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History: facts, each with its source
Wikipedia says the S55 was introduced in the F80 M3 and F82 M4, and differs from the N55 with a closed-deck block and twin turbos.1
- Block: Closed deck1
BMW S55 engine
This page is a draft. It has not been approved yet, so read it with care.
The F80 M3's twin-turbo 3.0L six, a closed-deck relative of the N55.