{{See also|Automotive aerodynamics}} {{short description|Resistance of a car to moving through air}} {{Use dmy dates |cs1-dates=yy|date=January 2022}}
[[File:Rumpler Tropfenwagen.jpg|thumb|Edmund Rumpler's 1921 [[Rumpler Tropfenwagen|Tropfenwagen]] was the first series-produced aerodynamically designed automobile, before the [[Chrysler Airflow]] and the [[Tatra 77]].]]
The [[drag coefficient]] is a common measure in [[automotive design]] as it pertains to [[aerodynamics]]. Drag is a force that acts parallel to and in the same direction as the airflow. The drag coefficient of an automobile measures the way the automobile passes through the surrounding air. When automobile companies design a new vehicle they take into consideration the '''automobile drag coefficient''' in addition to the other performance characteristics. Aerodynamic drag increases with the square of speed; therefore it becomes critically important at higher speeds. Reducing the drag coefficient in an automobile improves the performance of the vehicle as it pertains to speed and [[fuel efficiency]].<ref>{{cite news |url=http://nextbigfuture.com/2009/03/reducing-drag-on-cars-and-trucks-by-15.html |title=Reducing Drag on Cars and Trucks by 15-18% |first=Brian |last=Wang |work=Next Big Future |date=2009-03-16 |access-date=2018-01-28 |archive-url=https://web.archive.org/web/20180129004456/https://www.nextbigfuture.com/2009/03/reducing-drag-on-cars-and-trucks-by-15.html |archive-date=2018-01-29 |url-status = dead}}</ref> There are many different ways to reduce the drag of a vehicle. A common way to measure the drag of the vehicle is through the drag area.
==The importance of drag reduction== The reduction of drag in road vehicles has led to increases in the top speed of the vehicle and the vehicle's fuel efficiency, as well as many other performance characteristics, such as handling and acceleration.<ref>{{cite web |url=http://aerocivic.com/ |title=Aerocivic - Honda Civic modifications for maximum gas mileage - |first=Mike |last=Turner |website=aerocivic |access-date=2018-01-28}}</ref> The two main factors that impact drag are the frontal area of the vehicle and the drag coefficient. The drag coefficient is a unit-less value that denotes how much an object resists movement through a fluid such as water or air. A potential complication of altering a vehicle's aerodynamics is that it may cause the vehicle to get too much lift. [[Lift (force)|Lift]] is an aerodynamic force that acts perpendicular to the airflow around the body of the vehicle. Too much lift can cause the vehicle to lose road traction which can be very unsafe.<ref>{{cite web |url=http://www.camaro-untoldsecrets.com/articles/rpo_d80.htm |title=Camaro Spoiler Equipment |first=Wayne D. |last=Guinn |website=Camaro - Untold Secrets |location=US |archive-url=https://web.archive.org/web/20000519115318/http://www.camaro-untoldsecrets.com/articles/rpo_d80.htm |archive-date=2000-05-19 |url-status = dead}}</ref> Lowering the drag coefficient comes from streamlining the exterior body of the vehicle. Streamlining the body requires assumptions about the surrounding airspeed and characteristic use of the vehicle.
Cars that try to reduce drag employ devices such as spoilers, wings, diffusers, and fins to reduce drag and increase speed in one direction.<ref name=":0">{{Cite journal |last=Nath |first=Devang S. |last2=Pujari |first2=Prashant Chandra |last3=Jain |first3=Amit |last4=Rastogi |first4=Vikas |date=2021-01-28 |title=Drag reduction by application of aerodynamic devices in a race car |url=https://doi.org/10.1186/s42774-020-00054-7 |journal=Advances in Aerodynamics |volume=3 |issue=1 |pages=4 |doi=10.1186/s42774-020-00054-7 |doi-access=free |issn=2524-6992}}</ref>
==Drag area== While designers pay attention to the overall shape of the automobile, they also bear in mind that reducing the frontal area of the shape helps reduce the drag. The product of drag coefficient and area – drag area – is represented as '''{{CdA}}''' (or '''C<sub>x</sub>A'''), a multiplication of {{Cd}} value by area.
The term ''drag area'' derives from [[aerodynamics]], where it is the product of some reference area (such as cross-sectional area, total surface area, or similar) and the drag coefficient. In 2003, ''[[Car and Driver]]'' magazine adopted this metric as a more intuitive way to compare the aerodynamic efficiency of various automobiles.
The force F required to overcome drag is calculated with the [[drag equation]]: <math>F = \tfrac{1}{2} \times \text{air density} \times \text{drag coefficient} \times \text{reference area} \times \text{speed}^2 </math> Therefore:<math>F = \tfrac{1}{2} \times \text{air density} \times \mathbf{\text{drag area} } \times \text{speed}^2 </math> Where the drag coefficient and reference area have been collapsed into the drag area term. This allows direct estimation of the drag force at a given speed for any vehicle for which only the drag area is known and therefore easier comparison. As drag area '''{{CdA}}''' is the fundamental value that determines power required for a given cruise speed it is a critical parameter for fuel consumption at a steady speed. This relation also allows an estimation of the new top speed of a car with a tuned engine: :<math>\text{estimated top speed} = \text{original top speed} \times \sqrt[3]{\frac{\text{new power}}\text{original power}} </math> Or the power required for a target top speed: :<math>\text{power required} = \text{original power} \times \left( \frac{\text{target speed}}{\text{original speed}} \right)^3 </math> Average full-size passenger cars have a drag area of roughly {{convert|8|sqft|m2|abbr=on}}. Reported drag areas range from the 1999 [[Honda Insight]] at {{convert|5.1|sqft|m2|abbr=on}} to the 2003 [[Hummer H2]] at {{convert|26.5|sqft|m2|abbr=on}}. The drag area of a bicycle (and rider) is also in the range of {{convert|6.5|-|7.5|sqft|m2|abbr=on}}.<ref>{{cite web |title=(a bicycle's lower frontal area is offset by a higher drag coefficient) |url=http://www.lafn.org/~dave/trans/energy/bicycle-energy.html#aero_drag |url-status=live |archive-url=https://web.archive.org/web/20110717084256/http://www.lafn.org/~dave/trans/energy/bicycle-energy.html |archive-date=2011-07-17<!--DASHBot--> |access-date=2011-06-28 |publisher=Lafn.org}}</ref>
==Example drag coefficients== The average modern automobile achieves a drag coefficient of between 0.25 and 0.3. [[Sport utility vehicles]] (SUVs), with their typically boxy shapes, typically achieve a {{Cd|0.35–0.45}}. The drag coefficient of a vehicle is affected by the shape of body of the vehicle. Various other characteristics affect the coefficient of drag as well, and are taken into account in these examples. Many sports cars have a surprisingly high drag coefficient, as [[downforce]] implies drag, while others are designed to be highly aerodynamic in pursuit of a speed and efficiency, and as a result have much lower drag coefficients.
Note that the {{Cd}} of a given vehicle will vary depending on which wind tunnel it is measured in. Variations of up to 5% have been documented<ref>{{cite journal |url=https://books.google.com/books?id=duMDAAAAMBAJ&pg=PA131 |title=Shaping up tomorrow's cars |first=Wade |last=Hoyt |journal=Popular Mechanics |date=October 1985 |page=131}}</ref> and variations in test technique and analysis can also make a difference. So if the same vehicle with a {{Cd|long=yes|0.30}} was measured in a different tunnel it could be anywhere from {{Cd|0.285}} to {{Cd|0.315}}.
<!-- This isn't meant to be an exhaustive list of the most aerodynamic cars on earth, please keep it short! --> <!-- Please maintain alphabetic order within each Cd range (alphabetize all 0.30's for instance) --> <!-- Cd range for Column 1 >= 0.3, 0.3 > Column 2 => 0.29, 0.29 > Column 3 --> <!-- Please provide reliable sources for any additions to this list --> {| class="wikitable sortable" style="font-size:97%;" |+Production vehicles ! Calendar year!! Automobile ! {{Cd}} |- | 1938 || [[Volkswagen Beetle]] | 0.48<ref>{{cite web |title=Technique of the VW Beetle |url=http://www.maggiolinoweb.it/technique.html |access-date=2009-10-24 |publisher=Maggiolinoweb.it}}</ref><ref>{{cite web |title=The Mayfield Homepage - Coefficient of Drag for Selected Vehicles |url=http://www.mayfco.com/dragcd~1.htm |access-date=2009-10-24 |publisher=Mayfco.com}}</ref> |- | 2018 || [[Jeep Wrangler (JL)]] | 0.454<ref>{{cite web|url=https://www.sae.org/news/2017/12/level-zero-hero |title=Level Zero hero|last=Visnic|first=Bill |publisher=SAE International|date=2017-12-18|access-date=2019-05-29|archive-url=https://web.archive.org/web/20190529164225/https://www.sae.org/news/2017/12/level-zero-hero|archive-date=2019-05-29|url-status = live}}</ref> |- | 2012 || [[Pagani Huayra]] | 0.31 <ref name="topgear_paganih">{{cite web |url=http://www.topgear.com/uk/photos/topgear-pagai-huayra-2011-03-08?imageNo=10 |publisher=Topgear.com |date=2012-06-08 |title=TG meets the Pagani Huayra - BBC Top Gear |access-date=2013-04-05 |archive-date=2011-08-28 |archive-url=https://web.archive.org/web/20110828073443/http://www.topgear.com/uk/photos/topgear-pagai-huayra-2011-03-08?imageNo=10 |url-status=dead }}</ref> |- | 2019 || [[Toyota Corolla (E210)|Toyota Corolla (E210, UK)]] | 0.31 <ref>{{cite press release |url=https://media.toyota.co.uk/product_info/corolla-2019-current/ |title=Corolla |publisher=Toyota |location=UK |date=February 2019 |access-date=2019-02-14}}</ref> |- | 2001 || [[Toyota Prius]] | 0.29<ref>{{cite press release |url=https://toyota.pressroom.com.au/press_kit_detail.asp?clientID=2&navSectionID=6&categoryID=1000&kitID=25 |title=2001 Toyota Prius Press Kit |publisher=Toyota |location=Australia |date=2001-10-04 |access-date=2020-07-10}}</ref> |- | 2005 || [[Chevrolet Corvette C6]] | 0.286<ref>{{cite press release |url=https://media.gm.com/dam/Media/documents/CA/Archives/EN/Vehicles/chevrolet/2006Corvette.html |title=2006 Chevrolet Corvette |publisher=General Motors |location=US |year=2005 |access-date=2018-07-05}}</ref> |- | 2019 || [[Porsche Taycan|Porsche Taycan Turbo]] | 0.22<ref name="taycan">{{cite press release|url=https://newsroom.porsche.com/en/products/taycan/aerodynamics-18554.html|title=Aerodynamics: The best value of all current Porsche models|date=2019-09-04|access-date=2019-10-14}}</ref>{{efn|name=PT|in Range mode in combination with a low level and closed air intake flaps}} |- | 2023 || [[Tesla Model 3]] | 0.219<ref>{{Cite web |title=New Model 3 Has "Lowest Absolute Drag Of Any Tesla" With Cd Of 0.219 |url=https://insideevs.com/news/684644/new-model-3-is-tesla-most-aerodynamic-car-ever-cd-0-219/ |access-date=2024-09-28 |website=InsideEVs |language=en}}</ref> |- | 2023 || [[Hyundai Ioniq 6]] | 0.21<ref>{{Cite web |title=Hyundai IONIQ 6 Sweeps World Car of the Year, World Electric Vehicle and World Car Design of the Year|url=https://www.hyundaimotorgroup.com/news/CONT0000000000084879}}</ref> |- | 2016 || [[Tesla Model S]] | 0.208 <ref>{{Cite web |title=Model S {{!}} Tesla |url=https://www.tesla.com/models}}</ref> |- | 2021 || [[Mercedes-Benz EQS]] | 0.20<ref>{{cite press release|title=The new EQS: passion for electromobility |url=https://media.daimler.com/marsMediaSite/ko/en/49475387 |access-date=2021-04-06 |date=2021-04-03 |language=en|location=Stuttgart}}</ref>{{efn|name=EQS| w/ 19-inch AMG wheel/tire combination in "Sport" driving mode}} |- | 2022 || [[Lucid Air]] | 0.197<ref>{{cite press release|title=Lucid Air Touring and Air Pure Now Ready for the Road with Market-Leading Range and Aero; Air Sapphire Dominates Test Tracks on the Way to 2023 Introduction|url=https://ir.lucidmotors.com/news-releases/news-release-details/lucid-air-touring-and-air-pure-now-ready-road-market-leading |access-date=2022-11-15 |date=2022-11-15 |language=en|location=Newark, California}}</ref>{{efn|name=Air| w/ 19-inch wheel/tire combination}} |- | 2024 || [[Xiaomi SU7]] | 0.195<ref>{{Cite web |last=Lye |first=Gerard |date=2023-12-28 |title=Xiaomi SU7 debuts in China – brand’s first EV; up to 673 PS, 838 Nm, 800 km range, 265 km/h top speed |url=https://paultan.org/2023/12/28/xiaomi-su7-debuts-in-china/ |access-date=2023-12-28 |website=Paul Tan's Automotive News |language=en-US}}</ref> |- | 1996 || [[General Motors EV1]] | 0.19<ref>{{cite news |last1=Brown |first1=Aaron |title=Here's the story behind GM's revolutionary electric car from the 90s that disappeared |url=https://www.businessinsider.com/gm-ev1-history-2016-3 |access-date=2018-11-28 |work=Business Insider |publisher=Insider Inc. |date=2016-03-16 |language=en}}</ref> |}
{| class="wikitable sortable" style="font-size:97%;" |+Concept and experimental vehicles ! Calendar year!! Automobile ! {{Cd}} |- | 1952 || [[Alfa Romeo Disco Volante]] | 0.26 |- | 1933 || [[Dymaxion Car]] | 0.25 |- | 1954 || [[Alfa Romeo BAT|Alfa Romeo B.A.T. 7]] Concept | 0.19 <ref>{{Cite web|url=http://www.conceptcarz.com/vehicle/z4824/Alfa%20Romeo_BAT%207/default.aspx|title=1954 Alfa Romeo B.A.T. 7|access-date=2019-11-15|website=conceptcarz.com.}}</ref> |- | 2021 || [[Aptera (solar electric vehicle)|Aptera SEV]] (2019 relaunch) | 0.13<ref>{{Cite web|url=https://aptera.us/vehicle/|title= Aptera Vehicle Features|access-date=2024-05-01}}</ref> |- | 2000 || [[General Motors Precept|General Motors Precept Concept]] | 0.16 <ref>{{cite news |url=http://www.electrifyingtimes.com/gmprecept.html |title=GM Unveils Concept Car That Gets 108 Miles A Gallon |work=Electrifying Times |location=US |date=2000-01-11 |archive-url=https://web.archive.org/web/20000519033411/http://www.electrifyingtimes.com/gmprecept.html |archive-date=2000-05-19 |url-status=dead}}</ref> |- | 2022 || [[Mercedes-Benz Vision EQXX]] | 0.170 <ref>{{cite web|url=https://group-media.mercedes-benz.com/marsMediaSite/instance/ko.xhtml?oid=52282663&filename=VISION-EQXX--taking-electric-range-and-efficiency-to-an-entirely-new-level&ls=L2VuL2luc3RhbmNlL2tvLnhodG1sP29pZD01MjI4MjY2MyZmaWxlbmFtZT1WSVNJT04tRVFYWC0tdGFraW5nLWVsZWN0cmljLXJhbmdlLWFuZC1lZmZpY2llbmN5LXRvLWFuLWVudGlyZWx5LW5ldy1sZXZlbCZyZWxJZD0xMDAxJmZyb21PaWQ9NTIyODI2NjMmcmVzdWx0SW5mb1R5cGVJZD0xNzImZnJvbUluZm9UeXBlSWQ9NDA2MjY!&rs=28|title= VISION EQXX – taking electric range and efficiency to an entirely new level |publisher=group-media.mercedes-benz.com |access-date=2022-04-21}}</ref> |- | 2013 || [[Volkswagen XL1]] | 0.19<ref>{{cite web|last1=ZOELLTER|first1=JUERGEN|title=2014 Volkswagen XL1|url=https://www.caranddriver.com/reviews/2014-volkswagen-xl1-first-drive-review|website=Car and Driver|date=14 June 2013|publisher=Hearst Communications, Inc.|access-date=2017-12-25}}</ref> |- | 2018 || [[Eco-Runner Team Delft#The Ecorunner 8|Ecorunner 8]] (Shell [[Eco-marathon]]) Prototype | 0.045 |- | 2022 || [[UNSW Sunswift|Sunswift]] 7 | 0.095<ref>{{Cite news |date=2022-12-19 |title=Australian solar-powered race car nets Guinness World Record after nail-biting finish |language=en-AU |work=ABC News |url=https://www.abc.net.au/news/2022-12-19/solar-powered-car-unsw-sunswift-7/101790478 |access-date=2023-04-29}}</ref><ref>{{Cite web |last1=Martin |first1=Neil |date=2022-12-19 |title=EV record breakers! Sunswift 7 goes 1000km on a single charge in world's best time |url=https://newsroom.unsw.edu.au/news/science-tech/ev-record-breakers-sunswift-7-goes-1000km-single-charge-world%E2%80%99s-best-time |access-date=2023-11-12 |website=UNSW Newsroom}}</ref> |}
{| class="wikitable sortable" |+ Automobile examples of '''{{CdA}}'''<ref>{{cite web|url=http://www.mayfco.com/tbls.htm |title=The Mayfield Company Homepage - Coefficient of Drag Tables and Curves |publisher=Mayfco.com |access-date=2010-12-07}}</ref> |- ! {{CdA}} sqft!! {{CdA}} m2!! Automobile model |- | {{convert|3.00|sqft|m2|abbr=on|disp=table}} || 2011 [[Volkswagen XL1]] |- | {{convert|3.95|sqft|m2|abbr=on|disp=table}} || 1996 [[General Motors EV1|GM EV1]] |- | {{convert|5.52|sqft|m2|abbr=on|disp=table}} || 2019 [[Porsche Taycan|Porsche Taycan Turbo]]<ref name=taycan/> |- | {{convert|6.0|sqft|m2|abbr=on|disp=table}} || 2001 [[Honda Insight#First generation|Honda Insight]]<ref name="C&D">{{cite news|last1=Sherman|first1=Don|title=Drag Queens: Aerodynamics Compared|url=https://www.teslamotors.com/sites/default/files/blog_attachments/the-slipperiest-car-on-the-road.pdf|access-date=2017-12-29|work=Car and Driver|issue=June 2014|publisher=Hearst Communications}}</ref> |- | {{convert|6.05|sqft|m2|abbr=on|disp=table}} || 2012 [[Tesla Model S]] P85<ref name=C&D/> |- | {{convert|6.20|sqft|m2|abbr=on|disp=table}} || 2014 [[Toyota Prius]]<ref name=C&D/> |- | {{convert|8.79|sqft|m2|abbr=on|disp=table}} || 1956 [[Citroën DS]] Spécial<ref name=citroenetAero>{{cite journal |url=http://www.citroenet.org.uk/miscellaneous/aero/aero01.html |title=Aerodynamics |journal=Le Double Chevron |issue=#59 |year=1980}}</ref> |- | {{convert|13.0|sqft|m2|abbr=on|disp=table}} || 2019 [[Ram Pickup#Fifth generation (2019)|Ram 1500]]<ref>{{cite web|title=2019 Ram 1500 – More Space. More Storage. More Technology|url=https://www.ramtrucks.com/2019/ram-1500.html|website=www.ramtrucks.com|archive-url=https://web.archive.org/web/20180116135154/https://www.ramtrucks.com/2019/ram-1500.html|archive-date=2018-01-16|access-date=2018-02-24}}</ref> |- | {{convert|17|sqft|m2|abbr=on|disp=table}}|| 2013 [[Mercedes-Benz G-Class]]<ref>{{cite press release |url=https://media.daimler.com/marsMediaSite/en/instance/ko.xhtml?oid=9906403 |title=Taking the drag out of aerodynamics: Aerodynamics world champion in almost all vehicle classes |publisher=Daimler |date=2013-10-05 |accessdate=2021-03-02}}</ref> |- |}
{| class="wikitable sortable" style="font-size:97%;" |+Concept/experimental cars |- ! {{CdA}} sqft!! {{CdA}} m2!! Automobile model |- | {{convert|0.21|sqft|m2|abbr=on|disp=table}} || [[Pac-car II]]<ref>{{cite book|title=The world's most fuel efficient vehicle : design and development of Pac Car II|last1=Santin|first1=J. J.|last2=Onder|first2=C.H.|last3=Bernard|first3=J.|last4=Isler|first4=D.|last5=Kobler|first5=P.|last6=Kolb|first6=F.|last7=Weidmann|first7=N.|last8=Guzzella|first8=L.|date=2007|publisher=vdf, Hochschulverlag AG and der ETH|isbn=978-3-7281-3134-8|location=Zürich|page=113}}</ref> |- | {{convert|2.04|sqft|m2|abbr=on|disp=table}} || 2011 [[Aptera 2 Series]]<ref>{{cite web|url=http://igss.wikidot.com/power-consumption |title=Power Consumption - IGSS'13 |access-date=2015-09-30}}</ref> |- |}
==See also== * [[Automotive aerodynamics]] * [[Drag (physics)]] * [[Drag equation]] * [[Paul Jaray]]
==Notes== {{notelist}}
==References== {{reflist|colwidth=30em}}
==External links== * [http://rc.opelgt.org/indexcw.php Further 500 drag coefficients] * [https://web.archive.org/web/20070824155049/http://www.edmunds.com/advice/specialreports/articles/106954/article.html Improving Aerodynamics to Boost Fuel Economy] * [https://web.archive.org/web/20070607000714/http://tauac.typepad.com/ac/2007/05/tau_drag_reduct.html Tel Aviv University reduces drag on trucks by 10%] * [https://web.archive.org/web/20090318010755/http://physics.technion.ac.il/~rutman/car/Roll-down%20test.pdf Simple roll-down test for measuring Cd and Crr for cars and bikes]
[[Category:Automotive engineering]] [[Category:Drag (physics)]]