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12% Increase in Auto Fuel Efficiency - 10/28/2009 6:36:35 PM

MasterG2kTR

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I just finished watching it and this is without a doubt one of the best Mythbuster episodes I've seen in a while. I think that automakers should all be taking a serious look at the results the Mythbusters came up with. See link at end of post
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The Mythbusters must be closet car fans, because the hour-long show on the Discovery Channel seems to be producing more and more experiments involving automobiles than ever before. Their latest again involves fuel efficiency, this time testing if a dirty car is more fuel efficient than a clean one because of the golf ball-like dimpling effect of the dirt. Turns out dirt doesn't make a difference, but Adam and Jamie went one step further to test if covering a car in actual golf ball-like dimples would improve its fuel efficiency. According to cable's most crack scientists, yes, it will.

digg_url = 'http://digg.com/autos/Mythbusters_test_golf_ball_dimpling_effect_on_fuel_economy'; The show's team completely covered a last-gen Ford Taurus with modelers clay and figured out that it would achieve about 26 mpg at a constant 65 mph. They then went about adding over 1,000 dimples to the car's exterior. To keep the experiment consistent, all 1,082 dimples removed from the clay exterior were put in a box and set in the back seat so that the car would weigh exactly the same as before dimpling. The theory is that, like a golf ball, the dimples would reduce the car's drag through the air, thus allowing it to travel the same distance at the same speed using less fuel. The result? Over 29 mpg.

Follow the jump to watch the whole episode for yourself, though if you're only interested in watching the dimpled car do it's thing, skip ahead to about 40 minutes in.

Link to full episode after you click this link click the RED Play button if another window opens close it and then click the GREEN Play button and the video will start. The pop up window and anything else you see is just advertising crap.

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RE: 12% Increase in Auto Fuel Efficiency - 10/29/2009 10:09:55 PM

Termyn8or

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So that blond who got caught in the hailstorm should not have blown into the tailpipe ?

Sorry I just couldn't resist.

Actually the golf ball spins while it flies trough the hair, which changes things alot. The only way to achieve the effect is to have the body moving through the atmosphere to spin. Otherwise it is a drag. Unless there is something new under the sun. The key to aerodynamic efficently is to slightly cut through the atmosphere, and to close the gap once past that point. This dimple effect will not do that no matter what they say.

The olman told me of getting really kickass mileage on the highway, but that was when 57 Chevies were out ond many highways had very high limits, or none at all. A 1957 Chevy becomes very aerodynamic at about 95 MPH. Otherwise it is a load, windwise. You will not find data on this, but he did attest to the fact that if you got one of these airblobs going fast enough, it almost acted like a wing. This is almost analogous to the flight envelope of an aircraft designed for high speed, although I really don't see it. However it is not quite as fast, and personal testament is important to me. Why would he make this up ?

I know it doesn't seem quite right when considered only in the aerodynamics venue, but there are other factors involved with a ground based vehicle. The body shape, like the wing of an older aircraft produces lift. This takes part of the weight off the wheels, which are by far the biggest impediment to efficiency, or at least they were then.

Go ahead and get them to test a 1957 Chevy in a 110 MPH wind tunnel, it will reveal a reduction in weight, not mass but weight. This equals land load in a way. Look at the shape of the thing. It is plain to see that it acts as a plane's wing, actually producing lift. This is a matter of fact, because it is also plain to see the the air passes below the craft at a higher pressure than the air passing above the craft. This is indeed the basis of lift in any aircraft.

The only way a "mottled" shape could come close is to somehow make it so the vehicle "drafts" itself, and that will not happen this way.

T

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RE: 12% Increase in Auto Fuel Efficiency - 10/29/2009 10:45:52 PM

sappatoti

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I found that episode to be an eye opener as well. Having thought about it a week later, though, I'm not sure they can take that 11% increase (the amount the MB spoke about in the ep) and apply it to all driving conditions for all vehicles.

They started with a car that had a decent aerodynamic shape to begin with. Their test track was a one-mile stretch of straight road. They drove that course at interstate highways speeds, not city driving speeds. They made no mention of wind conditions; whether they were head, tail, or cross winds. They did not play with the size or spacing of the dimples, for obvious reasons.

Would that same dimpling pattern work on something the size and shape of a city bus, starting and stopping its way along its route filled with straight lanes, curves, and corners?

I will admit, for the very basic and simple test the MB performed, an 11% in fuel economy increase is impressive.

This reminds me of research I read about in the 1970s where the Navy and Air Force were studying the use of gelatinous type coatings for the surfaces of their boats and air planes. They studied the skin of porpoises and whales and found that as those animals moved through the water, the blubber of the skin would "give way", creating ad-hoc dimpling effects that rippled down the length of their body. Playing around with synthetic versions of blubber in the lab produced results that showed increases in speed and efficiencies in fuel consumption for small scale models using the blubbery surface coating vs. those that used shiny, yet hard coatings. I never did find any more information as to whether those experiments were actually tried full scale or not.

Like I stated, this was an eye opening episode which shows the possibilities of using dimpling to increase fuel efficiency.

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RE: 12% Increase in Auto Fuel Efficiency - 10/30/2009 12:51:36 AM

Termyn8or

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Indeed sapp, some fighter jets must not have any chips in the paint. Aerodynamics is that crucial in that.

T

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RE: 12% Increase in Auto Fuel Efficiency - 10/30/2009 5:31:01 AM

OneMoreWaste

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quote:

ORIGINAL: Termyn8or
The olman told me of getting really kickass mileage on the highway, but that was when 57 Chevies were out ond many highways had very high limits, or none at all. A 1957 Chevy becomes very aerodynamic at about 95 MPH. Otherwise it is a load, windwise. You will not find data on this, but he did attest to the fact that if you got one of these airblobs going fast enough, it almost acted like a wing. This is almost analogous to the flight envelope of an aircraft designed for high speed, although I really don't see it. However it is not quite as fast, and personal testament is important to me. Why would he make this up ?

No idea, my guess would be measuring error, but it opposes the laws of physics. While some cars do generate measurable lift at high speeds, this is a liability rather than an asset because it does bad things to handling and traction (aka "road friction"), which can result in a loss of control. At 110 MPH, rolling resistance is negligible compared to air resistance for a vehicle with a high drag coefficient, like a '57 Chevy, as air resistance increases roughly with the square of speed, whereas rolling resistance increases linearly.

Finally, older vehicles were not geared for a high terminal velocity. If one could even hit that speed (maybe with a 283/3sp combo, certainly not with a 6-cyl and a Powerglide), the engine would be operating near redline, and burning fuel as fast as it could.

Just as an FYI, older tires, being on average skinnier, harder, and lower-grip than modern tires, generated less rolling friction. A 350-horsepower family sedan from the 1960s put less rubber on the road than a Dodge Neon.

I'll have to watch the MB episode when I have a bit more time. Sounds interesting, if limited in practical implications.

< Message edited by OneMoreWaste -- 10/30/2009 6:02:59 AM >

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RE: 12% Increase in Auto Fuel Efficiency - 10/30/2009 7:38:47 AM

popeye1250

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quote:

ORIGINAL: Termyn8or

Indeed sapp, some fighter jets must not have any chips in the paint. Aerodynamics is that crucial in that.

T

Term, I seem to remember back in the 1980's that the big thing especially for Ford was called "coefficient of drag" designs that in and of themselves increased fuel economy.
I remember that the '85 Mercury Cougar I had at the time had a "cod" of "0.27" or something like that.

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RE: 12% Increase in Auto Fuel Efficiency - 10/30/2009 8:49:38 AM

Termyn8or

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Yes indeed, all I had to do was give a bit of time to think. Why do they put airfoils on racecars ? That is exactly the reason.

T

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RE: 12% Increase in Auto Fuel Efficiency - 10/30/2009 7:28:21 PM

MasterG2kTR

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Term,

I'm guessing you didn't even watch the episode and all of the preliminary testing they did to see if the full scale test was worthwhile. Their research showed promising results without any need for the car to be revolving like a golf ball.

Term & Sapp,

Granted the testing they did was limited in general, but the results cannot be denied. I will however concede that actual results would be lower if you are driving at slower speeds and doing stop & go driving. At the same time any increase just from changing the design of body panels seems like it should be worth investigating some more.

Next time we get a "big" hail storm I'm gonna park in the middle of it....lol

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RE: 12% Increase in Auto Fuel Efficiency - 10/30/2009 10:27:15 PM

einstien5201

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quote:

ORIGINAL: Termyn8or

Yes indeed, all I had to do was give a bit of time to think. Why do they put airfoils on racecars ? That is exactly the reason.

T

I was under the impression that airfoils on racecars serve the opposite purpose - they produce 'lift' in the opposite direction, forcing the car down to keep the tires in proper contact with the surface of the track. This allows better handling on curves and turns.

http://en.wikipedia.org/wiki/Downforce

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RE: 12% Increase in Auto Fuel Efficiency - 10/30/2009 11:28:56 PM

Termyn8or

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You are correct einstein. But that depends on the car design. Actually most of tjose thing are designed to produce zero lift and zero drag. They might come close, but it is not possible to put anything there without one or the other. Unless you make it pressure sensitive and responsive, it does no good period. It is just for looks. When you hav something going down the dragstrip at 240 MPH, then it is different. You and I are not likely to have that problem.

But my point is that most car bodies shapes do cause lift, which means all their datta on driving 55 MPH is out the window and always has been. I knew this. Does anyone else remember ? Nevada was the only state to tell them to take their money and shove it up their ass. they set their speed limits as they saw fit.

The federal government usually rules with dollars. This is nothing more than another form of legalised extortion, of which I have been aware for decades. "Do this or we will keep all of the money we stole from your Citizens instead of part of it". Faced with those choices, what would a governor or a mayor do ? Try to get back as much as possible, which means to comply, and that means more laws.

Under current law, if my car gets dented and it causes it to get better gas mileage, they can stop me because I am interfering with international trade. Do you think I am kidding ? Right in this forum exist many links to proof, need I find them for you ?

It is time to turn the TV off, uninstall flash and quit watching their shit. If they are ever telling the truth they are selling something, and that is the best case. Now anyone who's been alive more than thirty years tell me what the odds are.

I am building an army, and I won't hesitate to use them. But I will only use them when needed. This "You ran up my sister's cellphone bill" simply doesn't wash here. I am talking serious shit, and serious people.

This is getting too close to a hijack now, so I will stop now.

T

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