Volkswagen Self Study Program 246 – Variable Valve Timing with fluted variator SSP-246-Variable-valve-timing

Service.

Self-study programme 246

Variable Valve Timing

with fluted variator

Design and Function

The demands on combustion engines continue to
grow. On one hand, customers want more power
and torque, while on the other, one cannot lose
sight of fuel economy and increasingly stringent
emissions laws. In regard to valve timing, this
means that engine-speed and load dependent
adjustment of the inlet and exhaust camshafts is
indispensable.
Therefore, of course, adjustment systems are
continuously being improved in technical design
as well as in means of adjustment.

In this self-study programme, we would like to
introduce to you the design and operation of the
new camshaft adjuster with fluted variators. At
Volkswagen, first the 2.8 litre V6 and the 2.3 litre
V5 engines will be equipped with this system.
Later other engines, such as the W8 and W12
engines will be equipped with this variable valve
timing system.

The self-study programme presents the design and

operation of new developments.

The contents are not updated.

2

246_148

NEW Attention

Note

Please refer to the intended Service literature for current instructions for testing,

settings and repairs.

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Variable valve timing . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Advancing the inlet camshaft. . . . . . . . . . . . . . . . . . . . .10

Retarding the inlet camshaft . . . . . . . . . . . . . . . . . . . . . 11

Inlet camshaft regulation . . . . . . . . . . . . . . . . . . . . . . . .12

Exhaust camshaft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Exhaust camshaft, basic setting . . . . . . . . . . . . . . . . . . . 14

Exhaust camshaft, idle . . . . . . . . . . . . . . . . . . . . . . . . . .15

Oil system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Engine management . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

System overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Circuit diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Self-diagnosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Test your knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . .27

3

Introduction

The task of variable valve timing

Variable valve timing has the task of setting the most advantageous valve timing for the particular
engine for the operating modes idle, maximum power and torque as well as exhaust gas recirculation.

TDC

Idle

At idle, the camshafts are set so that the inlet
camshaft opens late and, consequently, closes
late as well. The exhaust camshaft is set so that it
closes well before TDC. Due to the minimal gas
residue from combustion, this leads to smooth
idling.

Ec

Io

Ic

Power

To achieve good power at high engine speeds,
the exhaust valves are opened late. In this way,
the expansion of the burned gases can act
against the pistons longer.
The inlet valves open after TDC and close well
after BDC. In this way, the dynamic self-charging
effect of the entering air is used to increase
power.

Eo

BDC

TDC

Ec

Io

Ic

246_001

Eo

BDC

Intake

Compression

Power

Exhaust

Io: Inlet opens

Ic: Inlet closes

Eo: Exhaust opens

Ec: Exhaust closes

246_002

4

Torqu e

TDC

To achieve maximum torque, a high degree of
volumetric efficiency must be attained. This
requires that the inlet valves be opened early.
Because they open early, they close early as well,
which avoids pressing out the fresh gases.

The exhaust camshaft closes just before TDC.

Exhaust gas recirculation

Internal exhaust gas recirculation can be
achieved by adjusting the inlet and exhaust
camshafts. In this process, exhaust gas flows from
the exhaust port into the inlet port while the
valves overlap (inlet and exhaust valves are both
open). The amount of overlap determines the

amount of recirculated exhaust gas. The inlet
camshaft is set so that it opens well before TDC
and the exhaust camshaft does not close until just
before TDC. As a result, both valves are open
and exhaust gas is recirculated. The advantage
of internal exhaust gas recirculation over
external exhaust gas recirculation is the fast
reaction of the system and very even distribution
of the recirculated exhaust gases.

Io

Ec

Io

Ic

Ec

BDC

TDC

Ic

BDC

Eo

246_003

Eo

246_004

The illustrated valve timing is intended to demonstrate the basic principle and the effects of
variable camshaft timing. Of course every engine has valve timing adapted to its mechanics
and its engine management.

5

Variable valve timing

Design of variable valve timing

The variable valve timing system consists of the following components:

● Two fluted variators

The fluted variator for adjusting the inlet camshaft is fitted directly on the inlet camshaft. It adjusts the
inlet camshaft according to signals from the engine control unit. The fluted variator for adjusting the
exhaust camshaft is fitted directly on the exhaust camshaft. It adjusts the exhaust camshaft according
to signals from the engine control unit. Both fluted variators are hydraulically operated and are
connected to the engine oil system via the control housing.

The illustration shows the arrangement of the variable valve timing system on the V5 and V6 engines.

Inlet camshaft fluted variator

Oil gallery to ring channels in camshafts

Control housing

N205

N318

6

Exhaust camshaft
fluted variator

246_146

● The control housing

The control housing is attached to the cylinder head. Oil galleries to both fluted variators are located
in the control housing.

● Two solenoid valves

There are two solenoid valves located in the control housing. They direct oil pressure to both fluted
variators according to the signal from the engine control unit.
Inlet camshaft timing adjustment valve -1- (N205) is responsible for the inlet camshaft, and exhaust
camshaft timing adjustment valve -1- (N318) is responsible for the exhaust camshaft.

The illustration shows the arrangement of the variable valve timing system on one cylinder head of the
W8 and W12 engines.

Oil gallery to ring channels in camshafts

Control housing

Inlet camshaft
fluted variator

N205

N318

Exhaust camshaft
fluted variator

246_025

The design and operation of the illustrated engine versions is the same. They differ only in the
arrangement and shape of some components.

7

Variable valve timing

Operation of variable valve timing

The engine control unit controls the variable
valve timing. To adjust the camshafts, it requires
information about engine speed, engine load
and temperature and the positions of the
crankshaft and camshafts.
To adjust the camshaft, the engine control unit
actuates the solenoid valves N205 and N318.

Hall sender 1 G40

Hall sender 1 G163

They in turn open oil galleries in the control
housing. Engine oil flows through the control
housing and camshaft into the fluted variators.
The fluted variators turn and adjust the camshaft
according to the specifications of the engine
control unit.

Inlet camshaft

Engine
control unit

Exhaust camshaft

N205

N318

Oil pump

Engine speed

Air mass and air temperature (engine load)

Coolant temperature

8

246_012

This section goes into more detail about the adjustment of the camshafts. The parts, the design and the
operation are the subject of the following pages.

Inlet camshaft adjustment

The inlet camshaft is regulated by the engine
control unit over the entire speed range of the
engine. The maximum adjustment is 52° CA. The
adjustment is dependent on the adjustment map
stored in the engine control unit.

Fluted variator

Design of the fluted variator for the inlet
camshaft

The adjusting mechanism consists of:

● Housing with outer rotor
(directly joined to timing chain)

● Inner rotor
(directly joined to camshaft)

Outer rotor

Oil galleries

Inner rotor

246_155

9

Variable valve timing

Inlet camshaft

How the camshaft is advanced

The inlet camshaft is set in the position “inlet
valves open before TDC” for exhaust gas
recirculation and for increasing torque. To
change the position, the engine control unit
actuates inlet camshaft timing adjustment
valve 1 (N205). When actuated, the valve moves
the control piston.
In the control housing, the oil gallery for timing
advance is opened according to the degree of
adjustment. Consequently, the engine oil under
pressure flows through the control housing into

If the variable valve timing fails to function, the fluted variator will be pressed by the oil
pressure to the basic position of 25° after TDC.

the ring channel in the camshaft. Then the oil
flows through the five drillings in the face of the
camshaft into the five advance chambers of the
fluted variator. There it presses against the flutes
of the inner rotor. The inner rotor turns relative to
the outer rotor (and crankshaft), turning the
camshaft with it. Consequently, the camshaft
turns further in the direction of crankshaft
rotation and the inlet valves open sooner.

Advance
oil gallery

Oil return

Control housing

Ring channels

Frontal
drillings

Control piston

10

Engine oil pressure

Oil return

246_150

How the camshaft is retarded

When the engine is idling or when a great deal
of power is required from the engine, the inlet
camshaft is rotated so that the inlet valves open
late, that is, after TDC. To retard the inlet
camshaft, the engine control unit actuates inlet
camshaft timing adjustment valve 1 (N205).
The solenoid valve opens the gallery for timing
retardation by moving the control piston. Oil
flows through the control housing into the ring
channel of the camshaft. The oil flows through
drillings in the camshaft to the pocket hole of the
securing bolt for the camshaft adjuster. From
there, it flows through 5 drillings in the camshaft

adjuster into the oil chamber for timing
retardation behind the flutes of the inner rotor.
The oil presses the inner rotor and the camshaft
in the direction of camshaft rotation and the
valves open later.

At the same time that the oil gallery for timing
retardation opens, the control piston opens the
oil return for the gallery for timing advance,
relieving pressure in it. The rotation in the
direction of retardation presses the oil out of the
timing advance oil chamber which flows out
through the timing advance oil gallery.

Pocket hole for
securing bolt

Timing retardation
oil gallery

Oil return

Control housing

Ring channel

Inner flute

Frontal
drilling

Control piston

Engine oil pressure

Oil return

246_151

11

Variable valve timing

How regulation works

Regulation enables continuous variation of the
inlet camshaft between advanced and retarded,
whereby the total variation is a maximum of
52° crankshaft angle. On the basis of the Hall
sender signal, the engine control unit detects the
momentary position of the inlet camshaft.
The camshafts can then be adjusted according to
the map saved in the engine control unit.
When actuated by the engine control unit, inlet
camshaft timing adjustment valve 1 (N205)
pushes the control piston in the direction, for
example, of advanced timing. Oil pressure
travels through the control housing into the

camshaft adjuster and presses the camshaft in
the “advanced” position. Pushing the control
piston in the “advanced” direction automatically
opens the oil return of the oil channel for
retarding timing. When the desired angle of
adjustment is attained, the control piston is
moved by the actuation of inlet camshaft timing
adjustment valve 1 (N205) to a position in which
the pressure is held in both chambers of the
adjuster. If the timing is later retarded, the
process runs in the opposite direction.

N205

246_150

N205

246_152

12

Exhaust camshaft

Exhaust camshaft adjustment

As you saw in the preceding pages, the inlet
camshaft is regulated by the control unit. In
contrast to that, the exhaust camshaft can only
be controlled. The control unit sets the variator
only to the basic position or the idle position. The
maximum angle of adjustment is 22° crankshaft
angle.

Design of the fluted variator for the exhaust
camshaft:
The fluted variator for the exhaust camshaft is
identical in design to the fluted variator for the
inlet camshaft. Only the inner rotor is wider
because the adjustment is only 22° crankshaft
angle.

Outer rotor

Oil galleries

Inner rotor

Wider flutes

246_156

13

Variable valve timing

Basic position

The exhaust camshaft is in its basic position when
the engine is starting and at engine speeds
above idle.
The exhaust valves then close shortly before TDC.
The exhaust camshaft is in this position in the
operating modes power, torque and exhaust gas
recirculation. The exhaust camshaft timing
adjustment valve 1 (N318) is not actuated in these
ranges.

How the basic position works

In the basic position, the exhaust camshaft is
positioned so that the valves close shortly before
TDC. The exhaust camshaft timing adjustment
valve 1 (N318) is not actuated by the engine
control unit. In this position, the oil gallery for
timing retardation is open. Through oil galleries,
oil pressure reaches the ring channel of the
exhaust camshaft. From there, it travels through
the frontal drillings in the camshaft to the oil
chamber of the camshaft adjuster. From there it
presses against the flutes of the inner rotor. The
flutes turn to stop, turning the camshaft along
with it. The camshaft remains in this position as
long as the solenoid is not actuated.

Pocket hole for
securing bolt

Oil gallery for basic
position

Oil return

Control housing

Ring channel

Flute

Frontal
drilling

Inner rotor

Outer rotor

Control piston

14

Engine oil pressure

Oil return

246_157

Idle

How the idle position works

The exhaust camshaft is set to the “advanced”
position from idle to engine speeds to about
1,200 rpm.

The exhaust camshaft timing adjustment
valve 1 (N318) is actuated by the engine control
unit. This pushes the control piston and opens
another oil gallery in the control housing.
The engine oil now flows into the other ring
channel in the camshaft and through the drilled
camshaft into the camshaft adjuster. There it
presses against the flutes of the inner rotor.
The flutes are pressed in the direction of engine
rotation, taking the camshaft with them, so that
the exhaust valves open and close earlier.
The oil from the chamber in front of the flutes
runs through the drilling in the camshaft adjuster,
the pocket hole of the securing bolt and the ring
channel of the camshaft back to the solenoid
valve. In the solenoid valve it flows through the
oil return in the control box cover.

Pocket hole for
securing bolt

Oil return

Control housing

Ring channels

Inner rotor

Frontal
drillings

Outer rotor

Control piston

Engine oil pressure

Oil return

246_156

15

Variable valve timing

Oil system

The following pages introduce the oil system.
The variable valve timing system operates at an oil pressure of 0.7 bar and above.

Course of oil under pressure

Oil pressure created by the oil pump flows
through the cylinder block to the cylinder head
and from there through an oil strainer into the
control housing of the camshaft adjuster.
Through galleries in the control housing, it
reaches the ring channel in the camshaft and
from there it travels through frontal drillings in
the camshaft into the camshaft adjuster.

Camshaft adjuster

Course of oil without pressure

Oil from the chambers in the camshaft adjuster
without pressure flows through the ring channel
in the camshaft back to the control housing.
Oil flows from the control housing back to the
solenoid valve.

From the solenoid valve, it flows through the
timing chain cover back to the sump.

Inlet camshaft

Exhaust camshaft

Camshaft adjuster

16

Control housing with

solenoid valves

Oil supply
Oil return

Oil

246_013

The oil course to the exhaust camshaft is identical with that to the inlet camshaft.

Cylinder head

Cylinder block

Oil pump

Sump

System overview for V5 and V6 engines

Engine management

Engine control unit

Hall sender 1 G40

Hall sender 2 G163

Engine speed
sender G28

Air mass meter G70

Inlet camshaft
timing adjustment
valve 1 (N205)

Exhaust camshaft
timing adjustment valve
1 (N318)

Coolant temperature
sender G62

Diagnosis
connection

246_029

17

Engine management

Engine control unit

The engine control unit, the sensors which provide it with information and the final controls which are
actuated by the control unit are the subject of the following pages. The descriptions of the final controls
and sensors in this self-study programme refer to engines with one exhaust and one inlet camshaft each.
Engines with more than one exhaust and one inlet camshaft require, of course, a Hall sender and a valve
for camshaft adjustment for each camshaft.

The engine control unit is responsible for
controlling camshaft adjustment. To this end,
maps for inlet and exhaust camshaft adjustment
are stored in the engine control unit. These maps
exist for each mode of engine operation in which
camshaft adjustment is active.
For example, these operating modes:

● engine warm-up phase

● or for the engine at operating temperature.

The new functional structure of the engine control
unit is based on engine torque as the base value
for all further engine management measures
calculated by the ECU.
The base value, torque, is calculated directly in
the engine control unit.
To calculate torque, the control unit uses the
signals from the air mass meter and the engine
speed sender.

18

246_017

Learning ability of the system

The entire variable valve timing system is
adaptive. This adaptability compensates for
component and assembly tolerances as well as
wear occurring during engine use.

The engine control unit automatically initiates
adaptation when the engine is idling and the
coolant temperature is greater than 60° C.

During adaptation at idle, the engine control unit
uses signals from the engine speed sender and
the Hall senders to check the idle settings of the
inlet and exhaust camshafts. If the actual value
does not agree with the specification stored in
the control unit, the next time that the camshafts
are adjusted, they will be corrected to the
specification.

TDC

BDC

Specification

Adaptation value

Actual value

246_009

19

Engine management

Air mass meter G70

The air mass meter G70 is located in the intake
tract of the engine.
The air mass meter signal is used by the engine
control unit to calculate the volumetric efficiency.
On the basis of volumetric efficiency, the lambda

) value and the ignition timing, the engine

(O

2

control unit calculates the torque.

Use of signal

Consequences of loss of signal

246_148

In the variable valve timing system, the signal is
used for load-dependent adjustment of the
camshaft.

If the air mass meter fails, the engine control unit
creates a substitute signal. Camshaft adjustment
continues to operate according to the given
operating conditions.

20

Engine speed sender G28

The engine speed sender G28 is located in the
crankcase. It senses electromagnetically the teeth
(60 minus 2) of the sender rotor on the
crankshaft.
With this signal, the engine control unit can
detect the engine speed and the TDC position of
the crankshaft. But to adjust the camshaft, the
engine control unit requires the precise location
of the crankshaft.
To detect precisely the position of the crankshaft,
the engine control unit uses the signals from the
individual teeth of the sender rotor. The gap in
the sender rotor serves as the zero point (TDC)
and each sender rotor tooth marks 6° crankshaft
angle.

246_149

Example:

1 tooth = 6° crankshaft angle x 60 teeth = 360°
crankshaft angle, corresponding to one revolution of
the crankshaft. The gap of 2 teeth (TDC detection)
corresponds to 12° crankshaft angle.

Use of signal

Consequences of loss of signal

In the variable valve timing system, the signal is
used for engine-speed-dependent adjustment of
the camshaft.

If this signal fails, the engine stops and cannot be
started again.

21

Engine management

Hall sender G40 and Hall sender 2 G163

Both Hall senders are located in the timing chain
cover. The have the task of informing the engine
control unit of the positions of the inlet and
exhaust camshafts. They do this by reading the
quick start sender rotor located on the respective
camshaft. With Hall sender 1 G40 the engine
control unit detects the position of the inlet
camshaft and with Hall sender 2 G163, the
position of the exhaust camshaft.

Use of signal

Hall sender 1 G40

The engine control unit uses the engine speed
sender signal to detect the position of the
crankshaft. With the signals for the camshafts in
addition, the control unit calculates the position
of the camshafts relative to the crankshaft. The
control unit needs these positions for the precise
adjustment of the camshafts and to start the
engine quickly.

Hall sender 2 G163

246_036

22

Consequences of loss of signal

Engines with more than one exhaust and one inlet camshaft require of course one Hall sender
per camshaft.

If only one Hall sender fails, camshafts will not
be adjusted. But the engine will continue to run
and will start after it has been stopped. If both
Hall senders fail, the engine will continue to run
until the next time that it is stopped. It will not be
possible to restart the engine.

Coolant temperature sender G62

The coolant temperature sender G62 is located
in the thermostat housing. It informs the engine
control unit of the current engine temperature.

246_028

Use of signal

Consequences of loss of signal

The sender signal is used for temperature­dependent start of camshaft adjustment.

If the signal fails, the control unit uses a substitute
temperature stored in it.

23

Engine management

Inlet camshaft timing adjustment valve N205 and
exhaust camshaft timing adjustment valve N318

Both valves are integrated in the camshaft
adjustment control housing. They have the task of
directing oil pressure to the camshaft adjusters
depending on the direction and distance of
adjustment according to specifications from the
control unit. To adjust the camshafts, the valves
are actuated with a variable duty cycle (on-off
ratio) by the control unit. Inlet camshaft timing
adjustment valve N205 adjusts the inlet camshaft
and exhaust camshaft timing adjustment valve
N318 adjusts the exhaust camshaft.

Consequences of loss of signal

N205

If an electrical wire to the camshaft timing
adjuster is defective, or a camshaft timing
adjuster fails, camshaft adjustment will not be
performed.

N318

246_143

24

Engines with more than one exhaust and one inlet camshaft require of course one camshaft
timing adjustment valve per camshaft.

Circuit diagram of V5 and V6 engines

87a

15

87a
15

S

N205 N318

J220

G163G40

G28 Engine speed sender
G40 Hall sender 1
G62 Coolant temperature sender
G163 Hall sender 2
J220 Engine control unit
N205 Inlet camshaft timing adjustment valve 1

G28

G62

G70

246_026

N318 Exhaust camshaft timing adjustment valve 1

Output signal
Input signal
Positive
Earth

87a Positive behind fuel pump relay J17

25

Engine management

Self-diagnosis

The components of the variable valve timing are
checked during self-diagnosis. To diagnose
camshaft adjustment, please use current
workshop literature and the vehicle diagnosis
device VAS 5051.

246_023

The sensors and final controls shown in colour will be tested during self-diagnosis and guided fault
finding.

Hall sender 1 G40

Hall sender 2 G163

Engine speed sender G28

Air mass meter G70

Engine control unit

Inlet camshaft timing
adjustment valve 1 (N205)

26

Coolant temperature
sender G62

246_030

Exhaust camshaft timing
adjustment valve 1 (N318)

Diagnosis connection

Test your knowledge

1. Which statement is correct?

a. With variable camshafts, valve timing can be better adapted to the varying operating modes of

the engine.

b. Valve timing has no effect on the operating modes.

2. The camshafts are adjusted with regard to which operating modes?

a. Torque

b. Idle

c. Exhaust gas recirculation

d. Power

3. How are the camshafts adjusted?

a. pneumatically

b. hydraulically

c. mechanically

4. Name the components.

1

2

1.) _____________________________________

2.) _____________________________________

3

4

3.) _____________________________________

6

5

4.) _____________________________________

5.) _____________________________________

7

8

6.) _____________________________________

7.) _____________________________________

246_012

8.) _____________________________________

27

Test your knowledge

5. Name the components

1.) ________________________________

1

6

5

3

4

246_036

6. How are the camshafts adjusted and by how many degrees?

a. The inlet camshaft can only be set to two positions.

The maximum adjustment path is 22° crankshaft angle.

b. The inlet camshaft can be set to any point along the adjustment path.

The maximum adjustment path is 52° crankshaft angle.

2

2.) ________________________________

3.) ________________________________

4.) ________________________________

5.) ________________________________

6.) ________________________________

c. The exhaust camshaft can be set to any point along the adjustment path

The maximum adjustment path is 52° crankshaft angle.

d. The exhaust camshaft can only be set to two positions.

The maximum adjustment path is 22° crankshaft angle.

7. To adjust the camshafts, the camshaft timing adjustment valves must be actuated. What
actuates them?

a. The camshaft timing adjustment control unit

b. The engine control unit.

8. What creates the pressure for adjusting the camshafts?

a. The vacuum pump

28

b. The engine oil pump

29

Answers

1.) a

2.) a, b, c, d

3.) b

4.)1Hall sender 1 G40

2 Hall sender 2 G163
3 Inlet camshaft
4 Exhaust camshaft
5 Inlet camshaft adjustment timing valve 1 N205
6 Exhaust camshaft adjustment timing valve 1 N318
7 Engine control unit
8Oil pump

5.) 1 Outer rotor, connected to timing chain
2 Inner rotor, connected to camshaft
3 Inlet camshaft adjustment timing valve 1 N205
4 Exhaust camshaft adjustment timing valve 1 N318
5Hall sender 1 G40
6 Hall sender 2 G163

6.) b, d

7. ) b

8.) b

Notes

246

For internal use only © VOLKSWAGEN AG, Wolfsburg

All rights reserved. Subject to technical change without notice

040.2810.65.20 Technical status 7/01

❀ This paper was made with chlorine free

bleached cellulose.