engine oil BMW 735i 1999 E38 M62TU Engine Workshop Manual

5
BASIC FUNCTION OF BMW VANOS SYSTEMS
All BMW VANOS systems are operated through electric/hydraulic/mechanical control.
Electric Control: The engine control module is responsible for activating a VANOS sole-
noid valve based on DME program mapping. The activation parameters are influenced
by the following input signals:
• Engine speed
• Load (intake air mass)
• Engine temperature
• Camshaft position
• Oil temperature (MS 42.0 only)
Depending on the specific VANOS system, the solenoid valve is one of two types:
• Basic black/white (on/off) solenoid valve. Found on M50 TU and M52 engines.
• Variable position solenoid valve. Found on the M52 TU and M62 TU engines.
Hydraulic Control:The position of the solenoid valve directs the hydraulic flow of engine
oil. The controlled oil flow acts on the mechanical components of VANOS system to
position the camshaft.
Mechanical Control: The mechanical components of all VANOS systems operate under
the same principle. The controlled hydraulic engine oil flow is directed through advance
or retard activation oil ports. Each port exits into a sealed chamber on the opposite sides
of a control piston.
• The control piston on six cylinder engine systems (M50TU, M52 & M52TU) is con-
nected to a separate helical gear cup.
• The control piston on the M62TU VANOS system incorporates the helical gear.
In its default position the oil flow is directed to the rear surface of the piston. This pulls
the helical gear forward and maintains the retarded valve timing position.
When the oil flow is directed to the front surface of the piston, the oil pushesthe helical
gear in the opposite direction which rotates the matched helical gearing connected to the
camshaft.
The angled teeth of the helical gears cause thepushingmovement to be converted into
arotationalmovement. The rotational movement is added to the turning of the
camshaft providing the variable camshaft positioning.

7
M62 TU VANOS COMPONENTS
M62 TU VANOS components include the following
for each cylinder bank:
•New cylinder heads with oil ports for VANOS
•VANOS transmission with sprockets
•Oil distribution flange
•PWM controlled solenoid valve
•Oil check valve
•Camshaft position impulse
VANOS CONTROL SOLENOID & CHECK VALVE:The VANOS solenoid is a two wire,
pulse width modulated, oil pressure control valve. The valve has four ports;
1. Input Supply Port - Engine Oil Pressure
2. Output Retard Port - To rear of piston/helical gear (retarded camshaft position)
3. Output Advance Port - To front of piston/helical gear (advanced camshaft position)
4. Vent - Released oil pressure
A check valve is positioned forward of the solenoid in the cylinder head oil gallery. The
check valve maintains an oil supply in the VANOS transmission and oil circuits after the
engine is turned off. This prevents the possibility of piston movement (noise) within the
VANOS transmission system on the next engine start.

VANOS TRANSMISSION:The primary and secondary timing chain sprockets are inte-
grated with the VANOS transmission. The transmission is a self contained unit.
The controlled adjustment of the
camshaft occurs inside the “transmis-
sion”. Similar in principle to the six
cylinder engine VANOS systems, con-
trolled oil pressure moves the piston
axially.
The helical gear cut of the piston acts
on the helical gears on the inside sur-
face of the transmission and rotates
the camshaft to the specific advanced
or retarded angle position.
Three electrical pin contacts are locat-
ed on the front surface to verify the
default maximum retard position using
an ohmmeter. This is required during
assembly and adjustment. (see service
notes further on).
OIL DISTRIBUTION FLANGES:The oil distribution flanges are bolted to the front surface
of each cylinder head. They provide a mounting location for the VANOS solenoids as well
as the advance-retard oil ports from the solenoids to the intake camshafts.
CAMSHAFTS: Each intake camshaft has
two oil ports separated by three sealing rings
on their forward ends.
The ports direct pressurized oil from the oil
distribution flange to the inner workings of
the VANOS transmission.
Each camshaft has REVERSEthreaded
bores in their centers for the attachment of
the timing chain sprockets on the exhaust
cams and the VANOS transmissions for
each intake camshaft as shown.
CAMSHAFT POSITION IMPULSE WHEELS:The camshaft position impulse wheels pro-
vide camshaft position status to the engine control module via the camshaft position sen-
sors. The asymmetrical placement of the sensor wheel pulse plates provides the engine
control module with cylinder specific position ID in conjunction with crankshaft position.

9
M62 TU VANOS CONTROL
As the engine camshafts are rotated by the primary and secondary timing chains, the
ME7.2 control module activates the VANOS solenoids via a PWM (pulse width modulated)
ground signal based on a program map. The program is influenced by engine speed, load,
and engine temperature.
•Shown below: In its inactive or default position, the valves direct 100% engine oil pres-
sure flow to achieve max “retard” VANOS positioning
•Top of next page: As the Pulse Width Modulation (PWM) increases on the control sig-
nal, the valve progressively opens the advance oil port and proportionately closes the
retarded oil port.
Oil pressure pushes the piston toward the advance position. Simultaneously the oil
pressure on the retarded side (rear) of the piston is decreased and directed to the vent
port in the solenoid valve and drains into the cylinder head.
•Bottom of next page: At maximum PWM control, 100% oil flow is directed to the front
surface of the piston pushing it rearward to maximum advance.
Varying the pulse width (on time) of the solenoids control signals proportionately regulates
the oil pressures on each side of the pistons to achieve the desired VANOS advance angle.