nascar drag coefficient nascar drag coefficient

So how does NASCAR test for coefficient of friction? Early in the process, the goal was to match the relative aero performance of the Gen 6 vehicle, primarily in terms of total downforce and balance. Cookie Policy. Perhaps the greatest departure of the Next Gen (Gen 7) vehicle from the Gen 6 is the move to a coupe-like roof line, and the symmetry of the rear of the vehicle. Left-side tires are softer, but wear faster. Did you notice that all the real-world numbers above are less than one? air density Race drivers - particularly NASCAR drivers - make a convincing case for platooning, although drafting is the term the drivers prefer. The new MSN, Your customizable collection of the best in news, sports, entertainment, money, weather, travel, health, and lifestyle, combined with Outlook, Facebook . A coefficient of friction greater than one means its easier to pick up the object than to slide it. Minimizing variables is always a good thing. Drafting can be a very powerful racing technique, but it has a serious liability. Rear downforce performance is largely constant over a range of ride heights, and floor pressures are very consistent across a range of ride heights. Privacy Policy | The harder the car is pushed against the track, the greater the frictional force. The highly concentrated vortex core suggests a stable vortex flow. Because speed is, obviously, the main factor in NASCAR races, aerodynamics is a crucial element in stock car design. Since the original introduction of the Next Gen was slated for 2021, it was decided that the only viable path to making the timeline was to go from CFD straight to full-scale testing. In order for the air to flow more smoothly around the wheel well, smooth wheel covers are often applied. A low coefficient is conducive to high top speed and low fuel consumption, while a higher drag coefficient is generally found in cars searching for high cornering speeds influenced by downforce. The advent of a new vehicle allowed NASCAR and the OEM aero teams to further refine an already tight Gen 6 submission process. With confidence in the CFD predictions and a need for more rear downforce, a multi-week CFD study began to refine the diffuser. The removal of this part has led to increases in fuel efficiency in several studies. NASCAR used a non-standard ratio that was taller (a lower numerical raio) and some engine tweaks in order . Extremes are created by such machines as the eco-friendly solar powered vehicles you see companies producing now and again like the Shell Ecorunner V that somehow achieves a coefficient of just 0.05. 2023 Chelsea Magazine Company | In the similar context, lift force is of the major concerns too for design engineers, as excessive lift can make the vehicle loose traction at high speeds and can result in fatal injuries both . The wheel wells are another area to shape. A larger cross-sectional area increases drag because more air molecules have to be moved out of the way" [source: Leslie-Pelecky]. "Passenger Car Aerodynamics." (Accessed 12/17/08 via Google Books) http://books.google.com/books?id=OAK3yFlHoTAC, Tierney, John. "A faster car experiences more drag because it has to push air molecules out of the way faster," Diandra Leslie-Pelecky explains in her book, "The Physics of NASCAR." [4], A roof rack is a common trait on many SUV and station wagon vehicles. A front air dam is often used which extends from the very front of the vehicle down to the lowest part of the vehicle. This makes a cars aerodynamic properties particularly important for hypercar developers like Bugatti. Its significance to the sport cannot be understated, and its promise has already yielded gains with increased team charter values and new team ownership entering. Aero push has become almost the dominant feature of NASCAR races. The original diffuser was relatively simple in its design so wind tunnel testing could begin and provide an early opportunity for validation against CFD. The submission process itself consists of two distinct components. Either louvred or open designs were permitted, based on the styling desires of the OEM, which is apparent when comparing the different design paths of the three vehicles. The Physics Behind Auto Racing. Studying downforce means paying attention to its opposing force, lift. Racecar Engineering is the worlds leadingpublication for motorsport technology and engineering. The Next Gen features the passively deployed bonnet (hood), and roof flaps NASCAR uses in all its vehicles, but the diffuser presented a new opportunity to add another safety device a diffuser flap. This map was later used in wind tunnel testing at Windshear wind tunnel in Concord, North Carolina. At the front of the car, one of the most substantial downforce-generating characteristics, aside from ground effect, is the outwash of the front splitter in front of the tyres. Lift -- colloquially called a skyward force -- is usually present to one degree or another in a moving object. Findings - By the CFD analysis, the drag coefficient without the spoiler is calculated to be 0. . Spoilers, front air dams and wings produce this effect. {\displaystyle F={\tfrac {1}{2}}\times {\text{air density}}\times \mathbf {\text{drag area}} \times {\text{speed}}^{2}} Without grip aka friction there is no racing. It is also a very effective device from a sanctioning body perspective for controlling top speeds, which is critical for fan and driver safety due to the proximity of both to the walls and fencing at most oval tracks. The above dataset yielded an average drag coefficient of 10.5 and a standard deviation of 1.9. Youve measured the coefficient of friction. It was evident as well that the outer tunnels were ingesting the front tyre wakes. If NASCAR makes measurements one year at Las Vegas with tire D1234 and the next year Goodyear bring tire D1235, how do you compare the two measurements? It also allows the car to correct itself when the driver oversteps the bounds of traction at the rear. However, the introduction of evocative coupes such as the Ford Mustang and Chevrolet Camaro meant fitting the production body style onto that sedan greenhouse proved challenging. It was understood early in the process that the reduction of rear side force due to body symmetry would impact the useable aero balance, but initially it was a guessing game, although not entirely without value. 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. coefficient and the aerodynamic interaction between the front wing and the vehicle other components is probably not quite simple. Lets examine the coefficients of friction, , for tire rubber on various surfaces. Automotive engineers and pit crews strive to keep the two forces in balance. Add in the fact that the ability of the rear of a car to generate downforce is hampered by the mass in front means, basically, that the front of any car has the first choice on making downforce. Comparison of Aerodynamic Measurements on a Full-Scale NASCAR in Open and Closed Jet Test . The process was primarily undertaken in CFD, with over 2000 runs dedicated to underwing development for both performance and lift-off safety testing. PJ1 Trackbite is a sticky, water-resistant substance that increases grip. The coefficient of friction between the metal cabinet and the shag rug is 75/100 = 0.75. Since drag accounts for roughly 90% total. The air that glides smoothly over the roof grows turbulent above the rear window and behind the car, exerting a backward force on the vehicle. Downforce is a downward force produced by air pressure, which creates a stronger pressure between the tire and the surface of the road. But the quest to engineer racecars with high net downforce sometimes leads to additional drag. Could NASCAR use more complex techniques to make this measurement? Just as a speedboat leaves the sharp line of a wake trailing behind it on the water, an automobile creates an aerodynamic impact as it slices through the air. Race cars occasionally become airborne despite these devices. The engineering goals are to curtail the amount of air flowing underneath the chassis to ensure a closer attraction between the tires and the ground and to provide easy escape for air that does get underneath. NASCARs last generation vehicle, the Generation 6, or Gen 6, as its known, was introduced in 2013. . The value of drag coefficient for a something of the general dimensions of a car lies around the 0.3-0.4 mark. This pushed the initial outer tunnel ramp forward and outward. [1] There are many different ways to reduce the drag of a vehicle. Because lift and downforce are opposing forces, part of the effort to build a stock car with a strong downforce involves overcoming lift. drag area If its hotter, it may need less. This is held in place at the centre of the diffuser and, when deployed, releases downward and blocks the central tunnel of the diffuser. Air swooshes over the top of the car and is deflected by the spoiler attached to the rear deck. [15], The effect that windshield wipers have on a vehicle's airflow varies between vehicles; however, they are often omitted from race vehicles and high efficiency concepts in order to maintain the smallest possible coefficient of drag. and alge-bra.. Aerodynamic force results from differences in pressure on the sides of the moving object. It is created as an extension of the rear of the vehicle, moving the rear backward at a slight angle toward the bumper of the car. [13] It is estimated that two side mirrors are responsible for 2 to 7% of the total aerodynamic drag of a motor vehicle, and that removing them could improve fuel economy by 1.52 miles per US gallon. 2 This is commonly seen in vehicles such as the first generation Honda Insight. 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Its a blunt instrument, but a historical element that completes the stock racecar look. 12h ago. (Accessed 12/17/08) http://www.bmwsideskirts.com/history.php, Boone, Jerry F. "Bad Air? Ideally F1. The Cd of a given vehicle will vary depending on which wind tunnel it is measured in. But how do you know how much grip a racetrack has? A flared wheel well opening, in front of the tire, will force onrushing air away from the sides and bottom of the car, further decreasing the air pressure [source: Boone, "Race Car Aerodynamics"]. The Physics of NASCAR: How to Make Steel + Gas + Rubber = Speed. While such application may be useful for racing, for most road vehicles this would produce minimal improvement in overall drag reduction. This is why something like a Bugatti Veyron sits nice and snug on the tarmac with a small and efficient frontal profile when compared to something like a family saloon or hatchback. A boattail can greatly reduce a vehicle's total drag. The higher the coefficient of friction, the harder it is for the two materials to slide against each other. The numbers along the line indicate several flow regimes and associated changes in the drag coefficient: The trailing vehicle, if it tailgates at a certain proximity, can take advantage of the lead car's aerodynamic force. I couldnt believe you hadnt heard the mu joke but then I realized that Ive never heard the mermaid joke. ", Circle Track. The introduction of more road courses and short tracks reduces the need for the cars design to focus on high-speed ovals, and more toward a shape that can do it all: ovals, road courses and short tracks. Source: Brad Bruno i This data was collected using a data acquisition system as well, and processed with a u0002u0004 u0001u0004 u0001 PC. [9] Some cars now feature automatically adjustable rear spoilers, so at lower speed the effect on drag is reduced when the benefits of reduced lift are not required. OEMs are allowed up to five different design attempts per shift though, practically speaking, it is difficult to get through more than three configurations. (Accessed 12/15/08) http://www.recumbents.com/car_aerodynamics/, BMW. Dr Eric Jacuzzi explains how those involved in the aero development of the NASCAR NextGeneration racecar see it not so much as the birth of a new era, but more like the completion of a study course. It first really dove into this experiment with the current S- and C-Class, getting these standard internal combustion sedans as low as a coefficient of drag number of 0.24. What worked in spring wont necessarily work in fall. But, of course, Goodyear engineers cant just make the stickiest tire possible, because soft tires wear out faster. You can do the same coefficient of friction measurement if you have a spring scale. A 2008 book called "The Physics of NASCAR: How to Make Steel + Gas + Rubber = Speed," by Diandra Leslie-Pelecky, explains aerodynamics and other scientific principles in auto racing. The submitted OEM bodies are scanned in the wind tunnel and compared to the submitted CAD for each design, with strict tolerances enforced to ensure each test article is representative of the design intent. With its forward emphasis on manufacturer identity, it was a breakthrough for the sport. As a result, this modification is more commonly seen in high efficiency vehicles rather than sports cars or racing vehicles. Drag force can either be seen as a help or a hindrance depending on the automotive application. Extremes are created by such machines as the eco-friendly solar powered vehicles. Save my name, email, and website in this browser for the next time I comment. speed This is where the front downforce-generating exercise paid dividends by knowing what could reverse the front downforce gains. It seems the industry has very much settled on producing cars in the 0.3 region, both from a design and practicality point of view, but stray below that and you will save plenty cash on your monthly fuel bill, along with a very healthy potential top speed. Body inspection at the track will still be conducted by NASCARs Optical Scanning Station, which compares a rapid photo scan of the car to the approved CAD surface of the vehicle. These designs reduce air resistance, or aerodynamic drag. In fact, downforce is a form of lift -- negative lift. The component within the equation that will have the largest effect on car design will be the frontal area, as this will shape the front profile of the car, influencing the rest of the design. After Daytona, the NASCAR R&D aerodynamics team embarked on a month-long extensive study of the problem, thermally modeling the entire vehicle in much more detail than it had previously. -3.80. The main purpose of a rear spoiler in a vehicle's design is to counteract lift, thereby increasing stability at higher speeds. "NASCAR's Screech and Slam? This is why: The actual values of coefficients of friction for race tires are trade secrets and closely guarded. Unseasonably cold weather may require more friction. The front bumper is the first part of the vehicle that the air must flow around. Another factor in moving toward a symmetric body was the evolution of the NASCAR racing calendar. PRO NOTE: This linear relationship doesnt hold for large downward forces. That means the coefficient of friction between your metal cabinet and the wood floor is 30 lbs/100 lbs = 0.3. This downforce is the key to maintaining traction through the tight and constant turns of a short-track race. Coastdown testing is a proven method for determining the drag coefficients for road cars whilst the vehicle is in its normal operating environment. Indeed the drag coefficient follows the same trend as the downforce (Fig. Stay safe. The drag coefficient of a vehicle is affected by the shape of body of the vehicle. If youre moving file cabinets, you want a low coefficient of friction. The grille in most production vehicles is generally designed to maximize air flow through the radiator where it exits into the engine compartment. The primary tool for tuning racing grip is the tire. The NASCAR Truck Aerodynamic Improvement team is tasked with providing aerodynamic analysis and improvement to Ford Performance and their factory supported team Brad Keselowski Racing for their Ford F-150 race trucks. More Technology", "2022 Wagoneer / Grand Wagoneer Specifications", "Taking the drag out of aerodynamics: Aerodynamics world champion in almost all vehicle classes", "Renault: la Vesta 2 plus performante en 1987 que l'Eolab en 2015", "Specs of Mercedes-Benz Bionic Car Concept (2005)", Improving Aerodynamics to Boost Fuel Economy, Tel Aviv University reduces drag on trucks by 10%, Simple roll-down test for measuring Cd and Crr for cars and bikes, https://en.wikipedia.org/w/index.php?title=Automobile_drag_coefficient&oldid=1136187000, Nissan 350Z Coupe Base and Enthusiast models, 0.212 (1:5 model test, 1:1 car = 0.36, see above), 2013 Mercedes-Benz CLA 180 BlueEfficiency, This page was last edited on 29 January 2023, at 04:24. A passenger car driving on the highway spends an estimated 60 percent of its energy overcoming air drag, a far greater percentage than tire friction and the energy needs of the drive train itself [source: Beauchamp]. "Going With the Flow." On the lift-off safety front, NASCAR evaluated the vehicle in CFD before testing at the Automotive Center for Excellence (ACE) in Oshawa, Canada and the Chrysler Technical Centers Aero Acoustic wind tunnel in Auburn Hills, Michigan. A Superbird has a .31 coefficient of drag while a Daytona's drag coefficient is .29about a 20-percent increase in aerodynamic efficiency over the standard Charger. Drag force on a vehicle acts on the same plane as the direction of motion (horizontally) and increases exponentially as speed increases. It is still the most important variable in racing conditions that place a smaller premium on downforce, such as longer tracks with more straightaways. The magnitude of this frictional force depends on the magnitude of the normal force. 1 Answer: Abyss lim The most successful design change was the rear deck lid modification which resulted in a drag coefficient of 0.472 and a lift coefficient of 0.816. First of all, which one? So there really is no replacement for either scale or full-size aerodynamic testing in a wind tunnel. The modern, curvaceous designs minimize the force that air creates against the car's motion, and the result is a sleeker, faster car. The flap was originally designed to operate via a pressure base deployment system, but it was found to be much more effective to deploy the diffuser flap via mechanical release connected to the right-side roof flap by a flexible cable. Defeating drag was the first major focus of automotive aerodynamics, beginning in the 1960s. Coefficient of Drag List Stock Vehicles Frontal Area formula = Height * Width * .84 (Height and Width in feet) Frontal Area formula = (Height/12) * (Width/12) * .84 (Height and Width in inches) CdA formula = Cd * Frontal Area EcoModded Vehicles This page was last modified on 9 July 2018, at 08:44. If youre racing, you want a high coefficient of friction. reference area Stay up-to-date on the second race of the 2023 NASCAR Cup Series season. The sleek lines, tilted windshields and rounded corners of modern race cars -- and passenger cars for that matter -- are designed to minimize drag. Theyre probably also reading the temperature of the track at each spot. In all cases, the reference area is the cross section orthogonal to the flow direction. This effect is more pronounced in the incremental drag data in Fig. Several concept cars of the 2010s are replacing mirrors with tiny cameras[12] but this option is not common for production cars because most countries require side mirrors. Several safety innovations are installed on NASCAR vehicles for such emergencies, such as a recessed right-side window. Cowl induction at the base of the windscreen has been a mainstay of NASCAR competition for decades but is not compatible with heated radiator air exiting out of the bonnet. The drag coefficient is a number that aerodynamicists use to model all of the complex dependencies of shape, inclination, and flow conditions on aircraft drag. In most high efficiency models or in vehicles with low drag coefficients, a very small grille will already be built into the vehicle's design, eliminating the need for a grille block. Sport utility vehicles (SUVs), with their typically boxy shapes, typically achieve a Cd=0.350.45. The drag coefficient is a common measure in automotive design as it pertains to aerodynamics. A Ford F-150 race truck is a "stock" truck that has some modifications for racing speed and safety. Aero push -- and all of racing aerodynamics, for that matter -- is all about the downforce. The dark line is for a sphere with a smooth surface, while the lighter line is for the case of a rough surface. Testament to all three of the manufacturer aero teams is they all passed their submission tests on the first attempt. As expected, an aerodynamic body makes a big difference in lap time. The main component that judges whether a car is aerodynamically efficient is known as the drag coefficient, effectively giving a value to how well a vehicle can cut its way through air. Introducing a symmetric body eliminated the majority of these issues and presented a car that is a near spitting image of its street counterpart. Because of the enormous time demands of three manufacturers wind tunnel testing in the same period, three clones of the submission vehicle were produced for the OEMs to use in their private testing efforts. This mitigates the amount of drag by decreasing the frontal area of the blade. In order to reduce this impact a grille block is often used. To ensure the most accurate and repeatable testing environment possible, NASCAR uses a dedicated submission vehicle capable of having different OEM body panels mounted to it. So its not like you can say that Bristol always needs x amount more friction in the upper lane. You reach a point where you dont get as much frictional force for increasing downforce. Sure. Attaining more downforce by manipulating racecar bodies is an obsessive task in the stock car business. The side profile of the Next Gen vehicle is therefore a blend of the lines of the Camaro, Mustang, and TRD Camry, featuring a lower roof line and swooping back glass design that works well for all three cars. The thing about aero development in general is, its much easier to make front downforce compared to rear downforce. The test opens with NASCAR setting the performance targets using its generic body, with several repeated runs at the start of the test. To understand exactly what this value means, lets take a look at the engineering equation used to calculate the coefficient: FD - Drag force - Air density V - Air speed A - Frontal area. u0001 This downforce is the key to maintaining traction through the tight and constant turns of a short-track race. Over two sweltering hot and humid days it became readily apparent the production cars were much hotter than either of the test cars NASCAR had previously utilised. The value of drag coefficient for a something of the general dimensions of a car lies around the 0.3-0.4 mark. We characterize this interaction by the coefficient of friction, represented by the Greek letter mu (), which is pronounced mew, like a kitten sound. [2] The two main factors that impact drag are the frontal area of the vehicle and the drag coefficient. The most common methods for increasing the downforce of a vehicle involve reducing the air pressure underneath the vehicle. [17], When air flows around the wheel wells it gets disturbed by the rims of the vehicles and forms an area of turbulence around the wheel. Comment with your thoughts below! Associated Press. An air dam is mounted underneath the front bumper to block air flow underneath the body. 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. Side mirrors both increase the frontal area of the vehicle and increase the coefficient of drag since they protrude from the side of the vehicle. tells you how easy or hard it is to slide one material on another.