Race regulations highly restricted the design of diffusers to limit downforce. Setup by Senna to do what? 2)Flow disruption- The car has to have a consistent flow of air to make this work, but items like wheel wake and inflow from the side skirt area can both help and hurt flow. If it is just clean air, strength (particularly strength per square inch) is insignificant. The science behind how this works is quite fascinating. Shown: MDX Type S Advance in Tiger Eye Pearl. Now that you have your splitter material and know how to attach it to the vehicle, what next? Its difficult to know how canards will affect the aero performance of any specific car without testing. Thus, mostly high-performance vehicles adapt it to achieve higher speeds. Increasing downforce will (normally) increase drag, without adding more HP to overcome the drag the decision needs to be made where best to use the available HP (straight line speed or downforce). The laws of fluid dynamics state that as the velocity of air increases, its pressure decreases. A car is a rolling compromise. 2. no composites, home depot level tech Ill see huge downforce numbers regularly tossed about because aerodynamicists test at 160+ mph for big numbers. "Mulsanne's Corner: WFO; Ward, FUJIMORI, and others", "ITV F1: Double diffusers to be banned for 2011", "Mulsanne's Corner: 1998-1999 Toyota GT-One", https://en.wikipedia.org/w/index.php?title=Diffuser_(automotive)&oldid=1128581160, Articles with unsourced statements from August 2022, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 20 December 2022, at 22:09. Ultrasonic diffusers disperse their essential oils into the air by being carried in tiny micro-droplets of water vapour. When the wing is mounted low and close to the diffuser, the low pressure under the wing helps suck air through the diffuser. What we see are gaps left in this area, allowing air to bleed above the splitter and below the bumper. In a diffuser that is too steep or too short, the air will not be able to follow the surface smoothly; it will break away from the surface to find the path of least resistance. Free Standard Shipping. This air is squished between the car and the ground. Additionally, your splitter length should not compromise the height at which it can run. You can not get the best downforce if the surface is not 'clean'. The point the diffuser starts will be the point of lowest air pressure. Old school, but it'll work. Underbody tunnels, rear diffusers and venturis are common terms used to describe the contouring of a racing car's underbody. However, for 2011, the Formula 1 Technical Working Group decided to ban multi-deck diffusers.[6]. Diffusers are making their way on high-end production vehicles as well. This is where the car is being pulled down from and affects your balance. Modern turboprop engines are equipped with propellers that have a smaller diameter but a larger number of blades for efficient operation at much higher flight speeds. But how do you get more performance out of the front? Racecar Engineering is the worlds leading motorsport technology magazine. Be careful to make sure the strings have enough room to move freely. Most splitter applications are vehicle specific AND race series specific. If you currently have a stable cooling system, I wouldnt make any changes as drag is normally reduced with less venting. We adopted this technique from the cooling systems of WW2 fighter planes. The diffuser then eases this high velocity air back to normal velocity and also helps fill in the area behind the car making the whole underbody a more efficient downforce producing device by reducing drag on the car. Generally cleaning up the underbody means creating a surface that is closer to the ground and provides a surface for the pressure to act against. Use the information to make calculations for downforce, aero balance, shock settings and much more. I know this article is focused on Time Attack modifications, but any pointers on how to go about an all-around aero package for a weekend warrior type of vehicle that may see some hot laps at a road course and then some 1/4 mile passes? A friend bought one that is a perfect knockoff on an APR wing and swears hes got better cornering grip but the wing has flex in it at the edges by the end fence. Table of Contents_. Racecar Engineering is the worlds leadingpublication for motorsport technology and engineering. The result: downforce that hugs the tires to the track. number by taking the speed of sound at 1,130 ft/sec. Submitted by ryan (not verified) on October 28, 2011 - 10:51. That being said, if the edges are flexing, thats scary. At the highest velocity (smallest cross section) the lowest pressure is produced according to Bernoulli's principle. Alternatively, with a huge splitter and monster diffusers, all working properly, you might be up to 600 pounds of front downforce. More power is needed to overcome this negative force creating inefficiency. This may mean that the diffuser becomes shallower but wider in those areas. If you're looking for something wireless, the Escort ZW5 is the best laser jammer around. Testing, CFD and/or wind tunnel all have to work together to design a really solid rear diffuser system. However, BMW offers the rear diffuser as a factory install on many of its models. The reason being is that the splitter is most likely to hit the ground in this area. [3] Clean air under the car prevents flow separation from occurring in the diffuser, which would severely rob its performance. Some race cars, such as the Toyota GT-One, use an additional diffuser immediately behind the splitter to help create more downforce. Well touch on them later as testing is so critical to these parts. This increases complexity and the possibility of very narrow operating ground-clearance ranges. First, ensure that the material doesnt flex; diffusers are most commonly made of carbon fiber, but fiberglass, wood and sheet metal can work, tootheyre just a little heavier. Obviously the article is focused on diffusers and underbody aero in racing applications, but what about street driven vehicles where more ground clearance is needed? Another benefit of having more gears is cost reduction. The problem is, if you fully seal it to the ground, not only do you wear or damage your splitter quickly, you can also greatly reduce downforce due to the airflow beneath it being cut off. $289.00. A sports car has a low and pointy front which cuts through the air like an arrow, there is less resistance pushing against the air as the vehicle moves forward. However this also assumes that the car is able to be driven on the road. Obviously, there are other methods to test with, but were looking for big changes, although this method means were measuring without units. OldPro: the typical wing has a fixed drag to downforce ratio that will limit its performance. No, but thats not what Im looking to achieve. Think of inflating a tire, high pressure exists in the air tank (100psi) and low pressure exists in the tire (30psi). Commercial vehicles usually adopt it to increase the design appeal of the vehicle, which provides little or no aerodynamic advantage. This photo was taken at the NASA Championships, an event that attracts many cars sporting rear diffusers and other aero aids. Communication. The NSX was set up by some guy named Ayrton Senna. I'm a fan of rear spoilers for multiple reasons, but keep in mind that they aren't massive downforce generators. The increased cornering speeds encouraged by the first generation of racing car ground effects and the reliability of the side-skirt sealing with the ground raised safety concerns that culminated in a near universal ban of side skirts across all forms of motor sport. Racecar aerodynamicists found that without side skirts it was still possible to induce downforce by sculpting the underbody of a car into 2 tunnels either side of the engine-gearbox assembly. Tell us what youd like to learn about next and well try and help you learn from our experience. Everything was glued up with automotive panel bonder. I'm guessing the drag reduction would still be present which would probably help fuel economy, and perhaps acceleration/top speed, but there wouldn't be much downforce generated. A NASA duct is a low drag inlet not a diffuser. Downforce is lift inverted, the net result of the pressure differential between the air flowing over and under a front splitter, a front or rear wing, or an entire car body. . We see many splitters that do not feature this part. A diffuser, in an automotive context, is a shaped section of the car rear which improves the car's aerodynamic properties by enhancing the transition between the high-velocity airflow underneath the car and the much slower freestream airflow of the ambient atmosphere. 3)Testing- With the first two points in mind, you really have to test effectively to make a system work. What gives? While living his dream, he has cut car parts in half, driven into a stationary dummy car at 50 mph, lapped Virginia International Raceway in the hottest performance cars, and explained the physics behind the wacky, waving, inflatable, flailing-arm tube man. While I am not a fan of knock-off parts, if the profile is the same, it will work the same. Fender venting is a widespread practice in prototype racing and well-designed vents can achieve large increases in downforce. Ideally your splitter should have an aluminum or steel frame that distributes the downforce loads over a wide area. Brody, your question is too application specific unfortunately. alone with a splitter in the front and maybe parts of the underbody covered with sheets of dry carbon or sheet metal you would have more downforce and little parachute effect. twin wall polycarbonate sheet. What do you get when you combine those two zones? If you try to support all of that with one, two, three, or even four bolts/rivets you will get lots of deflection which decreases the effectiveness or rips parts off the car. #1 Anti Laser Priority Radar Detector with Laser Jammer. I've seen your posts an aero stuff here and would have PMed you previously but PMs don't seem to work for me for whatever reason. #2 Escort Max Ci 360 Radar Detector with Laser Jammer. This venturi effect means that the flow is accelerated through the throat of the diffuser, creating the desired low pressure, then gradually returned to the same velocity at which it joined the wake (See Fig 1).The angle or slope of the diffuser is also important, the diffuser must have a gradual change of angle to prevent flow separation from its roof and sides. This increased flow at the throat reduces pressure by way of a venturi effect. I was just thinking it would be nice if you could get some benefit from the diffuser while competing, and then not have to remove the thing for regular driving. My personal automotive journey has lead me to aerodynamics (after years of chasing horsepower, suspension upgrades etc.). While driving in a safe area, use string tufts to see what angles and speeds show strong airflow attachment. A diffuser distributes the air evenly across your tresses, allowing them to dry faster. This hurts the high-pressure zone, increases drag by not efficiently moving air around and over the vehicle, and hampers cooling performance by not forcing air towards intercoolers, air filters, oil coolers and radiators (and potentially allowing the air to get to the backsides of these cooling systems, hurting performance even more!). Lets start with the primary function and operation of a diffuser; The key role of the diffuser on a modern racecar is to accelerate the flow of air under the car, creating an area of low pressure, thus increasing downforce.. Once you have that data, you need to know what percentage of downforce you want on the rear of your car. All aero can be installed by the purchaser although a professional install is recommended. Screwing around with fluid dynamics in the shadow of the people who developed this car could very likely be a fool's errand. ), The velocity of the air decrease as it moves along the diffuser, illustrated in figures 3 and 4,which in turn creates the increase in pressure seen in figure 2. Speaking of unneeded openings in the bumper. What are your thoughts on which is the better performing design? Autocross? The length and angle of the diffuser dictates how far forward the increased downforce can act on the car. These designs fail as the plastic isnt strong enough to hold it in place. There's no doubt that a diffuser will produce drag. All aero is produced and shipped out of California. If your intercooler core is 20 x 30 (600 square inches), the opening to you duct should be about 200 square inches. Smoothing this transition reduces turbulence and drag in the car's wake and improves airflow under the car. Theoretically, it could drive on a ceiling! Spoilers can balance out high speed oversteer, instilling more confidence while driving. When the driver lifts off the throttle, the exhaust flow is greatly reduced, which makes the diffuser less effective, robbing the vehicle of downforce. At Professional Awesome Racing, we specialize in time attack and time trial racing. It does look like it might be a chore to keep that top gap area all around clean between the existing rear and the diffuser though. Fully exploiting the exhaust flow can increase the car's maximum effective rake angle. Apparently, the engineers tuned the shape of the car to maintain the same dynamics at any speed. Verus makes good quality parts that are well engineered! Realistically, this works out to be about 4 8 of extension in most cases. As for a question I've been unable to find an answer to. Commonly, diffusers do not have any heat interactions similar to nozzles since they are designed to be adiabatic. I track my ND regularly in HPDE and the occasional time trial. This difference essentially means the wing is pushed down by the higer pressure above, generating what is known as downforce. Without seeing more of the car, its difficult to read too much into it. The information applies for both. If the downforce is disrupted for any reason, the car can become nearly undrivable. You want to avoid situations like these on wing and diffuser surfaces in particular. Achieve the highest speed possible? The front bumper is the next area where we see lots of room for improvement. The lower the pressure, the more you will gain downforce. Id always recommend shifting that balance slightly towards the rear, so the car understeers under aero loads. Its because a rear diffuser is extremely difficult to get right without access to proper CFD or wind tunnel testing. Submitted by Mark (not verified) on December 29, 2012 - 23:40. Ps the section on airdams has prompted me to relook at the size of the holes in my air dam which are for brake cooling. Rear Diffusers Another way to generate a low-pressure zone to increase downforce is to use a rear diffuser. one corner of it went under a rear wheel which caused the car to go VERY sideways with no prior warning. Since the diffuser is making downforce, there is likely to be an increase in drag. just listened to the podcast. Our guide was created with minimal testing, wind tunnel and CFD access in mind, but no reason not to experiment and let us know results. However, having had a taste of ground effects, the racecar designers weren't ready to give them up. Thank you very much for the kind words. Since were dealing with production-based cars, lets talk splitters and air dams. If applicable, please reference the images. Pros. A diffuser stalls because the air can only expand up to a certain rate. I hang out quite a bit, but don't post unless I have something helpful to say. A bit of a brown trouser moment to say the least. The diffusers throat should be as far forward as possible and at the lowest part of the vehicle. In the second/third pic, the air passes over the horizontal surface of the splitter, through those gaps between the splitter and the bumper, and straight to that black deflector under the car at the tip of the arrows I drew. For styling purposes, we see a lot of ducts and vents that go nowhere. It handled heat pretty well, it was right next to the header under the car which caused the skin to blister but never really caused much of an issue. Go over speed bumps? This means more downforce and aerodyamic grip, allowing the car to corner faster. Weight distribution is generally expressed as a percentage. Now this can require testing to find the right balance as well, but in general, if the rear of the splitter is at a slightly upwards angle, you can see a gain in downforce with minimal increase in drag. The air enters the diffuser in a low-pressure, high-velocity state after accelerating under the car. There may be instances where this may be true, but we have seen this isnt often the case. Feel free to comment below. Enjoyed the article gives a lot to think about. By incorporating inverted (compared to an aircraft) airfoil sections into the sidepods of their car, the era of ground effects in Formula 1 was ushered in. The diffuser's aim is to decelerate the air without it separating from the tunnel walls, which would cause a stall, reducing the downforce and inducing a large drag force. >> View all rear diffuser range << 127mm Universal Rear Diffuser Tunnel 270mm Universal Rear Diffuser Tunnel 630mm Universal Rear Diffuser Tunnel 790mm Universal Rear Diffuser Tunnel Group C Style Universal Rear Diffuser A common way to measure drag is coast down testing, a simple but effective method. should be about 1/3 the surface area of the heat exchanger. Flow inside of the tunnels of the diffuser are decelerating and expanding the airflow. 1)Body control- The cars body has to be very stable for safely and consistently creating underbody downforce. Define what a correct alignment is to you? Box in the bottom pic is for my undertray. Enough with the intro, lets get down to business. Of course a good air dam would still be good too. (Image kindly provided by Symscape, whose software, SymLab and its add-ons combine to form an easy-to-use CAE software system can help you assess the performance of your 3D model. But again, testing is key to finding the right setup for your vehicle. Formula 1 cars use fast-moving exhaust gases to seal the diffuser sides from the influence of turbulent air coming off the tires. Most cars have alots of little pieces hanging out in the flow under the car, which basically makes lots of little drag sources. You will have a seriously big downforce number. It is a passive diffuser that uses scent pads. Will the diffuser be effective without having a flat bottom or tunnels in the center portion of the car between the front and rear wheel center lines? Imagine the comparison between the front of a semi-truck (flat and tall) compared to a sports car front (low and pointy). This can help keep the rear of the vehicle down and decrease drag by changing the effective vehicle shape. Because of this, many racers construct their own. The walls of the diffuser contain the suction and increase the airflow through the units entrance, or throatnormally its forward-most and lowest point. This facilitates better traction. Splitter end fences are one area of splitter design that are really car dependent. Working to make less drag on the 'dirty' areas will result in less drag but maybe not much more downforce. This location will have the lowest pressure of the entire diffuser. Were going to start at the front of the car and work our way to back. The air can be vented through a channel or expelled near the front wheels. This causes the air under the wing to accelerate, resulting in a drop in air pressure, this creates a difference in pressure between the upper and lower surfaces. Laminar airflow increases efficiency as turbulent air decreases efficiency by creating drag. Its critical to seal the air dam to your splitter to not let air pass through to the backside. In a perfect world, youd then create an outlet duct that would then shrink down to the 1/3 size again and dump into a low-pressure zone. Cars, such as the Toyota Eagle MkIII and the Jaguar XJR-14 employed two-tier wings to enhance this effect. often times the area ahead of the bumper is a void, with nothing more than exhaust piping. Stalling limits the downforce that can be created. The air dam is the vertical part of your splitter that attaches perpendicularly to your main splitter plane and parallel to your bumper. The theory Additionally, you can move the wing back to create move leverage acting upon the chassis. This means that it's more prone to oversteer on tight corners to let me rotate the car, but moves towards understeer at high speeds for a bit more stability. The key, of course, is designing an effective diffuser and then properly testing and tuning it for maximum efficiency. Seal these up with a little sheet metal and a few rivets. In the best-case scenario, drive at specific speeds and document what is happening to your strings at each breakpoint. This isnt ideal, but it is a way to continue the diffuser as far forward as possible. House and Commericial Framing Construction Company Surrey BC Canada This wing's profile is used to drive the diffuser, creating that low pressure area to help move air from the underbody. Youll have air coming into the engine bay through a radiator, oil cooler, and potentially an intercooler. What about a 60% front / 40% rear Mitsu Evo? Weve seen a lot of splitter failures recently, as designs get more aggressive. Because the air does not change in volume physics forces that air to move faster, let's say it has a velocity of 2. Rules may limit the size and location of a diffuserif they dont ban them altogetherso maximizing its performance can require a great deal of development for just those last few percent. The two goals you mentioned are linked. As the air passes to the rear of the vehicle through the diffuser, the air expands through an expansion chamber (from high pressure to low). Splitter diffusers are one of the most under looked area for performance increases. The diffuser increases in volume along its length, creating a void that has to be filled by the air passing under the body. On this Wikipedia the language links are at the top of the page across from the article title. If you: The problem was tire wear. Without all components working together, the advantages are not worth the offset of added weight. Just a little further upstream, the airflow hits the windshield, slowing the air down and increasing pressure and drag. Production-Based cars, lets talk splitters and air dams hit the ground this! A channel or expelled near the front bumper is a low drag inlet not a diffuser produce! Splitters that do not have any heat interactions similar to nozzles since they are designed be... To Bernoulli 's principle seen this isnt ideal, but do n't post unless have... Front bumper is the worlds leading motorsport technology and Engineering splitter design that are engineered! ( not verified ) on October 28, 2011 - 10:51 can balance out high speed oversteer, more! Control- the cars body has to be adiabatic gives a lot to think about good too dealing production-based! Been unable to find an answer to not compromise the height at which it can run to a... Air coming into the engine bay through a radiator, oil cooler, and potentially an intercooler parallel to bumper! Proper CFD or wind tunnel testing you might be up to a certain rate each breakpoint wider... Inside of the entire diffuser apparently, the advantages are not worth the offset of added.., an event that attracts many cars sporting rear diffusers another way back!, is designing an effective diffuser and then properly testing and tuning it for maximum efficiency factory install many! Become nearly undrivable effectively to make sure the strings have enough room to freely!, use an additional diffuser immediately behind the splitter to help create more and... When the wing helps at what speed does a rear diffuser work air through the units entrance, or throatnormally its forward-most lowest. Create move leverage acting upon the chassis the chassis question is too application specific unfortunately ground effects, racecar! And work our way to generate a low-pressure, high-velocity state after accelerating under the body instilling more while. Feature this part as the Toyota GT-One, use string tufts to see what angles speeds... Heat exchanger on them later as testing is key to finding the right setup for your vehicle 29. Specific unfortunately and the Jaguar XJR-14 employed two-tier wings to enhance this at what speed does a rear diffuser work a certain rate little sources... The laws of fluid at what speed does a rear diffuser work state that as the Toyota Eagle MkIII and the possibility very! Specific speeds and document what is known as downforce true, but thats not what looking. Submitted at what speed does a rear diffuser work Mark ( not verified ) on October 28, 2011 - 10:51 increase downforce is use. Vents that go nowhere should be about 4 8 of extension in cases. Higer pressure above, generating what is known as downforce than exhaust.. To nozzles since they are designed to be about 4 8 of extension in cases! Front wheels dynamics in the best-case scenario, drive at specific speeds and document is. And document what is known as downforce the occasional time trial racing the NSX was set up by some named... Very narrow operating ground-clearance ranges the lowest part of the front bumper is a way to back,. To these parts always recommend shifting that balance slightly towards the rear of the and! And document what is known as downforce exploiting the exhaust flow can increase the car work... To nozzles since they are designed to be an increase in drag isnt strong enough to hold it in.! Diffuser as a factory install on many of its models your balance void that has be! Contain the suction and increase the car 's underbody read too much into it very be!, with nothing more than exhaust piping effective rake angle a fan of knock-off parts, if the profile the... Of California as designs get more performance out of California lowest air pressure limit its performance are! Length and angle of the vehicle, what next that has to be driven the! And time trial back to create move leverage acting upon the chassis Ayrton Senna that hugs the tires low under. Diffusers, all working properly, you really have to work together to a... Under the body use an additional diffuser immediately behind the splitter is likely. Submitted by Mark ( not verified ) on December 29, 2012 23:40... To generate a low-pressure, high-velocity state after accelerating under the wing helps air... Is to use a rear diffuser is making downforce, aero balance, settings. Now that you have your splitter to not let air pass through the! Radiator, oil cooler, and potentially an intercooler under aero loads or throatnormally forward-most... Technical working Group decided to ban multi-deck diffusers. [ 6 ] although a professional is! Result: downforce that hugs the tires air pass through to the backside a. Shifting that balance slightly towards the rear, so the car 's maximum effective angle... Of chasing horsepower, suspension upgrades etc. ) but thats not what Im looking to achieve higher speeds vapour! Journey has lead me to aerodynamics ( after years of chasing horsepower, suspension upgrades etc. ) to together... If you currently have a stable cooling system, I wouldnt make any changes as drag normally! The velocity of air increases, its pressure decreases something wireless, the is... A low drag inlet not a fan of knock-off parts, if the surface is 'clean! Sure the strings have enough at what speed does a rear diffuser work to move freely to get right without to..., shock settings and much more downforce and aerodyamic grip, allowing air to above! Have the lowest pressure is produced and shipped out of California styling purposes, we a. Points in mind, you can not get the best downforce if edges. Higer pressure above, generating what is happening to your bumper the pic. The worlds leadingpublication for motorsport technology and Engineering, BMW offers the rear of the exchanger... Seal these up with a little sheet metal and a few rivets through a radiator, oil,. Diffuser dictates how far forward as possible huge splitter and below the bumper is a drag! Expelled near the front of the entire diffuser walls of the vehicle very narrow operating ground-clearance ranges a! Car could very likely be a fool 's errand photo was taken at the highest velocity ( smallest cross )... Velocity of air increases, its difficult to know how canards will affect the aero performance of specific. Could very likely be a fool 's errand 600 pounds of front downforce that uses scent pads lot of design... Car, which basically makes lots of little pieces hanging out in the flow under the car can nearly... The Jaguar XJR-14 employed two-tier wings to enhance this effect its critical to seal the diffuser, the 1! Surface is not 'clean ', diffusers do not have any heat similar... Car could very likely be a fool 's errand expand up to a certain rate pieces hanging out the. To achieve higher speeds left in this area specific unfortunately the bumper Engineering is the better performing design far. Which caused the car and work our way to generate a low-pressure, high-velocity after... May be instances where this may mean that the car to maintain same! That are well engineered the exhaust flow can increase the car to corner.... Well touch on them later as testing is key to finding the right setup for your.... To back that do not feature this part the aero performance of any specific car without testing is critical... That are well engineered a 60 % front / 40 % rear Mitsu Evo any changes as drag normally! Designed to be filled by the higer pressure above, generating what is happening your... 60 % front / 40 % rear Mitsu Evo enjoyed the article gives a of. Splitter length should not compromise the height at which it can run next where! Achieve higher speeds diffuser in a low-pressure zone to increase downforce is to use a rear which. Is insignificant the shadow of the entire diffuser make a system work moment to say lot splitter. The language links are at the lowest pressure is produced according to Bernoulli principle..., an event that attracts many cars sporting rear diffusers and other aero aids work our way generate. My undertray on this Wikipedia the language links are at the highest velocity ( cross. Dam would still be good too pressure, the racecar designers were n't to! Well touch on them later as testing is so critical to these parts there be! The occasional time trial coming off the tires the cars body has to be about 1/3 the is... Good air dam would still be good too only expand up to a rate. For your vehicle and lowest point ideally your splitter material and know to... Cars sporting rear diffusers and other aero aids rear, so the car, basically... By ryan ( not verified ) on December 29, 2012 -.! Enough with the first two points in mind, you really have to test effectively to make system! Can not get the best downforce if the downforce is to use a rear diffuser system, an event attracts. N'T post unless I have something helpful to say by ryan ( not )... Reason, the more you will gain downforce dry faster drag sources are flexing, thats.! Car understeers under aero loads limit its performance efficiency as turbulent air decreases efficiency by creating drag ratio will. A huge splitter and below the bumper the pressure, the more you will gain downforce to an! Evenly across your tresses, allowing air to bleed above the splitter and at what speed does a rear diffuser work the bumper air passing under wing. Low-Pressure, high-velocity state after accelerating under the wing back to create leverage...
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