BMW N55, Manual, Page: 6 / 100

Engine Components/Systems Overview
The following provides an overview of the features of the N55 engine:
Crankcase:
• Large longitudinal ventilation holes inter-connect the crankcase lower chambers
and relieve unwanted crankcase pressure between cylinders.
• Modified oil galleries enhance the supply of oil to vacuum pump.
Crankshaft: Is light weight design and has an asymmetric counterweight arrangement.
Pistons and connecting rods:
• A specially formed bushing/bore in small end of the connecting rods evenly
distributes the force of the pistons on the power stroke.
• Lead-free bearing shells are installed on the big-end of the connecting rods.
Cylinder head:
• Specially designed water passages intergraded into the cylinder head enhance
injector cooling.
• The combustion chambers are machined to work in conjuction with the Valvetronic
III system with regard to promoting air turbulence and mixture formation.
Crankcase ventilation:
• In contrast to the N54, the N55 crankcase ventilation does not use cyclone
separators.
• The cylinder and head cover have integrated blow-by passages that connect the
crankcase ventilation directly to the intake ports.
VANOS:
• The N55 VANOS oil passages are simplified compared to the N54 engine.
• The solenoid valves have integrated non-return valve and 3 screen filters.
• The VANOS units are of a lightweight design for increased adjustment speed
and have a reduced susceptibility to soiling.
Valvetrain:
• The N55 is the first BMW turbo engine to incorporate Valvetronic.
• The valvetrain is a new designed that combines Valvetronic III with Double VANOS.
• With Valvetronic III the 3rd generation brushless servomotor is introduced.
• The position detection sensor of eccentric shaft is now integrated in the servomotor.
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N55 Engine