Part of the Wind –
Aerodynamics meet Design

Marlon Matthäus

Ulrike Myrzik

When it comes to aerodynamics and design, it’s usually a matter of a few millimeters – often under very different precepts. Frank Lamberty and Beat Heinzelmann explain how teamwork delivered the optimum solution for the new Audi A4. And how a car managed to lift the bar a good deal higher in both fields.

A matter of form – Powerful shoulders and wide wheel arches set challenges for the aerodynamicists.

Mr Lamberty, Mr Heinzelmann, if it was up to you individually, what would your perfect car look like?

Heinzelmann: For me as an aerodynamicist, a car has to be sleek and streamlined like the profile of an aircraft wing. The wheels on the car are fully clad and the design is based on the Type C streamline vehicles from the 1930s. That would give the vehicle the best possible cd figure.

What does the designer say to that?

Lamberty: My ideal looks somewhat different. For me, the top priority is good, strong proportions. This includes broad shoulders and powerful wheel arches to accentuate our quattro genes.

That looks like tough teamwork …

Lamberty: In the end, the result of our work has to be a great design and a similarly great cd figure. And it is precisely through constructive and intense cooperation that we are able to achieve good results. The best example is the new A4. The sedan has a cd figure of 0.23, the Avant 0.26. These are best-in-class figures that were achieved without cutting corners in the design.

Heinzelmann: I agree totally. There are, of course, always lots of areas of disagreement in the beginning. We then wrestle long and hard with these, but ultimately find common ground and the optimum solution. At the end of the day, we both want to put an outstanding car on the road (laughs).

Does that mean you shift from being competitors to colleagues?

Lamberty: It’s an exaggeration, but you could put it like that. For us designers, it is the fundamental idea that matters. We want to create a great new car. Obviously aerodynamics is an important part of that, but I can’t allow that to restrict me in the first instance. It’s the creativity that counts at the start.

The science of airflow – Thanks to refined technology on the underbody, the air is guided smoothly around the rear wheels.

Heinzelmann: Finding a joint basis is sometimes not easy at all. But it’s precisely for this reason that we work so closely together from the very start. We go into the wind tunnel with the first dimensionally accurate design models at a very early stage in the process and discuss the outcomes. Each of us has certain ideas and we manage to come closer together through our work on the models.

Lamberty: There are often interesting surprises. One form that we thought could be critical in terms of aerodynamics turns out to work really well.

You were heavily involved in the development of the new-generation Audi A4. Where did you have to make the biggest compromises? What were the major discussion points?

Heinzelmann: If it had been up to the designers alone, the A4 would have had a considerably wider track. We were a good 20 millimeters apart in our thinking. From an aerodynamic standpoint, that’s worlds apart.

Lamberty: As I mentioned, we entered the race for the A4 with far broader shoulders. For us, a wide car is a sporty car.

Heinzelmann: DThat was obviously a problem for us. If the car gets wider, it automatically gets harder to create low-loss airflow. This is ultimately detrimental to the cd figure as well as frontal area and leads to an increase in fuel consumption and emissions.

Lamberty: We talked extensively about the front skirt and the side air intakes. We wanted everything to be very three-dimensional and sculptural. Beat Heinzelmann was therefore faced with the challenge of addressing the turbulence caused by this.

Heinzelmann: Smooth surfaces are easier to deal with. There’s no question that the front end of the A4 turned out super – it’s an edgy and very sharp piece of design. But the more three-dimensional the design of this kind of detail is on a vehicle, the more uncontrolled the airflow becomes. We worked then with a simple air channel in the side intakes. This enabled us to guide the airflow around the front skirt without turbulence and blow it out along the sides of the wheels.

Beat Heinzelmann
As an expert in the field of aerodynamics and aeroacoustics, Beat Heinzelmann was involved in the Audi A4 project from the very start and, together with his colleagues, has set new benchmarks with the cd figure. After the game is before the game – the engineer is currently working on the development of the new generation of the Audi A5.

What other tricks did you use to unite design and aerodynamics?

Heinzelmann: Frank Lamberty and his colleagues definitely wanted to use a narrow and very sharply angled D-pillar on the Avant.

Lamberty: Although it didn’t turn out that narrow in the end (laughs). We added an extra line specifically to make it look narrower. We use this “fast” D-pillar to lean the rear windshield forward, which makes the rear end dynamic and sporty. This is what sets an Avant apart from a regular wagon. However, it’s not ideal for the aerodynamics because it shortens the separation edge at the rear.

You’ll have to explain that …

Heinzelmann: The separation edge ensures that the air separates at the rear in a defined manner and flows rearward with as few losses as possible. The longer and, above all, deeper the separation edge on the roof spoiler can be extended rearward, the better it is for the aerodynamics.

Lamberty: On the sedan, the air separation doesn’t occur until the end of the trunk lid. On the Avant, it takes place high up on the extended roof spoiler. We then decided jointly to place small, formed surfaces between the spoiler and the rear windshield, referred to as aero baffles. This enabled us to effectively shift the separation edge rearward.

Heinzelmann: In the end, we were all happy. Design got its narrow D-pillar and we were able to reduce the cd figure so much that we’re actually best-in-class with the Avant.

So design and aerodynamics are ultimately complementary?

Heinzelmann: We do actually have a lot of areas of common ground and often find ourselves fighting the same corner. For instance, we both wanted a diffuser that extended high up into the rear end. This makes the car sporty, while at the same time generating low rear lift and good balance. This is where we close ranks quickly if other departments question it …

Frank Lamberty
As Project Leader Exterior Design for the new Audi A4, Frank Lamberty and his team designed the new Audi A4. One of his responsibilities was to bring together all the requirements for the new model range – and, ultimately, to create a good piece of design.

Lamberty: When we develop a new car, we are faced with a diverse array of demands and requirements. The focus here is on package and functionality. For the customer, a spacious and comfortable interior is important, as are features like a retractable tow hook or even a virtual pedal for automatically opening the tailgate. All of this technology takes up space. As designers, we have to form these areas and the aerodynamicists have to streamline them. This is where we share a lot of common interests (laughs).

The number one purchasing reason was and is design. Is all this work on the cd worthwhile?

Heinzelmann: Good aerodynamics are very important as they have a direct impact on fuel consumption. A low cd figure means less fuel and, at the end of the day, lower CO2 emissions. This matters to customers.

Lamberty: Our vehicles are becoming increasingly efficient. And we have to tighten every single screw in order to achieve this. The A4 Avant ultra has emissions of just 99 grams of CO2 per kilometer, which is an absolute best.

Cast your eyes forward to the future: Where is this journey leading?

Heinzelmann: Everything that we have done well on this car will be carried forward into the next model. It’s a process of continual improvement – and a very gradual, laborious one at that (laughs). As far as the whole issue of cd figures is concerned, I see the potential for major savings through new technologies in the shape of movable aerodynamics.

Lamberty: I see it in broadly the same way. Movable aerodynamic elements will enable another whole new set of approaches for designers.

Heinzelmann: We started with the retractable rear spoiler on the first Audi R8. On the Audi Q7 and now on the A4, there is a controllable cooling air intake behind the Singleframe grille. What makes it special is that the development team designed the part and its control in such a way that it not only noticeably reduced the cd figure, but fuel consumption, too. Technologies of this nature give both designers and aerodynamicists even more creative freedom.