Jens, I was searching for a good link for an opposed piston engine and couldn't find one. They do the same kind of thing. Super or turbo chargers are not meant to pressurize the charge in these large diesels. They provide primary compression that takes place of the crankcase which is running in an oil bath.

Jens, have you ever looked at the Napier Deltic engines? What a piece of engieneering.