861 days ago Xtrac were announced as the sole gearbox supplier for the unified innovatory top-tier LMPh / GTP category for both the WeatherTech SportsCar Championship in the USA and Fédération Internationale de l’Automobile (FIA) World Endurance Championship (WEC).
A lot has happened in those 861 days that this weekend sees the GTP cars from Acura, BMW, Cadillac and Porsche compete against each other for the first time at the prestigious ‘Rolex 24 at Daytona’ 24 hour sportscar race at the Daytona International Speedway in Florida, USA.
The P1359 gearbox developed for the new LMDh regulations is a 7-speed transverse arrangement with an integrated motor-generator unit (MGU) driving into the gearbox through an optimised gear train. The integration of the hybrid system is a vital attribute of the LMDh specification. Xtrac has worked closely with the ACO, IMSA, and the two other appointed hybrid partners Bosch and Williams Advanced Engineering (WAE) to ensure that the package, function, and overall operation is optimised for cost, weight, performance, and reliability. The appointed chassis suppliers, Dallara, Oreca and Multimatic, and Ligier who’s chassis will start racing in 2024, and the OEM engine manufacturers worked collaboratively together to ensure the unified vehicle is a global success for years to come. Bosch is supplying the MGU and hybrid control system, while WAE is supplying the battery system.
“It’s a visionary hybrid transmission built on years of experience gained by operating at the highest level of motorsport, and global endurance sportscar racing,” says Xtrac chief executive Adrian Moore.
“An initial batch of fourteen P1359 transmissions were supplied in late 2021, and early 2022 for dyno and rig testing, and then initial car testing – with a 2nd interim batch of fifteen P1359 transmissions by the end of August 2022. This enabled the appointed chassis manufacturers Dallara, Mutimatic and Oreca along with the OEM engine manufactures Acura, BMW, Cadillac and Porsche to complete the appropriate system, calibration and ultimately the endurance testing of the gearbox and hybrid system in their particular application. Ahead of the first race over fifty P1359 transmissions have been supplied; a fantastic effort by the entire Xtrac workforce in the UK and the USA given the supply chain constraints that the global motorsport industry has been experiencing in 2022” adds Moore.
The P1359 gearbox uses Xtrac’s well-proven P1254 integrated valve actuator (IVA) gearchange system. It houses full form ground and Xtrem polished gears and shafts in a magnesium RZ5 casing, which is a structural part of the car taking all of the loads from the rear suspension and rear impact structure, rear wing, and safety wheel tethers.
The gearbox has a maximum combined internal combustion engine (ICE) and MGU power capability of 585kW (785bhp), with the engine speed operating within the range of 6,000 to 10,000 rpm. Each engine supplier homologates its drivetrain with specific gear ratios. The integrated MGU drives through a novel gear train homologated for each engine. It ensures that no matter what the maximum engine revs, the MGU is matched to the engine speed, thus ensuring that no engine gains an advantage; parity being the whole ethos behind the new class.
The gearbox also includes a limited-slip plate differential with an externally gas-charged pre-load and a semi-dry-sump oil system. Integral to the gearbox is a 3-litre engine oil catch tank which simplifies the powertrain installation, and the whole package including the MGU drive, but not including the MGU itself, weighs 78kg (172lb).
At the 2023 running of the ‘Rolex 24 at Daytona’, Xtrac has a full track-support operation including engineers and technicians located in a bespoke support trailer in the paddock. Xtrac customers include all nine GTP cars with the P1359 hybrid gearbox, all ten LMP2 cars with the P1159 gearbox, all nine LMP3 cars with the P1152/1352 gearbox, and over 50% of the GTD cars with a variety of gearboxes including the P529, P1276, P1369, P1337 and the P1529 across seven different OEM brands.
