Stagnation in aerodynamics

The automotive industry has entered an invisible wall in aerodynamics. In recent years, most cars have aerodynamic coefficients of about 0.3. This is a good value, but it strictly drives the limits of what is possible.

In 1989, Opel Calibra was launched with a drag coefficient of 0.26.

Yes, Calibra had some advantages with regard to the basic form, it was a long, low coupe. But this is 2009, 20 years have passed since then. Yet we only have a handful of cars that come anywhere near this value. One is the Toyota Prius with a Cd of 0.26 and the other is the Mercedes C Class Blue Efficiency with a Cd of 0.25. In the meantime, Prius 2009 has been revealed and claimed to have a Cd of 0.25.

So we are finally back at the point where we were 20 years ago. I find it very disappointing. I understand that there must be some compromises for design, practical and everyday usability, but I think we can do better than this.

Let's take the VW Polo Blue Motion, for example.

This is basically the same car as the Polo 1.4 TDI, but it has some tweaks in gear, aerodynamics and rolling resistance. They have equipped a grid with smaller ventilation holes in it and a roof spoiler to reduce the car's guard strength and another front bumper. This combined with narrower tires takes the CD down from 0.32 to 0.3. Now if it's that simple, why not produce each Polo like this? Instead of putting on the usual grille, put on this aerodynamic grille. How much does it cost for you?

Meanwhile, the Audi A2, which came out in 1999, had a Cd of 0.28 (standard version).

Ten years along the line, the VW Polo comes with 0.32. The 3L TDI version of the Audi A2 even had a Cd of 0.25, and the Blue Motion version of the VW Polo is 0.3 but 10 years later. Note that the Audi A2 did not have any benefits like Calibra in terms of basic form. It's a small hatchback like Polo. Do we make any progress here? I think we can come down to the range of ~ 0.2 in the near future. I think we could have been there already. What holds us back is the priority of styling and practical features over the car's aerodynamics. The car's basic form is not written by people who have a clear understanding of aerodynamics.

The Audi TT was an example of a car designed without regard to aerodynamics. The sloping rear window window produced a lot of high-speed rear axle lift. There were high-speed accidents and several people died. Then Audi acknowledged his mistake and mounted TT with an ugly back spoiler, some suspension changes and electronic stability control. Someone should have said during the design phase: "The rear window is the ideal angle of a wing that will not work on a car!"

Sometimes practical aspects of it come into play. When you have a sloping roof line, which is good for aerodynamics, it reduces available rear spaces. But in many cars, this compromise is perfectly acceptable for styling reasons.

One day someone must be bold and design a car with a Cd of 0.2. Of course, it must have nice style and exceptional fuel economy. Then you get people to buy such a car.

Why is all this important? On the highways, wind resistance is the most important force you need to overcome and it is directly proportional to the drag coefficient Cd. Changes in the drag coefficient almost translate directly to the fuel consumption at the motorways. In this climate of energy saving, should we, instead of discussing how to drive a car, first reduce the amount of power required to move it?

One day, the automotive industry will again move with regard to aerodynamic innovation. I just hope that the day will come rather than later.