I can see why one would want an early boundary layer separation on a spherical orb that is flying through the air.

Half of the sphere is always on the back, and the sphere is rolling or spinning, so that there is no static front or back, or outer diameter to the direction of travel, so the dimples have to be everywhere.

And separation of the boundary layer induces turbulence and spoils the airflow around the back side of the ball, so that there isn't just a big hole punched through the air, with low pressure behind the ball, in addition to the high pressure in front of it. filling in the low pressure zone behind effectively cuts total drag, without changing the frontal area or spherical shape of the ball itself.

But cars don't operate like golf balls. They don't roll, and tumble, there is a distinct back, front, side, and bottom, and they generally operate in one direction at speed, forward.

Having dimples on the front doesn't help much. Smoother and more tapered is more aerodynamic. The less overall frontal area, and the greater percentage of that frontal area that is not perpendicular to airflow is better. No dimples needed.

The back is a low pressure zone, but there are more efficient ways of separating or spoiling the boundary laminar flow, mostly by spoiler blades (fin like structures, rather than inverse airfoil wings, which are for downforce and traction... or usually decoration.)

Some race cars, and air craft use what are called vortex generators. Little fins and sleek spike structures at strategic locations that channel, and spoil the laminar airflow to have it fill in low pressure areas with eddie currents of air, again cutting drag by reducing low pressure in the wake of an object, in addition to whatever measures are taken to mitigate high pressure in the front of the object.

Vortex generators, dimples, and other devices at strategic locations might help spoil laminar flow, and reduce low pressure wake drag, but wrapping a car in dimpled vinyl, because it works for a golf ball, is a little too simplistic, and won't really help the inherent un-aerodynamic qualities of a Scion XB, which is itself a big brick of an economy car.

Presuming the advertising of 20% is correct, for the sake of argument, how much will this cost out-the-door? If the cost of the installation essentially amounts to the cost of the gas you would save over several years, the technology is worthless.

My initial reaction to this article was to be reminded of another company that sells some catalytic converter which somehow breaks down the incoming fuel to the engine to make the combustion so efficient, it is "guaranteed" to double or more the fuel efficiency of the vehicle. Unfortunately, based on both the cost of the device and its installation, no matter what vehicle you attached it to would, essentially, take the average life of the vehicle to pay off the difference between the tech and the money you would have otherwise spent on gas.

No sale.

A couple of F1 teams did look at using this a few years ago using a special paint.

I think it made the cars too heavy in the end - so it wasn't used.

Oh boy. I remember an episode of red green from way back when. Red noticed that golf balls are dimpled to go farther, so he decided to take a pickaxe to his car. Although this is obviously not as drastic as a pickaxe, it is still funny that sombody actually did it!

These are speed holes. They make the car go
faster.

Oh yeah. Speed holes!

Just a note, on new Volkswagen cars the underbody panels are dimpled, must be something there useful.

"...but the fact that aircraft and race cars aren't already covered in dimples seems a bit suspicious"

This is because they don't work. I'm an aero-engineer and I've done this before in the windtunnel. There is no noticeable difference. The best way to improve aero is to have a better aerodynamic vehicle.

Isn't the physics contingent on being able to keep the dimples clean? A relatively simple chore with a golf ball, but a car? And once it does get dirty, unless you buy the dirt colored paint job, you'll be driving a non-stop polka-dot nightmare everywhere you go, unless of course, you're especially fond of polka-dotted cars.

dimples like this only apply to a rotating sphere...
see link below...

http://www.vu.union.edu/~scottg/Senior_Project/Theory%20and%20Analysis.htm

I would do this just so I could have a bumper sticker made that reads "Dimpled for your driving pleasure."

Didn't Homer Simpson do this with an icepick? "DUH, I'm putting speedholes in my car! Stupid Flanders."

Yeah, he did... Read my above comment.

I cannot believe I am the only one that saw the MythBusters episode...
They covered a car in modeling clay (about 50mm thick), then gave it a dimple effect. Each dimple being about 60mm across.

Despite the fact that the clay must have weighed a ton, from memory, the mileage was about 25% better?

Their measurement methods appeared sound, so I am impressed!

I'm all for it, but I just cannot find a damn 60mm Ball Hammer?

Give it a try...

Paul

p.s. The 'captcha' images on this site suck - hard!

I put vortex generators on the roof of my car as per mitsubishi lancer evo 8 but with a shape based on a McDonnell Douglas Skyhawk v/g shape. After over a year of carefully refilled tanks of fuel I seem to have about a 10% increase in fuel economy.