BMW N55 Manual page 81

The cast iron cylinder liners are cast into the aluminum die-casting. The deck area (webs)
between the cylinders have grooved coolant passages. Coolant can flow along these
grooves from one side of the block to the other, thus cooling the deck area between the
cylinders.
N55, coolant passages and web cooling of the engine block
Index
1
2
3
4
5
Explanation
Cooling duct
Cylinder liner
Grooved coolant passage
Oil return ducts, exhaust side
Oil return ducts, intake side
81
N55 Engine