AUDI AG Product and Technology Communications 85045 Ingolstadt, Germany Tel: +49 (0)841 89-32100 Fax: +49 (0)841 89-32817 March 2012
The Audi A8 hybrid – systematic efficiency
The equipment and data specified in this document refer to the model range offered in
Germany. Subject to change without notice; errors and omissions excepted.
Efficiency on a grand scale –
the Audi A8 hybrid
Audi is also setting standards for hybrid technology. The A8 hybrid, which
debuts this spring, is the world’s most efficient luxury-class hybrid sedan
and also the only European full hybrid in the segment. It has an all-electric
range of up to three kilometers.
The Audi A8 hybrid combines the performance of a six-cylinder with the
fuel economy of a four-cylinder model. With 180 kW (245 hp) of system
power, the 2.0 TFSI and the electric motor deliver powerful thrust, yet the
brand’s flagship consumes just 6.3 liters of fuel per 100 km (37.34 US mpg).
The ultra lightweight aluminum body plays a major role in this efficiency.
The Audi A8 hybrid is a parallel hybrid – a high-efficiency concept. Its 155 kW
(211 hp) 2.0 TFSI and the electric motor are mounted one directly behind the
other and are linked by a clutch to work together, when necessary. System output
is 180 kW (245 hp) and peak system torque is 480 Nm (354.03 lb-ft
). The power
is delivered to the front wheels via a highly modified eight-speed tiptronic. The
lithium-ion battery in the rear provides 1.3 kWh of energy, and its sophisticated
air cooling system switches between two stages as needed.
The Audi A8 hybrid combines the performance of a six-cylinder with the fuel
economy of a four-cylinder model. The sprint from 0 to 100 km/h (62.14 mph
takes just 7.7 seconds, and top speed is 235 km/h (146.02 mph
). In the standard
cycle, the large sedan consumes just 6.3 liters of fuel per 100 km (37.34 US mpg
on average – a CO2 equivalent of 147 grams per km (236.57 g/mile
), and easily
In all-electric mode, the Audi A8 hybrid can cover roughly three kilometers
) at a speed of 60 km/h (37.28 mph
). Top speed in this mode is
100 km/h (62.14 mph
). The driver can choose between three driving programs,
on the basis of which the hybrid manager – the control unit in the drivetrain –
selects the best suited of five operating modes.
With a curb weight of 1,870 kg (4,122.64 lb
), the Audi A8 hybrid is by far the
lightest hybrid sedan in its class. This top value is due in part to the fact that the
additional components weigh in at only around 130 kilograms (286.60 lb
also to the ultra lightweight body. Featuring an aluminum Audi Space Frame
(ASF), it tips the scales at just 231 kilograms (509.27 lb
The chassis of the A8 hybrid also benefits from Audi’s expertise in ultra
lightweight construction, combining excellent ride comfort with sporty handling.
The links are made of a lightweight alloy; the power steering uses a special
electromechanical drive. The Audi drive select dynamic handling system and
adaptive air suspension with damping control are standard. The large 19-inch
Timeless and distinctive: the design
The exterior design of the large sedan is one of timeless elegance. The standard
LED headlights give the front end an unmistakable expression. The Audi
A8 hybrid is 5.14 meters (16.86 ft
) long; the long-wheelbase A8 L hybrid is
The interior features sporty and lightweight lines, simple controls and a finish of
handcrafted quality. The driver can read all key information about the hybrid drive
on special displays. The seats are available with optional ventilation and
massage functions, while the ambient lighting package uses LEDs to set subtle
accents. Other features include a continuous center console and a folding table.
Audi offers a wide range of infotainment systems for the A8 hybrid. The Bose
surround sound system is standard, with a high-end system from Bang & Olufsen
available as an option. The optional navigation and infotainment system MMI
navigation with MMI touch includes a touchpad for entering letters and numbers.
The ideal complement to this media center is the online Bluetooth car phone,
which connects to the Internet via UMTS. Passengers can use its integrated
WLAN hotspot to surf and e-mail. For the driver, the system delivers the services
of Audi connect to the vehicle, including up-to-the-minute Audi traffic information
The assistance and safety systems that Audi offers in the A8 hybrid are also state
of the art. These include the night vision assistant with highlighting of detected
pedestrians and a parking system that supports the driver with four small
cameras. The safety system Audi pre sense basic is also standard.
The Audi A8 hybrid will launch in Europe in May. The standard-wheelbase version has a base price of €77,700, while the long version lists for €85,400.
The Audi A8 hybrid
- Highly efficient parallel full-hybrid system, 2.0 TFSI and electric motor linked
- Special smooth-shifting hybrid transmission based on eight-speed tiptronic
- Lithium-ion battery with 1.3 kWh capacity and two-way air cooling
- System output 180 kW (245 hp); max. system torque 480 Nm (354.03 lb-ft
- Zero to 100 km/h (62.14 mph
) in 7.7 seconds, top speed 235 km/h
- EU-cycle fuel consumption just 6.3 liters per 100 km (37.34 US mpg
(147 grams CO2 per km (236.57 g/mile
- All-electric driving with a range of up to three km (1.86 miles
) and speed of up to
- Total weight of all hybrid components just 130 kilograms (286.60 lb
- Aluminum suspension, new electromechanical power steering
- Audi drive select dynamic handling system, adaptive air suspension
- 19-inch alloy wheels with a special hybrid design
- Weighs just 231 kilograms (long version: 241 kilograms) (509.27 lb and
531.31 lb respectively)
thanks to aluminum ASF
- Available with standard and long wheelbase; LED headlights standard
Interior and controls
- Finish of handcrafted quality, intuitively simple controls, special hybrid displays
- Seats optionally with ventilation and massage function
Infotainment and Audi connect
- Bose surround sound system standard, optional Bang & Olufsen Advanced
- Optional MMI navigation plus with touchpad (MMI touch), plus online Bluetooth
car phone for Internet access and services from Audi connect
Driver assistance systems
- Advanced assistance and safety systems available, including night vision
assistant, Audi side assist and Audi pre sense basic
Full version Luxury sedan with systematic efficiency –
The Audi A8 hybrid
The Audi A8 hybrid, which will be at dealers in the spring, is the only
European full-hybrid in the segment and is also the world’s most efficient
luxury-class hybrid sedan. Its 2.0 TFSI and the electric motor together
produce 180 kW (245 hp) of system power. The brand’s flagship consumes
on average just 6.3 liters of fuel per 100 km (37.34 US mpg).
The Audi A8 hybrid is designed as a parallel hybrid – a straight-line concept with
high efficiency. Its combustion engine and the electric motor are located one
directly behind the other and are linked by a clutch to work together, when
necessary. The interplay between the combustion engine and the electric motor
briefly results in a peak system output of 180 kW (245 hp) and a maximum
system torque of 480 Nm (354.03 lb ft
The Audi A8 hybrid combines the performance of a six-cylinder with the fuel
economy of a four-cylinder model. The sprint to 100 km/h (62.14 mph
7.7 seconds, and top speed is 235 km/h (146.02 mph
). In the standard cycle, the
luxury sedan consumes just 6.3 liters of fuel per 100 km (37.34 US mpg
average – a CO2 equivalent of 147 grams per km (236.57 g/mile
) and easily the
best in its class. For the A8 L hybrid, these figures (all figures provisional) are
7.9 seconds, 228 km/h (141.67 mph
), 6.4 liters per 100 km (36.75 US mpg
149 grams of CO2 per km (239.79 g/mile
). The 75 liter (19.81 US gallon
The 2.0 TFSI displaces 1,984 cc and produces 155 kW (211 hp). Its maximum
torque of 350 Nm (258.15 lb-ft
) is available between 1,500 and 4,200 rpm. The
four-cylinder engine, which has been chosen as Engine of the Year five times in a
row, combines gasoline direct injection with turbocharging – typical for the Audi
philosophy of downsizing, which replaces displacement by forced induction.
The Audi valvelift system (AVS) further increases power, torque and efficiency by
switching the stroke of the exhaust valves between two stages depending on the
The 2.0 TFSI has been overhauled in some respects for use in the Audi
A8 hybrid. The mechanical belt drive for the auxiliaries was eliminated; it was
electrified for the hybrid. A secondary air system at the cylinder head makes sure
that the exhaust gas treatment cuts in particularly fast after cold-starting.
Quiet on board: Active Noise Control
The Audi A8 hybrid comes standard with Active Noise Control (ANC). This
innovative system eliminates intrusive engine noise by broadcasting a precise antiphase sound to the cabin through the sound system’s speakers. This principle
is known as interference: If two waves of the same frequency are superimposed,
their amplitudes cancel each other out provided that they are equal and 180
A highly modified eight-speed tiptronic transfers the power to the front wheels.
Instead of a torque converter, it includes the disk-shaped electric motor, which is
combined with a multi-plate clutch operating in an oil bath. The clutch connects
and disconnects the electric motor and the TFSI very precisely and gently.
With its eight widely spaced gears, the comfortably and fast-shifting hybrid
transmission contributes significantly to the efficiency of the Audi A8 hybrid.
When the 2.0 TFSI is deactivated, an electric pump maintains the oil pressure in
the hydraulic system to safeguard the convenient start-stop feature.
The power electronics, connected to the battery and the electric motor by high-
voltage cabling, are located in the plenum chamber of the engine compartment.
They serve as a controller between the battery, which outputs direct current, and
the electric motor, which operates on alternating current. Innovative technologies
keep the volume and weight of the component low, with cooling provided by a
separate water-filled circuit. The power electronics include a DC/DC converter
that connects the consumers in the 12 V electrical system to the high-voltage
Electric drive is a permanent magnet synchronous machine; it serves as an
electric motor, as a starter and – during deceleration – as a generator. The
electric motor, which delivers up to 40 kW (54 hp) of power and 210 Nm
(154.89 lb ft
) of torque, is integrated into the engine’s cooling system.
Energy is stored in a lithium-ion battery system weighing a mere 38 kg (83.78 lb
It is located in a crash-safe area of the trunk and protected by a separate housing.
The battery consists of 72 cells; at 266 volts its normal energy is 1.3 kWh and its
The lithium-ion battery is cooled by air in two ways. At low-temperature load, it
draws temperature-controlled air from the vehicle interior by way of a fan. If its
temperature exceeds a certain limit, a separate refrigerant circuit is activated. It is
coupled to the main climate control system of the vehicle and uses a separate
evaporator. This powerful active cooling makes Audi A8 hybrid superior to many
The driver of the Audi A8 hybrid can use a button on the center console or the
tiptronic selector lever to choose between three driving programs. The EV
characteristic map gives priority to the electric drive; the D mode controls both
motors efficiently; and the S mode as well as the touch control gate of the
8-speed tiptronic are designed for a sporty driving style.
The hybrid manager, a proprietary Audi development, is integrated into the
control unit of the 2.0 TFSI and manages the transition between the modes. The
Audi A8 can be driven in five different modes. Driving with the combustion engine
alone, with the electric drive alone or in hybrid mode is possible, as are
recuperation and boosting. None of its European competitors in this segment
Both drive sources are deactivated when the vehicle is stationary. In this
convenient start/stop mode, the automatic air conditioning remains active – its
compressor has a high-voltage electric drive and is supported by a separate
Once the driver releases the brake, the Audi A8 hybrid starts rolling. It can drive
at up to 100 km/h (62.14 mph
) in all-electric mode. At a constant 60 km/h
), it has a range of up to three kilometers (1.86 miles
) – enough for
most residential areas. Top speed with the electric drive is 100 km/h
The TFSI becomes the power source as soon as the driver accelerates further.
In many situations, the engine management system increases the load
somewhat in order to operate at the ideal point with respect to fuel consumption.
The excess energy flows to the electric motor, which uses it to supply on-board
consumers and to recharge the battery. When accelerating quickly, or “boosting,” the electric motor operates together with the TFSI; at full throttle, the
full system output is briefly available. The hybrid drive then supplies the
propulsion power of a large, naturally aspirated engine, but with far more
When the driver releases the accelerator, the electric motor recovers energy and
stores it in the lithium-ion battery. In most situations the TFSI is then decoupled from the drive system and does not cause any drag losses. “Gliding” like this is
possible up to 160 km/h
). If the driver only brakes slightly, the electric
motor performs the deceleration itself; during more forceful braking, the hydraulic
braking system is simultaneously activated. A complex control strategy adapts all
braking actions to the conditions of electric driving and energy recuperation.
Well informed: the hybrid displays
The Audi A8 hybrid has a display concept on board for making the driving states
of the hybrid drive tangible to the driver. A power meter replaces the rev counter in the instrument cluster; its needle indicates the drive’s total output on a scale of
0 to 100 percent. Color segments with green and orange sections show at a
glance how efficiently the large sedan is currently operating. An additional
instrument displays the charge level of the lithium-ion battery.
At the same time, the energy flow display clearly depicts the current mode of
operation and active components of the hybrid drive. It can be called up via the
driver information system and the MMI monitor. The large screen shows a bar
diagram of the average consumption and presents the amount of energy
The Audi A8 hybrid combines luxurious ride comfort with sporty handling. Most of
the components of its five-link front suspension and the self-tracking trapezoidal-
link rear suspension are made of aluminum. The wheel brakes are large. Based
on a concept from sports car design, pins connect the internally vented, cast iron
friction rings to the aluminum brake caps. The ESC stabilization system offers a
sport mode and includes a tire pressure monitoring system.
The adaptive air suspension, which includes controlled damping, is standard. The
system modifies the performance of the dampers depending on the condition of the road and the driver’s style. It adjusts the body’s ride height in multiple steps in line with the car’s speed and is also used to level the suspension. Audi also
delivers the A8 hybrid with the optional adaptive air suspension sport, which
features a standard ride height that is 10 millimeters (0.39 in
The adaptive air suspension is integrated into Audi drive select. This dynamic
handling system enables the driver to switch the function of the engine
management system, the hybrid transmission and the power steering between the four modes “comfort,” “auto,” “dynamic” and “custom.” The belt tensioners in
the safety system Audi pre sense basic can also be adjusted via Audi drive select.
Anthracite-colored, semi-polished 19-inch wheels of “Turbine” design and fitted
with 255/45 R19 tires are standard. Optional 20-inch wheels with a 10 parallel-
spoke design and shod with 265/40-series tires provide even greater dynamics.
Two key chassis components have been modified for electric operation. The
hydraulic power steering has been replaced by an electromechanical unit that adjusts its level of boost according to the vehicle’s speed.
Because it consumes no energy when the car is traveling in a straight line, it
saves around 0.3 liters of fuel per 100 km. The electromechanical power steering
is designed for a direct, sporty response.
With a curb weight of 1,870 kilograms (4,122.64 lb
), the Audi A8 hybrid is the
lightest car in its class. It brings the full range of the Audi’s ultra lightweight
technology expertise to the streets. The special technical components and
equipment features for the hybrid drive contribute just 130 kilograms (286.60 lb
Except for the B-pillars, where hot-shaped, ultra-high-strength steel is used, the luxury sedan’s ASF (Audi Space Frame) body is made entirely of aluminum.
Weighing just 231 kilograms (509.27 lb
), it is roughly 40 percent lighter than a
comparable steel construction. The body of the A8 L hybrid, which is 13
centimeters (5.12 in
) longer, weighs 241 kilogram (531.31 lb
The ASF body of the A8 hybrid, assigns a specific task to each material and each
component. The cast nodes connect the components, the extruded sections
bridge spaces, the aluminum panels close off the spaces and lend rigidity to the
framework. The material is used only where necessary and always in a tailored
The ASF body, for which Audi received the Euro Car Body Award, the world’s
highest honor for innovative car body design, has other strengths as well. It is
very rigid and offers good protection in the event of a collision. The Audi adaptive
restraint system also stands guard in the cabin. Both body variants of the
A8 hybrid have a drag coefficient of just 0.26, thanks in part to the extensive fine-
tuning of the underbody and in the engine compartment.
The ASF design ensures comfortably low levels of vibrations and impressive
quietness, with additional noise reduction provided by an acoustically insulated
windshield. If desired, Audi can also provide noise-insulating side windows of
dual-pane acoustic glass, with tinting optional. A panoramic glass sunroof is
The exterior of the Audi A8 hybrid has a cohesive, homogenous appearance. The
coupe-like roofline with the inclined C-pillars makes the silhouette flow.
Sculptured surfaces conveying calmness and prestige contrast with sharp lines.
The luxury sedan is 5,137 millimeters (202.24 in
) long, 1,949 millimeters
) wide and 1,460 millimeters (57.48 in
) tall; its wheelbase measures
2,992 millimeters (117.80 in
). For the A8 L hybrid, these figures are
5,267 millimeters (207.36 in
) long, 1,949 millimeters (76.73 in
) wide and
1,471 millimeters (57.91 in
) tall. The wheelbase measures 3,122 millimeters
The single-frame radiator grille of the Audi A8 hybrid is three-dimensional and
rich in detail. The standard LED headlights use light-emitting diodes for all lighting
functions. They give the sedan a distinctive appearance, do an excellent job of
illuminating the road and are highly efficient. The integrated high-beam assistant
switches automatically between low-beam and high-beam headlights. The rear
lights also feature sophisticated LED technology.
Small hybrid badges on the trunk lid and the fenders indicate the new drive
concept. 11 paint finishes are available, with Arctic Silver available as an
exclusive option. The engine hood and key of the A8 hybrid also feature a unique
Audi has its own unique philosophy when it comes to luxury. Luxury does not
mean excess, but rather individual, cultivated style. The selection and
workmanship of all materials in the interior of the A8 hybrid are on a hand-built
level. The light, elegant interior design conveys the large sedan’s athletic
character. A large arc – the wrap-around – encircles the cockpit. The front of the
instrument panel is in the shape of a gentle wave.
The front seats feature 12-way electric adjustment. Audi also offers a number of
seating options up to the comfort sport seats. These can be further upgraded with
a ventilation system for the seat surface and backrest, and a massage function
with ten air cushions, five programs and five intensities to pamper the back.
The A8 hybrid has clearly structured, intuitive ergonomics. The driver information
system with 7-inch screen concentrates all important information and settings in a
logical menu structure. The driver can operate it via the leather multifunction
steering wheel. The MMI with its elegant, power-retractable 8-inch monitor serves
as a second control unit. Its control terminal with the large rotary pushbutton is located on the console of the center tunnel, ideally positioned for the driver’s right
The standard three-zone automatic air conditioning enables quiet and low-draft
indirect ventilation through a grate on the top of the instrument panel. It controls
the temperature of the driver and passenger areas plus the back seat, and offers
three climate styles. The ambient lighting, another standard feature, is an artistic
overall orchestration of LEDs, light guides and light strips. Many LEDs are two- or
three-colored. The driver can use the MMI control system to choose between and
make fine adjustments to three different lighting scenarios.
Luxurious: the spacious rear seat
The extended wheelbase of the Audi A8 L hybrid provides for a generous amount
of space in the back. Audi offers the option of two power-adjustable and heated
individual rear seats. These can also be equipped with optional ventilation and
massage functions, and features such as a folding table and a continuous center console make the passengers’ journey even more enjoyable.
Audi offers the interior components of the A8 hybrid in a variety of colors. The
headlining is available in a choice of three shades. A choice of three grades of
leather and a leather/Alcantara combination is available for the seat upholstery.
The two-segment decorative inlays are also available in a number of fine
materials. The entry sills feature aluminum strips with hybrid logos, and an
additional hybrid badge adorns the instrument cluster. A number of additional
suggestions for further customization are included in the Audi exclusive program.
The trunk of the Audi A8 hybrid features a luggage capacity of 335 liters
(11.83 cu ft
) and a low loading lip. As standard, Audi includes a five-piece
luggage set designed to optimally fill the available space. The trunk lid opens
automatically when unlocked, and a power-assisted function helps to close it.
Foot control of the trunk lid is available as an option.
Driver assistance systems
The Audi A8 hybrid can be optionally equipped with a series of assistance
systems that make driving even more relaxing and composed. Audi side assist,
whose radar sensors monitor what is happening behind the car, warns the driver
of critical lane changes. It is activated upon reaching 30 km/h (18.64 mph
Audi lane assist, which is active at speeds of about 65 km/h (40.39 mph
above, uses a camera to observe the lane markings. If the driver approaches one
of them without using the turn signal, there is an adjustable vibration at the
steering wheel. The speed limit display recognizes speed limit signs and presents
them on the display of the driver information system and on the MMI monitor. The
parking system plus with surround view camera makes parking easier.
Four small cameras monitor the surroundings of the car. A computer combines
their images and displays them in a variety of views.
The night vision assistant with highlighting of detected persons uses a far infrared
camera that reacts to radiated heat. It displays the information it collects as black-
and-white images on the display of the driver information system. The cooler
surroundings appear dark, while people and animals are conspicuously bright.
The system, which has a visual range of up to 300 meters (984.25 ft
), can detect
people at up to 100 meters (328.08 ft
away and highlights them with yellow
markings. In a hazardous situation, they are marked red and a warning gong
A standard feature in the A8 hybrid is the safety system pre sense basic. If the
ESC sensors report a critical state, the control unit activates the hazard warning
lights and closes the side windows and the sunroof, depending on the situation; it
also tensions the front seat belts and emits a tone to warn the driver.
If Audi side assist is also on board, then there is also the function pre sense rear,
which mitigates the consequences of a rear-end collision.
An attractive lineup of infotainment modules is available for the A8 hybrid. Their
centerpiece is MMI navigation plus. The high-end system includes a 60 GB hard
disk, a DVD drive and a whole-word voice control. A fast graphics processor
generates top-quality, three-dimensional images that are displayed tack sharp in
MMI navigation plus also includes MMI touch. The driver enters a destination or
the telephone number by drawing the letters and numbers – even using
characters from Asian languages – on the touch-sensitive control panel with a
finger. The system provides acoustic feedback after each character so that the driver’s eyes can stay on the road.
MMI navigation plus works closely together with the other systems in the A8
hybrid. It looks ahead on the route selected and forwards all relevant data to the
controllers that, for example, control the headlights and can thus illuminate bends
or junctions early on. They also influence the way the hybrid transmission works.
This means that these systems can adapt their function precisely to the given
The Audi A8 hybrid comes standard with the Bose surround system. A digital
amplifier drives 600 watts to 14 speakers including a subwoofer to produce a
finely balanced and simultaneously powerful sound on a strong base foundation.
The system can also play stereo recordings in five-channel surround sound.
The Bang & Olufsen Advanced Sound System is a high-end alternative for hi-fi
connoisseurs. It drives 19 active speakers with aluminum grilles via two amplifiers
with over 1,400 watts of power. Located in the instrument panel are two acoustic
lenses for the high frequencies. They extend outward when the system is
Upon request, Audi equips the A8 L hybrid with the rear seat entertainment
system, which includes a separate DVD drive and a hard disk jukebox.
Mounted on the backs of the driver and front-passenger seats are two 10.2-inch
displays that can display different content. Sound is supplied via the audio
systems or two sets of Bluetooth headphones. Additional components such as a
tuner for digital radio reception and a TV tuner round out the infotainment lineup.
The term Audi connect refers to all applications and developments that connect
Audi cars to their owner, the Internet, the infrastructure, and other vehicles. The
hardware module for this is the Bluetooth car phone online, an additional
component of MMI navigation plus. It connects to the Internet via a UMTS
module. Passengers can connect up to the eight mobile terminal devices to the
The Bluetooth online car phone is operated either via the MMI navigation plus
terminal, using the multifunction steering wheel or by voice control. Data are
encrypted and transferred via the roof antenna at rates of up to 7.2 MB per
second. If the A8 hybrid is traveling outside the UMTS network, the system
For the driver, the online Bluetooth car phone brings tailored Internet services to
the A8 hybrid. These range from navigation using images from Google Earth to
voice-controlled Google POI search and Google Street View to Audi traffic
information online, which provides a precise, highly differentiated image of the
traffic load along the chosen navigation route.
The Audi A8 hybrid will begin start arriving at dealers in Germany and all other
European countries in May. The standard-wheelbase version has a base price of €77,700, while the long version, which wil follow a short time later, costs €85,400.
A large share of the production is intended for export markets, primarily China.
Most of the future customers for the Audi A8 hybrid are relatively young, highly
educated and have a high income. They have an open, cosmopolitan lifestyle
with strong cultural interests and are striving to bring their economic success into
Summary of the Research Project „Data Base of the Building Stock – Data Sur- vey of the State and the Trends of Energy Saving Measures in the German Re- sidential Building Stock“1 Dr. N. Diefenbach, Dr. H. Cischinsky, M. Rodenfels (Institut Wohnen und Umwelt2, Darm-stadt) Dr. K.-D. Clausnitzer (Bremer Energie Institut3) Project Aims The project aimed at filling information ga
Meet the Expert 4 Nuts and bolts of cardiopulmonary exercise testing (CPET): theory, guidelines and practice 1. Palange, P., S. A. Ward, K. H. Carlsen, R. Casaburi, C. G. Gallagher, Rik Gosselink, D. E. O'Donnell et al. "Recommendations on the use of exercise testing in clinical practice." European Respiratory Journal 29, no. 1 (2007): 185-209. (available at- free acces