Audi TT (2007 year). Manual — part 235

Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.

21

Steering system

Electromechanical steering system EPS

The electromechanical steering system EPS which
has proved successful in the Audi A3 is also fea-
tured in the new Audi TT. The following modifica-
tions have been made compared to the Audi A3:

381_028

new track rod outer joint with
larger joint diameter and
modified journal geometry

reduced steering angle, steering rack
shortened from 80 mm to 78 mm

new control unit due to new

control software without dsr function

In the case of the Audi TT, the power steering assist maps

are determined by the powertrain type (front wheel drive

or quattro) In the case of the Audi A3, the weight of the

front axle is the determinant factor.

Reference

For detailed information on the design and
function of the EPS system, refer to SSP 313.

Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.

22

Steering system

Steering column

A mechanical steering column is used in the Audi
TT. The steering column is basically identical in
design and function to the steering column in the
Audi A3. The following modifications have been
made compared to the Audi A3:

381_029

Shear element for crash safety adapted to TT

Longer drive shaft

Larger adjustment range:
Longitudinal adjustment: ± 30 mm
Height adjustment: ± 25 mm

381_030

Steering wheel

A redesigned steering wheel is used in the Audi
TT.All models are fitted with three-spoke leather-
bound steering wheels with integrated two-stage
airbag module. In addition to the standard version,
combinations are also available of multifunction,
Tiptronic and leather stitching in various colours.
The skeleton is made of magnesium. The diameter
of the steering wheel rim is 5 mm less than on the
Audi A3. As in the Audi A3, the airbag unit is bolted.
A new feature is the use cage nuts are used for tol-
erance compensation.The airbag module is centred
in the steering wheel with two locating pins.

Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.

23

Audi magnetic ride

Overview

The Audi TT is the first Audi to feature Audi mag-
netic ride - a new semi-active suspension system
with magneto-rheologically controlled dampers.
Sport or comfort damper settings can be selected at
the touch of a button.

381_031

Shock absorber damping
adjustment warning lamp K189

Vehicle level senders
G76-78,G289

Shock absorber damping
adjustment valves N336-339

ECD control unit (electronically
controlled damping) J250

Shock absorber damping
adjustment button E387

Audi magnetic ride improves driving dynamics and driving comfort for the following reasons:

– reduced body movement (pitch and roll)
– optimised vibration behaviour
– improved road-holding
– improved handling

Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.

24

Audi magnetic ride

381_033

Magnetic coil not
activated

Magnetic coil
activated

Piston bores

Operating principle

When the magnetic coils are not activated electri-
cally, the magnetic particles are arranged irregularly
in the damper oil.During the piston stroke, the indi-
vidual particles are forced with the fluid through the
piston bores. The particle-laden suspension damp-
ing fluid has a low resistance to the movement of
the piston. As a result the damping force is low.

When the magnetic coil is activated electrically, the
magnetic particles are aligned with the magnetic
field lines. Thus, long particle chains form in the
vicinity of the piston.
These particle chains are aligned cross-wise before
the fluid enters the piston bores. During the piston
stroke, individual particles break up and are forced
with the fluid through the piston bores. To "break
up" these chains, force must be applied, i.e. work
must be done. The resistance which the piston must
overcome is greater than in the case of a non-ener-
gised magnetic coil, and is dependent on the
amount of electrical current and the strength of the
magnetic field.
This allows greater damping forces to be achieved.

The damping function is based on the magneto-rhe-
ological effect. The prerequisite for this is the use of
a special damping fluid. This magneto-rheological
fluid is a suspension consisting of a hydrocarbon-
based synthetic oil in which soft magnetic particles
with a diameter of 3-10

µ

m are held in suspension.

To stabilise the fluid, various additives are added.
Applying a magnetic field changes the properties of
the magneto-rheological fluid. The magnetic parti-
cles are aligned in the direction of the magnetic
field lines. This alters the flux voltage of the fluid.

381_032

Magneto-rheological fluid in
non-magnetised state

Magneto-rheological fluid in
magnetised state

Magnetic particles

Magnetic field