Audi TT (2007 year). Manual - part 236

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System components

Damper

The magneto-rheological dampers are much sim-
pler in design than conventional dampers. The com-
plex conventional damping valves are no longer
required. These have been replaced by bores in the
piston through which the fluid is displaced. In addi-
tion, single-tube dampers are used. The magnetic
coils are integrated in the pistons.

Power is supplied through the hollow piston rods
along discrete lines from control unit J250. Depend-
ing on engine type (4 cylinder or 6 cylinder engines),
different front axle dampers are used.A single
damper is used for all engine types on the rear axle.

381_034

Pistons

Bores

Cable to electrical control
device

Front axle damper

Rear axle damper

Connector

Damper

Variable activation of the solenoid valve allows the
shock absorber damping force to be adjusted over a
wide range.

Audi magnetic ride

381_035

Damping speed [m/s]

Adjustment range of Audi magnetic ride

Conventional damper

mper

e [N]

Compression (bump)

Tension (rebound)

Comparison of the damping force characteristics of Audi magnetic ride and conventional dampers

Sport setting

Comfort setting

Sport setting

Damping force adjustments are made within millisec-
onds. This allows the damping force to be adapted to
requirements during the bump and rebound cycles.

ECD control unit (electronically controlled damping) J250

The control unit receives the measured data from
the vehicle level sender, as well as information on
the current driving condition from the ESP. The con-
trol unit processes the data and thus determines
the momentary activation currents for the dampers.
Each damper is activated individually. The dampers
are not activated when the vehicle is stationary. The
control unit is located under the front passenger
seat.

381_036

Vehicle level senders G76-78, G289

The vehicle level senders are identical in design and
function to those used in the Audi A6 and Audi A8.
The sampling rate is 800 Hz. Design and function
are described in detail in SSP 343. Measured data is
read in by control unit J250 across discrete lines,
processed and relayed to the headlight range con-
trol, control unit via the CAN bus.

Shock absorber damping adjustment button E387

Warning lamp K189

The button is used to select a damper setting. In
standard operation the dampers are configured for
comfort. A sport damping characteristic can be acti-
vated pressing the button. The LED indicator inte-
grated in the button indicates that the sport setting
is active. Depending on dash panel variant, an addi-
tional text message may appear.The signal from the
button is read in by the control unit across a dis-
crete line.

Warning lamp

System faults are indicated by a warning lamp in
the dash panel insert.The warning lamp is checked
whenever the ignition is turned on.
The warning lamp also comes on if the dash panel
insert has been coded incorrectly.

381_037

381_038

381_039

Audi magnetic ride

Special functions

Temperature model

The suspension damping becomes softer with
increasing magneto-rheological fluid temperature.
A software module for temperature compensation
is integrated in the control unit. The rising tempera-
ture is compensated by increasing the magnetic coil
activation current.
Likewise, the activation current is reduced at low
ambient temperatures.
Temperature is determined indirectly by measuring
the resistance of the magnetic coil.
A current of 3A is applied to the coil for the duration
of 40 ms.

The required voltage is determined and the resist-
ance is calculated.
The basic value is the resistance measured in a vehi-
cle which has been shut off for at least 6 hours. The
following measurements are correlated with the
basic value. Based on the change in resistance, the
control unit determines the actual temperature in
the shock absorber damper.In addition, the temper-
ature of the control unit is calculated. This is done
by evaluating the electrical currents provided by the
control unit to activate the coils.

Temperature shut-off

The magnetic coil activation current must be
increased in order to compensate for the effect of
temperature increase in the dampers. However,
increasing the electrical current causes further
heating of the magnetic coil.Upwards of a defined
threshold temperature of (90°C), therefore, it is no
longer possible for the driver to select 'Sport' mode.

Emergency operation in case of failure in electrical activation of the magnetic coil

In 'Sport' mode, higher damping forces are pro-
duced by increasing the magnetic coil activation
current. Activating the 'Sport' mode would, there-
fore, cause a further increase in the already high
temperature in the suspension damper. The control
unit is shut down when its temperature exceeds
110°C.

381_040

Damping speed [m/s]

Adjustment range of Audi magnetic ride

mper

e [N]

Compression (bump)

Tension (rebound)

Suspension damper force characteristic of Audi magnetic ride

Most comfortable damper setting

In case of failure in electrical activation of multiple
magnetic coils, the magnetic coils of all suspension
dampers are no longer activated.

In this case, the most comfortable suspension
damping characteristic is set.

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