Unlike any hybrid powertrain currently on the road, one of the engines in BMW's split-hybrid technology remains completely dormant unless more power is needed than the first engine and electric motor combination can provide. The patent application specifies that each internal combustion engine would have two cylinders – a configuration that BMW has a great deal of experience in on the motorcycle side.
Like BMW's current hybrid systems, the electric motor would be integrated into the transmission, and it seems that the two gasoline-fed engines are mounted together as one unit. We have no idea if the German automaker has plans to put such a system into production, but it's obvious that it's at least considering the possibility. Stay tuned.