BMW N55 - Pistons, Connecting Rods, and Oil Cooling

Pistons and Rings
A full slipper skirt type piston with a diameter of 82.5 mm is used. The first piston ring is a
plain rectangular compression ring with a chrome-ceramic coating on the contact surface.
The second piston ring is a tapered faced Napier type ring. The oil scrape ring is
designed as a steel band ring with spring that is also known as VF system.
N55 piston with piston rings
Index Explanation
1
Plain rectangular compression ring
2
Ta p e r e d faced Napier ring
3
VF system ring
4
Steel inlay for first piston ring
5
Groove for first piston ring
6
Groove for second piston ring
7
Groove for oil scraper ring
8
Hole for lubricating oil drain
9
Graphite coating
18
N55 Engine