Audi TT 2016 - Page 45

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Electro-mechanical power steering
(EPS)
In terms of its design, functional principle and service
operations, the electro-mechanical power steering
system is identical to the system already implemented in
the 2015 A3.
Operation
Depending on whether auto, dynamic or comfort mode is
selected, the system activates steering maps which provide
universal, dynamic or comfort-oriented power steering.
When individual mode is selected, the driver can freely
select one of threemaps.
Progressive steering
The Audi TT receives progressive steering as standard.
Progressive steering is provided by a variable steering ratio
using a special rack spline geometry. The steering ratio is at
its highest when driving in a straight line and during minor
steering inputs around the center position. Rotation of the
steering wheel through an angle of about 14° produces a
steering angle of about 1° at the front wheels (steering
ratio of approximately 14). The ratio decreases with
increasing steering angle, and thus becomes more direct.
This gives the AudiTT agile and precise handling in city
trac and on windy country roads with little steering
eort.
At large steering angles (for example, in inner-city areas or
when parking), the steering ratio is reduced to signicantly
reduce steering eort for the driver. The diagram below
clearly shows that with progressive steering, the steering
wheel has to be moved much less in order to turn the front
wheels to full lock.
This reduces amount of steering input required and gives
signicantly better dynamics during sporty driving maneu-
vers.
Steering lock with progressive steering
Steering lock with conventional steering
Progressive steering in the AudiTT
Conventional steering in the AudiA3
630_116
630_109
630_090
Reference
For more information about the electro-mechanical power steering (EPS), refer to eSelf-Study Program 960143, The 2015
Audi A3 Running Gear and Suspension System.
Rack
Steering ratio (-)
Pinion angle(°)
Steering pinion
Key:
630_096
Vehicle: Audi drive select
comfort
auto
dynamic
individual
68°F