Prototypes of a new X6 model with a unique front bumper, featuring the aggressive styling of BMW’s M cars, were spotted testing at the Nurburging recently. Initially, these prototypes were thought to be running the same twin-turbo 4.4-litre V8 engine as the standard xDrive50i models but with extra boost, however latest reports indicate that test vehicles could be featuring a advanced hybrid system designed under BMW’s F1 program.

Unlike the majority of the F1 paddock, however, BMW’s factory team is not taking advantage of the Kinetic Energy Recovery System (KERS) developed jointly by industry transmission and technology companies Torotrak, Xtrac and Flybrid. Instead, BMW-Sauber has opted for an electric motor and generator approach. The regulations allow either approach, with the only restrictions being on the output of the push-to-pass system.

Advantages and disadvantages to both electrical and mechanical hybrid systems
Based on reports from the field, BMW’s development process for the F1 system hasn’t been entirely smooth, with at least one engineer requiring medical attention after receiving a strong shock upon touching a car fitted with a prototype system. The advantages of working with the purely electrical battery-based system include the crossover from BMW’s passenger car hybrid technology development and the ability to work innovations made in F1 testing back into its road car lineup.

The KERS system, on the other hand, represents a system developed specifically for F1 based on a combination of existing and proprietary technologies by Torotrak, Xtrac and Flybrid. The result is a package that weighs in at under 24kg, requires only 13L of space and generates the maximum allowed boost of 60kW, with a total of 400kJ than can be delivered over the course of a single lap, meaning maximum power can be delivered for a total of 6.67 seconds.

The purely mechanical KERS system uses a highly sophisticated steel and carbon fibre flywheel encased in a vacuum to store energy taken from the car's motion as kinetic energy. A continuously variable transmission links through a secondary clutch to the primary driveline, which is linked to the standard V8 combustion engine. When the driver pushes the button, the clutch engages the always-spinning flywheel, which seamlessly adds its power to the standard engine's.

Aadvantages of the KERS system are clear: small size, potent power output and no hassles with bulky, heavy and dangerous batteries.  The downsides include limited ability to transfer the system into road cars because of potential licensing issues with the underlying elements of the system.

Motorsports-inspired hybrid systems will be in passenger cars in the near future
The system going into the BMW X6 is rumoured to be a kinetic system, however. Whether the team is developing both methods in testing, or whether the information regarding the production car system is simply mistaken is not clear. However, using the purely mechanical KERS-type system in its road cars would be a good idea for BMW.

Going to the kinetic system for extra power is a necessary step if BMW is going to deliver both the performance and the efficiency it wants. Current conventional hybrid systems simply can’t deliver both - they either meet power requirements and only minimally improve efficiency, or vice versa. The calculus is especially true on the large X6. Whether BMW has any plans to include the high-tech system on other models remains unknown.

Ferrari president Luca Cordero di Montezemolo recently confirmed that the Italian supercar manufacturer was also working on a similar system for its production cars, however its first systems aren’t expected to arrive until 2015. BMW’s version, meanwhile, could appear in the next couple of years or so.

BMW X6 M Prototype gallery

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