Napier were apparently not shy of adding extra bits - not an aero engine but this one seemed to work very well. The superchargers (pumps) are essential to its operation.
9 and 18 cylinder versions were produced. 3 banks and 6 banks respectively. Assembly and maintenance looks like fun!
https://www.youtube.com/watch?v=D3bj47TAYiU
https://en.wikipedia.org/wiki/Napier_Deltic