wing on the back of a car increasing MPG? Color me dubious.
May 5, 2006 8:12 AM Subscribe
Last night on ABC news there was a guy with a VW beetle (silver) who put a wicked-huge wing on the back and claimed some ridiculously-high MPG figure. Alas, my google fu fails me. Why would this wing possibly work? They guy wasn't a tuner, AFAICT.
Response by poster: sorry, no. I found that one too. The guy you link to put a jet engine in his beetle, I'm looking for a guy who bolted on a homemade looking wing.
The horizontal portion was large, and may have connected to the car directly under the rear window. It had a large surface area (IMO, about the same horizontal surface area as a VW Jetta trunk lid.)
The wierdest thing about it though were the *large* side-surfaces of the wing. They seemed to be ~18" guitar-pick shapes on each side, standing vertically.
I would think the vertical bits would make the car more stable at speed (go in a straight line better), but I don't know why it would have *any* effect on mpg. If anything, I'd think their weight would be a hinderance.
posted by Wild_Eep at 8:24 AM on May 5, 2006
The horizontal portion was large, and may have connected to the car directly under the rear window. It had a large surface area (IMO, about the same horizontal surface area as a VW Jetta trunk lid.)
The wierdest thing about it though were the *large* side-surfaces of the wing. They seemed to be ~18" guitar-pick shapes on each side, standing vertically.
I would think the vertical bits would make the car more stable at speed (go in a straight line better), but I don't know why it would have *any* effect on mpg. If anything, I'd think their weight would be a hinderance.
posted by Wild_Eep at 8:24 AM on May 5, 2006
TonyRoberts' linked article attributes a 5-8% increase in mileage to the wing. Not bad, but not miraculous.
posted by MrMoonPie at 8:34 AM on May 5, 2006
posted by MrMoonPie at 8:34 AM on May 5, 2006
So, it's a turbo diesel that gets like 50mpg without the wing. Looks like the wing takes it up to 60mpg. Maybe less stunning because of the high baseline mpg?
posted by Mid at 8:34 AM on May 5, 2006
posted by Mid at 8:34 AM on May 5, 2006
The wing plus new, low-rolling-resistance tires takes it up to 58.8 mpg, from a starting point of 52.5. That's a 12% increase, about half of which is due to the wing.
posted by MrMoonPie at 8:41 AM on May 5, 2006
posted by MrMoonPie at 8:41 AM on May 5, 2006
I don't know if the numbers are true or not, but TonyRobots' article summarizes how the energy is saved pretty well.
As to how the wing would work, for the kind of drag improvement described the spoiler would be preventing or reducing flow separation from the back end of the car. The Beetle's hidquarters have a pretty bad aerodynamic shape (put there in the name of style) so there is much room for improvement there.
posted by cardboard at 8:45 AM on May 5, 2006
As to how the wing would work, for the kind of drag improvement described the spoiler would be preventing or reducing flow separation from the back end of the car. The Beetle's hidquarters have a pretty bad aerodynamic shape (put there in the name of style) so there is much room for improvement there.
posted by cardboard at 8:45 AM on May 5, 2006
Google: vw wing mpg
posted by TonyRobots at 8:48 AM on May 5, 2006
posted by TonyRobots at 8:48 AM on May 5, 2006
sorry, slight correction, it was: vw wings mpg
posted by TonyRobots at 8:49 AM on May 5, 2006
posted by TonyRobots at 8:49 AM on May 5, 2006
Response by poster: Wow, I wonder how much LRR tires cost, and what the break-even point is for them.
posted by Wild_Eep at 8:55 AM on May 5, 2006
posted by Wild_Eep at 8:55 AM on May 5, 2006
Rear-mounted spoilers take effect only when you hit about 90 mph. Also, they push the rear down, so that the tires are pressed harder against the pavement, increasing traction. If anything, this would increase rolling resistance, since it would increase the amount of flexing in the sidewalls.
In words of one syllable, it's a hoax.
posted by KRS at 10:23 AM on May 5, 2006
In words of one syllable, it's a hoax.
posted by KRS at 10:23 AM on May 5, 2006
KRS, are you an aerospace engineer that collected and published data to support your hypothesis?
posted by parallax7d at 10:37 AM on May 5, 2006
posted by parallax7d at 10:37 AM on May 5, 2006
traction ! = acceleration, except at the drag strip, which is pretty irrelevant in a discussion about fuel economy.
posted by Kirth Gerson at 10:39 AM on May 5, 2006
posted by Kirth Gerson at 10:39 AM on May 5, 2006
The guy gives a rather cursory explanation on how it works here.
IANAAE, but probably what it does is reduce the turbulence of airflow coming off of the end of the car. The winglets probably work as they do on aircraft, to reduce drag caused by the wing itself.
posted by zsazsa at 11:01 AM on May 5, 2006
IANAAE, but probably what it does is reduce the turbulence of airflow coming off of the end of the car. The winglets probably work as they do on aircraft, to reduce drag caused by the wing itself.
posted by zsazsa at 11:01 AM on May 5, 2006
its not a hoax. this isnt a spoiler in the traditional sense, its designed to smooth the airflow over the back of the car, to prevent friction losses due to turbulence.
although he's kind of cheating since he went for the LRR tires as well :)
posted by joeblough at 11:09 AM on May 5, 2006
although he's kind of cheating since he went for the LRR tires as well :)
posted by joeblough at 11:09 AM on May 5, 2006
Even if acceleration traction were equivalent to stopping traction (it isn't) - stopping distance has what to do with fuel efficiency?
posted by Kirth Gerson at 12:20 PM on May 5, 2006
posted by Kirth Gerson at 12:20 PM on May 5, 2006
B1tr0t, there is a difference between Rolling Resistance, and Static Friction. A tire with low RR does not essentialy have to also have low static friction.
posted by nomisxid at 1:10 PM on May 5, 2006
posted by nomisxid at 1:10 PM on May 5, 2006
That's a false comparison, bitrot. Regular tires are designed to run at a particular inflation and using them out of spec certainly doesn't "simulate LRR tires" in any meaningful way. LRR tires are designed though particular textures and tread patterns to have less rolling resistance while preserving stopping ability.
They may indeed suffer somewhat but given how litigious our society is I find it impossible to believe they are simply inferior tires.
posted by phearlez at 1:26 PM on May 5, 2006
They may indeed suffer somewhat but given how litigious our society is I find it impossible to believe they are simply inferior tires.
posted by phearlez at 1:26 PM on May 5, 2006
Rear-mounted spoilers take effect only when you hit about 90 mph. Also, they push the rear down, so that the tires are pressed harder against the pavement, increasing traction. If anything, this would increase rolling resistance, since it would increase the amount of flexing in the sidewalls.
Maybe in a car that wasn't design primarily for athsthetics, like the VW beetle, rather then aerodynamic performance, like the Honda Insight or Toyota Prius. The wing, in this case, corrects an aerodynamic flaw.
posted by delmoi at 11:47 PM on May 5, 2006
Maybe in a car that wasn't design primarily for athsthetics, like the VW beetle, rather then aerodynamic performance, like the Honda Insight or Toyota Prius. The wing, in this case, corrects an aerodynamic flaw.
posted by delmoi at 11:47 PM on May 5, 2006
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posted by Baud at 8:18 AM on May 5, 2006