Cd for Volkwagen XL1 8

[DukeGlacia]

So VW XL1 is claimed to have the lowest coefficient of drag in the world. Is it the rear wheel skirt that makes it so aerodynamic? And how much of significance does Cd have in aerodynamics ?I have attached the pic below

 

[itsmoked]

Who said it has the lowest?

Volkswagen?

The "truth in engineering" company?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[DukeGlacia]

Its on wiki. Cd value =0.189

 

[IRstuff]

And Wikipedia is such an excellent independent source? ;-)

"And how much of significance does Cd have in aerodynamics ?"

It defines the aerodynamics -- 1/2 Cd V^2

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[3DDave]

Cd affects the expected drag values, but that's all one can tell. It might have a sufficient lift coefficient that it lifts off at high speed. It's limited to 99mph.

I suspect it's also got a smooth underside to cut turbulence there and it looks like the front wheels fit the wells pretty closely, like pack-with-snow and break something in the winter kind of close.

Lack of outside mirrors helps as well.

There is probably only a small radiator to force air through due to the tiny motor/power output

If skirts would work than a Buick Electra 225 would have been low-drag.

 

[GregLocock]

I'd usually put a rho and an A in that equation, but hey it was worth a star apparently!

Just a couple of other points - firstly there is a big difference in Cd as measured in different tunnels, and even in Cd measured in the same tunnel using different company's procedures and software.

Secondly 0.189 is a fine achievement for a production (ish) car, but the EV1 was there, years ago. If you can accept a car shaped thing with taped doors and no internal ventilation and no wipers and narrow tires etc etc etc then 0.13 is probably a lower bound. If you can accept many other shape compromises and a laminar flow shape then you might get down to 0.07, basically skin friction+inertia recovery drag from the laminar flow section.




Cheers

Greg Locock


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[IRstuff]

https://en.wikipedia.org/wiki/Automobile_drag_coefficient

has a nice set of tables of drag coefficients. The GM EV1 supposedly had 0.196 in 1996

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[drawoh]

How important is drag coefficient for something low powered? If this thing is tootling around city streets, the important use of energy is acceleration.

--
JHG

 

[DukeGlacia]

Acceleration ? you mean not pressing the accel too much

 

[IRstuff]

Or, possibly, that in city driving, you're accelerating and decelerating most of the time; steady state forward motion is rare.

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[rb1957]

city driving gives you lots of opportunity to experience steady state driving ... fantastic fuel consumption ... on a per hour basis (not so good per km).

drag is important for fuel burn ... though I wonder if we'd be better off attacking the other side of the equation ... make a more efficient power source?

another day in paradise, or is paradise one day closer ?

 

[IRstuff]

"make a more efficient power source?"

no need for that; we just need to make the auto suppliers cough up their 150 mpg carburetors...

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[rb1957]

do you mean the magic magnetic ones ?

another day in paradise, or is paradise one day closer ?

 

[dgallup]

Technology for High Mileage Auto Currently Available

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[3DDave]

I got four of those carbs and now get 600mpg. I also make money from home. Ask me how.

Also - just kidding; please don't flag unless there's no humor left at all.

 

[itsmoked]

Keith Cress
kcress -

http://www.flaminsystems.com

 

[tbuelna]

To get this low Cd you must accept a car with less than 40hp, and staring at the back of the driver's head as a passenger.

 

[SomptingGuy]

The car doesn't need to be small to brag about a low Cd. Could be huge. Customers are never told about the frontal area.

Steve

 

[dgallup]

Yes, they should give Cd*A for it to be a meaningful drag number. Then all the passengers would be sitting behind the driver.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[BUGGAR]

Early Corvairs had the aerodynamics of a brick but a (relatively) small frontal area. They were surprisingly easy to get up close to 100 mph (as verified by police radar).