BMW 5251 Service Manual page 69

Engine identifying features
4
The M52 engine (MY97-98 528i) used a single on-off vari-
able intake valve timing system (called VANOS). The cylinder
block is cast iron and the cylinder head is aluminum. The en-
gine management system is Siemens MS 41
.I
and features
NGK-type (0-5 volt) oxygen sensors.
NOTE-
VANOS is an acronym based on the German words Variable
Nocltenwellen Steuerung (variable camshaft timing).
4
The M52 TU engine (MY99-00 5281) and the M54 engines
(MY01-02 525il530i) are fitted with double VANOS. The en-
gine blocits are constructed of aluminum alloy with cast iron
cylinder sleeves.
4
The double VANOS (variable camshaft control) system incor-
porates true variable control of both the intake and exhaust
camshafts, as compared to the single VANOS system on the
M52 engine (onloff control of the intaite camshaft only).
The M54 engines use a fully electronic throttle control (drive
by wire). There is no accelerator cable connecting the throttle
pedal to the throttle housing in these cars.