Concept Studies Should Sound Out Extremes
Concept Studies Should Sound Out Extremes

Video: Concept Studies Should Sound Out Extremes

Video: Concept Studies Should Sound Out Extremes
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Reiner Weidemann considers a drag coefficient of 0.20 for series vehicles to be feasible. "Underneath it would look too exotic for a series," says the head of aerodynamics at Opel in an interview with Autogazette.

Aerodynamics is playing an increasingly important role in automobile construction. It is an integral part of the development work, says Reiner Weidemann, who is responsible for aerodynamics at Opel, in an interview with Autogazette. Weidemann assumes that with conventional setups “Cd values of 0.20 are certainly still feasible”, “below that it would look too exotic for a series”.

Involve aerodynamics earlier in design creation

In order to ultimately achieve the best possible result in improving the Cd value, the manufacturers would have to coordinate the necessary measures even better. For example, Opel is thinking about “possibly taking aerodynamics into account earlier than before when considering future design”.

It depends on the interaction of all aspects

Autogazette: Have the majority of car manufacturers neglected aerodynamics in the past few years?

Reiner Weidemann: Not at all. The aerodynamic properties of a vehicle have been continuously improved since the 1980s. In addition to the drag coefficient, I would also like to mention the subject of lift. The drag coefficient of our vehicles is getting better and better on average.

Autogazette: Why is aerodynamics moving more into the focus of car manufacturers? Is that mainly due to the strict CO2 guidelines for fleet consumption?

Weidemann:This does not depend so much on changes in the specifications, because the aerodynamics department is an integral part of every development activity for a vehicle. Especially with regard to CO2 guidelines, the interplay of all aspects in development is important. The aim here is to achieve an optimal result for the entire fleet across all platforms.

Autogazette: Is it easier and, above all, cheaper to improve the efficiency of a vehicle through aerodynamic measures than through lightweight construction?

Weidemann: It can at least be said that against the background of the new WLTP driving cycle, which is to be introduced in the EU before 2020, the topic of aerodynamics can and will make an even greater contribution than before.

Drop shape always present

The rear of the new Opel Insignia
The rear of the new Opel Insignia

Autogazette: Will aerodynamics change the design of cars in the future?

Weidemann: Design lives in cycles regardless of aerodynamic requirements. But we will possibly involve aerodynamics even earlier than before when considering future design.

Autogazette: Is the one-liter VW XL1 with a drag coefficient of 0.189 pointing the way for future generations of vehicles or is it just a finger exercise for designers and aerodynamicists?

Weidemann:In the end, concept studies should also explore extremes. The one-liter car is obviously intended to show what is theoretically possible with conventional technology. We are also pursuing similar studies. However, there is still a long way to go before conventional series production can be introduced in larger quantities in such a way that it can make a noticeable contribution to the CO2 emissions of an entire fleet.

Autogazette: Does the teardrop shape have a future again in future vehicles?

Weidemann: The teardrop shape is always present in a different form - but certainly not as obvious as it was with the Rumpler teardrop car 90 years ago.

«In reality there is no such conflict»

Autogazette: Where do you see the greatest trade-off between design and aerodynamics?

Weidemann: This question is a little academic. In reality, this conflict does not exist. It is always the sum of the requirements of all technical areas that must be merged into an optimal result. In the course of this discussion, the respective requirements for aerodynamics and vice versa for the other development areas arise.

Autogazette: Do the increasing demands on vehicle safety, such as pedestrian protection, pose particular problems for aerodynamics?

Weidemann:The aerodynamics are indirectly affected. Some design measures for vehicle safety require appropriate space, which leads to larger frontal areas, which then cause greater driving resistance.

Only physics sets the limits

Opel chief designer Ivo van Hulten explains the Insignia
Opel chief designer Ivo van Hulten explains the Insignia

Autogazette: The Rumpler teardrop car from 1921 had a drag coefficient of 0.28. If you compare that with the drag coefficients of today's vehicles, no quantum leaps have taken place since then. Has aerodynamics been more of a standstill than progress in the past 92 years?

Weidemann: Rumpler could probably even have reached 0.22 back then. However, the example shows one thing: There are always different goals and requirements, and since Rumpler the number of additional requirements to be taken into account has grown steadily and immensely. If you look at aerodynamics in isolation, ultimately only physics sets the limits. Today the Rumpler value is of course average. In the future, hardly any vehicle will be higher than this.

Autogazette: The Mercedes CLA is currently the aerodynamics champion among the series vehicles with a drag coefficient of 0.22. What reduction can you imagine in the future?

Weidemann: With conventional setups, Cd values of 0.20 are certainly still feasible, below that it would look too exotic for a series. At least that can be said against the background of today's customer acceptance. But it is well known that design tastes can change. As aerodynamicists, we will be prepared for this.

The questions to Reiner Weidemann were put by Thomas Flehmer and Frank Mertens

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