Audi's modular efficiency platform encompasses technologies relating to engines, transmissions, energy management, body construction, and driver assistance systems to increase efficiency. Some key technologies include the TDI, FSI, and TFSI engines, start-stop systems, thermo-management, and the Audi Space Frame construction. Audi aims to improve efficiency through a holistic approach across all areas of the vehicle while maintaining sporty driving performance.

1. Efficiency technologies
from A to Z
Efficiency technologies
from A to Z

2. Efficiency technologies 02 | 03 || Foreword
from A to Z
Aerodynamics | 41 Foreword
Air suspension | 75
Audi Space Frame | 39
Audi valvelift system | 13
Audi stands for sporty vehicles, uncom-
Climate control system | 59
Common rail system | 19 promising quality, attractive design and
innovation – in a nutshell: for Vorsprung
Demand-controlled oil pump | 47 durch Technik. Our brand plays a leading
Dynamic route guidance | 69 role in the key areas of automotive
technology – with the TDI, FSI and TFSI
Economical route guidance | 71 engine concepts, transmission systems
Electromechanical steering | 49 and Audi Space Frame lightweight
Energy recovery | 55 construction technology.
FSI | 09
In all of these technologies, efficiency
plays an essential role. Efficiency is the
Gear-change indicator | 67
intelligent use of every drop of fuel
LEDs | 61 through specific application of state-
of-the-art technology. To achieve its
multitronic | 27 efficiency goals, Audi adopts a holistic
approach.
On-board computer
with efficiency program | 65 One of our most important tasks in the
Optimised power steering pump | 51 future is to increase efficiency even
further. With this in mind we set up the
R tronic | 29 modular efficiency platform, which
encompasses a host of technologies –
Seat occupancy sensor system | 73
relating to the engine sector, ancillaries,
Start-stop system | 35
S tronic | 23 transmissions, energy management,
body construction and driver assistance
TDI | 15 systems. Nonetheless, we will further
TDI clean diesel | 17 enhance the sporty profile of our brand.
TFSI | 11 For efficiency and dynamic performance
Thermo-management | 57 are not mutually exclusive – on the
tiptronic | 25 contrary, they are mutually inspirational.
Transmission fluid heating | 33
Transmission spacing | 31
Travolution | 77
Tyre technology | 43 Michael Dick
Member of the Board of Management of
AUDI AG, Technical Development

3. 04 | 05 || The modular efficiency platform || Basis
The modular efficiency platform Energy expenditure in the vehicle –
past and present
For Audi, efficiency is the sum of many Reducing internal friction is also a way Before a car is able to move it must
individual steps which ultimately of enhancing transmission efficiency. overcome many forms of resistance –
accomplish one major goal – the Another approach is to lower engine rolling resistance, aerodynamic drag and
combination of low fuel consumption, speeds, and consequently fuel inertia of mass when accelerating, or
excellent comfort and tremendous consumption. The new start-stop resistance to acceleration. An analysis of
driving pleasure. systems switch off the engine when the relationship between fuel consump-
the vehicle is stationary. There is also tion and engine output reveals that the
Audi set the benchmark long ago in much efficiency to be gained from the Audi product range has become much
the powertrain sector with its TDI, steering components – a servo pump more efficient over recent years.
FSI and TFSI engines. The TDI is the that only operates when needed saves
most successful efficiency technology fuel. Tyres with low rolling resistance A 1997 Audi A4 with a 1.8-litre turbo
in the world and the TFSI is an example reduce driving resistance, as does engine delivered 110 kW (150 bhp) and
of Audi’s philosophy of downsizing, aerodynamic fine-tuning of the vehicle required an average of 8.1 litres of fuel
which aims to substitute engine body. In this technical area, the per 100 kilometres. Today’s A4 featuring
displacement with turbocharging and aluminium construction principle a 2.0 TFSI musters up 132 kW (180 bhp)
innovative technology. And progress developed by Audi – the Audi Space and is content with 7.1 litres per 100
continues – Audi is working intensively Frame (ASF) – makes a major contri- kilometres overall.
on the topics of mixture preparation, bution towards lowering weight and
ancillaries and internal friction. thus reducing fuel consumption. Remarkable progress has been made –
but Audi is not willing to settle for what
Energy management also offers huge has been achieved to date. The brand
potential for efficiency – for the air with the four rings is continuing to
conditioning system, for example, pursue its line of action and is working at
energy recovery and thermo-manage- full speed to further improve efficiency.
ment. Last but not least, intelligent
assistance systems, such as the
on-board computer with efficiency
program, offer the driver behind the
wheel valuable support. For despite
this concentrated high-tech – more
than 30 percent of fuel consumption is
still down to the individual’s personal
driving style.

4. 06 | 07 || Powertrain technologies
technologies
Powertrain
Petrol direct injection with turbocharging – TFSI
Common rail system
Petrol direct injection – FSI
Turbo diesel – TDI
Variable valve control – Audi valvelift system Powertrain
technologies
Ultra low emission system – TDI clean diesel In the engine sector, Audi engineers are
working on several topics. One of them is
mixture preparation. The common rail
systems in some TDI engines already operate
with an injection pressure of 2,000 bar –
this allows combustion to be managed with
utmost precision and efficiency. The Audi
valvelift system optimises the gas exchange
in many petrol engines; in the naturally-
aspirated V6 units it varies the valve lift of
the intake valves, while in the turbocharged
2.0 TFSI it operates on the exhaust valves.
At every step in the engine development
process Audi also has an eye on another
objective – lower emissions. The ultra low
emission system in the TDI clean diesel
drastically reduces nitrogen oxides in the
exhaust gas, making it the cleanest diesel
engine in the world.

5. 08 | 09 || Powertrain technologies || FSI
The fuel injector
is located on the side of the cylinder; the
injection spray is precisely metered and finely
distributed in the combustion chamber. The
centrally positioned spark plug ensures smooth
and clean combustion.
FSI
At Audi, FSI stands for petrol direct injection
in spark ignition engines. Unlike conventional
systems, the injectors do not inject fuel into
an intake manifold, but under high pressure
directly into the cylinders. The evaporating
fuel has a considerable cooling effect on
the cylinder charge. The tendency to knock –
i.e. self-ignition of the fuel/air mixture – is
reduced. This means that Audi engineers
can achieve a higher basic compression ratio
for the engine. High-compression engines
are more efficient and powerful than
conventional units.
Petrol direct injection “made by Audi” first
demonstrated its superior potential in
June 2001, when a direct-injection petrol
engine took the Audi R8 sports prototype
to overall victory in the Le Mans 24 Hours –
an achievement due in no small part to its
lower fuel consumption. In the years that
followed, the R8 equipped with an FSI engine
entered 80 races and celebrated a further
64 wins.

6. 10 | 11 || Powertrain technologies || TFSI
TFSI
The turbocharger
(pictured to the right of the engine) is driven by
the exhaust-gas flow and compresses the intake
air. Since the air is heated during the process, At Audi, TFSI stands for the combination of
an intercooler is mounted downstream of the two of the brand’s core areas of expertise –
turbocharger to reduce the temperature. Its direct injection and supercharging. Audi
density thus increases and the air/fuel mixture was the first manufacturer worldwide to
in the combustion chamber remains cooler.
combine turbocharging and direct injection in
volume production. Usually a turbocharger is
used. In the case of the new V6 3.0 TFSI, a
compressor offers advantages in terms of the
overall concept and power characteristic.
As petrol direct injection draws heat from
the combustion chambers, it solves a
fundamental problem posed by all super-
charged engines: high-pressure charging of
the combustion chamber and the resulting
increased tendency to knock (uncontrolled
self-ignition of the mixture at hot points
of the combustion chamber) if engine
compression is not reduced at the same time.
With its TFSI engines Audi can achieve
efficiency-enhancing compression ratios
of more than 10.0:1 – previously only
attainable by naturally aspirated engines.
This significantly improves engine efficiency
and performance – and consequently power
build-up. Injection pressure on the current
TFSI engines is up to 150 bar.
TFSI is one of the key technologies in
Audi’s downsizing strategy, which aims to
substitute engine displacement with
supercharging without forfeiting dynamism.
It already operates in the majority of the
highly popular four-cylinder petrol engines –
the 1.4 TFSI, the 1.8 TFSI and the 2.0 TFSI.
The new 2.5-litre five-cylinder TFSI in the
Audi TT RS is another particularly emotionally
charged example of high performance
combined with outstanding efficiency.

7. 12 | 13 || Powertrain technologies || Audi valvelift system
The operating principle of the AVS
is ingeniously simple – and thought through in
every detail: sliding cam pieces are located on
the intake camshafts. They control valve lift by
way of their varying contours. Lightning-fast
Audi valvelift system
electromagnetic actuators engage in a spiral
groove on the cam piece – the respective cams
are then brought into position through the
camshaft’s rotation. More power and torque together with lower
fuel consumption – that is what every engine
designer strives to achieve. With the Audi
valvelift system (AVS) Audi has come
significantly closer to achieving this goal.
Audi uses this innovative technology in two
different ways. In the case of the 2.8 and
3.2-litre V6 FSI engines it acts upon the
intake valves. It regulates the amount of air
drawn in by switching between two valve lift
settings to open and close the valves. The
throttle butterfly can remain fully open in
most cases – throttle losses, i.e. the drop in
efficiency when air is drawn in against the
resistance caused by the closed throttle
butterfly, are largely eliminated. The engine
is able to breathe freely, and achieves higher
output and torque in combination with low
fuel consumption.
In the case of the 2.0 TFSI, the AVS operates
on the exhaust side. Specific valve timing
allows the fresh charge in the cylinders of
the turbo to be significantly increased,
particularly in the lower engine speed range.
The combustion gases are discharged more
quickly and the flow to the turbocharger is
improved. More torque, even more dynamic
response and therefore considerably more
pulling power are the result. In this way the
system provides palpably more driving
“small” cams “large” cams enjoyment for the driver. In addition, the AVS
low engine speeds high engine speeds permits longer gear ratios, leading to a
substantial reduction in fuel consumption.

8. 14 | 15 || Powertrain technologies || TDI
Turbochargers
and intercoolers are an integral part of every
TDI powerplant from Audi – the V6 TDI with a
displacement of three litres is shown here. The
variable turbine geometry of the turbocharger
ensures spontaneous engine response and a
homogeneous torque curve.
TDI
Audi is the inventor of the world’s most
successful efficiency technology. The TDI
principle, i.e. the combination of direct
injection and turbocharging in a diesel engine,
has enjoyed a unique career since it made its
debut in 1989 in the Audi 100 TDI. Today,
almost every manufacturer employs this
technology.
Since TDI technology was first introduced,
Audi has not only cut emissions to below
ten percent, but also doubled specific power
output and increased specific torque by
70 percent. This not only permits a smooth,
confident and thus fuel-efficient driving style,
but also enhances driving pleasure.
Unlike their predecessors in the passenger
car sector, today’s TDI engines have no pre-
chamber or swirl chamber where combustion
begins; instead, the fuel is supplied directly
to the combustion chambers. This procedure
prevents heat and overflow losses which
would occur as the gas travels from the
pre-chamber to the combustion chamber.
In terms of thermodynamics it is the ideal
solution – expecially in conjunction with the
turbocharger, which substantially increases
the flow of intake air and consequently
combustion quality, power, torque and
efficiency.

9. 16 | 17 || Powertrain technologies || TDI clean diesel
TDI clean diesel
The ultra low emission system The TDI clean diesel from Audi employs the
operates with the AdBlue additive: the solution
cleanest diesel technology in the world: the
is injected into the hot exhaust gas stream by
the metering valve (bottom picture). technology presented as the Audi ultra low
emission system further reduces nitrogen-
oxide emissions by up to 90 percent. It is an
integrated system boasting the utmost in
technical sophistication.
Both in and on the engine, a further enhanced
common rail injection system, innovative
combustion chamber pressure sensors – which
constantly deliver precise information on the
combustion process – and a high-performance
exhaust gas recirculation system ensure highly
efficient combustion. An innovative DeNOx
catalytic converter reduces the remaining
nitrogen oxide. A pump injects a small amount
of precisely metered “AdBlue” additive directly
upstream of the converter. In the hot exhaust-
gas stream, the solution initially separates
into its components of urea and water. Urea is
converted into ammonia, stored in the DeNOx
catalytic converter and reacts with nitrogen
monoxide and nitrogen dioxide from the
exhaust gas to become nitrogen and water.
AdBlue is a biodegradable, 32.5 percent
solution of carbonic acid diamide. The AdBlue
supply is divided between a heated active
container and larger passive container, which
together offer a capacity of around 20 litres.
This suffices for the total mileage covered
between regular service intervals. The
containers are refilled via a filler pipe directly
next to the diesel tank cap.
The ultra low emission system, with its
combination of internal engine measures
and an innovative exhaust gas treatment
system, allows emissions to be effectively
minimised while fuel consumption is reduced
at the same time – creating the cleanest
diesel in the world.

10. 18 | 19 || Powertrain technologies || Common rail system
The piezo actuators in the injectors
consist of numerous tiny ceramic discs stacked
on top of each other to form a package. If an
electric voltage is applied, their crystal structure
changes – the so-called piezo effect. The discs
expand with great force but only minimally,
thus operating the control valve rapidly and
Common rail system
with precision, which in turn activates the
injector needle.
The rail in the common rail system is an
accumulator, which is supplied by a pump
and stores the fuel at a pressure of up to
2,000 bar – the equivalent of the weight of
a luxury saloon car on the space of one
square centimetre.
Thanks to the high pressure and a very fine
bore diameter of only one tenth of a millimetre
in the nozzles, the injectors in a common rail
system achieve extremely fine atomisation of
the fuel. This ensures excellent, homogeneous
mixture preparation and highly efficient
combustion, which in turn delivers enormous
power, low emissions and low consumption.
The piezo injectors used by Audi open and close
within a fraction of a millisecond and can inject
precise and minute quantities weighing less
than one thousandth of a gram. The highly
dynamic action allows the number of injection
processes per operating cycle to be widely
varied – on the 3.0 TDI, for example, up to five
injection sequences are possible. This strategy
reduces emissions and, through pilot injection,
makes the combustion process smoother, so
that the engine’s noise pattern is also more
satisfactory. Selective post-injection into the
combustion chamber increases the tempera-
ture in the downstream emission control
systems and ensures that they are clean and
efficient.

11. 20 | 21 || Transmission technologies
Transmission
technologies
Dual-clutch transmission – S tronic
Torque-converter transmission – tiptronic
Transmission spacing Transmission
Transmission fluid heating technologies
R tronic Reducing internal friction is an important
issue for transmission systems. Audi has
invested much time and effort in this area to
Start-stop system optimise its manual gearboxes. Furthermore,
many intricate measures on the six-speed
Continuously variable transmission – multitronic tiptronic and the continuously variable
multitronic have enhanced efficiency; the
multitronic additionally features wide
transmission spacing with countless gear ratio
options. The new seven-speed S tronic also
has the same advantage. This dual-clutch
transmission has a long ratio for the last gear
– to lower revs and fuel consumption – thus
taking advantage of the high-torque engines
from Audi. A number of models are already
equipped with a start-stop system, which
switches off the engine when the vehicle is
stationary. Another efficiency technology
will makes its debut in the near future – trans-
mission heating, which increases efficiency
especially after a cold start.

12. 22 | 23 || Transmission technologies || S tronic
S tronic
S tronic Audi has designed the new seven-speed
changes gear by disengaging and engaging S tronic to provide both exhilarating driving
both clutches. It is controlled by the so-called and maximum economy. The new high-tech
mechatronic module, a compact block of control engine is notable for its very high efficiency.
units and hydraulic actuators. The required
Its highly intelligent controls also allow
pressure is generated by an oil pump.
economical driving in automatic mode.
The maximum possible transmission-ratio
spread of 8.0:1 allows a sporty, short trans-
mission ratio for the first gear as well as an
rpm-sinking, long ratio for the last gear.
It is therefore ideally suited to modern TDI,
FSI and TFSI engines with high torque at
low engine speeds.
The seven-speed S tronic consists of two
transmission structures and two multi-plate
clutches. The outer clutch K1 transmits power
through a solid shaft to the gearwheels for
gears 1, 3, 5 and 7. A hollow shaft rotates
around the solid shaft. It is connected with
inner clutch K2 and operates the gearwheels
for gears 2, 4 and 6 as well as reverse gear.
Both transmission structures have one
gear permanently engaged, but only one is
actively connected to the engine at any one
time via the engaged clutch. For example,
when the driver accelerates in third gear, the
First gear fourth gear is already engaged in the second
transmission structure.
The gear shift takes place as the clutch
changes – K1 opens and K2 closes. This takes
only a few hundredths of a second and is fluid
and smooth, without any interruption in the
power flow. High-performance electronics
ensure lightning-fast gearshifts, optimally
adapted to the respective driving situation.
Gearshifts are made with the selector lever
or by paddles on the steering wheel; alterna-
Second gear tively, an economical automatic mode is
available. With its superior efficiency and
wide spread of gears the S tronic is designed
to provide maximum economy.

13. 24 | 25 || Transmission technologies || tiptronic
The torque converter
for the tiptronic has been further developed and
now operates even more efficiently. In addition,
the Dynamic Shift Program (DSP) adapts the
tiptronic to the respective situation at lightning
speed – taking into consideration the driver’s
driving style and road conditions.
tiptronic
The great strength of this classic automatic
six-speed torque-converter transmission lies
in its remarkably smooth shift action and
starting performance. In order to improve
this even further while also increasing
efficiency, Audi engineers have modified the
damping system in the latest version’s torque
converter.
The torque converter is equipped with a new
type of torsional vibration damper. This
allows the lockup clutch to remain engaged
over a wide range of engine speeds and loads,
i.e. without energy-sapping converter
slippage, cutting fuel consumption as a
result. When the car is at a standstill, a
controlled drive-off clutch disconnects the
transmission from the engine even if the
selector lever remains in position D. As soon
as the driver releases the brake, the clutch
is engaged.
The modified tiptronic is more dynamic than
the previous version. It responds faster and
shifts gear more rapidly, without compromi-
sing its superior shifting comfort. This is due
to the improved layout of the oil passages
used to fill the converter and more powerful
software for the control unit.

14. 26 | 27 || Transmission technologies || multitronic
multitronic
The variator
The multitronic is a continuously variable
is the heart of the multitronic. A steel link-plate
chain transmits power between two variable transmission. It combines the dynamics and
pairs of conical pulleys. Pushing together and economy of a manual gearbox with the
pulling apart the bevel gear surfaces varies the convenience of an automatic transmission.
range in which the chain runs – changing the Thanks to its continuously variable ratios and
ratio continuously.
adaptive map control, the multitronic always
uses the engine’s optimum rev range.
The technology permits smoother accelera-
tion in comparison with conventional
automatic transmissions. At the same
time, because the engine is kept running
close to its optimum operating point, fuel
consumption is generally lower than with
a manual transmission.
A power-transmitting steel link-plate chain
(tension chain) runs in an oil bath between
two pairs of variable conical pulleys. These
form the variator. The link-plate chain
consisting of more than 1,000 links and
75 pin pairs reliably transmits the available
engine torque. By pushing together or
pulling apart the two bevel gear surfaces,
the link-plate chain runs further inside or
outside the pairs of conical pulleys – in this
way the ratio is continuously varied. This
ensures continuous adjustment in order to
obtain the optimum gear ratio in every
driving situation.
The hydraulic multi-plate clutch achieves
better ride comfort and agility thanks to
its electronic control. It also helps to reduce
Starting Vmax fuel consumption. If the driver applies the
brakes when waiting at traffic lights, for
example, the electronics reduce the tendency
to creep forwards, i.e. the unnecessary
transmission of power from the engine to the
transmission when the vehicle is stationary,
by decoupling the engine and the gearbox.

15. 28 | 29 || Transmission technologies || R tronic
The sequential-shift transmission
has been standard in top-class motorsport for
years. The name comes from the fact that the
gears are engaged “in succession”, without the
foot touching the clutch, i.e. one after the other
as on a motorcycle – with the R tronic boasting
similarly short shifting times and the optimum
efficiency of a racing car.
R tronic
Audi offers the sequential-shift R tronic
with six gears as an exclusive option for the
high-performance Audi R8 sports car. Its
shifting unit has a separate oil circuit with an
electric pump, which operates the single-
plate clutch at a pressure of 40 to 50 bar. A
valve block takes the place of the mechanical
gearshift control; the shift commands are
transmitted electrically “by wire”. The
compact and lightweight transmission offers
the advantages of a conventional manual
gearbox – high efficiency and low mass.
The R tronic is notable for its rapid gear
shifts. Its operating speed varies according to
engine speed and shift program. Four modes
are available, two manual and two fully
automatic. If a moderate driving style is
adopted, gearshifts are particularly smooth;
at high engine loads and revs they take place
in a fraction of a second.

16. 30 | 31 || Transmission technologies || Transmission spacing
Downspeeding
is a way of further increasing efficiency. It
involves reducing engine revs at the same
road speed by means of longer ratios or
wider transmission spacing.
Transmission spacing
The term transmission spacing is understood
to mean the gear ratio range, i.e. the spread
between the smallest (“shortest”) and the
largest (“longest”) gear ratio. Audi has
continuously increased the spacing on many
of its transmissions. In the case of the
seven-speed S tronic, a gear ratio spread of
8:1 is possible – this allows a sporty, short
transmission ratio for the first gear as well as
an rpm-sinking long ratio for the last gear.
An optimised variator for the multitronic in
the Audi A4 increases the spread between the
largest and smallest ratio from 6.25 to 6.73.
The extended ratios in the upper gears
harmonise perfectly with the modern TDI,
FSI and TFSI engines from Audi, which offer
powerful propulsion even from low engine
speeds. This low rpm spectrum – known by
experts as downspeeding – has a direct effect
on both driver and environment, i.e. lower
fuel consumption.

17. 32 | 33 || Transmission technologies || Transmission fluid heating
Transmission fluid
is a very special substance, chemically tailored
to its specific application. The hypoid oil in the
wheel sets and differentials of the seven-speed
S tronic ensures low friction losses and is quite
different from the ATF (Automatic Transmission
Fluid) that lubricates the twin clutch and
mechatronic module.
Transmission fluid
heating
During cold starts, particularly at low
temperatures, oil is viscous – this applies to
the engine, differential, transmission and
clutch. Cold oil with a low viscosity requires
more energy to circulate. Friction losses are
Transmission fluid heating also much higher when the transmission is
cold – with corresponding effects on
Efficiency
efficiency. In order to further improve this
situation, Audi is working intensively on
methods of heating the oil to operating
temperature as quickly as possible.
The Audi A4 TDI concept e, a technical
design study, adopts a pragmatic approach:
a foam-lined shell completely insulates the
six-speed transmission; the fluid remains
warm for a long time after the engine has
been switched off. The Audi Sportback
concept, another design study, features a
transmission fluid heating function which is
connected to the coolant circuit. It works in
conjunction with the seven-speed S tronic.
The high-tech transmission from Audi uses
two oil circuits in which different types of oil
circulate. Their total volume amounts to
around 11.5 litres.

18. 34 | 35 || Transmission technologies || Start-stop system
Deactivation
Assistance and efficiency systems are there to
serve the driver – not the other way round. The
start-stop system can be switched off if the
driver does not wish to use it.
Start-stop system
The Audi start-stop system realises its
efficiency potential especially in urban traffic.
The system shuts down the engine once the
car has come to a stop, the gear lever stands
at idle and the driver releases the clutch
pedal. Operating the clutch then starts up the
engine again. The start-stop system is quiet,
convenient to operate, and fast: the engine
returns to idle speed while the driver engages
the gear.
Audi combines the start-stop system with
particularly efficient battery technology
and sophisticated engine management – to
maintain the function over a wide operating
area, even at temperatures around freezing,
for instance. The system is active after only
a brief warm-up phase. In the standardised
driving cycle the start-stop system lowers
fuel consumption by about 0.2 litres per
100 km, and therefore reduces CO2 emis-
sions by around 5 grams per kilometre. In
urban traffic it reduces consumption by up to
1.5 litres per 100 kilometres, depending
on engine and driving style.

19. 36 | 37 || Driving resistance / lightweight design
Driving resistance /
lightweight design
Tyre technology
Lightweight aluminium construction – Audi Space Frame
Driving resistance /
lightweight design
Aerodynamics
Vehicle body and tyres are technical areas
that offer significant potential for reducing
driving resistance. Tyres with low rolling
resistance, offered as standard by Audi on
the e models, play a major role here.
Elaborate aerodynamic fine-tuning – e.g. a
fully clad underbody for the Audi A4, A5 and
Q5 model lines – improves air flow. With
regard to body manufacture the objective is
to save weight: in the case of the Audi TT, A8
and R8, the body – built according to the
Audi Space Frame principle – is made largely
or entirely of aluminium. Fuel consumption
is cut as a direct consequence of the weight
savings achieved.

20. 38 | 39 || Driving resistance / lightweight design || Audi Space Frame
Audi Space Frame
Aluminium
exhibits properties that make it ideal for body
construction. It is two-thirds lighter than
conventional steel and is easy to machine; The letters ASF stand for Audi Space Frame
magnesium and silicon alloys provide superior – the pioneering aluminium technology that
rigidity. Aluminium can be recycled effectively, gave Audi the lead in lightweight construc-
which further improves its energy balance sheet.
tion at the beginning of the 1990s. The
ASF is a high-strength aluminium structure
of cast nodes and extruded sections; sheet
aluminium panels are integrated to provide
a load-bearing function. All components
combine low weight with optimum function,
thus following the design principles of
nature.
The ASF body impresses with its high rigidity
and crash safety; but above all it is much
lighter than a steel body. The ASF body of the
luxury Audi A8 saloon tips the scales at only
220 kilograms – making it even lighter than
an average midsize car. The high-performance
R8 sports car weighs a mere 210 kilograms.
For the TT and TT Roadster Audi combines
the ASF construction principle with steel –
a further step into the future. The body
consists largely of aluminium; steel
components are used in the rear section.
This construction principle – known as a
“hybrid concept” in view of the combination
of various materials – results in optimum
axle load distribution and consequently
sporty handling. The bodyshell of the Coupé
weighs 206 kilograms; if constructed purely
of steel it would be 48 percent heavier.
A weight saving of almost 100 kilograms
means enhanced dynamic performance and
around 0.3 litres less fuel consumed per
100 kilometres.

21. 40 | 41 || Driving resistance / lightweight design || Aerodynamics
Cd value
A motorcycle manages a Cd of 0.7 and a
truck 0.8. By contrast, an aircraft wing has
a Cd value of 0.08. But the penguin is unbeatable
with a Cd of 0.03.
Aerodynamics
The aerodynamic drag of a car has a
considerable influence on fuel consumption.
If the Cd value, i.e. the drag coefficient,
is reduced by ten percent – say from 0.36
to 0.32 with the same frontal area –
consumption is cut by around 0.15 litres
per 100 km. This effect occurs on the test
rig in the standardised driving cycle – in fast
motorway driving the benefit is even greater
since aerodynamic drag increases as the
square of speed.
Audi attaches great importance to the
aerodynamic fine-tuning of its car bodies –
the sporty, elegant design has boasted a
low aerodynamic drag for many years now.
The Audi Q5, for example, is the best in its
segment with a drag coefficient of 0.33.
This is thanks to intensive and detailed
work involving the body and the underbody.
With a practically fully-clad underbody,
aerodynamics engineers achieved a reduction
in drag of 0.022. In addition, the plastic
elements provide excellent protection from
salt, moisture and stone chippings for the
panels and assemblies.

22. 42 | 43 || Driving resistance / lightweight design || Tyre technology
Rolling resistance
is of major importance when developing
tyres aimed at optimising efficiency. At the
same time, due attention is paid to safety
and comfort.
Tyre technology
Tyres that meet all the necessary require-
ments in terms of driving safety and
comfort consume energy – and to a degree
that should not be underestimated. Energy
consumption when driving at a constant
speed of 120 km/h, due to the rolling
resistance of the four wheels, lies at around
4 kilowatts, the equivalent of around 1 litre
of fuel per 100 km or CO2 emissions of
25 grams per kilometre.
Rolling resistance occurs when tyres flex
excessively while in motion, i.e. they are
constantly deformed. It decreases when the
tyre pressure is increased. Rolling resistance
on gravel is twice as high as on asphalt; on
potholed surfaces it is much higher again.
In conjunction with suppliers, Audi is driving
forward the development of tyres with
optimised rolling resistance as a matter of
priority for all original-equipment tyres.
Special low-resistance tyres are already in
use on the ultra-efficient e models – on the
Audi A3 and A3 Sportback 1.9 TDI e, the
A6 2.0 TDI e and the new A4 2.0 TDI e.
Tyres on the midsize A4 2.0 TDI e saloon are
a sporty size 205/60 R 16 – a typical example
of Audi’s philosophy of combining efficiency
and dynamic performance.

23. 44 | 45 || Ancillaries
Electromechanical steering
Optimised power steering pump
Demand-controlled oil pump Ancillaries
The ancillaries of the steering system and
Ancillaries
engines represent a separate area of action
for the modular efficiency platform.
The Audi A3 and TT feature electromechanical
power assistance – and this is provided only
when needed. For the Audi A4, A5 and Q5,
an innovative hydraulic power steering pump
is used, which likewise operates on demand.
The same applies to the new oil pump, which
serves to lubricate a number of engines. Audi
engineers succeeded in substantially reducing
internal friction in some components thanks
to sophisticated methods of machining the
cylinder barrels. As a result, tension forces
at the piston rings, and consequently friction
in the barrels, are significantly lower.

24. 46 | 47 || Ancillaries || Demand-controlled oil pump
A variable oil pump – a vane-type pump is
shown here as an example –
with volumetric flow and pressure control is Demand-controlled
oil pump
also employed to deliver the engine oil.
The engine ancillaries offer enormous
potential for efficiency; an important
component is the oil pump. Audi already
employs a new generation of variable oil
pumps in various engines. The pumps’
delivery volume has been significantly
reduced and they now operate by controlling
the volumetric flow, i.e. on demand and with
superior efficiency. At a defined engine speed
the pump switches from the low to the high
pressure stage, after which spray jets are
low delivery volume high delivery volume activated to cool the piston crowns. This
prevents temperature peaks and overloading.
The new oil pump is only one of many further
developed engine components, which
together reduce engine drag torque: the
power required by an engine if driven by an
external force. Resistance of this kind means
permanent energy expenditure, which
engineers reduce time and again by applying
a host of detailed measures.
The timing chains and gear wheels, for
example, were optimised in terms of friction
and the water pump was downsized. On
almost all engines, piston friction sharply
declined thanks to sophisticated methods
of machining the cylinder barrels. With
so-called plate-honing and laser exposure,
tension forces at the piston rings – and
consequently friction in the barrels – can
be substantially reduced.

25. 48 | 49 || Ancillaries || Electromechanical steering
The rack-and-pinion steering
with electromechanical power assistance is not
only very efficient – it is also networked with the
safety systems and can assist the driver by
undertaking minor corrections.
Electromechanical
steering
An electromechanical rack-and-pinion steering
system is used on the Audi A3 and Audi TT,
with power assistance provided by an electric
motor. It is characterised by its compact
design and low energy consumption. As
the electric motor does not have to provide
steering power assistance when driving in
a straight line, the system does not tap the
power supply at all. This saves an average of
0.25 litres of fuel per 100 kilometres.
The steering offers even more benefits.
It is networked with the sensors of the ESP
stabilisation program and automatically
undertakes minor corrections if the car should
deviate from its straight course – due to a side
wind, for instance. If there is an imminent risk
of skidding, a second function becomes active.
When exaggerated steering corrections by
the driver threaten to aggravate the situation,
it intervenes by briefly reducing the level of
power assistance. By contrast, power
assistance is increased if the right corrective
action is taken.

26. 50 | 51 || Ancillaries || Optimised power steering pump
The vane-type pump
optimally adjusts the volume of oil it delivers
according to requirements and therefore
always operates using the lowest possible
amount of energy.
Optimised power
steering pump
low delivery volume high delivery volume In many Audi models a regulated vane-type
pump supplies the power steering with
hydraulic energy. Simply put, this construction
is a hollow cylinder (stator) in which a second
cylinder (rotor) rotates, thus supplying the oil.
Compared with conventional servo pumps,
which also circulate large volumes when the
car is driven in a straight line, the regulated
vane-type pump has two major advantages
that make it around 50 percent more efficient:
it moves a relatively small volume of oil and
always delivers only as much oil as is needed at
the respective operating point. A floating ring
controls the oil reservoir and precisely adjusts
the delivery rate to current requirements.
Audi employs this latest-generation power
steering pump in the Audi A4, A4 Avant, A5,
A5 Cabriolet, in the Audi Q5 and in the A6 and
A6 Avant. As it requires less energy, it reduces
vehicle fuel consumption on average by
around 0.1 litres per 100 km.

27. 52 | 53 || Calorifics / electrics
Thermo-management
Ultra-efficient air conditioning
Calorifics / electrics
Energy recovery
The energy management system is another
important efficiency topic. The automatic air
LEDs conditioning for the Audi A4, A5 and Q5
model lines combines high performance with
low consumption. Another technology is now
being introduced on a number of models in
series production – an energy recovery
Calorifics / electrics
system, which produces electrical energy
during braking and coasting phases. An
intelligent thermo-management system
ensures that the engine reaches its operating
temperature faster. In this area, too, many
more attractive solutions will emerge in the
near future. On many Audi models the
optional daytime running lights featuring
ultra-efficient LEDs are already helping to
lower consumption.

28. 54 | 55 || Calorifics / electrics || Energy recovery
The complex vehicle electrical system
requires a generous amount of electricity.
In braking and coasting phases, the alternator
converts kinetric energy into electrical energy
and stores it in the battery.
Energy recovery
Audi employs a technology as standard in a
range of models that increases efficiency,
particularly in urban traffic – the energy
recovery system, which uses kinetic energy
Acceleration during deceleration.
The alternator operates with a new intelligent
control system. It increases its secondary
voltage during coasting and braking phases,
producing more electric power. It then
converts kinetic energy – i.e. energy of motion
– into electrical energy, which is stored
temporarily in the battery. When the car
accelerates again, electrical consumers are
supplied with power from the battery. In this
way the alternator can operate at a low load
Deceleration when driving off and accelerating. This saves
fuel – up to three percent, depending on the
driving cycle.

29. 56 | 57 || Calorifics / electrics || Thermo-management
Efficiency Thermo-management
Thermo-management Thermo-management is concerned with
bringing powertrain components up to
operating temperature as rapidly as possible
following a cold start in order to cut
efficiency losses. The focus is placed on the
engine – even more so than the transmission,
which can be heated separately.
Audi uses a regulated heating shut-off valve
for many engines – the 1.8 TFSI, 2.0 TFSI
and the four-cylinder and V6 TDI. In the
early warm-up phase it ensures that the
coolant remains in the small circuit in the
engine so that it quickly reaches the required
temperature. A further development is about
to be introduced in production vehicles –
the on-demand water pump, which allows
the entire coolant circuit to be precisely
controlled.

30. 58 | 59 || Calorifics / electrics || Climate control system
The internal heat exchanger
of the new automatic air conditioning system,
a double-walled pipeline, is among the many
examples of how efficiency can be effectively
enhanced with smart ideas.
Climate control system
Every climate control system requires
energy to operate. Its compressor is driven
by the engine and the cooling fan needs
electricity to pass air through the condenser.
In summer, additional consumption in urban
traffic amounts to around one litre of fuel
per 100 km.
Audi has lowered this extra consumption
significantly with the new automatic air
conditioning system for the Audi A4, A5 and
Q5 model lines. On average it uses up to
0.2 litres per 100 km less than the already
very efficient system in the A6. Yet its cooling
capacity is higher and at the same time its
weight has been cut by around ten percent
compared with the previous version.
The thermostatically controlled system from
Audi is a completely new design. Its high-
lights: a small, highly efficient compressor,
dethrottled in the inlet area, and a so-called
counterflow-type internal heat exchanger,
which is an aluminium tube-in-tube solution in
which coolant flows in opposite directions.
This generates an additional exchange of
heat and increases the performance of the
evaporator – whilst simultaneously reducing
the power consumption of the compressor.
At high load, an increase in efficiency of up to
20 percent is achieved overall.

31. 60 | 61 || Calorifics / electrics || LEDs
Light-emitting diodes
are electronic semiconductor components.
Although only about one square millimetre in
size, they can generate a remarkable amount of
white light from electrical energy compared with
conventional light sources. Their service life is
practically unlimited.
LEDs
Audi is the pioneer of daytime running lights
throughout the automotive industry world-
wide. These lights provide enhanced safety,
look good – and save a considerable amount of
energy, particularly when generated by LEDs.
In this area, too, the brand with the four rings
leads the way.
Conventional vehicle lights consume up to
200 watts of power – LED daytime running
lights on the Audi A5 Cabriolet get by on
around 16 watts and also create a much more
distinctive light pattern than an incandescent
bulb. Overall, a saving of up to 0.2 litres of
fuel per 100 kilometre can be achieved. The
cars with LED daytime running lights that Audi
sold to customers in 2008 alone saved around
25,000 metric tons of CO2 during their first
year of use.
Audi is driving forward further developments.
All-LED headlights are already available for the
R8 high-performance sports car. Today’s LED
headlights are already much more efficient
than halogen headlights, and rapid progress is
being made. The development engineers
anticipate that by 2018 this advantage will
have increased eightfold.

32. 62 | 63 || Driver-oriented assistance systems
Economical route guidance
Dynamic route guidance
Driver-oriented
Travolution
assistance systems
Gear-change indicator
The assistance systems from Audi focus on
On-board computer with efficiency program the most significant consumption factor: the
driver. The latest versions of the navigation
systems offer numerous support functions –
Seat occupancy sensor system e.g. dynamic route guidance and economical
route selection. The new on-board computer
Air suspension with efficiency program monitors the energy
consumed in the car, gives practical tips on
how to save fuel and incorporates a newly
designed gear-change indicator. In the large
model series with adaptive air suspension the
body is automatically lowered by several
millimetres at high speeds. This improves
aerodynamic drag and thus saves fuel.
Attention to detail is important to Audi: a
smart function ensures that the seat heating
for the passenger seat is automatically
switched off if the seat is not occupied –
assistance systems
another example of the brand’s constant
efforts to reduce consumption.
Driver-oriented