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The new Audi A4
Greater than the sum of its parts

Text
Johannes Köbler

Photos
Bernhard Huber

Even more powerful, even more efficient, even more intelligent

The new Audi A4 and A4 Avant set the bar a good deal higher. Who are the brains behind the new technologies and solutions?

Stefan Gmelch
Die schwere Kunst des Leichtbaus

Fahrwerk
Komfortables Abrollen und sportliches Handling – das Fahrwerk der neuen A4-Reihe ist in weiten Bereichen neu entwickelt. Im Fokus standen vor allem konsequenter Leichtbau und intelligente Regeltechnik.

Der Leichtbau ist eine schwere Kunst – aber Audi setzt hier einmal mehr neue Maßstäbe. Je nach Motorisierung wiegt der neue A4 bis zu 120 Kilogramm weniger als sein Vorgängermodell, ein großer Anteil davon geht auf das Konto des Fahrwerks. „Wir haben uns jede Komponente gründlich vorgenommen“, sagt Stefan Gmelch, Fachteamleiter für das Fahrwerk des neuen A4. „In vielen Fällen haben wir uns für eine komplette Neuentwicklung entschieden.“

Eines dieser neuen Bauteile ist die elektromechanische Servolenkung, sie bringt 3,5 Kilogramm Gewichtsersparnis. Die neuen Einrohrdämpfer bauen gemeinsam über zwei Kilogramm leichter. Gmelch nennt einen weiteren Vorteil: „Hier strömt das Öl nur durch das Kolbenventil, deshalb sprechen die Einrohrdämpfer direkter und spontaner an.“ Bei vielen A4-Motorisierungen verzögern Bremsen mit leichten Aluminium-Festsätteln die vorderen Räder – Vorteil: fünf Kilogramm.

Bei den Achsen sparten die Entwickler insgesamt elf Kilogramm ein – alle wesentlichen Lenker bestehen jetzt aus Aluminium, viele Bauteile sind geschmiedet statt gegossen, selbst die Radnabenträger in Pentagonform zahlen auf das Leichtbau-Konto ein. ähnlich wie die Vorderachse ist jetzt auch die Hinterachse als Fünflenker-Konstruktion aufgebaut. „Das bringt uns zwei große Effekte“, erklärt Gmelch. „Wir haben die ungefederten Massen verringert, und wir können die Längs- und Querkräfte sauber voneinander trennen. In Querrichtung legen wir die Gummi-Metall-Lager sportlich steif aus, in Längsrichtung halten wir sie geschmeidig weich.“

Stefan Gmelch
“Our chassis sets new benchmarks in
all the relevant criteria,”
says Stefan Gmelch, Team Leader Chassis.
Fachteamleiter Fahrwerk.

We took a close look at every single
chassis component. In many cases, we opted for
acompletely new design.

Stefan Gmelch
Team Leader Chassis

Drivers of the new Audi A4 and A4 Avant will experience a car that runs even more smoothly than its predecessor – without any loss of sporting character. “The optional CDC dampers make the bandwidth even greater,” says Gmelch. The acronym stands for continuous damping control, with the dampers regulated by the electronic chassis platform (EFP). The highly integrated control unit – another new feature in the new A4 and in the MLB evo – processes all the signals related to longitudinal and lateral acceleration and wheel movement.

The chassis with damper control allows customers to choose from two settings and two ride heights, either sporty and 23 millimeters lower than with the normal chassis or more comfortable and 10 millimeters lower. The damper control is set via the Audi drive select system (standard as of 140 kW/190 hp). In the base configuration, the system works with the throttle flap, the automatic transmission and the steering. It also includes the optional elements of dynamic steering and the quattro sports differential (as of 2016).

Aluminum swivel bearing –
The new forged swivel bearing in the new A4 weighs
800 grams less than the cast bearing in the
last model. 30 Furthermore, its manufacturing consumes
far less energy.

As far as the wheels for the new A4 were concerned, there was a strict upper weight limit of 12.5 kilograms. The electromechanical parking brake at the rear axle comes with new functions for stopping and pulling away. The electronic stability control (ESC) functions even more precisely and sensitively than in the previous model. Stefan Gmelch sums up: “The chassis of the new A4 offers an even broader bandwidth between comfort and sporting character. It sets new benchmarks in all relevant criteria.”

Tiziana Mauri
“Open-pore wood is currently a
major trend in furniture,” reports Tiziana Mauri,
Designer Color & Trim.

Tiziana Mauri
Translating design trends into automotive applications

Color & Trim
The paint shades, add-on parts, interior materials and colors have been extensively revised. The atmosphere in the new A4 range is one of calm, modern elegance.

The designer runs her finger very gently over the trim piece. The open-pore oak possesses its very own tactile qualities – slightly rough, extremely natural, authentic. “Open-pore wood is a strong trend in modern and progressive furniture,” says Tiziana Mauri, Designer Color & Trim. “In the new Audi A4, we are offering the veneer in oak grey natural as part of the design selection.”

Color & Trim – this is the design department that gives Audi cars their surface finish. It decides on the exterior paint shades and add-on parts, and on the use of materials and color in the interior. The job of the designers of Color & Trim includes examining broader megatrends and fastmoving design trends and filtering out those that can be translated into Audi’s cars – for products that will be on the market for around seven years and will remain on the road for even longer.

Tiziana Mauri speaks with great enthusiasm about the new features in the Audi A4. “For the exterior, we have added three completely new colors to the Audi palette – Matador red, Manhattan grey and Gotland green,” explains the Italian. “All three tones are very calm and elegant because we use the effect pigments very sparingly. This is something of a tendency for us that fits very well with the A4. But every model has its own character – the Q7, for instance, needs a bit more effect.”

Chassis and Design
Strict lightweight design and intelligent
control technology define the chassis of the new Audi models.
Inside, progressive materials and
colors convey an atmosphere of modern elegance.

With the model changeover, Audi is introducing new equipment lines for the A4 that also encompass many exterior details. Besides the base model, there are the sport and design lines, the S line sport package and the design selection. The differentiations are subtle, yet have a distinct impact on the look-and-feel of the vehicles, as Tiziana Mauri explains: “For the design line, the Singleframe grille is in high-gloss titanium black and combined with chrome fins. For the sport line, we use a sporty matte paint finish for the grille and aluminum fins.”

Calm and elegant exterior colors are a tendency for Audi that also fits very well to the new A4.
But every model has its very own character.

Audi offers a wide choice of new colors and combinations for the interior, too. In the design line and the design selection, the dashboard can be split into two colors. Serving as a dividing element is a large trim piece, available in fine wood veneer, deep gloss piano lacquer or classic aluminum.

The designers of Color & trim are making increased use of new, technical textures in the interior and of cool, modern grey and brown tones that combine to create extremely sporty and elegant effects. This concept is particularly evident in the design selection, which offers the seat upholstery and the dashboard in combinations such as wapiti brown with rock grey. “I saw this combination a while ago at the Milan Fashion Fair,” reports Tiziana Mauri. “This reinforced our thinking that our design is exactly right.”

Intake camshaft –
Under partial load, it is open for
140 degrees of crankshaft angle and under
full load for 170 degrees.

New and old pistons –
The piston on the right comes from
the previous engine.
The piston topology 32 has been revised
for the new 2.0 TFSI (left).

Dr. Rainer Wurms and Dr. Ralf Budack
140 kW of power, but just 109 grams of CO2

2.0 TFSI with new combustion process
Downsizing becomes rightsizing. The 2.0 TFSI with its new combustion
process unites the efficiency of a lower-displacement engine with
the performance of a larger power unit.

Audi is starting a new chapter in spark-ignition engines – with the highly efficient 2.0 TFSI in the new A4 range. The four-cylinder delivers a fulsome 140 kW (190 hp) and 320 Nm of torque, the latter from 1,450 to 4,200 rpm. Yet, in the A4 Sedan, it consumes just 4.8 liters of fuel per 100 kilometers (109 grams of CO₂ per kilometer) – 21 percent less than the preceding engine with less power. Part of this progress is attributable to the vehicle as a whole, with the other major contribution made by the high efficiency of the engine.

The explanation comes from Dr. Ralf Budack, Advance Development Charge Cycle/Thermodynamics, and Dr. Rainer Wurms, Head of Advance Development Spark-Ignition Engines. “We have developed Audi’s downsizing strategy into rightsizing,” says Dr. Wurms. “In the new 2.0 TFSI, we have combined increased displacement with the right technologies.” The outcome is the consumption benefits of a small-displacement engine when driving moderately, with the performance of a large engine when adopting a sportier driving style.

The combustion process of the new 2.0 TFSI uses the base thinking of the well-known Miller cycle, but takes it a decisive step further. Added to the shortened compression and extended expansion phases is an increased compression ratio flanked by turbocharging, dual injection and the Audi valvelift system (AVS). Dr. Budack tells us more: “We could already tell at the start of the project in 2006 that the process would work. The big task, however, was in the detail work – the adjustment of control times, swept volumes and compression ratio.”

The new engine is particularly notable for its efficiency under partial load. This is where mainly the multi-point injection is active. It enables mixture formation that ensures efficient and extremely clean combustion. The intake valves are open through just 140 degrees of crankshaft angle. In combination with the increased pressure in the intake manifold, this lowers throttling losses during induction.

Dr. Rainer Wurms
Dr. Wurms (left) is Head of Advance Development Spark-Ignition Engines. “We have developed downsizing into rightsizing,” he says.

Dr. Ralf Budack
“We saw right away that the new process will work,” says Dr. Ralf Budack, thermodynamics specialist.

The new combustion process forms
a good basis for fulfilling
the forthcoming exhaust legislation.
It is alsoparticularly well
suitedto hybridconcepts because
it can makegood useof
the bestconsumption points. 

Dr. Rainer Wurms
Head of Advance Development
Spark-Ignition Engines

In the compression phase, the newly developed 2.0 TFSI compresses the gas like a small-displacement 1.4 TFSI – although at a compression ratio of 11.7:1, which is unusually high for a turbo engine. Because the subsequent expansion phase lasts longer than the compression phase, more energy is transmitted to the crankshaft. The greater expansion of the gas during the extended expansion phase increases efficiency.

To ensure the charge air tumbles sufficiently, despite the short induction time, the intake ports, valves, pistons and combustion chambers of the 2.0 TFSI have been extensively redesigned. Under higher loads, the AVS, which has been moved from the exhaust side to the intake side, ensures later closing of the valves at 170 degrees of crank angle. The higher fill facilitates good power and torque delivery.

Dr. Rainer Wurms outlines the potential unlocked by the new technology. “We have established a very good basis for fulfilling future exhaust legislation. Plus, the new combustion process is particularly well suited to hybrid concepts that can make targeted use of its best consumption points. We are right at the beginning of a highly interesting development.”

Reimund Limbacher
“Up to ten percent less
fuel consumption out of town,”
says Reimund Limbacher,
Development Vehicle Functions Drive.

Reimund Limbacher
Patent leather or mountain boots?

Predictive efficiency assistant
Sometimes, drivers don’t see areas where they have to drive slowly until very late.
The predictive efficiency assistant knows where they are and helps aid an
economical driving style.

The new Audi A4 is also the benchmark in its class with its broad portfolio of driver assistance systems. They deliver more safety and more comfort to drivers – along with lower fuel consumption. The latter applies particularly to the predictive efficiency assistant, which was largely conceived by Reimund Limbacher from Development Vehicle Functions Drive.

The new system works closely with the adaptive cruise control, the navigation system and the camera-based traffic sign recognition. It draws information on vehicles traveling in front from the video camera. Using route data, the predictive efficiency assistant can recognize in many countries worldwide when the A4 is approaching a bend, roundabout, intersection, downhill stretch, city limits sign or a speed limit sign – even when it is over the crest of a hill and not visible to the driver.

If it would make sense to lower speed, a symbol illuminates in the driver’s line of sight to signal “lift off the gas”. “We discussed the graphic for ages,” recalls the Limbacher. “For a while, we were talking about a three-dimensional representation, then about an Italian designer shoe. It ended up as a simple, concise symbol.”

When the ACC Stop & Go is active, the predictive efficiency assistant does even more – using the engine control unit to automatically adapt the pre-selected speed of the car to accommodate bends and speed limits. Depending on the situation, it decides whether it would be more cost effective to slow down via engine braking or to use the automatic transmission’s freewheel clutch. By supporting an anticipatory driving style in this way, the predictive efficiency assistant helps reduce fuel consumption on outof- town roads by up to ten percent.

Engine and Predictive Efficiency Assistant
In terms of fuel consumption,
the new A4 is far better than its predecessor.
This is thanks to technologies like the
2.0 TFSI with the new combustion
process and the predictive efficiency assistant.

We have given the predictive efficiency
assistant different characteristics. They are dependent
on the drive mode set in Audi drive select.

Reimund Limbacher
Development Vehicle Functions Drive

But how does a system that seeks to avoid braking fit in with the sporty character of the Audi brand? “We have given the predictive efficiency assistant different characteristics,” answers Limbacher. “They adapt to the drive mode setting in Audi drive select. In the efficiency mode, it recommends lifting off the gas early and makes extensive use of coasting. In the auto and comfort modes, this happens considerably later and not at all in the dynamic mode and when the transmission is in S. And when Audi side assist, our rear-end radar, identifies another vehicle approaching rapidly from behind, the “lift off the gas” recommendation is likewise suppressed.”

Audi is already introducing a further evolution of the predictive efficiency assistant in the Q7 e-tron, which will soon be coming to market. This system works in combination with the so-called active drive pedal. If required, it knocks briefly against the sole of the foot to recommend lifting off the gas. An electromagnetic actuator carries out this function – likewise entirely in the name of efficiency.

Ole Eichberg
Eichberg (left) conceived the gas tanks for the
g-tron model. “They are very lightweight
and extremely safe.”

Christopher Mohns
“The A4 Avant is actually CO2 neutral when it runs
on Audi e-gas,” Christopher Mohns,
Technical Project Manager.

Gas tanks –
The mixed weave of CFRP and GFRP,
which serves as the second layer,
can be seen here on the tanks. 34 The third layer
of GFRP only is not pictured.

Ole Eichberg and Christopher Mohns
Environmentally friendly driving with Audi e-gas

Audi A4 Avant g-tron
The g-tron model, which will join the lineup in 2016, is another choice for sustainable mobility. When running on Audi e-gas, the powerful Avant is actually CO2 neutral.

A powerful, versatile car fully prepared for CO2- neutral driving – with the A4 Avant g-tron, Audi is offering its customers yet another route to sustainable future mobility. Following the A3 Sportback g-tron, the A4 Avant, which comes to market at the end of 2016, is the brand’s second model to use natural gas and/or Audi’s environmentally friendly e-gas. “The technical challenges in this project were considerable,” says Christopher Mohns, Technical Project Manager A4 CNG. “We solved them with the help of some great team spirit.”

When running on Audi e-gas, the A4 Avant g-tron is actually CO2-neutral. The driver can refuel with an Audi e-gas card that serves as an accounting instrument. Audi e-gas is synthetic methane produced by Audi in several power-to-gas plants from water and CO₂ with the aid of eco-electricity. In cooperation with partners, the company is working hard to drive the technology forward, also with new production processes featuring a biological approach.

The A4 Avant g-tron is extremely clean to run, as well as highly economical. It is powered by the 2.0 TFSI with a new combustion process, generating 125 kW (170 hp). In the NEDC, it consumes less than four kilograms of gas per 100 kilometers – equating to CO₂ emissions of less than 100 grams per kilometer. The tank volume of 19 kilograms means a range of more than 500 kilometers in the NEDC. When the amount of gas remaining in the tank drops to around 0.6 kilograms, which is 10 bar residual pressure, the control unit switches to gasoline. The dual-fuel A4 Avant g-tron can then go on to cover a further 450 kilometers or so.

Safety is the number one priority.
The gas tanksare designed for an operating
pressure of 200 bar, but are
tested to 300 barduring production.

Ole Eichberg
Coordination High-Pressure Fuel Systems

The four cylindrical gas tanks are located in the rear of the Avant, each one of them formed specifically for the best possible fit within the available space. A sheetsteel framework holds the containers and protects them from damage. The large module, which also incorporates the 25-liter gasoline tank, extends forward of the front axle. During production of the A4 Avant, it is fastened to the bodyshell at 16 points. Unlike the TDI and TFSI Avant, there is no spare wheel well. The load surface is on the same level as the loading edge, while the battery has been relocated from the trunk to the engine compartment.

The tanks fit perfectly with Audi’s lightweight design philosophy – thanks to their innovative layout, they weigh far less than conventional steel bottles. A matrix of gas-tight polyamide forms the inner layer. The second layer – a mixed weave of CFRP and GFRP – is incredibly strong. The third layer, made entirely from GFRP, serves primarily for visual checks – damaged areas turn milky white./p>

Safety is the number one priority for the Audi A4 Avant g-tron, as explained by Ole Eichberg, from Coordination High- Pressure Fuel Systems. “The tanks are designed for an operating pressure of 200 bar at 15 degrees Celsius. During production, however, each container is pressure tested to 300 bar before being fitted to the car. During testing, we used a 62-ton military tank to drive over the bottles, which still contained a residual pressure of 50 bar. The structure remained fully intact.”

Dr. Wolfgang Huhn
“Our competence in electronics is a key factor for success,” says Dr. Wolfgang Huhn, Head of Development Light/Sight.

Dr. Wolfgang Huhn
Electronics expertise as the key to success

Lighting technology
Audi is the world’s leading brand in vehicle lighting. In the new A4 family,
the brand presents its Matrix LED technology, which regulates the high beam
extremely precisely for every situation.

Lighting technology is one of the many technical fields in which Audi drives the competition. The brand’s major innovations include its Matrix LED headlamps, which debuted at the end of 2013 in the A8 flagship. “We then successively introduced them into the smaller model lines,” explains Dr. Wolfgang Huhn, Head of Development Light/Sight. “Now we’re presenting them in the new A4. The success of our new technologies brings us the economies of scale that enable us to make them affordable to an increasing number of customers.”

In the new Audi A4, twelve LEDs generate the high beam. Their control unit switches them on and off individually as required or dims them in 64 stages. The corresponding signals come from a newly developed camera that also handles part of the image processing. The Matrix LED headlamps can realize several million different light patterns. In all cases, its high beam provides bright and homogenous illumination, without dazzling other road users, which are masked precisely out of the beam.

The dynamic cornering light function of the Matrix LED headlamps is generated by shifting the center of the light. In cooperation with the optional MMI Navigation plus system, it uses predictive route data to illuminate the bend before the steering wheel is turned. “There’s a new function in the new A4,” says Dr. Huhn. “When the light falls on a highly reflective traffic sign, we dim it locally by around one third.”

One major factor for Audi’s leading role in lighting technology is its electronics expertise. “We have established our own team within the department to develop the function software for the control units,” reports Dr. Huhn. “Increasingly tighter networking within the car and networking of the car with the outside environment present us with enormous possibilities for managing the light in an even more intelligent way. The pace of progress here is rising constantly.”

And in what direction is it going? “We see two paths,” answers Dr. Wolfgang Huhn. “One of them is to make the new technologies even simpler and more cost effective, so that we can offer them as standard equipment in a few years. Ever greater integration of control units will help us achieve this. The other path is the hi-tech route. We are currently working with new modulation processes that enable us to disperse the light into several hundred thousand points. We can use this, for instance, to generate graphics for the driver. In any event, we will continue to work closely with our designers – which is one of the major keys to success. Our new light technologies will keep delivering added value and look great at the same time.”

Headlamp technology and Audi A4 Avant g-tron
The new Audi A4 always provides
excellent road illumination with its Matrix LED headlamps.
The g-tron model, which follows in 2016,
runs on synthetic methane – the environmentally friendly Audi e-gas.

The success of our
new technologies also benefits
Audi customers. High volumes
allow us to make our
innovations affordable.

Dr. Wolfgang Huhn
Head of Development Light/Sight