1999 BMW 540i intake

3
M62 TU VANOS
OVERVIEW
The variable intake valve timing system on the M62 TU continues to be identified as
VANOS. This acronym comes from the German words; V
Ariable NOckenwellen Steuerung,
which means Variable Camshaft Control.
The M62 TU VANOS system is a new variant providing stepless VANOS functionality on
each intake camshaft. The system is continuously variable within its range of adjustment
providing optimized camshaft positioning for all engine operating conditions.
While the engine is running, both
intake camshafts are continuously
adjusted to their optimum posi-
tions. This enhances engine per-
formance and reduces tailpipe
emissions.
Both camshafts are adjusted
simultaneously within 20
O(maxi-
mum) of the camshafts rotational
axis.
This equates to a maximum span
of 40
Ocrankshaft rotation. The
camshaft spread angles for both
banks are as follows.

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VANOS BENEFITS
The design of a camshaft for a non adjustable valve timing system is limited to the required
overallperformance of the engine.
• An intake camshaft with an advanced(early) profile will provide a higher performing
power curve at a lower engine speed. But at idle speed the the advanced position will
create a large area of intake/exhaust overlap that causes a rough, unstable idle.
• On the other hand, an intake camshaft with a retarded(late) profile will provide a very
smooth, stable idle but will lack the cylinder filling dynamics needed for performance
characteristics at mid range engine speeds.
The ability to adjustthe valve timing improves the engines power dynamics and reduces
tailpipe emissions by optimizing the camshaft angle for all ranges of engine operation.
VANOS provides the following benefits:
• Increased torque at lower to mid range engine speeds without a loss of power in the
upper range engine speeds.
• Increased fuel economy due to optimized valve timing angles.
• Reduction of exhaust emissions due to optimized valve overlap.
• Smoother idle quality due to optimized valve overlap.

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.

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.

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INTEGRAL ELECTRIC THROTTLE SYSTEM (EML)
FUNCTIONAL DESCRIPTION
When the accelerator pedal
is moved, the PWG pro-
vides a change in the mon-
itored signals. The ME 7.2
compares the input signal
to a programmed map and
appropriately activates the
EDK motor via proportional-
ly high/low switching cir-
cuits. The control module
self-checks it’s activation of
the EDK motor via the EDK
feedback potentiometers.
Requirements placed on the Electric Throttle System:
• Regulate the calculated intake air load based on PWG input signals and programmed
mapping.
• Control idle air when LL detected with regard to road speed as per previous systems.
• Monitor the driver’s input request for cruise control operation.
• Automatically position the EDK for accurate cruise control (FGR) operation.
• Perform all DSC III throttle control interventions.
• Monitor and carryout max engine and road speed cutout.

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PWG SIGNAL MONITORING & PWG FAILSAFE OPERATION:
• As a redundant safety feature the PWG provides two separate signals from two integral
potentiometers (Pot 1 and Pot 2) representing the driver’s request for throttle activation.
• If the monitored PWG potentiometer signals are not plausible, ME 7.2 will only use the
lower of the two signals as the driver’s pedal request input providing failsafe operation.
Throttle response will be slower and maximum throttle position will be reduced.
• When in PWG failsafe operation, ME 7.2 sets the EDK throttle plate and injection time
to idle (LL) whenever the brake pedal is depressed.
• When the system is in PWG failsafe operation, the instrument cluster matrix display will
post “Engine Emergency Program” and PWG specific fault(s) will be stored in memory.
EDK FEEDBACK SIGNAL MONITORING & EDK FAILSAFE OPERATION:
• The EDK provides two separate signals from two integral potentiometers (Pot 1 and Pot
2) representing the exact position of the throttle plate.
• EDK Pot 1 provides the primary throttle plate position feedback. As a redundant safe-
ty feature, Pot 2 is continuously cross checked with Pot 1 for signal plausibility.
• If plausibility errors are detected between Pot 1 and Pot 2, ME 7.2 will calculate the
inducted engine air mass (from HFM signal) and only utilize the potentiometer signal that
closely matches the detected intake air mass.
- The ME 7.2 uses the air mass signalling as a “virtual potentiometer” (pot 3) for a
comparative source to provide failsafe operation.
- If ME 7.2 cannot calculate a plausible conclusion from the monitored pots (1 or 2
and virtual 3) the EDK motor is switched off and fuel injection cut out is activated
(no failsafe operation possible).
• The EDK is continuously monitored during all phases of engine operation. It is also
briefly activated when KL 15 is initially switched on as a “pre-flight check” to verify it’s
mechanical integrity (no binding, appropriate return spring tension, etc). This is accom-
plished by monitoring both the motor control amperage and the reaction speed of the
EDK feedback potentiometers. If faults are detected the EDK motor is switched off and
fuel injection cut off is activated (no failsafe operation possible). The engine does how-
ever continue to run extremely rough at idle speed.
• When a replacement EDK is installed, the ME 7.2 adapts to the new component
(required amperage draw for motor control, feedback pot tolerance differences, etc).
This occurs immediately after the next cycle of KL 15 for approximately 30 seconds.
During this period of adaptation, the maximum opening of the throttle plate is 25%.

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INPUT SIGNALS/COMPONENTS
CAMSHAFT POSITION SENSORS
Located on the upper timing case covers, the camshaft position sensors monitor the posi-
tion of the camshafts to establish start of ignition firing order, set up sequential fuel injection
triggering and for accurate camshaft advance-retard (VANOS) timing feedback.
Each intake camshaft’s advance-retard angles are adjusted simultaneously yet indepen-
dently. For this reason ME 7.2 requires a camshaft position sensor on each cy linder bank
for accurate feedback to monitor the VANOS controlled camshaft positioning.
The sensors are provided with operating power from the ECM main relay. The sensors pro-
duce a unique asymmetrical square-wave signal representative of the impulse wheel shape.
The sensors are new in the fact that they are “active” hall effect sensors. Active hall sen-
sors provide:
• low signal when a tooth of the camshaft impulse wheel is located in front of the sensor
• high signal when an air gap is present.
The active hall sensors supply a signal representative of camshaft position even before the
engine is running. The ME 7.2 determines an approximate location of the camshafts posi-
tions prior to engine start up optimizing cold start injection (reduced emissions.)
UNIQUE SIGNAL
AS SEEN IN
MEASUREMENT
SYSTEM
OSCILLOSCOPE

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HOT FILM AIR MASS SENSOR (HFM 5)
The M62 TU is equipped with a new Hot Film
Air Mass Sensor identified as HFM 5. It is a
combined air mass/intake air temperature
sensor. The separate intake air temperature
sensor is no longer used on the M62 TU.
The HFM 5 is provided with operating power
from the ECM main relay. Based on calcu-
lated intake air mass, the HFM 5 generates
a varying voltage between 0.5 and 4.5 volts
as an input signal to the ME 7.2
An additional improvement of the HFM 5 is that the hot
film element is not openly suspended in the center bore
of the sensor as with previous HFMs. It is shrouded by
a round fronted plastic labyrinth which isolates it from
intake air charge pulsations.
This feature allows the HFM to monitor and calculate the
intake air volume with more accuracy. This feature adds
further correction for calculating fuel injection “on” time
(ti) which reduces emissions further.
HFM 5 WITH
NEW CONNECTOR
HOT
SENSING
FILM
ROUNDED
LABYRINTH