COLUMNS: BMW Vision EfficientDynamics

November 9, 2009
A midst insincere electric and hybrid promises and over-the-top, 500-plus-hp, 200-mph cars close to the hearts of German engineers and executives, there was one concept at the Frankfurt auto show that actually represented a credible synthesis of green and mean: BMW's Vision EfficientDynamics. I thought it was excessively busy but highly interesting. A little to my surprise, it was the clear favorite of many serious top-level designers from other companies whose work - and opinions - I respect. But then, who wouldn't like a three-cylinder diesel that gives you, with its associated electrical helpers, 351 hp, a bunch of torque, superlow emissions, and a claimed 63 mpg?
0912 02 Z+bMW Vision EfficientDynamics+side View
Make an abstraction of the surface complexity and look only at the centerline profile. It is nicely proportioned and elegantly sporty, and it favorably recalls a number of equally exciting past concept cars. The transparent sides were seen on Marcello Gandini's 1966 Bertone concept - the Lamborghini Marzal - and have been recapitulated several times since, most notably by Giorgetto Giugiaro's 1972 Maserati Boomerang and 1998 Structura, as well as by Ghia for the 1977 Ford Megastar four-door. It might not be good to live with, but it's great show stuff and right at home here.
Look at the surface complexity in light of what it represents in reality. According to BMW design chief Adrian van Hooydonk, the Vision has a drag coefficient of just 0.22. That's a CFD (computational fluid dynamics) figure, not one measured in a wind tunnel, but I would be willing to bet that it is not more than five percent away from truth. Suddenly, all the hanging panels, flaps, and fences make more sense: this car is clearly related to what has been going on in Formula 1 for quite some time now - and in aviation long before that. All those little bits sticking out in the breeze direct the airflow somewhere other than where it would have gone on its own, and the flux effects positive behavioral change on the vehicle ensemble, however messy it may be to the eye.
The next time you are on a Boeing 737, look at the engine nacelle. There are some little winglike elements just behind the leading edge. They might be thought to increase drag, and indeed they do, a little, but they also result in a considerably lower landing speed. So, do the dramatic, free-floating red plastic taillight assemblies on the Vision reduce drag? I have no idea, but I suspect that they do channel the airflow in directions that are beneficial to the Vision's overall performance.
BMW's Vision is not elegant in the classical humanistic sense, but it certainly is in terms of the mathematical sense of the word, and I imagine all those admiring designers intuited that quality. The final key to a good car design lies in whether it incites a desire to drive it.
For this car? Give me the keys!
1. Ignore all the lines and openings along the side of the car and note the elegant and sporty centerline profile.
0912 02 Z+bMW Vision EfficientDynamics+side View
2. The side daylight-opening line is subtly faceted rather than being the smooth single curve one might expect. The Hofmeister kink is just barely retained.
3. This hanging panel makes one think of the "barge boards" on a modern Formula 1 car, no bad thing for a coupe, however unexpected.
4. High-pressure air in the front wheelhouses is evacuated in linear flow between the undercut body side and the hanging board.
5. The body side rolls under and inward, while the leading edge of the lower rear fender directs air inward toward the rear brakes and what might be thought of as a downforce-generating diffuser.
0912 01 Z+bMW Vision EfficientDynamics+side View
6. Fan-shaped wheels completely fill the opening, obviating the necessity for fender skirts as a drag-reduction measure.
7. This extension of the rear fender hangs down, unattached to other parts of the body. It directs airflow from beneath the car.
8. The way the doors open is not new, but the effect is much like the wings of an insect.
9. The polycarbonate roof covers a few structural elements that both provide strength and reassure passengers.
0912 03 Z+bMW Vision EfficientDynamics+front View
10. An electrical plug on a BMW? Around town, one might never engage the diesel, so a full battery charge first thing in the morning is important.
11. Traditional four headlamps are rectangular, a big change for BMW.
12. Looking rather like the protective side plates on a Roman helmet, these panels direct air toward the front brakes and down the side of the body.
13. New grille texture with two chrome bars per side again represents change within continuity. Expect to see this in production soon.
14. The center bumper fascia rolls from vertical to horizontal and extends outward in blades beneath the headlamps.
15. A subtle crease line defines the inner edge of the front-fender form, which extends back into the A-pillar base.
16. This thin blue line ties together disparate elements front to rear, adding character without weight.
17. The engine compartment is ventilated by dramatic ductwork that allows heat energy to flow over the roof.
18. Both tips of the rear fender profile are totally separate, again evoking F1.
0912 04 Z+bMW Vision EfficientDynamics+rear View
19. Taillights are slim vertically but extremely long and give the impression of floating in space.
20. The statutory CHMSL is external to the overall body form, presumably to keep glare out of the enclosed cabin.
21. The C-pillar is flared horizontally, then swings inward across the rear to shroud the red lamp blades, with the thin blue definition line at its edge.
22. Large openings imply downforce diffusers, one more racing hint in the composition.

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