# [EVDL] Drag coefficient, frontal area data?



## EVDL List (Jul 27, 2007)

Is there a good resource, online or elsewhere, to look up the drag
coefficient and frontal area of modern vehicles? (Yes I already know
about the mayfco.com list; it doesn't include any vehicles less than 10
years old, and most are 15 or more years old). So far Google hasn't been
helpful on half the cars I've tried to look up.

Is this the kind of thing for which some kind of publication is
available, that I might find in a library somewhere? I'd even be willing
to pay a reasonable amount for ongoing access to this kind of
information, if it's kept up to date.


-- 
Christopher Robison
[email protected]
http://ohmbre.org <-- 1999 Isuzu Hombre + Z2K + Warp13!

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## EVDL List (Jul 27, 2007)

> Christopher Robison wrote:
> > Is there a good resource, online or elsewhere, to look up the drag
> > coefficient and frontal area of modern vehicles?
> 
> ...


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## EVDL List (Jul 27, 2007)

Try this:
<http://en.wikipedia.org/wiki/Automobile_drag_coefficients>

--
Martin K



> Christopher Robison wrote:
> > Is there a good resource, online or elsewhere, to look up the drag
> > coefficient and frontal area of modern vehicles? (Yes I already know
> > about the mayfco.com list; it doesn't include any vehicles less than 10
> ...


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## EVDL List (Jul 27, 2007)

Yeah, that first table is from mayfco.com; however, the 2nd table is new
since I last looked. Sadly, the 2nd table lists only the Cd, so you're
left to approximate (guess) what the frontal area is. Sigh....

--Steve



> Martin Klingensmith wrote:
> > Try this:
> > <http://en.wikipedia.org/wiki/Automobile_drag_coefficients>
> >
> ...


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## EVDL List (Jul 27, 2007)

On Thu, 2007-09-20 at 23:02 +0200, [email protected] wrote:
> > From: Christopher Robison <[email protected]
> > Subject: [EVDL] Drag coefficient, frontal area data?
> > Is there a good resource, online or elsewhere, to look up the drag
> > coefficient and frontal area of modern vehicles? (Yes I already know
> > about the mayfco.com list; it doesn't include any vehicles less than 10
> > years old, and most are 15 or more years old). So far Google hasn't been
> > helpful on half the cars I've tried to look up.
> 
> http://en.wikipedia.org/wiki/Automobile_drag_coefficients has some.

I had seen this; I probably should have mentioned it too. There are
combined Cd and frontal area measurements for 45 vehicles here. I was
hoping for something comprehensive, a database where I could look up any
mass-produced vehicle including OEM body style variants up to the
current year. (The second list, while longer, only states Cd values,
which aren't very useful without frontal area).

I'll assume such a resource doesn't exist. There are descriptions online
for using the deceleration curve of a vehicle to determine drag values
(and, interestingly, to separate aerodynamic drag from rolling
resistance), but these require that I actually get to drive the
vehicles, on an otherwise vacant road. Maybe I can rent or do test
drives...

Makes me curious though ... some vehicle reviews do contain this kind of
data -- where do they get it? If it's not published somewhere, do they
call the manufacturer? Surely a car review site isn't going to do its
own wind tunnel tests....?

-- 
Christopher Robison
[email protected]
http://ohmbre.org <-- 1999 Isuzu Hombre + Z2K + Warp13!

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## EVDL List (Jul 27, 2007)

I'm interested in this too so I propose a team effort - 
if you can find front and side drawings or pics with scale,
I'll calculate A and approximate Cd (assuming car is 2d extrusion)
and put it up at 
http://imby.biz/saymoo/EvdlGems/DragAndRollingCoefficients
or if u like the nerd stuff I'll find the pics and you do the calcs.

>I was hoping for something comprehensive, a database where I could look up any
>mass-produced vehicle including OEM body style variants up to the
>current year. (The second list, while longer, only states Cd values,
>which aren't very useful without frontal area).
>I'll assume such a resource doesn't exist. There are descriptions online
>for using the deceleration curve of a vehicle to determine drag values
>(and, interestingly, to separate aerodynamic drag from rolling
>resistance), but these require that I actually get to drive the
>vehicles, on an otherwise vacant road. Maybe I can rent or do test
>drives...
>Makes me curious though ... some vehicle reviews do contain this kind of
>data -- where do they get it? If it's not published somewhere, do they
>call the manufacturer? Surely a car review site isn't going to do its
>own wind tunnel tests....?

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## EVDL List (Jul 27, 2007)

The U.S. gov't EPA databases have some really neat information, like the weight and Cd*A, as well as fuel economy.

Unfortunately, the newer databases only have fuel economy info, but 1996 and earlier there is alot of neat stuff.

http://www.fueleconomy.gov/feg/download.shtml

----- Original Message ----
From: "[email protected]" <[email protected]>
To: [email protected]
Sent: Friday, September 21, 2007 4:26:16 AM
Subject: Re: [EVDL] Drag coefficient, frontal area data?

I'm interested in this too so I propose a team effort - 
if you can find front and side drawings or pics with scale,
I'll calculate A and approximate Cd (assuming car is 2d extrusion)
and put it up at 
http://imby.biz/saymoo/EvdlGems/DragAndRollingCoefficients
or if u like the nerd stuff I'll find the pics and you do the calcs.

>I was hoping for something comprehensive, a database where I could look up any
>mass-produced vehicle including OEM body style variants up to the
>current year. (The second list, while longer, only states Cd values,
>which aren't very useful without frontal area).
>I'll assume such a resource doesn't exist. There are descriptions online
>for using the deceleration curve of a vehicle to determine drag values
>(and, interestingly, to separate aerodynamic drag from rolling
>resistance), but these require that I actually get to drive the
>vehicles, on an otherwise vacant road. Maybe I can rent or do test
>drives...
>Makes me curious though ... some vehicle reviews do contain this kind of
>data -- where do they get it? If it's not published somewhere, do they
>call the manufacturer? Surely a car review site isn't going to do its
>own wind tunnel tests....?

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## EVDL List (Jul 27, 2007)

Depending on what the need for aerodynamic data is, I would assume that 
you could use highway fuel economy as a scale for how aerodynamic a 
vehicle is. If you're just trying to prove that a Honda Civic is more 
efficient in general than a Hummer H2. Things change rapidly when you 
start talking about hybrids and electric conversions with half a ton of 
lead but if you compare the gas-only list it should provide a good 
analog. City MPG is not a good comparison of aerodynamics, but it is 
directly related to size of engine and weight of vehicle.
--
Martin K



> David Dymaxion wrote:
> > The U.S. gov't EPA databases have some really neat information, like the weight and Cd*A, as well as fuel economy.
> >
> > Unfortunately, the newer databases only have fuel economy info, but 1996 and earlier there is alot of neat stuff.
> ...


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## EVDL List (Jul 27, 2007)

In April 2006, Neon John posted a clever low-tech way to measure the 
frontal area of a given vehicle.

Start with a frontal photograph of the vehicle. If you are taking the 
picture yourself, include a one-foot square, propped up vertically.. If 
not, make sure there's something in the photograph, in the plane of the 
front of the car, that has a known length. Like a state license plate, 
for example.

Now use scissors/hobby knife and cut the outline of the car out of the 
photograph.

Then cut out the one-foot square, or calculate what a one-foot square 
would look like based on the scale of the known measurement and cut that 
out of the same paper.

Weigh the one-foot square on a laboratory scale. This tells you how 
much the paper weighs per square (photographed) foot.

Now weigh the cutout of the vehicle. Divide this number by the weight 
of the one-foot square, and you have the frontal area of the vehicle in 
square feet.

<http://www.mail-archive.com/[email protected]/msg06421.html>

Sometimes I miss that guy.

Later,

Doug

Steve Peterson wrote:
> Yeah, that first table is from mayfco.com; however, the 2nd table is new
> since I last looked. Sadly, the 2nd table lists only the Cd, so you're
> left to approximate (guess) what the frontal area is. Sigh....
>
> --Steve
>
>


> Martin Klingensmith wrote:
> >
> >> Try this:
> >> <http://en.wikipedia.org/wiki/Automobile_drag_coefficients>
> ...


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## EVDL List (Jul 27, 2007)

The current administration has made it a policy to pull all non required 
info from government websites to make it harder for evinomentalists to 
make their cases for alternatives to the oil economy and global 
warming.

They literally have destroyed whole offices with reasearch. The congress 
issued a injunction to stop some of it.




> David Dymaxion wrote:
> > The U.S. gov't EPA databases have some really neat information, like
> > the weight and Cd*A, as well as fuel economy.
> >
> ...


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## EVDL List (Jul 27, 2007)

I suggest an improvement to that method
rather than print it and weigh parts of the image, use a photo app and 
color the part that is car in the image all white and the rest all 
black. photoshop has a filter called 'average' which is the average 
color of the entire image. then pick that color and that intensity is a 
percentage of the car area of the picture area. you have your yard stick 
(sic) in the picture to determine the 'area' of the picture and 'voila' 
you have your cross section

be sure to take the picture from a good distance to closely approximate 
isometric view (to avoid perspective distortion of the profile)
even if you can't zoom in to make the car fill the entire frame, 
distance will work. of course if you go too far the precision will drop.

Dan


Doug Weathers wrote:

>In April 2006, Neon John posted a clever low-tech way to measure the 
>frontal area of a given vehicle.
>
>Start with a frontal photograph of the vehicle. If you are taking the 
>picture yourself, include a one-foot square, propped up vertically.. If 
>not, make sure there's something in the photograph, in the plane of the 
>front of the car, that has a known length. Like a state license plate, 
>for example.
>
>Now use scissors/hobby knife and cut the outline of the car out of the 
>photograph.
>
>Then cut out the one-foot square, or calculate what a one-foot square 
>would look like based on the scale of the known measurement and cut that 
>out of the same paper.
>
>Weigh the one-foot square on a laboratory scale. This tells you how 
>much the paper weighs per square (photographed) foot.
>
>Now weigh the cutout of the vehicle. Divide this number by the weight 
>of the one-foot square, and you have the frontal area of the vehicle in 
>square feet.
>
><http://www.mail-archive.com/[email protected]/msg06421.html>
>
>Sometimes I miss that guy.
>
>Later,
>
>Doug
>
>Steve Peterson wrote:
> 
>
>>Yeah, that first table is from mayfco.com; however, the 2nd table is new
>>since I last looked. Sadly, the 2nd table lists only the Cd, so you're
>>left to approximate (guess) what the frontal area is. Sigh....
>>
>>--Steve
>>
>>


> Martin Klingensmith wrote:
> >>
> >>
> >>
> ...


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