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Originally Posted by mx5-kiwi
(Post 1188077)
Well it's not very TOP SECRET now is it!!! :facepalm:
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Originally Posted by Leafy
(Post 1187638)
chevy isnt going to sell a car to the public that makes the majority of its downforce from under effects. Its exceptionally dangerous, see the lotus 79; kerbing, dips, and other surface imperfections were a good way to find yourself spinning off into the armco after loosing the majority of your downforce. Its the reason limits got put on under body aero in NASCAR back then.
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K
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CFD, wind tunnel testing, blah blah. Does anyone just have lap times under same conditions comparing their car with spoiler vs wing? Surely someone must have done it.
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How effective do you guys think these wheel vents are? I feel like it's mostly for looks with some function.
http://www.lotustalk.com/forums/atta...re-okkkkkk.jpg |
Originally Posted by MX5JER
(Post 1189244)
CFD, wind tunnel testing, blah blah. Does anyone just have lap times under same conditions comparing their car with spoiler vs wing? Surely someone must have done it.
Google it. They do two different things. Spoilers reduce the speed of the air moving over the trunk surface, thereby reducing the lift created through the principle identified by the 16th century Swiss mathematician Bernoulli. A rear "wing" is an airfoil making use of the airflow to generate force exerted downward. So, essentially one eliminates lift and the other creates downforce. Both actually make use of Bernoulli's principle but in different ways. |
Originally Posted by sixshooter
(Post 1189259)
They do two different things. Spoilers reduce the speed of the air moving over the trunk surface, thereby reducing the lift created through the principle identified by the 16th century Swiss mathematician Bernoulli. A rear "wing" is an airfoil making use of the airflow to generate force exerted downward. So, essentially one eliminates lift and the other creates downforce.
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It depends on your horsepower level and the particular track. A big fucking wing will make slower laptimes on a faster track if you don't have the horsepower to overcome the drag created at high speed. So the answer is math.
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No, you just don't understand the question. The answer is not math. Because the question wasn't what will work for me. The question is what have others found in their own experiences? Which may or may not apply to my situation. Now some will take the position that they did the work and cost and choose to keep the info to themselves. Go pay to find your own answers. Totally justifiable. But others don't tend to think that way.
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Originally Posted by MX5JER
(Post 1189266)
The question is what have others found in their own experiences?
Originally Posted by sixshooter
(Post 1189263)
It depends on your horsepower level and the particular track.
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Originally Posted by SchmoozerJoe
(Post 1189272)
The answer is right there. No one size fits all.
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The answer is almost never so simple as you hope it to be, and the question is a bit too narrow-focused.
In terms of absolutes, the wing can generate more downforce than the spoiler (yes referring to the net effect of each as creating downforce for simplicity's sake). But back to back comparisons are few because the recipe for making the most of each differs. The real magic to increasing downforce on one end of the car is that you're then open to increase the downforce on the other end of the car to keep the car balanced and have an overall faster car. Generally, a front aero set up that pairs well with a spoiler will be insufficient for most wings, unless we're talking about spoiler vs. GTC-200 with stock endplates and at standard height, which I've seen pair decently with roughly the same front aero as a SuperMiata has, which run rear spoilers. Regarding balance, most miatas that are not anemic (140whp and up) can translate the benefits of more rear downforce into lowered lap times, even if the balance is less than ideal, and this is particularly true as power increases. Plenty of guys have experienced bolting a wing onto an otherwise un-aero'd car, pushed wildly all around the track, and still saw their lap times drop. In my own personal experience on my car, I ran a very aggressive spoiler with a modest splitter and nose with dive planes for a couple seasons long ago. When I changed up to a wing, I redesigned the nose and splitter to compensate, and dropped several seconds the next time I returned to a track I had ran previously. But these anecdotes are always flawed as undoubtedly there were other areas of the car that were improved in the same time, and even the driver is not completely consistent ;) -Ryan |
I totally understand your point that pure comparison data is hard to come by because conditions are never the same unless you go to considerable effort to make it so. But some people do that.
Here's a hypothetical of what I was hoping for: "Running the long course at LimeWillow I was doing 1:28s before aero, 1:27's with front and rear spoilers, and am currently down to 1:25's with a splitter/wing combo. No other significant changes during the aero upgrades." He is not me, his car is not mine and it's a different part of the country. So clearly his experiences are only of general interest. And of course I made it up, so no one take it seriously. But it's the type of info I was interested in. If you were to get a few responses, you might define the trend. I figure that's unlikely, but you never know if you don't ask. |
So, the answer is a spoiler is faster.
And a wing is faster. And both are faster than none at all. Unless they aren't. Big wing or spoiler + low power + fast track with few sweepers = slower A lot of F1 tracks are like that^. A COT wing is much lower drag than some other wings but also offers less downforce as a compromise. At some tracks certain cars will be faster with it than a spoiler car and on others the spoiler car will have better times. |
This is a stupid question if your rules allow a wing you run a wing because not only is it possible to make more downforce with the wing its also going to have a better lift to drag ratio. On top of that the endplates of the wing give you additional stability effects which the spoiler doesnt generate. If your rules allow both you can add a spoiler under the wing at a very low angle which will actually generate a bit of lift but noticeably reduce your drag.
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MX5JER, this is the thread you are looking for:
https://www.miataturbo.net/race-prep...ro-pics-63769/ |
Originally Posted by MX5JER
(Post 1189266)
No, you just don't understand the question. The answer is not math. Because the question wasn't what will work for me. The question is what have others found in their own experiences? Which may or may not apply to my situation. Now some will take the position that they did the work and cost and choose to keep the info to themselves. Go pay to find your own answers. Totally justifiable. But others don't tend to think that way.
If you have a spoiler, lower speed more downforce, and some drag, but at speed it makes tons of drag at high speed so will kill your top end A wing, will not make much downforce at low speed, and when at speed will give a lot more downforce, but due to its shape will not make near as much drag as the spoiler.. so you might have a track that has real technical section but then a high speed section.. it is at this point that you have to figure what works for *your* car, there is no one size fits all It is at this point where it does take math.. you might use a spoiler and gain 4 sec in the twisty bits, but then lose 3 sec in the high speed due to drag Then you put on a wing and you lose 3 sec in the twistys, but gain 4 in the high speed section So then you find out that maybe they are both making the same lap times.. but say you as a driver are more comfortable with the spoiler in the twistys because the car felt planted.. it will then be physiological to make the driver more comfortable. Hell, even if one set up has an overall slightly worse time, but you are consistsnt vs the car being on edge and about to spin out if you twitch the wrong way.. Maybe the car felt good with the wing, it all comes down to how you the driver feels about it. At this point it just comes down to your driving style and the car and then use math to figure the pros and cons for each |
Originally Posted by mx5autoxer
(Post 1189674)
MX5JER, this is the thread you are looking for:
https://www.miataturbo.net/race-prep...ro-pics-63769/ The reason I'm looking for quantitative results is to help decide how much money to throw at aero. Spoilers are much cheaper than wings and will allow money to be spent on better tires and suspension. I don't think I have the talent for a DIY high tech wing system, so if I go that way everything else on the car is going to have to wait a year. |
$/gains a cheap wing beats the hell out of a decent spoiler. You can get yourself into a cheap wing setup for a few hundred dollars for an APR GTC knockoff. Expect to spend quite a while and at least $150 for a spoiler thats going to do anything worthwhile and not look like a complete piece of redneck crap, and still be slower than the cheap wing setup.
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Originally Posted by Leafy
(Post 1189879)
$/gains a cheap wing beats the hell out of a decent spoiler. You can get yourself into a cheap wing setup for a few hundred dollars for an APR GTC knockoff. Expect to spend quite a while and at least $150 for a spoiler that's going to do anything worthwhile and not look like a complete piece of redneck crap, and still be slower than the cheap wing setup.
But they don't always look bad. https://www.miataturbo.net/attachmen...ine=1418822235 |
Most auto-x guys you see are running spoilers because thats all the street prepared or DP rules allow. My wing actually makes downforce below 45mph where the spoiler isnt noticable, make way more downforce at any other speed, and it makes less drag at all speeds than an SP spoiler. That corvette spoiler cost him about $70 for the piece of lexan and nearly $100 in fasteners. Yeah you can home depot something with luan and heavy steel shit from home depot for more like $60, but ass it will look like.
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Fantastic photos!
Porsche GT1 mmmmm, nice! |
Originally Posted by mx5-kiwi
(Post 1190123)
Fantastic photos!
Porsche GT1 mmmmm, nice! |
Some of those photos caused me to inadvertently let out some sexual noises in my office. Hope nobody heard.
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Great pics. Thanks for posting.
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Originally Posted by mx5autoxer
(Post 1190531)
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Originally Posted by mx5autoxer
(Post 1190531)
Originally Posted by cordycord
(Post 1190533)
Adjustable plane diffuser? Since that car is going for drag reduction over best traction, the vanes probably adjust based on speed to give the best Cd...my guess.
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That is an airfoil. In the downforce orientation..
Interesting that that whole diffuser assembly is made up of identifiable materials that certainly don't fall into the category of OE BMW level construction. -Ryan |
The diffuser fins were made of rubber instead of metal or composite
https://www.miataturbo.net/attachmen...ine=1418823278 |
Originally Posted by mx5-kiwi
(Post 1190123)
Fantastic photos!
Porsche GT1 mmmmm, nice! |
I will probably do the bottom of my diffuser fins in ABS or rubber/conveyor belt material so it won't get destroyed on rough courses.
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Originally Posted by cordycord
(Post 1190533)
Adjustable plane diffuser? Since that car is going for drag reduction over best traction, the vanes probably adjust based on speed to give the best Cd...my guess.
And btw I looked, but couldn't find any info on this because every bit of information out there is focused on the hydrogen engine instead of the aero. |
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I'm not seeing anything in that photo that implies that the airfoils adjust as anything more than fixed position. However, Andrew Brilliant runs an underbody wing in lieu of a traditional diffuser.
https://www.miataturbo.net/attachmen...ine=1419010104 I do wonder if there is a benefit to a "wing" underneath the car, as opposed to the more traditional diffuser, especially on cars that don't have a perfectly flat bottom to feed the wing. I know mounting a wing under the ass of my car would in my case be an easier install than a more traditional diffuser, and the increased ground clearance would be a welcome addition... |
Would aid in airflow re-attachment too wouldn't it? (drag reduction...)
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As an addition to the rearward part of a diffuser which is creating nice laminar, smooth flow to the airfoil, I like it. I like it less as an independent element just hanging out under the bumper. An airfoil relies on airspeed. Turbulent air is slow.
-Ryan |
Are you sure that's a wing element? I'm looking at the picture on my phone, but I'm not seeing it. Looks like a typical diffuser to me.
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Originally Posted by jpreston
(Post 1190746)
Are you sure that's a wing element? I'm looking at the picture on my phone, but I'm not seeing it. Looks like a typical diffuser to me.
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Spoilers create a great deal of drag as a consequence of the downforce. This is bad on track. Much less significant at auto-x speeds.
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Originally Posted by Supe
(Post 1190754)
Yes, to both photos. On AB's car, it's suspended between the two vertical strakes. Bit dark, but you can still make out the end plates and all.
https://www.miataturbo.net/attachmen...ine=1419032835 |
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Could be wrong, wonder if its been changed? Thought there used to be an open section forward of the diffuser/wing/whatever it is, but you're probably right.
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I've often wondered if you could do both... Using the picture of the c6r vette as a reference. One could use the a diffusor like this, albeit a large one with more clear space behind it... and drop an aerofoil in behind/beneath it. Although I'm not sure one could achieve this with the proper angle of egress for the speeds for our typical none of the horsepower speeds.
http://gearheadsmag.com/wp-content/u...ngTest2220.jpg the C7 used a similar setup but it was adjustable instead of fixed angle. http://i.ytimg.com/vi/tlo005zpq2c/maxresdefault.jpg Just to show the evolution - The c5r had a more standard diffusor/strake setup that us meer mortals are more familiar with. https://www.miataturbo.net/attachmen...ine=1419187379 |
Originally Posted by EErockMiata
(Post 1191010)
I've often wondered if you could do both... Using the picture of the c6r vette as a reference. One could use the a diffusor like this, albeit a large one with more clear space behind it... and drop an aerofoil in behind/beneath it. Although I'm not sure one could achieve this with the proper angle of egress for the speeds for our typical none of the horsepower speeds.
http://gearheadsmag.com/wp-content/u...ngTest2220.jpg the C7 used a similar setup but it was adjustable instead of fixed angle. http://i.ytimg.com/vi/tlo005zpq2c/maxresdefault.jpg Just to show the evolution - The c5r had a more standard diffusor/strake setup that us meer mortals are more familiar with. https://www.miataturbo.net/attachmen...ine=1419187379 edit--check out that massive transaxle cooler with fan on the back of the Corvette. :) |
Originally Posted by cordycord
(Post 1191015)
A diffuser only really works well when you also have a flat under-body. Unlike a standard wing, it is free aero as the only induced drag is already there (the car).
edit--check out that massive transaxle cooler with fan on the back of the Corvette. :) |
Wasn't the change to the new-style short/wide flat rear planes due to a change in the rules by IMSA that no longer allowed diffusers with vertical fins?
So an airfoil builds pressure on the top surface, and for a diffuser you want less pressure/faster moving air on the underside. These two interests clash a bit. A pressure map of a typical diffuser shows the majority of the vertical force happening at the beginning of the angle change, so that is where you would least want to have an airfoil undernath - that's ok because that wouldn't work anyways as there is no ground clearance there. So then looking further back... even though the forces are towards the front of the diffuser, the air's behavior all along the length of the diffuser dictate how effective it is. Placing the airfoil underneath the diffuser surface near the back (like the BMW on the last page) is going to create an obstruction to the diffuser's airflow as the topside of the airfoil slows air and builds pressure in the region between it and the diffuser. I think the best application of the idea would be for the airfoil to be placed behind the diffuser exit. Use a wing with swan-neck style mounts or mount via endplates, suspended from the rear of the car, and the wing aoa adjusted for the airflow angle coming out of the diffuser. This way, the pressure build up above the wing can occupy the space behind the center of the rear of the car, and the diffuser's function isn't jeapordized. That's how I'd do it at least.. but if the concept can work or not? Only one way for someone to find out. -Ryan |
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So this might not be aero related but, it is my thread. I think it's cool how the process of a test vehicle. So when I was at the Porsche Museum in Stuttgart Germany they had there Porsche 918 test car on display. So here are my pics
Production 918 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 918 Test Car https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 https://www.miataturbo.net/attachmen...ine=1419290853 |
Bloody Hell that has Mad Max or Back to the Future written all over it!
Pretty cool and intriguing to see that. |
How come my race cars always look more like the test mules than the production cars? :dunno:
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Originally Posted by ThePass
(Post 1187627)
On an F1 car, upwards of 50% of the downforce can come from the underbody/diffuser, and that is with significant limitations on what they can do. An unrestricted car built around the most effective floor/tunnels their engineers dream up could produce incredible downforce without the use of relatively high-drag elements like conventional wings.
-Ryan It's one of the most appealing and creative uses of unrestricted aero that I've ever seen. For My Ally Is The Force, And A Powerful Ally It Is - Speedhunters Not much obvious on the outside: https://www.miataturbo.net/attachmen...ine=1421510459 But inside: https://www.miataturbo.net/attachmen...ine=1421510459 https://www.miataturbo.net/attachmen...ine=1421510459 https://www.miataturbo.net/attachmen...ine=1421510459 Using the low pressure behind the car to suck air out from under the car. Lots of downforce with extremely minimal addition in drag, if any at all. It might even be a drag reduction since the low pressure zone behind the car is partially pulling on air under the car, and less on the car itself |
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This is something I am working on this weekend. I will be placing a quite a few NACA ducts in my underbody to help move air for cooling.
Before resin https://www.miataturbo.net/attachmen...ine=1421517444 and finished for now https://www.miataturbo.net/attachmen...ine=1421517444 https://www.miataturbo.net/attachmen...ine=1421517444 https://www.miataturbo.net/attachmen...ine=1421517444 |
What are you trying to achieve with the fibreglass rear?
Is there more to come? |
Originally Posted by yenadar
(Post 1197439)
https://www.miataturbo.net/attachmen...ine=1421510459
https://www.miataturbo.net/attachmen...ine=1421510459
Originally Posted by 1993ka24det
(Post 1197463)
But that's might be what RJ's showing? |
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I should show those NASA jocks how to REALLY torture the air with a Hornet!
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In the article I found these pictures, they were talking about outer most part of the diffuser isn't getting proper flow.
Rear Diffuser Issues - Forum - F1technical.net https://www.miataturbo.net/attachmen...ine=1422673187 https://www.miataturbo.net/attachmen...ine=1422673187 https://www.miataturbo.net/attachmen...ine=1422673187 https://www.miataturbo.net/attachmen...ine=1422673187 |
seems as though the strakes aren't doing what they are designed to do.
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So I was looking around again at diffuser designs and I seen what slimjim8201 wrote on f1technical.net.
Interesting data on Straight, convex and concave diffusers. Each are tested at 5, 10 and 15 degs. https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 https://www.miataturbo.net/attachmen...ine=1422740199 |
From that first set of images it looks like the strakes need to extend in front of the start of the diffuser. And thats on a car that already has a flat floor. Imagine how much of a disaster it looks like on a car without a flat floor.
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