Talk:Automobile drag coefficient

Chevy Volt Cd source
the table states .26 but the gm-volt.com fansite quotes a recent release of test score as 0.28. what is the source for the 0.26? is it completely made up? Dan Frederiksen (talk) 07:04, 7 December 2009 (UTC)

Sports cars not terribly aerodynamic
Hi

Although the article _does_ mention that sports cars sometimes tend to sacrifice lower Cd values for negative lift at higher speed, it is misleading to represent normal family cars as having such poor aerodynamic values. Modern sedans, such as many Lexus models, BMWs and Mercedes-Benzs all have Cd values of around 0.26 and 0.27. Additionally, I think a discussion of drag needs to take frontal area into account, as it is the product of these two figures that produces an indicator to the vehicle's true aerodynamic efficiency. Looking at either one in isolation is not particularly useful.


 * Perhaps the article on the drag equation might be a better place to add this discussion, since that brings in all the contributing factors. However it's still not the full story since without knowing the power of a vehicle's engine it still doen't give you much of an indication of performance. Given enough power, even the most brick-like of vehicles can be made to perform well, at least in terms of speed/acceleration, if not economy. My feeling is that since car frontal areas are more or less of the same order (certainly within a reasonable range, since frontal area derives ultimately from the size of the human body), Cd gives you some relative measure of a car's "draginess", without saying anything about how this affects performance. In fact it's like a lot of figures - they tend to get picked up by marketers and used rather disingenuously, i.e. the try to blind the public with science. Witness the commercials for the 80s model Audi 100, which strongly featured its drag coefficient, as if the average person had a clue what it meant. They even put a decal "Cd 0.3" on the C pillars! So, while I agree with you and think the article could be expanded to include these points, it should also point out the meaninglessness of it, given that it's not a predictor of performance. Graham 00:51, 2 Jun 2004 (UTC)


 * I was just about to query the absence of frontal area, which is very important to aerodynamic efficiency. A blocky Jaguar XJ40 might not have a great Cd, but it can be efficient as its frontal area is not great. I'm sure mpg figures with more "slippery" rivals such as the Mercedes S-class would bear this out. I'll try to work something in as without it, the discussion of efficiency is incomplete. Stombs 11:56, Jan 28, 2005 (UTC)

Added some cars
I added the Alfa Romeo BAT, Alfa Romeo Disco Volante, Dodge Charger Daytona/Plymouth Superbird, Hotchkiss Gregiore, Triumph Spitfire, Daihatsu UFE-III, Loremo, Opel Eco Speedster, GM Precept, Dodge Intrepid ESX, 1921 Rumpler, Fiat Turbina, 1933 Dymaxion.

A google search will yield results for most of these, but the Mk I, II, III Spitfires have their Cd quoted in a book titled "Streamlining and Car Aerodynamics" by Jan P. Norbeye.

The Mk IV Spitfire is quoted at the following page:

http://web.archive.org/web/20041118043051/http://www.teknett.com/pwp/drmayf/tbls.htm

The Fiat Turbina is quoted here:

http://www.velocetoday.com/cars/cars_46.php

The Alfa BAT7 is quoted at .19 here:

http://www.velocetoday.com/cars/cars_76.php

Google searches will easily find the rest.

A little rant aside from this topic:

Hard to beleive that such efficient designs could be made back in the 1920s and 1930s. We could have easily used them to double fuel economy during the 70s fuel crisis to around 35-40 mpg without shrinking car size while KEEPING musclecar V8s, but we didn't. Imagine a full size Plymouth Fury-like car, with perhaps a .20 drag coeffiicient. Horsepower required at highway speeds would have been cut by about 1/2, doubling fuel economy.

Less drag = less horsepower required at speed = less maintenance and longer engine life = less money for the Detroit pricks(and Euro tarts, and Japs too, all said tongue in cheek of course. :-)

Today's hybrids are just now catching up to the best cars from 70-80 years ago in drag coefficient, and cutting aero drag is reponsibile for about 70% of their fuel economy improvement over typical gas cars. Slightly reduced weight and a hybrid powertrain along with use of CVT and smaller engine is the rest. This is embarassing. There's no reason we should be driving around in such inefficient bricks today, except that the auto monopolies are very slow to ration out new technology so as to maximize profits on each advancement, even if some of those advancements are over 70 years old, and they want to keep maintenance high and profits up. With the looming oil crisis, I hope they all go belly up, so a bunch of smaller, less centralized companies that are actually responsive to consumer demand like AC Propulsion, Factory Five, Caterham, and Mosler take their place.

Good aerodynamics can also allow 150 mile range pure electric cars without a need for advanced batteries, but again, the auto industry ain't budgin' on that one, considering EVs have one moving part, no oil changes, tune ups, valves, pistons, pulleys, belts, and all that other crap, and with electric motors lasting 500,000+ miles and all! They'd be making less money from us stupid saps on electrics. Think about that, the possibility of 150 miles electric car range with ~1,500 pounds of lead acid golf cart batteries translates to over 750 miles possible with equal weight of today's lithiums, or cut the battery weight in half with today's lithiums, ~300-400 miles in an aerodynamically efficient design! Not enough range?

I also own a 1969 Triumph GT6 MkII converting it to electric, which I've heard had a .32 from multiple racers and enthusiasts, but I nor have any of them never been able to find a verifiable source, so I didn't add it. Also of note is that Triumph never wind tunnel tested their cars, so the .39 and .42 for the Spitfires, while cited from seemingly reputable sources, may have been estimates. But they appear accurate running through an automotive technical analysis(ie. calculate horsepower from the flywheel required at various speeds, usually the top speed, and go from there).

Duplicate Content in coefficient examples
The example drag coefficients are listed in a long list, then repeated in the image table. I reccommend deleting the list and just keeping the image table. The information is identical, and even if users have images turned off, they will still see the numbers. Also, it seems like there is a lot of examples that aren't providing a lot of value. I reccomend paring down the list, to have a greater difference between examples. We don't need 4 example cars that have .36, four cars at .34 etc. If I dont see objections, I am going to remove the text only list, and reduce the image list as well. Gaijin42 21:03, 1 August 2006 (UTC)


 * Hi, I made the arduous job of adding the pictures to the numbers. Well, I object to the removal of pictures: Four cars that have 0.36 are of great interest, because you can see that so dispare and distant cars as the Citröen DS and the Ferrari Testarrossa have, in fact, the same Cx. A shorter list could be neater for the less interested person, but the complete list if of great value for the more enthusiastic aficionado. In fact, I would like to have more cars listed here, even cars with the same Cx.


 * I added the pictures because we had an (amiable) discussion about which shape was aerodynamically better, the sedan or the hatchback...well, the best compromise shape seems to be the Kammback. The rare occurrence of sedans (or saloons, as you wish) in the lowest Cx part of the list would be lost if you start to eliminate "duplicate" Cxs...or maybe a new pattern would emerge adding more cars.


 * The deletion of information for the sake of "neatness" is not a good thing: The information that is "superfluous" for one reader is "indispensable for another. Please take advantage of the condition of not being printed on paper that Wikipedia has and include all the possible information.Randroide 14:20, 2 August 2006 (UTC)


 * (NB: See "Gallery" section below for suggested everyone's-happy solution) -- tiny plastic Grey Knight  ⊖  13:40, 13 July 2007 (UTC)

Gallery
Is the large gallery all that encyclopedic? Might it be possible to move it to Commons? --Interiot 18:19, 9 October 2006 (UTC)


 * I agree. This list of Cd values and gallery is tedious and seemingly endless. While perhaps useful, the list would do better in an article titled, say, ``List of Cd values.'' I offer this as a suggestion to the maintainers of the list, since I don't want to start rearranging things. Mbelisle 03:48, 22 April 2007 (UTC)


 * Maybe it all belongs in Automotive aerodynamics where there is already a list? It should be easy to link there so everyone could still find it. Meggar 04:17, 22 April 2007 (UTC)


 * The article is a bit of a "wall-of-tables" at the minute (as I know only too well, having just restyled them). We should have a selection of values and accompanying images on this page, with the full information on a supplementary page like Mbelisle's suggestion above, I think. -- tiny plastic Grey Knight   ⊖  13:40, 13 July 2007 (UTC)

Convert the picture tables into a real table
Is it possible for someone to transform the picture table into a real Wiki Table? --82.121.249.129 16:34, 13 October 2006 (UTC)
 * I have added it to my list of Things To Do. :-) --GreyKnight 12:51, 5 January 2007 (UTC)
 * I did it. -- tiny plastic Grey Knight  ⊖  13:40, 13 July 2007 (UTC)

nomenclature
It would be nice to describe what each variable represents and how it is determined, especially the area "A". —Preceding unsigned comment added by 129.107.97.131 (talk • contribs)
 * That is explained on the main drag equation page. I don't think we should duplicated it all here, so I have added another link right after the formula. Meggar 01:17, 27 November 2006 (UTC)

Claimed Cd vs. Actual Cd
It should be noted that the Cd quoted from the manufacturer is not verified in any way - it is a claimed figure. The actual Cd can be significantly higher. I have verified that the Cd from one current production car is 18% higher than the figure quoted by the manufacturer, but unfortunately cannot quote the source. 69.226.56.93 16:37, 25 April 2007 (UTC)


 * Very interesting point. which model car was this? if anyone can offer more values it would be nice to shed more light on this issue since we know how they can be lying bastards vis a vis who killed the electric car. Dan Frederiksen 11:21, 12 May 2007 (UTC)


 * It's worth noting that in many cases the manufacturer's quoted figure is for a skinny-tyred base model which nobody actually buys... Mr Larrington (talk) 14:59, 22 December 2010 (UTC)

I'd like to add that different testing environments can also give differing results on the same test subject. Not all wind tunnels are created equally. — Preceding unsigned comment added by 196.2.126.176 (talk) 10:11, 13 March 2012 (UTC)

Bus?
It would be interesting to get Cd for some buses. Particularly the flat-fronted tour buses and a comparison between the old truck-like front and new flat front of Blue Bird Corp. school buses. —Ben FrantzDale 18:33, 30 April 2007 (UTC)

Automotive Examples
Why was the Ford Probe removed from the list that shows vehicles with the least Drag Coefficient? --Settinghawk 23:23, 11 June 2007 (UTC)

SI Units
Why does this page not use SI Units? —Preceding unsigned comment added by 196.2.99.28 (talk) 17:28, 27 January 2008 (UTC)

Yes, this article should be in SI units since Wikipedia is an international encyclopedia! —Preceding unsigned comment added by 220.233.219.214 (talk) 07:45, 27 March 2009 (UTC)

Fair use rationale for Image:Mercedes-Benz Bionic.jpg
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If there is other fair use media, consider checking that you have specified the fair use rationale on the other images used on this page. Note that any fair use images lacking such an explanation can be deleted one week after being tagged, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you.

BetacommandBot (talk) 14:07, 8 March 2008 (UTC)

Chevrolet Corvette Z06 drag coefficients of 0.34 and 0.28??
The Z06's drag coefficient is 0.28 in the table yet in the pictures it is 0.34, why is this? --90.213.246.184 (talk) 17:31, 18 April 2008 (UTC)

F1 Cars?
Someone needs to check their decimals... Shouldn't the Formula 1 cars' drag coefficients be listed as 0.07 to 0.11, not 0.7 to 1.1? Last time I checked, F1 cars were far more aerodynamic than "a typical truck." Same goes for the Caterham Seven and Legends Car. 69.244.136.156 (talk) 03:31, 28 August 2009 (UTC)


 * 0.7 to 1.1 is correct. Formula 1 cars aren't exactly teardrop shaped. Open wheels, suspension, etc. Aerofoils create a lot of drag in order to convert it into downforce. --Itinerant1 (talk) 23:01, 28 October 2009 (UTC)

Don't equate fast with aerodynamic. You are aware all the wings and spoilers INCREASE drag, right? Else they wouldn't stay on the ground. — Preceding unsigned comment added by 204.210.203.189 (talk) 17:29, 10 September 2011 (UTC)

Complete Lack of Credibility
Rarely is there an instance where the wikipedia article has less credibility than every(!) other online article. This entry says late model Chargers and Avengers have lower CDs than 98 MR2s. This is backwards...not only according to the respective manufacturers (Dodge quotes over 0.33; Toyota is under 0.32), but any Joe on the street.

And, as noted by other people here, other CD figures are suspect. I don't care how long the tail on the Tatra is, the streamlining is a far cry from the likes of one-man solar racers -- the quoted CD absurd! If you're going to post on Wikipedia use some discretion regarding what is remotely plausible.

~go2toa —Preceding unsigned comment added by Go2toa (talk • contribs) 20:02, 7 September 2009 (UTC)

Missing important figures
In this list there are important figures which are missing. Here is the list: Audi 80 (value should be similar to Audi A4)

By the way, I confirm that the pre-WWII war Tatra was one car with the lowest drag figures even for today's standard.

However, there are problems with some figures since Citroen DS-ID, CX and SM (The idealists who started this true race for aerodynamics which was not just an airplane look alike with stupid big fins which was going on in America) It should be much lower than a Ford Crown Victoria.

Citroen CX was a name coinded for that purpose of being in 1975 the lowest drag among world's production cars. Its shape has inspired GMC EV1, so the same value applies.

I suggest that every figure be backed by an official reference, otherwise this article might fall into propaganda like too many Wikipedia subjects.

Yes, indeed, it took people a lot of times fo follow Citroen on the path of efficient cars. Citroen engineers believed that better designed car meant improving drag coeff with that funny shape which stunned the world with its DS in 1956 (the acronym means Goddess) and this also resulted in smaller engine requirements and they considered fuel consumption as an important issue even in a luxury car. The Citroen DS 2.0 liter engine could send the car to speeds up to 150 km/h. In the fifties, that was not the idea of the luxury cars since UK and US prefered huge vehicles with big motors only good for straight line motorways. Of course, these big cars could not follow a DS in the curvy roads of the Alps and the DS could handle well any surface. That is why they were used horse races: they could put a camera on top of the DS and even riding on the grass, the image would be still. Only the french knew how to make a smooth suspension car to hold the road like a sports car. —Preceding unsigned comment added by 144.122.156.61 (talk) 16:32, 10 October 2009 (UTC)

Erroneous data
I think I've figured out where the crap data in this article is coming from. Some hokey website posts CDs, someone picks it up and pastes it here on wikipedia. Then other websites start to quote the figures in this article, creating erroneous circular references, especially with regard to the Tatra 77.

It appears much, if not all, the data is coming from here:

http://rc.opelgt.org/indexcw.php

and that's sloppy. In the 1970s, a Tatra with a "77" type shape was found to have a CD well in the .30s, which isn't surprising as a Type I VW Beetle given a tear drop rear would not cut it's CD in half, which is basically what this website rc.opelgt.org says. Also, this article claims the CD of 0.35 for a 1998 MR2. The web site does list this, and that is probably accurate for an entirely different generation of MR2. In fact, the site is so sloppy it doesn't even say what model year of the MR2!!! So the wikipedia article/author randomly chooses 1998!!

As mentioned last year, this is the only article on Wikipedia I know of, with absurd data that persists, and unfortunately now, is quoted by countless, low quality sites. Sites like supercars.net and carfolio.com are staying clear of this garbage, but sites like conceptcarz.com are picking it up. —Preceding unsigned comment added by Go2toa (talk • contribs) 21:08, 23 May 2010 (UTC)
 * Go to library. Go google. Go search googlebooks. There is multiple sources for this claim. The claim stands for T77a 1935 model. And numerous authors support it. Moreover different books claim that Tatra T87 had CD of 0,24 - and T87 was already compromise aimed to make less heavy rear of the car (while T77a was aimed solely to achieve the least drag possible) Cimmerian praetor (talk) 22:19, 23 May 2010 (UTC)
 * I added other sources which pop up when going through google books. There are also claims of higher CD, but they stand for model T77, not T77A. When citing T77A authors seem to agree with the low drag which is in wikipedia. Cimmerian praetor (talk) 22:51, 23 May 2010 (UTC)

It's difficult to find a website that is not a circular reference. In other words, you can find a link quoting the exact three digit figure, because they took it from your table! On the other hand, here is a website that is closer to reason.

http://www.tatraplan.co.uk/

about .32 for the 77 and .36 for the 87. somewhat optimistic, but at least it's plausible. but the question remains...what do credible sources say? for that matter, is tatraplanco.uk credible? —Preceding unsigned comment added by 69.231.220.73 (talk) 04:56, 27 May 2010 (UTC)


 * You are right, it is hard to find a website which is not a circular reference. That is also why I took the time to find a book. The one in references moreover deals with optimization of engineering. The chapter that talks about Tatra CD 0.212 focuses on automotive dynamics. Optimization and computational fluid dynamics, Gàbor Janiga, Springer, 2008, page 196
 * Cimmerian praetor (talk) 08:42, 27 May 2010 (UTC)

I see the figure in the book; the author has no business writing that book if he cannot see something so obvious. If you have his contact info I will gladly call and tell him. Perhaps the Tatra factory originally quoted 0.21. It appears the T87 was originally quoted as 0.25 but actual testing found it to be 0.36. A huge difference. A big lie. This is mentioned on howstuffworks.com. To see what it takes to get down to 0.20 CD, look at the Mercedes C-111-iii. I'm going to leave this issue alone but keep an eye out for independent testing results. —Preceding unsigned comment added by 69.231.220.73 (talk) 04:05, 28 May 2010 (UTC)


 * I agree, I doubt the full vehicle tested in a modern tunnel would be at 0.212, but here's a link to the book that makes the claim https://books.google.com/books?id=fhV6CD25XF8C&pg=PA17&lpg=PA17&dq=Optimization+and+computational+fluid+dynamics,+G%C3%A0bor+Janiga,&source=bl&ots=refF8a4uPF&sig=BBrnCUy4wKq-3RSt6HlyTKPukdY&hl=en&sa=X&ved=0ahUKEwjqrYqz9t7JAhUD7B4KHZoBDAAQ6AEINzAD#v=onepage&q=Tatra&f=false I guess we have to let the Eastern Europeans have these little victories, they don't seem to have much else to brag about. Greglocock (talk) 22:39, 15 December 2015 (UTC)

The frontal area figures are way off too. Even the VW 1-Litre concept car has 1m2 frontal area. Not many modern cars will come close to that, most will be 1.8 or more. See http://www.carfolio.com/specifications/models/car/?car=98263 —Preceding unsigned comment added by 196.30.31.182 (talk) 04:00, 22 June 2010 (UTC)

Typical values and examples
It is getting looong, a bit too long to draw any conclusion from it I suggest we take about a dozen cars (from Hummer to Tatra) and put it into a sovereign table of examples, and than leave the big table separately under it for the public to find/add a car's coefficient. Cimmerian praetor (talk) 07:09, 16 July 2010 (UTC)

tatra t 77
it had a cx of 0.212. could u insert it? thanks source: http://www.europeancarweb.com/tech/0610_ec_aerodynamics_tech_buyers_guide/tables.html — Preceding unsigned comment added by 87.20.234.39 (talk) 16:05, 18 September 2011 (UTC)

Inappropriate references
I'm not sure how to tackle this, but http://www.mayfco.com/tbls.htm is used as a reference in numerous places, yet the page itself states that it is extrapolating figures using some derived formula. This shouldn't pass for a reference to actual figures. Not sure what to do about the numerous references to it though. — Preceding unsigned comment added by 196.2.126.176 (talk) 10:07, 13 March 2012 (UTC)

Inconsistent ratings
Reading around this subject over the years has left me with the impression that measuring automobile drag coefficients is a pretty approximate "science". Readings can vary between different wind tunnels, and you need ideally to control for things like differences in temperature and air pressure. And there's regularly a difference between what is modeled on a computer and what is measured in a wind tunnel. If that's right, then the table comparing measurements for different cars, with data captured from different tests over the space of about forty years, implies a level of precision that is spurious. Or am I merely being old and cynical?

If someone reading this has some knowledge of the subject and access to a relevant source, I wonder if a little para on the variability of data readings should be added to this entry?

Regards Charles01 (talk) 13:19, 19 March 2012 (UTC)

Merger Proposal
I propose that Automotive aerodynamics be merged into Automobile drag coefficient because it contains data of the same type and thus is redundant. As per Wikipedia guidelines, if nobody disagrees with me within a week or so, I will go ahead and execute the merge. Please note that I have never merged an article before, so if I am doing something wrong, please tell me. --The Quirky Kitty (talk) 20:56, 2 August 2012 (UTC)

Kammback section
From what I understand, a kammback is not the same as a Sears-Haack body yet the article seems to suggest they are the same. Needs a little re-wording, which I could do if no experts come forward. Warren (talk) 09:27, 1 March 2013 (UTC)

A lot of care should be taken in positing that a Kammback absolutely reduces drag. By introducing a rounded yet steep backlight, it is possible to *increase* drag rather than reduce it, as the action of sucking the air down over the rear of the vehicle can result in a larger magnitude pressure drop than would otherwise be the case. For this to be effective, the down-sweep must occur over a large distance (compare, say, a Toyota Prius to an AMC Pacer) so that the air is pulled down slowly, rather than suddenly. 193.35.217.253 (talk) 14:54, 5 March 2013 (UTC)

Comparison of Cd from different tunnels
The worst case I have seen was for a truck 0.37 claimed, vs 0.47 measured, and the worst I've seen for a car is 0.27 claimed, 0.32 measured. These figures are proprietary but they illustrate that the Popular Mechanics article is not exaggerating. There are some windtunnels which seem to always produce low estimates, whoever tests there. As such the rankings in these tables should be treated with a large grain of salt. The European Aero Data Exchange is currently calibrating all the tunnels using a set of 3 standard test items- the DrivAer car http://www.aer.mw.tum.de/en/research-groups/automotive/drivaer/. Greglocock (talk) 04:02, 25 May 2015 (UTC)

This is really bad
Many years ago, this was a viable source of Cd info. Today it's rubbish. Where are the accuracy police?

According to this article, a 2006 Corvette is good for 0.34 and 2006 Charger is 0.33. Respectively these should be around 0.31 and 0.36.

With comparable horsepower, gear ratios, and any speed limiter defeated, the Charger should outrun the Corvette in top speed, according to the editors. It doesn't. As we've seen with the Hellcat, the Charger would need about a 200 hp advantage to rival a Corvette.

What excuse could possibly be given for the editor? The Charger must have drivetrain oil twice as thick and wheel bearings borrowed from a tank. — Preceding unsigned comment added by 2605:E000:1527:8074:6983:BBCF:7731:1482 (talk) 20:13, 14 June 2015 (UTC)


 * Frontal area. Obviously a big four-door saloon is going to have to push more air out of the way than a hip-high two seater. Mr Larrington (talk) 13:57, 17 August 2015 (UTC)

Tatra Experiment
Here's an experiment for you. Add a two foot, streamlined extension to the tail of a type 1 Volkswagon Beetle. Add rear wheel skirts. Now see if that results in a CD of 0.24 (or whatever absurd number you claim). — Preceding unsigned comment added by 2605:E000:1527:8074:6983:BBCF:7731:1482 (talk) 20:26, 14 June 2015 (UTC)

The ridiculous table
I see editors are now astroturfing the table with multiple claims for the same value by the same company. I propose we get rid of all (a) unreffed values (b) scale model results (c) dupes for similar vehicles. Greglocock (talk) 22:33, 15 December 2015 (UTC)


 * I suggest a new policy. All claims must be supported by a reliable source. In order to not overload the fanbois, I'll do 8% of the list per month, so in ayear it'll be tidied up. Greglocock (talk) 01:22, 14 May 2017 (UTC)

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Substituted at 08:40, 29 April 2016 (UTC)

Saabs at 0.28
What the heck is going on with the Saabs at the low 0.28 mark? NearCry (talk) 08:04, 5 August 2016 (UTC)


 * Yeah, that was pretty bad. I fixed the links, formatted the reference, merged the duplicated reference and sorted them by Cd and the by name.  Stepho  talk 15:09, 5 August 2016 (UTC)

Spoilers section
The spoiler section is terribly incorrect and equates rear wings, which increase drag in favour of downforce, to spoilers, which have negligible downforce and simply disrupt flow to reduce drag. For example in hatchbacks, the large flat back causes a lot of shape drag when air is laminar, this can be reduced by inducing turbulence, which is what spoilers along the back do. Mind you they are sometimes only cosmetic or even detrimental depends on if its marketing or not. In any case spoilers attempt to reduce drag by "spoiling" laminar airflow.

Source: Aero Engineer, wikipedia's own page of car spoilers, most books on car design, simple experiments on spheres (case 5 in https://www.grc.nasa.gov/www/k-12/airplane/dragsphere.html and golf vs plain spheres) I wish I could update it myself but its the first time I even comment on here, have no clue how to use wiki, and don't have time to dig out the proper references. (Pandalism)137.205.0.160 (talk) 17:17, 12 November 2016 (UTC)

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European model versions
What's the best way to go about indicating that several of the European versions have a different drag coefficients than the American model versions, eg. the Audi A4 has 0.27 in the USA but is shown as lower in the table. The same thing is going on with the other German cars. 2600:6C64:7580:39:B8B1:2450:67E8:F7CB (talk) 17:29, 25 January 2018 (UTC)


 * Assuming that it is a real difference and not just a difference in measuring (different wind speed, differnt wind tunnel width, different temperature and many other factors can skew the results if care is not taken), then I would just put the country/market in brackets after the car name. just like we do for image captions.  Stepho  talk 00:53, 26 January 2018 (UTC)

External links modified (January 2018)
Hello fellow Wikipedians,

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2014 Car and Driver Wind Tunnel test
Car and Driver tested the 1st generation Honda Insight in a undisclosed wind tunnel and got a drag coefficient of 0.3 while Honda claims 0.25, a significant difference. Did somebody screw up?


 * "The worst case I have seen was for a truck 0.37 claimed, vs 0.47 measured, and the worst I've seen for a car is 0.27 claimed, 0.32 measured. " variability between different tunnels is huge. Even when two car companies test at the same tunnel they can get different results due to differences in test procedure. As such these enormous tables are just anorak fodder. Greglocock (talk) 07:06, 2 February 2018 (UTC)

Subaru XT
According to this old video (https://www.youtube.com/watch?v=aqKKI8xz4Aw&list=PL8HILNMicoi6frBzfDro05x0W-44D1ZWz&index=12) the Subaru XT has a .29 Cd. Could this be added? — Preceding unsigned comment added by 2600:1700:F8B0:EC70:3CAE:959F:DFE4:2234 (talk) 04:45, 1 June 2019 (UTC)


 * Mo problem, Motor Week seems to be a reliable source. Cd=0.29 is mentioned just after the 4:00 mark.  Stepho  talk 07:16, 1 June 2019 (UTC)

Columns
The 3-column table for production cars has always bothered me in how each column is a different height. I tried an experiment (see https://en.wikipedia.org/w/index.php?title=Automobile_drag_coefficient&oldid=899773674) to see if we could convince the machinery to even them out automatically. It does so (even reformats when the browser width is changed) but the column headers get lost and sometimes a multi-line cell can be split at the the bottom of one column and the top of the next column. Thoughts?  Stepho  talk 08:02, 1 June 2019 (UTC)


 * On Firefox 67 I see only one column with a 1920 x 1080 display. Besselfunctions (talk) 15:27, 2 June 2019 (UTC)

Panhard LM 64
Much as I like this little car, a claimed Cd of 0.12 is ridiculous, and that's before they start talking about downforce. The top speed, 61 m/s, would need about 26 kW to overcome the 0.12 drag, assuming frontal area of 1.58 square meters. The engine was 58 kW, so they um, were keeping plenty in reserve? The true story is more likely to be that the clay was measured at 0.12, and once ugly things like door gaps, cooling, and rotating wheels were added you'd get back to a still impressive 0.20-0.22. This page is a disgrace. Greglocock (talk) 06:35, 4 January 2022 (UTC)

CFD vs windtunnel tests of full size vehicles vs clays
I think we should not use CAE predictions of Cd, and I'm not very keen on the use of clays, especially 1:5. This is relevant in the case of the unlikely claims for the Tarta, and the EQXX, which is currently a bunch of very nice renders and simulations. Greglocock (talk) 22:55, 4 January 2022 (UTC)

Tatra 0.212 claim, scale models vs full size
http://www.tatraplan.co.uk/tatra-t600-tatraplan.html has the following

​Tatra T600: 1:1 = 0.32 (tunnel), 0.33 (road), 1:5 = 0.24 (tunnel) For comparison: Tatra T57: 1:5 model = 0.735 [1936]; Tatra T77: 1:5 model = 0.245 [1936], 1:1 = 0.38 [estimated]; Tatra T77a: 1:1 = 0.36 [estimated]; (0.212 quoted in other sources for the T77a in fact relates to a T87 model test, although the source cannot be ascertained, see below!!!) Tatra T87: 1:10 model = 0.251, 1:5 model = 0.244, 1:1 = 0.36; (Erich Ledwinka quoted 0.212 for the T87 in his lecture about Hans Ledwinka, see ‘Leben und Werk des Automobilpioniers Dr. tech. h.c. Hans Ledwinka’, as spoken by Erich Ledwinka at Akademischen Feier der Technischen Universität Wien on May 19th, 1978, published in Blätter für Technikgeschichte 39/40 Heft, Springer Verlag, Wien, 1980, p. 151.)

So in EVERY case scale models gave much smaller Cds than full size vehicles, and the 0.212 figure is disputed in any case. Greglocock (talk) 21:18, 6 January 2023 (UTC)


 * Agreed, scale models are good indicators of relative improvements (ie new version is 5% better than old version) and really good at showing causes/effects of turbulence but are not good indicators of absolute figures. Air does weird stuff when scaled. See Reynolds number.  Stepho  talk 23:42, 7 January 2023 (UTC)

Wiki Education assignment: 4A Wikipedia Assignment
— Assignment last updated by Ahlluhn (talk) 00:57, 31 May 2024 (UTC)

Aptera 0.13 claim
Great, it was in a wind tunnel. Not so great - the wheels weren't going round, and the ground wasn't moving. This modifies the drag coefficient. Modern automotive wind tunnels have various methods to emulate the moving road and allow for rotating wheels. Of course this applies to many of the other claims in this article. Greglocock (talk) 00:05, 3 May 2024 (UTC)