The P66/3 eight-cylinder hybrid turbo engine in the BMW M Hybrid V8!

Thomas Wachsmuth July 15, 2022 BMW, Tips, products, information & Co.

Reading time 5 Min.

In a few weeks, the intensive test phase will begin for the BMW M Hybrid V8, with which BMW M Motorsport will fight for overall victories in the IMSA GTP class of the WeatherTech SportsCar Championship in 2023. Before the rollout, the project had already reached an important milestone: the successful fire-up of the hybrid drive after installation in the test vehicle at the end of June. The BMW M Hybrid V8 is powered by the P66/3 eight-cylinder turbo engine with an additional electric drive. The basis for the combustion engine is the DTM unit that was used in the BMW M2017 DTM in 2018 and 4. It was extensively adapted to the high requirements of the LMDh hybrid drive in two conversion phases.

P66/3 eight-cylinder hybrid

Even before the BMW Group Board of Management had given the green light for BMW M Motorsport to enter the LMDh category in June 2021, Ulrich Schulz, Head of Powertrain Design at BMW M Motorsport, and his group started evaluating which racing engine would be best for the Conversion to a high-performance hybrid drive is suitable. Both for reasons of time and with a view to sustainability, which is playing an increasingly important role not only in the automotive industry in general but also in motorsport, it was not an option to design a completely new engine at the drawing board and manufacture it from scratch at great expense. Consequently, the question was which proven racing engine best meets the high requirements and specifications of the LMDh regulations.

fully load-bearing component in the BMW M Hybrid V8

The choice fell on the P66/1 eight-cylinder naturally aspirated engine that was used in the BMW M2017 DTM in the 2018 and 4 seasons. One of the things that spoke in its favor was that it could be used as a fully load-bearing component in the BMW M Hybrid V8 without an additional subframe in a monocoque chassis and, even after its conversion to a hybrid turbo engine, best met the requirements of the regulations.

"During the evaluation phase, we also looked at the P48 turbocharged four-cylinder engine from the BMW M4 DTM and the P63 turbocharged eight-cylinder engine from the BMW M8 GTE, but potential durability issues with the P48 and the heavy weight of the P63 spoke against it." , Schulz explains the decision in favor of the P66 engine. “It is a big plus that we were able to use materials such as steel and aluminum that were still available from the BMW Formula 1 era for the base of the engine and for individual components – for example shafts, housing and small parts.

This saved time and a lot of money and was therefore both efficient and sustainable. Efficiency is crucial in this project because the time window from the starting gun to the first race in Daytona 2023 is extremely tight. Converting the P66/1 naturally aspirated engine first to a bi-turbo and then, in cooperation with the electric drive colleagues, to a hybrid drive was very complex. Thanks to the expertise, the good cooperation and the high motivation of all departments, we were able to successfully complete the fire-up of the entire drive unit a few weeks ago. From our point of view, nothing stands in the way of test operation.”

Cylinder block and cylinder heads recast

In the first phase, the P66/1 DTM naturally aspirated engine was essentially converted by adapting two turbochargers and adjusting the crank mechanism to form an interim unit with the designation P66/2. The focus was on durability, increased performance and temperature management of the engine. To this end, the P66/2 completed many test units on the test bench, including complete racetrack simulations. In the next step, the P66/3 racing engine was created with, among other things, two turbos, adjustments to the special requirements of the Dallara chassis, final exhaust system, oil tank, wiring and integration of the high-voltage environment. Furthermore, the cylinder block and cylinder heads were recast in the BMW Group foundry in Landshut (GER) and the injection system was redesigned for direct injection.

At the same time, the electric motor was tested and integrated by engineers who already had a great deal of experience with electric drives from the Formula E project. The unit that forms the hybrid drive in the vehicle consists of an electric motor, inverter and high-voltage battery. There is a separating clutch between the electric motor and the combustion engine, which enables purely electric driving – for example in the pit lane. The first combination of both drive components took place when they were installed in the vehicle at the end of June. The first fire-up of the hybrid system was successful. This will be followed by the rollout in Varano de Melegari (ITA) at the end of July. The intensive test phase begins immediately afterwards.

Technical data on the P66/3 engine of the BMW M Hybrid V8.

designation	Otto four-stroke bi-turbo engine in V design
Capacity	3.999 cc
number of cylinders	8
cylinder construction	Cylinder block and cylinder head in cast aluminium, cylinder liner as an iron layer using the LDS process
V angle	90 °
drilling	93 mm
Hub	73,6 mm
cylinder spacing	102 mm
valves per cylinder	4
number of revolutions	Max. 8.200 rpm
Performance (Regulations)	about 640 PS
torque	approx. 650 Nm
injection	High-pressure direct injection at 350 bar
oil system	Dry sump system with six-cell oil scavenge pump and oil tank

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