Vanos (Variable Camshaft Timing) - BMW 1999-2005 M3 Service Manual

Engine-General
10 of 19
http://ebahn.bentleypublishers.com/BMW/3/E46/Repair%20Manuals/1...
The intake manifold includes intake
turbulence ports. The 5.5 mm (0.217 in.)
turbulence ports channel idle and low
speed air directly from the idle speed
control valved to one intake valve of each
cylinder.
Routing intake air to one intake valve per
cylinder causes the air charge to swirl in
the cylinder. Together with the high flow
rate of intake air across the small (5.5
mm) port, intake fluctuations are
reduced for more stable combustion.
VANOS (Variable Camshaft
Timing)
A double VANOS system is used on
both the M52 TU and the M54 engines.
VANOS is fully variable and operates
independently on both intake and
exhaust sides.
When the VANOS solenoid is actuated,
engine oil pressure is applied to the front
side of the gear cup piston. This forces
the gear cup into the camshaft helical
gears to change camshaft timing.
In addition to offering increased power,
the double VANOS system offers the
following advantages:
Increased torque at lower and
medium RPM ranges
More efficient combustion and
improved idle quality
Internal EGR in part-load range for
lower NOx emissions.
Quicker warm-up cycle for catalytic
2/25/2009 9:58 PM