nascar drag coefficient

As production parts began to arrive in early 2021, the first major test of team cars occurred at Daytona International Speedway. Deletion can be as simple as removing an aftermarket part, or part that has been installed on the vehicle after production, or having to modify and remove an OEM part, meaning any part of the vehicle that was originally manufactured on the vehicle. Actually if NASCAR cars had the same drag coefficient (Cd) as F1 cars they would be considerably slower. That said, the Generation 6 cars had become substantially developed to take advantage of the high-speed undercar flows. Several safety innovations are installed on NASCAR vehicles for such emergencies, such as a recessed right-side window. Today's fleet of cars is a vast improvement over the ornamental tailfins and boxy structures of yesteryear. 2023 Chelsea Magazine Company | "Aero Push." This is where the front downforce-generating exercise paid dividends by knowing what could reverse the front downforce gains. 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. Please copy/paste the following text to properly cite this HowStuffWorks.com article: "How Stock Car Aerodynamics Work" I couldnt believe you hadnt heard the mu joke but then I realized that Ive never heard the mermaid joke. Goodyear produces different tire compounds for different tracks, as well as different left- and right-side tires. A potential complication of altering a vehicle's aerodynamics is that it may cause the vehicle to get too much lift. Some examples of Cd follow. 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. A properly angled nosepiece, placed low to the ground, directs the majority of the air upward over the top of the car. NASCARs last generation vehicle, the Generation 6, or Gen 6, as its known, was introduced in 2013. Plus free access to the digital archive over 100 back issues! Aerodynamic force results from differences in pressure on the sides of the moving object. As expected, an aerodynamic body makes a big difference in lap time. Various other characteristics affect the coefficient of drag as well, and are taken into account in these examples. [4], A roof rack is a common trait on many SUV and station wagon vehicles. Racecar Engineering is the worlds leadingpublication for motorsport technology and engineering. So how does NASCAR test for coefficient of friction? Most production sports cars and high efficiency vehicles come standard with many of these deletions in order to be competitive in the automotive and race market, while others choose to keep these drag-increasing aspects of the vehicle for their visual aspects, or to fit the typical uses of their customer base. 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. The wide slicks used for racing are designed to maximize the coefficient of friction between the tire and the racetrack. The body must fall within this box, or the test is considered a failure. Two cars drafting together can go 3 to 5 miles an hour faster than a solo car, and extra trailing cars add a little more speed, which is why the drivers spend so much time in single-file. 97.47. The magnitude of this frictional force depends on the magnitude of the normal force. This is done to direct airflow around and over the vehicle rather than allowing air to travel under it. A large share of the drag on a NASCAR race car is due to the highly separated underbody flow (see Figure 6). For the men and women of NASCAR R&D, Dallara, and the industry involved in making the new car a reality, the start of the regular season in Daytona will be not so much the birth of a new era, but more like a college graduation. u0001 On the one hand, many drivers can remain competitive in a close race by piggybacking on the lead vehicle, taking advantage of the increased force and decreased engine strain. The objective is to create a low-pressure area, or partial vacuum, underneath the nose [source: Circle 304]. While roof racks are very useful in carrying extra storage on a vehicle, they also increase the frontal area of the vehicle and increase the drag coefficient. 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. The trailing car suffers a reduction of downforce on its front tires, resulting in a loss of stability and handling coming out of turns. It's All Aerodynamics." The difference is one is purposefully built, the other had to pretend to be for other reasons. The sharp edge to the right-side window deflects air instead of letting it flow freely over the roof. Two zones were opened up for OEMs to place their radiator exits, with the majority of the underlying radiator ducting common. These designs reduce air resistance, or aerodynamic drag. HPDs CR-V Hybrid Racer: A 2024 INDYCAR Powertrain Lab, McLaren Motorsport confirms the new 720S GT3 EVO. The drag coefficient of a vehicle is affected by the shape of body of the vehicle. 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. The rear spoiler found on NASCAR vehicles is a case in point: It increases drag by distributing weight from the front to the back of the car [source: Circle Track]. With the 426 Hemi producing 425 horsepower, the zero to sixty acceleration was just 4.8 seconds, but they produced only 135 of these. 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. Aero push -- and all of racing aerodynamics, for that matter -- is all about the downforce. So its not like you can say that Bristol always needs x amount more friction in the upper lane. Its a blunt instrument, but a historical element that completes the stock racecar look. 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. Its drag coefficient is 1.42. If youre moving file cabinets, you want a low coefficient of friction. At the corners, though, the dangers come into play in reduced maneuverability and greater likelihood of losing control. [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. Streamlining the body requires assumptions about the surrounding airspeed and characteristic use of the vehicle. [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. 2 . Finally, Goodyear constantly improves their tires. 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. But how do they know when they need it? Although both methods can be accurate, nothing in the engineering world beats physical testing, where the true real world effects of the air passing over the car can be recorded to influence any design tweaks needed to the bodywork. This leads to various interpretations of what is acceptable, and often lengthy lists of revisions from NASCAR in terms of qualitative styling, as compared to the production vehicle. This meant moving the downforce balance rearward by 12-14 per cent, a significant departure from the existing Gen 6 architecture. This design can actually create too much airflow into the engine compartment, preventing it from warming up in a timely manner, and in such cases a grille block is used to increase engine performance and reduce vehicle drag simultaneously. For the most part, any increase in downforce will also bring an accompanying increase in aerodynamic drag. Cookie Policy. Learn how your comment data is processed. Even casual fans are constantly exposed to the terminology of automotive aerodynamics. [10][11] In order to decrease the impact that side mirrors have on the drag of the vehicle the side mirrors can be replaced with smaller mirrors or mirrors with a different shape. Mazda RX-729P. Introducing a symmetric body eliminated the majority of these issues and presented a car that is a near spitting image of its street counterpart. The submission process itself consists of two distinct components. Smooth wheel covers are hub caps with no holes in them for air to pass through. The most common methods for increasing the downforce of a vehicle involve reducing the air pressure underneath the vehicle. It has changed the culture and practice of car racing in ways some fans find infuriating. 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. Its much harder to slide, so it takes you 75 lbs of force to move it. Optimizing that is up to the teams. This mitigates the amount of drag by decreasing the frontal area of the blade. NASCAR has always placed a premium on safety for both drivers and fans in all instances, so it was important to establish early in the process that no design decisions would adversely affect the lift-off speed of the car. .70. Fender skirts are more commonly found on the rear wheel wells of a vehicle because the tires do not turn and the design is much simpler. The thing about aero development in general is, its much easier to make front downforce compared to rear downforce. 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. Another was at the rear of the car, where the production wheel tubs further closed off the rear of the boot (trunk) area, sealing in hot air from the transaxle cooler. If you're curious about aerodynamics, do further research on the Internet or at your local library. Aerodynamic drag is the force of air along the length of the traveling car, opposing the car's force. The main purpose of a rear spoiler in a vehicle's design is to counteract lift, thereby increasing stability at higher speeds. 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. Im guessing an airplane tire satisfies the bill without a lot of extra fiddling about. While skirts are effective at generating downforce in a simple manner, they give the appearance of the cars being sealed to the track, along with the inevitable and undesirable wrinkling and deformation they experience. When automobile companies design a new vehicle they take into consideration the automobile drag coefficient in addition to the other performance characteristics. (Accessed 12/14/08) http://www.circletrack.com/techarticles/0304_aerodynamics_tech_definitions/index.html, Cislunar Aerospace. Please confirm you agree to the use of tracking cookies as outlined in the Cookies Policy. The Physics of NASCAR: How to Make Steel + Gas + Rubber = Speed. But there are other forces involved too such as Newton's Law of Motion and centripetal force. Indeed the drag coefficient follows the same trend as the downforce (Fig. Here the incremental drag force increases with angle of attack but drops after suspected wing stall at dtp = 29 deg. 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. Findings - By the CFD analysis, the drag coefficient without the spoiler is calculated to be 0. . = Overall, the Next Gen car has been a once-in-a-lifetime project for most of those involved, who may never see another project quite as revolutionary to an ecosystem as this. "BMW Side Skirts." To keep up with the latest innovations in aerodynamics, visit the links on the next page. 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. Your email address will not be published. More Storage. 1 Sport utility vehicles (SUVs), with their typically boxy shapes, typically achieve a Cd =0.35-0.45. A well-prepared student entering a world of possibility and excitement, with a proud group of invested parents standing behind it, wishing it every success. 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. Do you know of any cars that have particularly low drag coefficients? Drag force on a vehicle acts on the same plane as the direction of motion (horizontally) and increases exponentially as speed increases. PRO NOTE: There are three components to the coefficient of friction when dealing with soft, stretchy materials like rubber: adhesion ( molecular interaction between tire and road); hysteresis (due to deformation of the tires) and cohesion (due to wear and tear). Covering much of the rear deck with a new sloped piece of glass and significantly shortening the decklid was a quick, cost-effective solution that lowered the drag coefficient from 0.375 to 0.365 in wind tunnel testing. 12h ago. However, achieving all that presented significant aesthetic challenges for manufacturers and NASCAR, since car designs not only had to be stretched at the rear, but also have different shapes on the left and right sides. Speaking of the tail, another key feature of NASCAR vehicles is the spoiler. A rod with a hemispherical cross section will even have a drag coefficient of 2.3 (right column in the graph below). Stock cars circling oval tracks to the left are more likely to show their right face in a spin. Ideally F1. Too much lift can cause the vehicle to lose road traction which can be very unsafe. This is aero push, also called a "tight" condition, requiring the trailing driver to ease off the accelerator to regain traction [source: ESPN]. The grille in most production vehicles is generally designed to maximize air flow through the radiator where it exits into the engine compartment. The vehicles were so aerodynamic they achieved a drag coefficient of 0.28, which was unheard of at the time. . Comparison of Aerodynamic Measurements on a Full-Scale NASCAR in Open and Closed Jet Test . (Accessed 12/17/08) http://www.bmwsideskirts.com/history.php, Boone, Jerry F. "Bad Air? Drivers challenge each other less, riding in tight single-file rather than side by side. Scale model options were evaluated as well, but with confidence in the simulation work and world class local wind tunnel facilities, it was decided to move ahead and target only four development tests of 20 hours each to finalise the underwing. In a streamlined design the air flows around the vehicle rather than through; however, the grille of a vehicle redirects airflow from around the vehicle to through the vehicle, which then increases the drag. In order for the air to flow more smoothly around the wheel well, smooth wheel covers are often applied. 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. But the advantage of the way theyre doing it is that they can make measurements quickly enough to determine whether they need to apply more PJ1 Trackbite before a race. Minimizing variables is always a good thing. Table 8.1 lists the drag coefficient for some simple shapes, (each of these objects has a Reynolds number of order 104 ). Where the drag coefficient and reference area have been collapsed into the drag area term. Figures given are generally for the basic model, which may not be available in some markets. For short-track racing, the strategy is reversed -- because the driver spends more of the race negotiating curves, an emphasis on downforce will lead to greater overall speed as well as increased safety [source: Tierney]. It is still the most important variable in racing conditions that place a smaller premium on downforce, such as longer tracks with more straightaways. Some sports cars have a surprisingly high drag coefficient (such as the Ariel Atom at 0.40), but this is to compensate for the amount of lift the vehicle generates, while others use aerodynamics to their advantage to gain speed and as a result have much lower drag coefficients. 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. When youre pulling at constant speed, note how much the scale reads. 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. The behavior of the Drag Coefficient was further investigated by analyzing how it varies with velocity. "Aerodynamics and Race Cars. The obvious element in the physics of NASCAR is the aerodynamic design required by these cars in order to achieve top speeds of near 200 mph with the minimum drag coefficient. The harder the car is pushed against the track, the greater the frictional force. This scan is located off targets on the chassis and has a tolerance of +/- 0.15in for the body, which presents challenges to the teams to build to that tolerance but also keeps the competition on a level playing field. 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With the greenhouse decided, the next step was to move to another stylistic sore point: the tail. 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. As the car cuts a path through the air, some air molecules collide with the front bumper, producing resistance. Much anecdotal information pertaining to the drag reduction (drag benefit) of platoon operation exists. At 180-200 MPH, aerodynamic drag accounts for 90 percent of the total resistance. [5], Mudflaps are now rarely specified as standard on production cars as they interfere with the clean airflow around the vehicle. The test opens with NASCAR setting the performance targets using its generic body, with several repeated runs at the start of the test. 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. Some of this was attributable to inadequate insulation and material changes in production, but a great deal was due to the ingestion of hot radiator air into the cockpit and inadequate evacuation of air from the cockpit. Speed, air density, and car size, shape and design all determine the magnitude of a car's drag force.

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