggling issues” with the hybrid kit, but Leschiutta has found it “a positive experience” all told, with the biggest issue resulting from supply chain delays that are impacting the entire motorsport industry.

“Your lead times are much longer than what you are used to working with maybe five or six years ago,” he says, “but you just have to work that into your planning.”

LMH or LMDh?

Leschiutta is in discussions with the organising bodies over how the equity model from convergence between LMDh and LMH manufacturers running bespoke hybrid systems will be reached. He accepts that tolerances in manufacturing and ageing of the components may conceivably mean that not all hybrid systems have the same efficiency, but is confident that BMW has chosen the right path.

“A key attraction of LMDh as a category is that it doesn’t escalate into a technological war, whereas the LMH category, which allows a lot of technical freedom to the manufacturers, could conceivably do so,” he says.

“We have a cost-effective solution which appealed to us with a very well-defined boundary condition, and the hybrid system in the LMDh car absolutely hits that target on the head. The advantage to the spec system is indeed the same for everyone. It’s just one less thing to worry about.”

#24 BMW M Team RLL, BMW M Hybrid V8, GTP: Philipp Eng, Marco Wittmann, Nick Yelloly, Sheldon Van Der Linde

#24 BMW M Team RLL, BMW M Hybrid V8, GTP: Philipp Eng, Marco Wittmann, Nick Yelloly, Sheldon Van Der Linde

Photo by: Michael L. Levitt / Motorsport Images

shares
comments

Related video

Porsche unveils driver line-ups for 2023 WEC and IMSA campaigns
Previous article

Porsche unveils driver line-ups for 2023 WEC and IMSA campaigns

Next article

Jarvis lands LMP2 drive for Daytona 24 with Era Motorsport

Jarvis lands LMP2 drive for Daytona 24 with Era Motorsport
The big question concerning IMSA's new LMDh cars on their debut Plus

The big question concerning IMSA's new LMDh cars on their debut

The new LMDh era finally begins in earnest this weekend with the IMSA SportsCar Championship curtain-raiser at Daytona. The prospect of multiple marques going all guns blazing for victory over 24 hours is a salivating one for fans of sportscar racing, but what are the chances of the new hybrid machines (known as GTP cars Stateside) proving reliable enough to win on debut?

IMSA
Jan 27, 2023
Inside BMW's long-awaited prototype racing return Plus

Inside BMW's long-awaited prototype racing return

Much like German OEM rival Porsche, BMW's absence from sportscar racing’s top flight will be ended this weekend when a pair of M Hybrid V8 prototypes make their debut in the Daytona 24 Hours. A programme focused on the IMSA SportsCar Championship for now will expand to the World Endurance Championship and Le Mans next year, in a sign of both its ambition and pragmatism

IMSA
Jan 26, 2023
How Porsche and Penske are gearing up for sportscar racing's bold new era Plus

How Porsche and Penske are gearing up for sportscar racing's bold new era

Porsche and Penske have teamed up to tackle the world's biggest sportscar races in 2023 with the new 963 LMDh car. Autosport was on hand at the recent Daytona test to hear from key players in the partnership as it prepares for dual campaigns across the IMSA SportsCar Championship and World Endurance Championship

IMSA
Jan 5, 2023
The plug in and play stand-ins who got their timing just right Plus

The plug in and play stand-ins who got their timing just right

Nyck de Vries’s Italian GP exploits weren’t the first post-eleventh-hour call-up in motorsport history, and won’t be the last either. Here are some offbeat tales from the past

General
Dec 26, 2022
The long road to convergence for sportscar racing's new golden age Plus

The long road to convergence for sportscar racing's new golden age

The organisers of the World Endurance Championship and IMSA SportsCar Championship worked together to devise the popular new LMDh rule set. But to turn it from an idea into reality, some serious compromises were involved - both from the prospective LMDh entrants and those with existing Le Mans Hypercar projects...

IMSA
Nov 25, 2022
How Porsche's Le Mans legend changed the game Plus

How Porsche's Le Mans legend changed the game

The 956 set the bar at the dawn of Group C 40 years ago, and that mark only rose higher through the 1980s, both in the world championship and in the US. It and its successor, the longer-wheelbase 962, were voted as Autosport's greatest sportscar in 2020 - here's why

WEC
Aug 25, 2022
Why BMW shouldn't be overlooked on its return to prototypes Plus

Why BMW shouldn't be overlooked on its return to prototypes

OPINION: While the focus has been on the exciting prospect of Ferrari vs Porsche at the Le Mans 24 Hours next year, BMW’s factory return to endurance racing should not be ignored. It won't be at the French classic next year as it focuses efforts on the IMSA SportsCar Championship, but could be a dark horse in 2024 when it returns to La Sarthe with the crack WRT squad

Le Mans
Aug 21, 2022
The British pair at the heart of Lexus's IMSA push Plus

The British pair at the heart of Lexus's IMSA push

Have you heard the one about two northerners driving for a Japanese manufacturer in America’s top sportscar series? Time to sit down and talk with Jack Hawksworth and Ben Barnicoat about racing across the pond… and your accent being mistaken for Australian

IMSA
Mar 16, 2022