According to the source, the application filed by BMW describes the technology as "comprising a first internal combustion engine unit… and a second internal combustion engine unit.”
The operating principle would be as simple as this: the first internal combustion engine will drive the electric motor at low speeds, while for use at higher speeds the second engine would kick in. According to the application, BMW's split engines could differ in size, with one being a four-cylinder and the other a two cylinder.
Now, don't go on and believe that BMW will stuck two separate engines under the hood and send the car on its way.
A bit of research will tell you a split engine does not consist of two separate engines being stacked together and forced to work. A split engine is in fact one engine, with its cylinders divided into two separate groups (which may explain the use of four and two cylinders, respectively.)
Such a configuration is already being used in engines like the Scuderi engine, helping it to achieve greater efficiency and less emissions than the conventional engine.
The Scuderi engine separates the four strokes of a cylinder (intake, compression, power, and exhaust) in intake/compression (performed by one group of cylinders) and power/exhaust, performed by the other.
The system in the works with BMW is not to be confused with the two-mode hybrid system used on the ActiveHybrid X6, which uses two electric motors.
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