engine AUDI S8 2009 Repair Manual

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& WARN ING (continued )
vehicle and have it towed to the nearest Aud i dealer or qualified
workshop.
;:a
Brake booster
The brake booster a dds ex tra braking power.
The bra ke booster works wit h vacuu m pressure w hich is created
only when the engine is running =>& .
& WARNING
• Never let the vehicle roll to a stop with the engine shut off .
• If the brake boo ster i s not wor king , for e xample when towing
your vehicle, or because the brake booster has somehow been
damaged , the brake pedal must be pre ssed considerably harder to
make up for the lack of booster as sistance. •
Functioning of Anti-Lock Brake System {ABS)
A BS prevents the wheels from l ocking up under braking.
The ABS contributes effective ly to vehicle contr ol since i t preven ts
t he whee ls from
locking whe n the brakes are appl ied. This mea ns
that the vehicle remains steerable and is less likely to skid .
With ABS you do not need to pump the brake. Ju st hold the brake
pedal down .
However, do no t ex pect the ABS to sho rten braking distance u nder
all circumstances. When drivin g on gravel or on new ly fallen snow
on top of icy surfaces, bra king distance may be even longer, there­
f ore, under these c ircu msta nces, it is especially importa nt that you
drive slow ly and with great care.
How the ABS system works
An au toma tic c heck is made when a s peed of about 4 mph (6 km/h)
is reached. When this happens, a pumping no ise can be heard.
I f an individual wheel begins to rotate too slowly in relation to
veh ic le speed and tends to lock, the ABS au tomat ically reduces
brake pressure to prevent that whee l from locking.
Th is au tomatic a djust ment pr oces s wi ll cause a
slight vibration o f
the brake peda l and some noises to alert you that vehicle speed
m ust be ada pted to e xisting road and traff ic conditio ns.
& WARNING
Although the ABS is very effective , alway s remember that braking
capability is limited by tire traction . Always adjust your driving
speed according to the road and traffi c conditions. Do not let the
extra safety afforded by the ABS tempt you into tak ing extra risks.
The ABS cannot overcome the laws of physics.
[ i ] Tips
• I f ABS is not functioning properly, a wa rning light will come on .
See=>
page 27.
• I f a faul t occurs in t he ABS, t he EDL is also n ot fu nctio ning . Th is
is indicated by the ABS warning light. •
Brake assistant
T he brak e assi stant i s designe d to ac hie ve th e optimu m
bra kin g eff ec t.
The bra ke assistant helps to increase the effective braking power
an d th us to achieve a shorter s top ping dis tan ce. If the dr iver
presses the brake pedal very quic kly, the brake assistant automati ­
c a lly bo osts t he braking force to the max imum level, up to th e point
where the anti -lock brake function (ABS) intervenes to stop the
whee ls from locking. You shou ld then keep the brake peda l pressed .,

until the vehicle has braked to the required speed. The brake assis­
tant switches itself off as soon as you release the brake pedal.
The brake assistant will not be operative if there is a malfunction in
the ABS.
& WARNING
Please remember that the accident risk always increases if you
drive too fast, especially in corners or on a slippery road, or if you
follow the vehicle ahead of you too closely. Increased risk of an
accident cannot be compensated for even by the brake assistant,
so always maintain a safe speed. •
Servotronic® -advanced power
steering system
The power steering systems uses the power of the
running engine to allow precise steering with little effort.
The advanced Servotronic ® power steering system senses the road
speed and electronically adjusts power assistance to provide
comfortable and safe steering response exactly matched to the
vehicle speed.
Power steering will not work if the engine is off. As a result, the
steering whee l wil l be hard to turn.
The power steering fluid level is checked during the scheduled
maintenance services.
0 Note
If there is an electronic malfunction, servotronic will sti ll function
like a conventional power steering system, providing a constant
steering support force that is no longer proportionate to the vehicle
speed. This is most noticeable when turning the steering whee l at
Controls and equip­
ment Safety first Vehicle operation
Intelligent technology
low speeds (for examp
le when parking), -more effort will be
requ ired than usual.
• Be aware of the different than usual steering response and
adjust your steering force accordingly .
• Have the problem checked and set right by an Audi dealer as
soon as possible.
[ i ] Tips
• When the engine is running, never hold the steering whee l
turned all the way to the right or to the left for longer than 15
seconds. The power steering pump will overheat the hydraulic fluid
if you keep holding the steering whee l turned a ll the way. This is
likely to damage the power steering system.
• If the power steering system shou ld fail entire ly, or if the engine
is not running (for examp le, while being towed), you will still be able
to steer the vehicle . However,
considerably more effort will be
required to do so.
• If the power steering system shou ld have a leak, or is not func ­
t ioning properly, contact your authorized Audi dealer immediately.
• The power steering system requires a special ly formulated
hydraulic fluid. The power steering reservoir is the one located most
forward on the left side of the engine compartment=>
page 310. The
correct fluid level in the reservoir is important for proper func­
tioning of the power steering .•
Driving with your q attro®
With All Wheel Drive, all four wheels are driven.
General information
With All Whee l Drive, power is distributed to all four wheels. This
happens automatically depending on your dr iving style and the
road conditions at the time. See also=>
page 271, "Electronic differ ­
entia l lock (EDU".
Vehicle care Do-it-yourself service Technical data

ll}Jl __ ln_ t _e_ ll-'"ig ...,_ e_ n_t _t_ e_ c_ h _ n_o _ l_o _,.g= y,_ __________________________________________ _
Winter tires
When driving in the winter, your vehicle with All Wheel Drive has an
advantage, even with regular tires. In winter road conditions it may be advisable to mount winter tires (or all -season tires) for improved
driveability and braking: these tires must be mounted on
all four
wheels.
See also ~ page 343, "Winter tires".
Tire chains
Where tire chains are mandatory on certain roads, this normally
also applies to vehicles with All Wheel Drive~
page 344, "Snow
chains".
Replacing wheels/tires
Vehicles with All Wheel Drive must always have tires of the same
size. Also avoid tires with different tread depths . For details see
page ~
page 338, "New tires and replacing tires and wheels".
Off-Road driving?
Your Audi does not have enough ground clearance to be used as an
off-road vehicle. It is therefore best to avoid rough tracks and
uneven terrain as much as possible. Also refer to~
page 281.
& WARNING
Always adjust your driving to road and traffic conditions. Do not
let the extra safety afforded by All Wheel Drive tempt you into
taking extra risks.
• Although the All Wheel Drive is very effective, always
remember that braking capacity is limited by tire traction. You
should therefore not drive at excessive speeds on icy or slippery
road surfaces.
• On wet road surfaces, be careful not to drive too fast because
the front wheels could begin to slide on top of the water (aqua­
planing).
If this should occur, you will have no warning from a
sudden increase in engine speed as with a front-wheel drive
vehicle. Always drive at speeds which are suited to the road condi­
tions - risk of crash. •
Energy management
Starting ability is opt:m·zed
Energy management controls the distribution of electrical
energy and thus optimizes the availability of electrical
energy for starting the engine.
If a vehicle with a conventional energy system is not driven for a
long period of time, the battery is discharged by idling current
consumers (e.g . immobilizer) . In certain circumstances it can result
in there being insufficient energy available to start the engine.
Intelligent energy management in your vehicle handles the distribu­
tion of electrical energy. Starting ability is markedly improved and
the life of the battery is extended.
Basically, energy management consists of
battery diagnosis, idling
current management
and dynamic energy management.
Battery diagnosis
Battery diagnosis continuously determines the state of the battery.
Sensors determine battery voltage, battery current and battery
temperature. This determines the current state of charge and the
power of the battery .
Idling current management
Idling current management reduces energy consumption while the
vehicle is standing. With the ignition switched off, it controls the
energy supply to the various electrical components . Data from
battery diagnosis is considered.
Depending on the battery's state of charge, individual consumers
are gradually turned off to prevent excessive discharge of the
battery and thus maintain starting capability.
Dynamic energy management
While the vehicle is being driven, dynamic energy management distributes the energy generated according to the needs of the indi-•

vidual components. It regulates consumption, so that more elec­
trical energy is not being used than is being genera ted and ensures
an optimal state of charge for the battery.
[ i ] Tips
• But even energy management cannot negate the limits of
physics. Consider that the power and life of a battery are limited.
• If starting ability is threatened, you are informed by a warning
~ page 277, "Driver notification in the instrument cluster
display". •
What you should know
The highest priority is given to maintaining starting capa ­
bility.
The battery is severely taxed in short -distance driving, in city traffic
and during the cold time of year . Abundant electrical energy is
required, but only a little is generated . It is also critical if the engine
is not running and e lectrical components are turned on. In this
instance energy is being consumed but none is being generated .
It is in precisely these situations that you wi ll notice energy manage ­
ment actively regulating the distribution of energy.
Vehicle stands for an extended period
If you do not drive your vehicle over a period of several days or
weeks, electrical components are gradually cut back or switched off.
This reduces energy consumption and maintains starting capability
over a longer period.
Be aware that when you unlock your vehicle, some of the conve ­
nience functions may not operate, such as the Convenience key, the
remote control or the power seat adjustment. The convenience
functions will be available again when you turn on the ignition and start the engine.
Controls and equip­ ment Safety first Vehicle operation
Intelligent technology
With the
engine turned off
If you listen to the radio, for examp le, with the engine turned off or
use other MMI functions, the battery is being discharged.
If starting capability is jeopardized due to energy consumption, the
following warning appears in the MMI display:
Please start engine, otherwise system will switch off in 3
minutes .
The warning indicates that the system wi ll be turned off automati­
cal ly after 3 minutes. If you wish to continue using the functions,
you have to start the engine .
With the engine running
Although e lectrica l energy is generated when the vehicle is being
driven, the battery can become discharged. This happens mostly
when little energy is being generated and a great deal consumed
and the battery's state of charge is not optimal.
To bring the energy balance back into equi librium , consumers
which require especia lly large amounts of energy are temporarily
cut back or switched off. Heating systems in particular require a
great deal of energy. If you notice, for example, that the heated
seats* or the heated rear window are not heating, they have been
temporarily cut back or switched off. These systems will be available
again as soon as the energy balance has been restored.
You wil l also notice that engine idle speed has been increased
s lightly . This is norma l and not a cause for concern . By increasing
engine idle speed the additiona l energy required is generated and
the battery is charged. •
Driver notification in the instrument cluster
display
If the battery's state of charge is not in the optimal range, this driver
notification appears in the instrument cluster display:
Low battery charge: battery will be charged while driving ~
Vehicle care Do-it-yourself service Technical data

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This notification reminds you that the starting capability of the
engine may be limited . As soon as you s tart driv ing again, the
battery wi ll be recharged and the notification wi ll go out .
Driver notification appears and goes out again
If this driver notification appears after the ignition is turned on or
wh ile dr iving and i t go es out again after a w hile, the ba ttery has
been adequately recharged .
Driver notification appears and does not go out again
If this driver notification appears after the ignition is turned on or
w hile driving and d oes not go out aga in, the batte ry's s tate of
charge is not in the optimal range . Starting abi lity is restricted . Have
t he battery checke d as soon as p ossi ble at a deale rship .•

Driving and environment
The first 1,000 miles (1,500 km) and afterwards
!\Jew engine
The engine needs to be run-in during the first 1,000 miles
(1,500 km).
F o r th e fir st 600 mil es (1,000 kilomet ers):
Do not use full throttle.
- Do not drive faster than 3/4 of the top speed marked on
the speedometer.
- Avoid high engine speeds .
From 600 t o 1,000 mil es (1,000 t o 1,500
kil om eter s):
- Speeds can
gradually be i ncreased to t he maximum
permiss ible road or engine speed .
During and aft er br eak-in p eri od
- Do not rev the engine up to high speeds when it is cold. This applies whether the transm ission is in N (Neutral) or
1n gear.
Aft er the br eak-in p eriod
- D o not exceed max imum e ngine speed unde r any
circumstances.
- Upshift into the next higher gear
before reac hing the red
area at the end of the tachome ter scale ~
page 12 .
Controls and equip­
ment Safety first Vehicle operation
Dri
ving and environm ent
During the first few hours of driving, the eng ine's internal friction is
higher than later when all the moving parts have been broken in.
How well this break -in process is done depends to a considerable
extent on the way the vehicle is driven during the first 1,000 miles
(1,500 ki lometers).
0 Not e
Extreme ly high engine speeds are automatically reduced. However,
these rpm limits are programmed for an engine well run-in, not a
new engine .
~ For the sake of the environment
Do not drive with unnecessarily high engine speeds -upshifting
early saves fuel, reduces noise and protects the environment .
New tires
If your v ehic le is running on new tires, driv e particularly
carefu l for the first 350 miles (500 ki lometers) after fitting.
& WARNING
N ew tir es tend to be slipp ery and mu st al so be "broken -in ". B e
su re to r ememb er thi s during th e fir st 350 m ile s ( 50 0 k ilome te rs).
Brak e gen tly. Av oid follow ing close ly behind other vehicl es or
o the r s ituati ons that mig ht requi re su dde n, ha rd b raking.•
Vehicle care Do-it-yourself service Technical data

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New brake pads
--
Remember that new brake pads do not have a full braking
effect during the first 250 miles (400 kilometers) after they
are installed .
New brake pads have to be "burnished in" before they have optimal
grab =>& .
During the break -in period, you should avoid putting severe loads
on the brakes . Severe loads include, for examp le, sudden hard
braking, in particular at very high speeds or, for example, on moun­
tain passes.
& WARNING
New brake pads don't have the best stopping power and must be
"broken-in" during the initial 100 to 150 miles (150 to 200 kilome­
ters) of normal city driving. You can compensate for this by
pressing the brake pedal more firmly . This also applies later when
new pads are installed.
:J
Catalytic converter
It is very important that your emission control system
(catalytic converter) is functioning properly to ensure that
your vehicle is running in an environmentally sound
manner.
- Always use lead-free gasoline:=> page 303, "Fuel supply".
- Never run the tank down all the way to empty.
- Never put too much motor oil in your engine ==>
page 314,
"Adding engine oil 't=:;r\11
•
Never try to push- or tow-start your vehicle.
The catalytic converter is an efficient "clean-up" device built into the
exhaust system of the vehicle. The catalytic converter burns many
of the po llutants in the exhaust gas before they are released into the
atmosphere.
The exclusive use of unleaded fuel is critically important for the life
of the catalytic converter and proper functioning of the engine.
& WARNING
• Do not park or operate the vehicle in areas where the hot
exhaust system may come in contact with dry grass, brush, fuel
spill or other material which can cause a fire .
• Do not apply additional undercoating or rustproofing on or
near the exhaust manifold, exhaust pipes, catalytic converter or
heat shields. During driving, the substance used for undercoating
could overheat and cause a fire .
0 Note
• Be aware that just one tank filling with leaded fuel will alr eady
seriously degrade the performance of the catalytic converter.
• Do not exceed the correct engine oil level=>
page 314.
• Do not drive until the fuel tank becomes completely empty. The
engine could misfire. Unburned fuel could also get into the exhaust
system and this could cause the catalytic converter to overheat.
• Do not turn off the ignition while the vehicle is moving.
• Do not continue to operate your vehicle under these conditions,
as otherwise fuel can reach the catalytic converter. This could result
in overheating of the converter, requiring its replacement .
• To assure efficient operation of the Emission Control System:
- Have your vehicle maintained properly and in accordance with
the service recommendations in your Warranty
& Maintenance
booklet. •

- Lack of proper maintenance as wel l as improper use of the
vehic le wi ll impair the func tion of the emission con tro l system
and could lead to damage.
<£> For the sake of th e envir onm ent
Even when the Emission Control System is operating properly, the
exhaust gas can have a su lfur -like exhaust gas smell under some
operating states . This depends on the sulfur content of the fuel
being used. Using a different brand of fue l may help, or filling the
tank with lead-free super grade gasoline. •
Avoid damaging the vehicle
When you are driving on poor roads, or over curbs, steep ramps,
etc., make certain that low- lying parts such as spoi lers and exhaust
system parts do not bottom out and get damaged.
This is especially true for vehicles with low-slung chassis (sports
chassis) * and fully loaded vehicles .
a
Operate your vehicle economically
and minimize pollution
General
Your personal style of driving will determine the economy
of your vehicle, as well as exhaust and noise levels.
Fuel economy, environmental impact, and wear on your engine,
brakes and tires largely depend on three factors:
• your personal driving style
• operating cond itions
• technica l limitations
Controls and equip­
ment Safety first Vehicle operation
Dri
ving and environm ent
If you anticipate what you need to do next and drive economica lly,
you can easily cut your fuel consumption by 10 -15 percent . This
section wil l give you some tips on how you can help the environ­
ment and your pocketbook.
[ i ] Tips
The consumption estimates as published by ENV IRONMENTAL
PRO TEC TION AGENCY (EPA) and Transport Canada may not corre ­
spond to your actua l consumption on the road, which wi ll vary
depending upon vehic le load and speed, road and weather condi­
tions, trip length, etc. •
Drive smoothly and keep a lookout ahead
Vehicles use the most fuel when they ore accelerating.
-Avoid unnecessary accelerat ing and braking.
Vehicles use the most fuel when they are accelerating . If you antici­
pate what is going to happen next, you wi ll need to brake less and,
thus, acce lerate less. Let the vehicle coast whenever possib le - for
examp le when you see that the next traffic light is red. •
Avoid full throttle
Driving at moderate speeds saves fuel and improves your
mileage.
-Try and keep well below your car 's max imum speed.
Acce lerating gently reduces fue l consumption , engine wear, and
does not disturb the environment.
Fue l consumption, exhaust emissions and engine noise increase
disproportionately at high speeds . If you drive at approximate ly
three quarters of top speed, fuel consumption wil l be reduced by
Vehicle care Do-it-yourself service Technical data

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one half. Never drive faster than the posted speed limit and weather
conditions permit. •
Reducing unnecessary =citing
Even when your car is just idling it burns up fuel.
- Shut the eng ine off when you are not driving the vehicle .
- Do not warm up the vehicle by letting the engine run at
idle.
It makes sense to shut off the engine in traffic jams, when waiting
for trains to pass at rai lroad crossings , or at traffic lights that have
long waits on red. Turning the engine off for just 30 -40 seconds
saves more fuel than is burned starting the engine again .
It takes a long time for the engine to warm up fu lly when it is
running at idle. However, wear and noxious emissions are especially
high when the engine is warming up. So you should drive away as
soon as you start the engine and avoid running at high rpms while
the engine is still warming up.
0 Note
Do not leave engine idling unattended after starting . If warning
lights should come on to indicate improper operation, they would
go unheeded. Extended idling also produces heat, which could result in overheating or other damage to the vehicle or other
property .•
Regu1ar ma1--.tenance
A badly tuned engine unnecessarily wastes a lot of fuel.
-Have your vehic le serviced at regular intervals .
By having your vehicle regularly serviced by an Audi dealer helps to
ensure that it runs properly and economically. The condition of your
vehic le not only affects its safety and abi lity to hold its value, it also
affects
fuel con sumpt ion.
C hec k your o il e ach time you fill your t ank.
The amount of oil used is related to engine load and speed.
It is norma l for the oil consumption of a new engine to reach its
lowest va lue after a certain mileage has been driven.
You must drive your vehicle about 3,000 miles (5,000 kilometers) before you can properly assess oil consumption .
This also applies to fuel consumption and engine output .
0 Note
• Have your vehicle maintained properly and in accordance with
the service recommendations in your Warranty
& Maintenance
booklet. Lack of proper ma intenance as well as improper use of the
vehic le wi ll impair the function of the emission control system and
cou ld lead to damage.
• Do not alter or remove any component of the Emission Control
System unless approved by the manufacturer.
• Do not alter or remove any device, such as heat shields,
switches, ignition wires, valves, which are designed to protect your
vehicle's Em ission Control System and other important vehicle
components .•
Fewer short tr ips
Fuel consumption will always be relatively high on short
trips.
- Try to avoid driving short dista nces wi th a cold engine. _,

The engine and catalytic converter have to reach their optimal oper­
ating temperature to reduce fuel consumption and noxious emis ­
sions effectively.
Just after starting, a cold engine in a mid -size car only achieves a
fuel economy of 6-8 miles per gallon (30-401/100 km). After about a
half a mile, fuel economy climbs to 12 mpg (201/100 kml. After about
2.5 miles (4 km), the engine is at its proper operating temperature
and fuel economy has reached a normal level. So you can see that
you should avo id short tr ips whenever possible.
The outside temperature is also critical in this regard. Your car
consumes more fuel in the winter than in the summer. •
Controls and equip­ ment Safety first Vehicle operation
Driving
and environment
Vehicle care Do-it-yourself service Technical data