LMP3 is the third tier in the Le Mans sportscar racing hierarchy, sitting below LMH / LMDh and LMP2. Since its debut in 2015, the category has been a cost-effective way to run a prototype and a stepping stone towards the bigger leagues including the 24 Hours of Le Mans.
LMP3 cars race around the world, but their main territory is in the European Le Mans Series and Le Mans Cup, both run by the category’s governing body, the ACO. Over the years, LMP3 has become known for its soundtrack: a rumbling Nissan V8 engine built by ORECA. However, next year, the song will change as the ACO introduces a new V6 twin-turbocharged Toyota unit. ORECA is again building and supplying the next-generation engines, which produce more power but come with fresh challenges.
Why has LMP3 gone turbocharged?
You can discover the full story of LMP3’s major technical change in the November 2024 issue of Racecar Engineering magazine, AVAILABLE NOW!
But the short answer is that change was needed because LMP3’s current engine, the 5.6-litre Nissan VK56, is going out of production. ORECA has enough spare parts to service LMP3 cars that won’t be using the new turbo unit next year (essentially, every series except for the ELMS and Le Mans Cup – the Asian Le Mans Series will go turbo at the end of 2025). However, VK56 parts will be thin on the ground after that. Interestingly, there are even some cars running the original Nissan VK50, which the VK56 replaced in 2020, albeit in non-competitive track day settings with private owners.
The ACO’s reasons for introducing a twin-turbo engine, rather than go like-for-like with a new naturally aspirated one, were financial and technical. The financial aspect was to keep costs as low as possible by using a production-based unit. A next-gen LMP3 powertrain costs €89,200 within the €299,000 price for a complete car. The technical aspect was that the ACO wanted to align LMP3 with current road car and motorsport technologies, as well as increase fuel and sound efficiency. ORECA successfully pitched for the LMP3 engine supply contract with the Toyota V35A, a twin-turbo engine found in several of the company’s road cars including the Lexus LS 500.
ORECA’s winning pitch
ORECA first held discussions with Nissan, considering their existing LMP3 partnership. However, none of the Japanese manufacturer’s off-the-shelf engines met the technical and timeline requirements of the LMP3 2025 project, which has a minimum duration of five years.
‘Most manufacturers are doing a V6 turbocharged engine, so there were several options,’ says Loïc Combemale, technical project director at ORECA. ‘We started to look at what the manufacturers could offer in terms of support and engine availability.’
‘We wanted to have a latest-generation engine with good efficiency, direct injection and twin-turbo. We went for this [Toyota engine] because, for us, it gives satisfaction in terms of performance and current technology. We found a very good cooperation with Toyota.’
ORECA has close ties with Toyota Gazoo Racing Europe, having supported the running of its factory LMP1 programme. The French engineering firm used that prior relationship to start discussions about using a Toyota engine for LMP3. After preliminary talks, contact is now held between ORECA and Toyota’s road car engine division in Japan. All LMP3 engines are built at ORECA’s engine facility near Magny-Cours.
How does the LMP3 engine differ from the road?
Internally, the LMP3 engine is the same as the production unit, which produces 415bhp in the Lexus LS 500. In racing trim, it achieves 470bhp, marking a 15bhp increase on its Nissan V8 predecessor.
‘We made all the necessary modifications to be able to fit in a single seater or an LMP3 car,’ says Frédéric Eymere, design office chief at ORECA. ‘That means mainly the oil system has been drastically modified. The original engine is a wet sump engine. We had to swap to a dry sump system to be able to fit it, and to have the right height for the crankshaft axis regarding the reference plane of the car. We didn’t succeed exactly because we had to raise it by 4mm, but this was one of the targets.’
ORECA’s priority was to introduce a neatly integrated engine that would be easy to service and relatively cheap to run.
‘On the system, everything on this engine is quite integrated,’ confirms Eymere. ‘On the VK56, we had to move to a complete oil pump for the dry sump system, including the scavenge and pressure stages. On this engine, we decided to keep the pressure stage and to have only an additional pump for the scavenging. That was one of the big steps.’
Integrating the engine to each LMP3 chassis – which are licensed to be built by four manufacturers – provided another challenge. The next-gen cars from ADESS, Duqueine, Ginetta and Ligier will use the same chassis as the previous 2020-2024 generation.
‘As on all the modern engines, all the fixing points are made on purpose [for the road car],’ explains Eymere. ‘So it was very difficult to find areas on which you can fix it properly on the engine. On the front of the engine, there were many water and oil circuits, and even a turbocharger air circuit. This was something we had to deal with, and it was quite a challenge.’
How is the engine integrated with the chassis?
To address this challenge, ORECA built a bracket to integrate the engine and its cooling apparatus with the monocoque. Cooling has been a big topic in the switch to turbo, for the system is more complex and heavier than before. The Nissan VK56 was cooled by a water-cooling package, whereas the Toyota V35A has a similar set-up plus an intercooler to chill the air that has been compressed by the turbocharger before it enters the engine. In the V8 era, car manufacturers could bring their own radiators to cool the engine fluid, but the turbo unit now features an ORECA-supplied heat exchanger.
‘The first step was to remove everything which was not necessary for our [race] engine,’ says Eymere. ‘We then saw what space was available for the new fixing. We had to integrate all the water piping on the front. We also decided to integrate an oil cooler, contrary to the Nissan engine which had an oil radiator. We thought it was good for everybody, including the car manufacturers, to have everything integrated on the engine. So, we put an oil cooler directly on the bracket. It is quite a complicated part and includes many functions including the water and oil cooling systems.’
A key difference between the naturally aspirated V8 and the twin-turbo V6 is the presence of an integrated exhaust manifold on the latter.
‘It means the turbocharger is directly fitted on the cylinder head,’ explains Combemale. ‘To avoid having a too hot turbocharger, you are also cooling down the integrated exhaust manifold with the engine water. Before, you had a big exhaust manifold which was cooled by the ambient air under the bonnet. Now, I would say you are taking part of this heat through the water going inside the cylinder head. This is what makes the difference compared to the VK56.’
Why a bespoke turbocharger was needed
The racing version of the Toyota VA35 has done away with the production turbocharger in favour of a bespoke racing unit developed by Japanese turbo specialist IHI.
‘We were able to make the performance [target from the ACO], that was not the issue,’ stresses Combemale. ‘But to make life easier for everyone, especially the manufacturers, we tried to be as close as possible to the VK56 in terms of performance and usage.
‘In fact, one of our targets was to keep the same gear ratio [from a retained Xtrac gearbox]. For that, we had to move the power up a bit compared to what it was with the serial one. We were a bit close to the limit of the turbocharger. To be safe, reliable and closer to the VK56 curve, we made this change.’
How has LMP3 testing gone?
ORECA first put a production version of the new LMP3 engine on its static dyno test rig in September 2023. This enabled it to gather some baseline figures. It then built up the race engines, testing the new cooling system on its dynos (in a non-manufacturer specific layout) and delivered the first units in spring 2024. However, an issue that manifested through fickle gearshifts resulted in the engines being recalled, delaying the onset of track testing to July once an engine control software patch had been introduced. ORECA did a ‘complete review’ of the cooling and engine systems, according to Combemale.
‘At the beginning, the shifting was not the best possible,’ he admits. ‘But we are not able to do shifting on the dyno. We started with shifting from the VK56 and then you improve it for this engine. You do not have the same inertia.’
Eymere adds: ‘The mechanical braking of the engine is not the same, either. There was a feeling on the braking that the engine was pushing a bit. It is a turbocharged engine with big volumes of air and pressure, so managing the engine and airflow through it was important. We first had to understand what was happening and to find a way how to solve it. This behaviour was expected at the beginning. We made a first version of software that did not allow us to modify what we wanted, after those [real-world] results. So we had to work on this. It is part of the development work.’
Despite those teething issues, which were spotted during a shakedown of the Ligier JS P325, the four car manufacturers had collectively racked up almost 8000km on track by mid-September. They have prioritised running in hot conditions to validate the cooling system. Homologation is next on the agenda, although timing is tight because cars need to crash test again due to the increased car weight caused by the new engine and cooling system. Once that has been ticked off, cars will be delivered to customers ready for racing next year, ushering in the start of LMP3’s turbocharged era.
