Insight: The Unseen Battleground in LMDh's Spec Ruleset

Sportscar365 explores how Porsche works with lubricant partner Mobil 1 to extract the maximum from a spec gearbox…

Even though we’re still very much in the middle of the LMDh era of global sports car racing, it’s already safe to say that this ruleset will go down in history as one of the great success stories of the sport. It brought two governing bodies together in partnership and resulted in a boost in manufacturer racing that has arguably never been seen before.

The list of brands that have flocked to LMDh since it was first announced in January 2020 is as long as it is impressive. Early adopters Acura, BMW, Cadillac and Porsche were later joined by Lamborghini and Alpine, with the likes of Genesis, McLaren and Ford still to arrive in the coming years.

One of the core tenets of the LMDh ruleset has been the introduction of off-the-shelf components, with Bosch supplying the hybrid system, Fortescue (formerly Williams Advanced Engineering) providing the batteries, while every LMDh car has an identical Xtrac gearbox.

Because the gearbox is a spec unit, there is effectively no development that each manufacturer can do on their own. Parity isn’t just a target, it’s written into the rules.

However, that does not include one key differentiator where teams can make their own decisions: the gearbox oil. Each LMDh manufacturer usually has a dedicated lubricants partner as part of its program, often visible through branding on the car.

BMW has Shell, while Alpine is partnered with Elf. Porsche and Cadillac, meanwhile, both work alongside Mobil 1. Through working with these lubricant firms, each manufacturer will seek to gain its own advantages and gain as much of an edge on the competition as the spec LMDh ruleset allows.

To find out how exactly a choice of gearbox lubricant can impact a team’s performance, Sportscar365 went behind the scenes with Porsche Penske Motorsport and Mobil 1 to discuss the application of gearbox oil in the Porsche 963.

As Stefan Moser, Porsche LMDh technical director, points out, the development of lubricants for the gearbox is a key area of focus simply because the spec ruleset prevents development in other areas.

“That basically means if you want to improve something, you have to work with the parameters that you have in your hands,” says Moser. “With Mobil 1 we can work together on the oil, but we can’t change anything in the gearbox. Whatever we want to adjust, whatever we feel we have to adjust, we have to do it [via] the oil.”

The question then becomes: what areas of improvement do you pursue the most? What metric is then most actively targeted by manufacturers and lubricants partners alike?

“We are most interested in preventing gearbox wear,” says Moser. “We are doing long endurance racing and running 24 hours, and of course, we want to have constant efficiency from the gearbox. The oil is a very important factor in this one and we have to take care of friction. That is the most important stuff.

“The way the rules are written, the power is controlled due to the torque sensors. You don’t gain power if you find something [to help with] friction with this set of rules. But usually [when] we find something [with] friction it also helps in terms of wear. Those two things usually go hand in hand.

“Basically whenever we get a better oil, then it gives us better friction and then we usually also gain something in terms of long term durability. On top of that there is less of a cooling requirement and that is definitely [good].

“As we said before, 24 hours, that means in the night you have colder conditions as during the day. So the condition changes quite significantly compared to every other race series. And so we are looking for oil which is very constant about different temperatures and stuff. Compared to other race series, for us it's an important factor.”

Moser hints that Porsche has found a clever way of measuring the temperature of the transmission lubricant.

“On our car, the gearbox oil is actually fed into the hybrid coolant system and there is a thermostat,” he says. “For us, due to this concept it’s pretty easy to have that same constant temperature because of thermostat control.”

Ultimately, the end goal for Porsche is to reduce the amount of gearbox rebuilds it will be required to carry out through a FIA World Endurance Championship or IMSA WeatherTech SportsCar Championship season. After all, better durability means a greater chance that a gearbox will be able to go the distance.

“The gearbox is actually designed to do one entire season,” says Moser. “But you never show up on a race track without a spare gearbox. That the gearbox is capable of doing an entire season doesn't mean you only have one.

“On top of that, when you say you use a gearbox for one season, there are rebuilds in between and when you rebuild the gearbox you have to have another one to run the car and because it will take some time.”

Mobil 1’s Tobias Klande, who works as an expert in powertrain and thermal management fluids, has collaborated with Porsche on a number of projects including the brand’s Formula E program as well as customer racing and its all-electric GT4 E-Performance.

When it comes to developing the gearbox lubricants for the 963, he explains that comes as part of a process in which the two sides work largely side-by-side.

“Teams like Porsche kind of tell you what you have to develop," says Klande. “Depending on the specifications, you just start building together with the partner on those specifications. And then specific testing is carried out, typically bench testing and track testing.

“We are making sure to supply the oil in the quality that is needed, and then closely working together to see if it's working or not.”

This is part of what Klande describes as a “fail fast approach” to the development process.

“If it's not working, then think of something else and do it over,” he says. “This is basically very important to ensure that everything is working well and the [gearbox] can go longer, can perform and gives the right efficiency, durability.

“This is always the question: have the right compromise between efficiency, durability and also, I would say, consistency in certain spec parts.”

Porsche is not the only manufacturer to make use of Mobil 1 products, as Hypercar rivals Toyota and Cadillac are also partnered with the company.

Klande, who specifically only works on Porsche projects, explained that there is an ‘internal firewall’ in place to avoid any crossover of information between manufacturers.

“I don’t know what [other teams] are doing,” he says. “We formulate for one team, for one strategy. It could be that other teams maybe use different strategies, who knows There could be a certain overlap. But I think unless the teams are not using a commercial product from somewhere, then there's at least some tweaks you do to get this extra percent of performance to help the team achieve the victory.

“One thing is also clear: you can not wait. Because if you wait then the competition will come up with better solutions. If you stand still, then you will lose the battle.”

Gearbox lubrication might not be something you immediately think about when it comes to an area of development. After all, unless something goes very wrong, you’ll hardly ever see it. But in an arena as competitive as the LMDh ruleset, every small detail could make the difference between winning and losing.

Photos: DPPI, MPS Agency & Porsche