BMW is working on a hybrid system that uses two engines, detailed in a recent patent application.
Described as a ‘hybrid vehicle having a split engine’, the idea is for the car to be driven by one of the engines and the electric motor at low speeds or when power demands are low. When more speed or power is needed, the second engine cuts in.
The engine is described as “comprising a first internal combustion engine unit… and a second internal combustion engine unit,” suggesting that the two engines will effectively form one unit. The second engine effectively supports and assists the first.
Although the application does not specify the size of the engines, it does mention the possibility of each being a two cylinder unit. It also says that the two engines could be different sizes – so a four-cylinder unit could be supported by a two-cylinder, for example.
The electric motor would automatically generate extra torque to compensate for any loss when the system switches between the two engines. As with BMW’s current hybrids, the electric motor is contained within the transmission.