engine AUDI S8 2008 Repair Manual

Intellig ent tec hnol ogy -
------------ -=--=-= '-
& WAR NIN G (c onti nued )
acc ident canno t b e co mp ensat ed for even b y th e br ake assis tant,
s o alway s maintain a safe sp eed . •
Servotronic® - advanced power
steering system
The power steering systems uses the power of the
running engine to allow precise s teering with little effor t.
The advanced Servotronic® power steering system senses the road
speed and electronically adjusts power assistance to provide
comfortab le and safe steer ing response exactly matched to the
vehic le speed.
Power s teeri ng 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 serv ices.
0 Note
If there is an electron ic ma lfunction, servotronic will sti ll funct ion
like a conventiona l power steering system, providing a constant
steer ing suppor t force that is no longer proportionate to the vehicle
speed . This is most noticeable when turning the steering wheel at
low speeds (for examp le w hen parking), -more effor t wi ll be
required than usual.
• Be aware of the different than usua l steering response and
adjust your steering force accordingly .
• Have the problem checked and set right by an Aud i dea ler as
soon as possib le.
Controls and equip­ ment Safety first Vehicle operation
[
i ] Tip s
• When the engine is running, never hold the steer ing whee l
turned all the way to the right or to the left for longer than 15
seconds. The power steer ing pu mp wil l overheat the hydraul ic fluid
if you keep ho lding the steering whee l turned a ll the way. This is
like ly to damage the power steering system.
• I f the power steering system shou ld fail entire ly, or if the engine
is not runn ing ( for examp le, wh ile be ing towed), you w ill st ill be able
to steer the vehicle . However, considerably more effort will be
requ ired to do so.
• I f the power steering system shou ld have a leak, or is not func ­
tioning properly, contact your author ized Audi dealer im mediately.
• The power stee ring system requires a special ly formulated
hydrau lic fluid . The power steer ing reservo ir is the one located most
forward on the left side of the engine
compartment => page 308. The
correct flu id level in the reservo ir is important for proper func ­
tioning of the power steering. •
Driving with your quattro®
With All Wheel Drive, all four wheels are driven.
Genera l inf orm ati on
With All Whee l Drive, power is d istributed to all fo ur wheels. This
happens automatically depending on your driving style and the
road condi tions at the time . See
a lso => page 269, "Electronic differ ­
entia l lock ! EDU" .
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
driveabi lity and braking: these ti res must be mounted on all four
wheel s. See
also=> page 341, "Winter tires". ~
Vehicle care Do-it-yourself service Technical data

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Tire chains
Where tire chains are mandatory on certain roads, this normally
also applies to vehicles with All Wheel
Drive:::::, page 342, "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 336, "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 279.
& 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 optimized
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 -_,,,

Intellig ent tec hnol ogy -
------------ -=--=-= '-
vidual components . It regulates consumption, so that more elec­
t rical energy is not be ing used than is be ing genera ted and ensures
an optimal state of charge for the battery .
[ i ] Tip s
• 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 275, "Driver notification in the instrument cluster
display" .•
What you should know
The highest priority is given to maintaining starting capa ­
bility.
T he battery is severely taxed in short -distance driving, in city traffic
and during t he co ld time of year . Abundant e lectrica l energy is
required, but on ly 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 .
I t is in precisely these situations that you wi ll notice energy manage ­
ment active ly regulating the d istr ibut ion of energy.
Vehicl e stands for an extended period
If you do not drive your vehicle over a per iod of several days or
weeks, electrica l components are gradually cut back or switched off.
This reduces energy consu mpt ion and maintains starting capability
over a longer period .
Be aware t hat when you unlock you r ve hicle, some o f the conve ­
nience functions may not operate, such as the Advanced Key, the
remote contro l or t he power seat adjustment. T he convenience
functions will be available again when you turn on the ignition and start the engine .
Controls and equip­
ment Safety first Vehicle operation With th
e engin e turned off
If you listen to the radio, for examp le, with t he engine tu rned off or
use other MMI functions, the battery is being discharged.
I f starting capabi lity is jeopardized due to energy consumption, the
f o llow ing warn ing appears in t he MMI display:
Ple ase start engine , other wise sy stem will s witch off in 3
minute s.
The warning indicates that the system wi ll be turned off au tomat i­
ca lly 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 vehic le is being
driven, the battery can become discharged. This happens mostly
when little energy is being generated and a great deal co nsumed
and the battery's state of charge is not optimal.
To br ing the ene rgy balance bac k into equi librium , cons umers
which require especially large amounts of energy are temporar ily
cu t back or switched off . Heating systems in part icu lar require a
great deal of energy. If you notice, for example, that the heated
seats* o r the heated rear w indow are not heating, they have been
temporari ly cut back or switc hed off. These systems wil l be avai lable
again as soon as the energy balance has been restored.
You wil l also notice t hat engi ne idle speed has been increase d
s lightly . This is norma l and not a cause for concern . By increasing
engine idle speed the addi tiona l energy required is ge nerated a nd
the battery is charged. •
Driver notification in the instrument cluster
display
I f the battery's state of charge is not in the optima l range, this driver
no tificat io n ap pears in the instrument cl uster d isplay:
t:3 Low battery ch arge : battery will be charged while dri ving .,_
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 d riv ing aga in, 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
w hile dr iv ing 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 a nd do es n ot go out aga in, t he bat te ry's state of
charge is not in the optimal range . Starting abi lity is restricted . Have
th e battery checke d as soon as p ossi ble at a deale rs h ip . •

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Driving and environment
The first 1,000 miles (1,500 km) and
afterwards
New engine
The engine needs to be run-in during the first 1,000 miles
(1,500 km).
For the first 600 miles (1,000 kilometers):
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 to 1,000 miles (1,000 to 1,500
kilometers):
- Speeds can gradually be increased to the maximum
permissible road or engine speed.
During and after break-in period
-Do not rev the engine up to high speeds when it is cold.
This applies whether the transmission is in N (Neutral) or
1n gear.
After the break-in period
- Do not exceed maximum engine speed under any
circumstances.
- Upshift into the next higher gear
before reaching the red
area at the end of the tachometer
scale => page 12.
Controls and equip­
ment Safety first
Vehicle operation
During the first few hours of driving, the engine'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 kilometers).
0 Note
Extremely 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 vehicle is running on new tires, drive particularly
careful for the first 350 miles (500 kilometers) after fitting.
& WARNING
New tires tend to be slippery and must also be "broken-in". Be
sure to remember this during the first 350 miles (500 kilometers).
Brake
gently. Avoid following closely behind other vehicles or
other situations that might require sudden, hard braking.
•
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
effec t 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 s hou ld 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 ­
t ain passes.
& WARNING
N ew brake p ad s don 't h ave the be st stopping po wer and mu st be
"broken -in " during the initial 100 to 150 mile s (150 to 200 kil ome ­
t e rs) of norm al c ity dri ving . You can comp en sa te for thi s by
pr ess ing the brake ped al more firmly . Thi s al so appli es later when
ne w pad s a re in sta lled. •
Catalytic converter
It is very important tha t your emission control sys tem
(catalytic converter) is functioning properly to e nsure that
y o ur vehicle is running in an environmentally sound
manner.
-Always use lead-f ree gasoli ne :=> page 301, "Fuel supply".
-Never run the tank down a ll the way to empty.
-Never put too much motor o il in your engine :=> page 312,
"Adding eng ine oil 'l=;r111
•
-Never try to push -or tow -s ta rt yo ur vehic le.
T he catalytic converter is an efficient "clean -up" device built into the
exhaust system of the vehicle. The catalytic converter burns ma ny
of the po llutants in the exhaust gas before they are released into the
atmosphere.
The exclusive use o f un leaded fue l is critica lly important for the l ife
of the cata lytic converter and proper functioning of the engine.
& WARNING
• Do not park or operate th e veh icle in ar ea s where the hot
e x hau st sys tem m ay come in cont act w ith dr y grass, brush , fuel
s pill or other material which can cau se a fire .
• Do not appl y additi ona l u ndercoating or ru stpr oofing on or
near the exhau st manifol d, exhau st pipe s, ca tal ytic converter or
h ea t shield s. Du ring dri ving , the sub sta nce u sed f or under coating
c ould overhe at and cau se a fir e.
0 Note
• Be aware that just one tank filling with leaded fue l wi ll already
seriously degrade the performance of the catalyt ic converter.
• Do not exceed the correct engine oil
level => page 312 .
• Do not drive until the fuel tank becomes comp letely empty . The
engine cou ld misfire. Unburned fuel could also get into the exhaust
system and this could cause the catalytic converter to overheat .
• Do not turn off t he ignition wh ile the vehicle is moving.
• Do not continue to operate your vehicle under these conditions,
as otherwise fuel can reach the cata lyt ic converter . This cou ld result
in overheating of the converter, requiring its rep lacement .
• To assure eff ic ient operat ion of the Emiss ion Contro l System:
- Have your vehicle maintained properly and in accordance with
the service recommendations in your Warranty
& Maintenance
booklet. _,.

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- Lack of proper maintenance as wel l as improper use of the
vehic le will impair the func tion of the emission con tro l system
and cou ld lead to damage .
<£> For the sake of the envir onment
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 b rand of fue l may help, or fil ling the
tank with lead-free super grade gasol ine. •
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.
T his is especial ly true for vehicles with low -s lung chassis (sports
chassis)* and ful ly loaded vehicles .•
Operate your vehicle economically
and minimize pollution
General
Y o ur personal style of driving will determine the economy
of your vehicle , as well as exhaust and noise levels.
Fuel economy, environmenta l impact, and wear on your engine,
brakes and t ires largely depend on three factors :
• your personal driving style
• operat ing cond it ions
• t echnica l limitations
Controls and equip­
ment Safety first Vehicle operation
I
f you anticipate what you need to do next and drive economica lly,
you can eas ily cut your fuel consumptio n by 10 -15 percent . This
section wil l give you some tips on how you can help the environ­
ment and your poc ketboo k.
[ i ] Tips
The consumption estimates as published by ENV IRO NME NTA L
PRO TECTION AGENCY (EPA) and Transport Canada may not corre ­
spond to your actua l consumption on the road, which wi ll vary
depe nding upon veh ic 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 .
-Avo id unnecessary accelerat ing a nd braking .
Vehicles use the most fue l when they are accelerating . If you antici ­
pate what is going to happen
ne xt, 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 we ll below your car 's max imum speed.
Acce lerating gently reduces fue l consumption, engine wear, and
does no t disturb the envir onment.
Fue l consumption, exhaust emissions and engine noise increase
dispropo rtionately at h ig h speeds . If yo u drive at approxi mate ly
three quarters of top speed, fuel consumpt ion 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
co nditions permit. •
Reducing unnecessary idling
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
id le .
It makes sense to shut off the engine in traff ic 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 fue l 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 em issions are espec ially
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 sti ll 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 .•
Regular maintenance
A badly tuned engine unnecessarily wastes a lot of fuel.
- H ave your vehicle serviced at regular intervals .
By having your vehicle regularly serviced by an Audi dealer helps to
ensure t hat it runs properly and economical ly . The condit ion of your
vehic le not only affects its safety and abi lity to hold its va lue, it also
affects
fuel con sumpt ion .
C hec k your oil each time you fill your tan k.
The amount of oil used is related to engine load and speed.
I t is norma l for the oi l 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 .
T his also applies to fuel consump tion and engine output .
0 Note
• Have your vehicle maintained properly and in accordance with
t he service recommendat ions 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 Contro l
System unless approved by the manufacturer.
• Do not alte r or remove any device, such as heat sh ields,
switches, ignition wires, valves, which are designed to protect your
vehic le's Emission Control System and other important vehic le
components .•
Fewer short trips
Fuel consumption will always be relatively high on short
trips.
- Try to avoid driving short dista nces with a cold engine. ~

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T he engine and catalytic converter have to reach their optimal op er­
a ting t emp era tur e
to reduce fuel consumption and noxious emis ­
sions effective ly .
Just after starting, a cold engine in a mid -size car only achieves a
fue l economy of 6-8 m iles per gal lon (30-40 1/100 km). After about a
half a mi le, fue l economy climbs to 12 mpg (201/100 km). After about
2.5 m iles (4 km), the engine is at its proper operat ing temperature
and fuel economy has reached a normal level. So you can see that
you should avo id short tr ips whenever poss ib le .
The
out sid e te mperature 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
Vehicle care Do-it-yourself service Technical data

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Operating instructions
M ax im um tra iler weig ht
A trailer for your vehicle is limited to a typ ical c lass 1 or class 2
trailer.
T ra ile r l oad d is tributi on
Be sure the load in the trailer is he ld securely in place to prevent it
from shifting forward, backward or s ideways .
Never a llow a pass enger to r ide in a trailer:::::, & in "Driving instruc­
t ions" .
Engin e coo lin g sys te m
Tow ing a trai ler makes the engine work harder. It is important that
the cooling system's performance is up to the additiona l load. Make
sure that the coo ling system has enough fluid .
Tire press ure
When towing a trailer, inflate the tires of your veh icle to t he co ld tire
pressure listed under "Full load" on the labe l located either on the
driver's side B -pil lar (visible when the door is open) or inside the fuel
filler flap . Inflate trailer tires to trai ler and tire manufacturers' spec­
ifications.
L ig ht s
The head light settings should be checked wit h the trai ler attached
before driving off. Check to make sure both vehicle and trai ler lights
are working properly .
Safe ty c ha in s
Be s ure trailer safe ty chains are properly connected from the trailer
to the hitch on the vehicle. Leave enough slack in the chains to
permit turning corners . When yo u insta ll safety chains, make sure
they will not drag on the road when you are driving.
T he chains should cross under the trailer tongue to prevent it from
dropping in case of separat ion from the hitch.
Controls and equip­
ment Safety first
Vehicle operation
0 Note
If you are go ing to tow a trai ler, you must activate the tra iler opera­
tion
mode :::::, page 189, "Towing a Trailer". •
Driving instructions
Driving with a trailer always requires extra care and
consideration.
To obtain the best possib le handling of ve hicle and trailer,
p lease note t he following :
- Do not tow a loaded trailer when your car itself is not
loaded.
- Be especia lly careful whe n passing other vehic les .
- Observe speed limits .
- Do not drive at the maximum permiss ible speed .
- Always apply brakes early.
- Monitor t he temperature ga uge .
W eight d istr ibu tion
Towing a loaded trailer with an empty car results in a highly
unstable d istribution of weight. If this cannot be avoided, drive at
very low speeds only to avoid the risk of losing steering control.
A "balanced" rig is easier to operate and control. This means that
t he tow vehicle should be loaded to the extent possible and permis ­
sib le, while keeping the trailer as light as possib le under the circum ­
stances . Whenever possible, transfer some cargo to the luggage
compartment of the tow vehicle whi le observing tongue load
requirements and vehicle loading considera tions .
.,,.
Vehicle care Do-it-yourself service Technical data