2001 AUDI A4 ESP

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5
High safety standards
With a thoroughly optimised body design and
comprehensive safety equipment, the new
Audi A4 is able to comply with all current valid
safety standards, throughout the world.
Crash sensors for the front airbags integrated
directly into the bumper bar, improve occu-
pant protection.
Finely-tuned aerodynamics
Despite the greater frontal area and the cool-
ing air current for the air conditioner (stand-
ard), it was possible to improve the C
D

value
by 5 %, in comparison to its predecessor,
to 0.28.
A special feature is the so-called aero-floor,
which provides for optimal airflow on the
underside of the vehicle.
Communication centre on wheels
With regard to infotainment, the new
Audi A4 leaves nothing to be desired.
4 different audio systems, 2 differently config-
ured Navigation systems and a car phone
with voice operation are on offer.
Electronic stability programme (ESP)
including brake assistant
For the latest ESP generation, the hydraulic
brake assistant is an integral part of the
standard equipment.
It is intended to assist the driver by automati-
cally increasing the brake pressure during
emergency braking.
SSP254_048

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14
Crash sensors for front airbag G283, 284
Both sensors for front impact detection func-
tion in conjunction with the crash sensor and
the safe sensor which are integrated into the
airbag control unit J234.
Deceleration load
Time [ms]
Vehicle rebound Impact
Triggering of belt tensioners
Triggering of front airbags
Front airbags inflated
Belt force limiter
response
Damping function
response in
the steering column

SSP254_063
SSP254_064
Upper body
Head

If a certain signal threshold is exceeded in the
front airbag crash sensor, a threshold reduc-
tion is activated in the airbag control unit,
which results in a shorter triggering time.
Occupant protection
SSP254_058

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21
Injector
For the first time, an ICU injector (
I
nverse
C
av-
ity
U
ndercut) is used, which has a dual needle
guide.
The advantage of this ICU geometry is a sig-
nificantly improved spray formation, espe-
cially in the part throttle range for small
injection quantities and short needle lift.
SSP255_042
ICU seat geometry
Dual needle guide

Due to the improved spray formation through
the use of the ICU injector, it was possible to
reduce the exhaust emissions and the particle
values by up to 20 %.
ICU seat geometry Standard seat geometry
SSP255_041

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23
P
R+NDS

Innovations - automatic
gearbox
5-speed 01V automatic gearbox
The Audi A4 quattro MJ01 with 5-speed auto-
matic gearbox features a new shift lever gate,
together with a new shifting concept.
The existing selector lever positions, 4,3,2 are
discontinued and are replaced by the "S"
position.
Gearshift positions 4,3,2 have been discontin-
ued as they are hardly ever used in practice.
The DSP (dynamic shift programme) and "tip-
tronic" function have basically rendered them
superfluous.
With the selector lever is in the "S" position, a
sports shift programme provides the relevant
driving dynamics. In position "S", the DSP
also provides for adaptation of the driving set
values to the driving conditions.
The introduction of the "S" programme ena-
bles a significant extension of the useful shift
range between economy and sports.
The "S" programme comprises the following
special features:
– If, during driving with constant accelerator
pedal position, the selector lever is set to
the "S" position, the system always shifts
down, within defined limits.
– In order to achieve a direct driving reaction
in response to accelerator pedal actuation,
the converter clutch is closed during driv-
ing operation, where possible.
– If, in conjunction with the overall gearbox
ratio, 5th gear is designed as overdrive
gear (overdrive, 4+E), only 1st -4th gears
are shifted.
We recommend the multi-function steering
wheel (available as optional extra) with steer-
ing wheel "tiptronic" ("thumb shifting").
Gearbox output speed [rpm]
Throttle valve angle [%]

SSP254_103 SSP254_117
D - normal driving programme
S - sports driving programmeExample: Dynamics code 40
Shift map 1

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Brake system
The new Bosch ESP 5.7 is introduced in the
Audi A4. The ESP 5.7 is distinguished by the
following special features:
– The hydraulic unit and control unit form a
single unit.
– The charging pump (actuation of ESP
hydraulic pump V156) is discontinued.
– A brake assistant is included.
Hydraulic modulator
Due to the increased brake fluid viscosity at
extremely low ambient temperatures, the
required delivery rate for the return pump for
ABS V39 could not be achieved without a
charging pump (resulting from the increased
suction resistance in the system).
The purpose of the development of the
ESP 5.7 was to improve the suction of the ABS
return pump so that the charging pump was
no longer necessary.
The charging pump could be discontinued
through the use of a two-stage ABS return
pump, enlarging the cross-section of the
brake lines and the use of a larger-dimen-
sioned central valve in the brake master cylin-
der.
SSP254_094

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UTUTOTOTUT
UTUTOTOTUT

Running gear
The graphic shows a comparison of the
suction volumes of both pump versions.
In the single-stage ABS return pump, the
entire suction volume must be drawn in and
flow through the suction line during one
piston stroke (piston stroke from TDC to BDC). The suction pressure is correspondingly high
and increases with increasing viscosity.
Cavitation and the associated drop in
performance on the pressure side, are the
results.
Single-stage ABS return pump
Suction volumes
SSP254_095
Suction volumes

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Brake assistant
Investigations in accident research have
shown, that the majority of drivers fail to ade-
quately actuate the brakes in an emergency
situation.
This results in insufficient brake pressure
being generated to achieve maximum vehicle
deceleration.
This lengthens the braking distance.During emergency braking, the brake assist-
ant aids the driver by increasing the brake
pressure automatically, to a level exceeding
the locking limit.
The ABS (
A
nti-lock
b
raking
s
ystem) is thus
quickly brought into the operating range,
which enables a maximum vehicle decelera-
tion to be achieved.
Brake servo pressure sensor G294 is used for
detection of emergency braking.
Time [t]
Pressure [p]

For this purpose, the pressure increase gradi-
ent (pressure build-up with respect to time) is
evaluated and, if necessary, the brake assist-
ant is activated.
SSP254_093
Emergency braking
Normal braking distance
Pressure sensor G294

Running gear
SSP254_092

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• Phase 2
If the pressure determined by the driver falls
below a certain value after triggering of the
brake assistant, the system pressure is
restored to the pedal pressure determined by
the driver. The function of the brake assistant is
sub-divided into 2 phases:
• Phase 1
If the pressure increase gradient exceeds a
specified value (emergency braking), the ABS
return pump and the relevant solenoid valve
are activated by the ESP control unit and the
brake pressure is thus increased into the ABS
control range, in a similar manner to that of
the control system for an electronic differen-
tial lock.
The integral inlet and outlet valves in the
hydraulic modulator are no longer sim-
ply switched on/off, but are regulated
via supplied voltage.
This enables more precise control on
extremely slippery surfaces, e.g. ice.
SSP254_084
Time [t]
Brake pressure [p]
Brake pressure determined by an
experienced driver
Regulated brake pressure
(brake assistant)
Determined brake pressure
insufficient inexperienced driver Brake assistant activated Brake pedal unloaded Brake assistant
switches off
Phase 1Phase 2
ABS control
range