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Couple of things. We didn’t post exact angles, adjustments, heights, wing or splitter details; or exact results because they are proprietary. Sorry. We are not looking for validation of our tests; just sharing our conclusions. We have worked with the scientists, researchers, engineers and staff at the university to develop a system and process that takes all the science and gives us net aero force data that racers can understand and use. All of the down force, lateral force and drag values were actual forces recorded by the system rather than calculated and inferred data.
The car with the restricted air intake in the front did gain front down force while still maintaining adequate cooling. The car does have vents in the hood and will most likely get more. We ran a tufted version of the car a few weeks ago in the tunnel and got to see where the flow and high/low pressures areas were at race speeds.
We were testing three different cars, each over a number of different configurations and all over a range of speeds so we did not have time to do any tests in yaw. The dyno plate/floor in the tunnel at ACE/UOIT can rotate so that is something we would like to look at. The tunnel climate is also controlled and can actually be programmed to simulate any temperature and any humidity.
...and J Richard, I think the problem is your vehicle has too much caster.
Also don't forget Mark that you're kinda talking in absolutes. As in a 911 has X roof angle, 928 Y...etc but as you yourself have said, what happens during a turn? (Turns and downforce go hand in hand) As the cars in question aren't wedged shaped in the rear quarters there are curves involved which are going to have an effect on the wing edges. This is also dependent on how wide the wing is plus all the the other aero going on at the front and middle of the car that has an effect on the wing. Canards/dive planes being a prime example that can disrupt the rear wing adversely. This is why a lot of cars have had these removed more recently. Wind tunnels are great but they can be somewhat 2 dimensional. Track testing might be anecdotal, but they would be able to fine tune this just a tad more than your 'Washed car' simile. Teams put a lot of time and money into testing which bears fruit.
Couple of things. We didn’t post exact angles, adjustments, heights, wing or splitter details; or exact results because they are proprietary.
We are not looking for validation of our tests; just sharing our conclusions. We have worked with the scientists, researchers, engineers and staff at the university to develop a system and process that takes all the science and gives us net aero force data that racers can understand and use.
All of the down force, lateral force and drag values were actual forces recorded by the system rather than calculated and inferred data.
It's important to point out that while the details and results are proprietary, the science of measure and the general relationship between each component is known. You don't need external validation, because you have the results! <grin>
Race Tech International magazine, IIRC, has had a long running series of articles covering this very topic with changes throughout the workflow measured before and after.
I applaud your effort as a club-level racers to quantify this important information and do so in a proven, professional and scientific way!
It is most important that you find a happy medium using existing or fabricated parts. There's no silver bullet, but you can make your parts MUCH happier with one another AND imbue the driver with great confidence with the positive results of your test.
__________________ -Peter Krause www.peterkrause.net www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
Agree totally with Larry’s thoughts. Reality in this tunnel will tell you what works, how well it all works and how well balanced it is. Now you know what to do at different tracks. We have been working with the University to open up their world class research facility to all levels of racers; with practical, useable results in an accessible and affordable way. On Saturday in the wind tunnel with three different cars we did over 30 aero test runs and 1 thermal test in less than 5 hours.
Couple of things. We didn’t post exact angles, adjustments, heights, wing or splitter details; or exact results because they are proprietary. Sorry. We are not looking for validation of our tests; just sharing our conclusions. We have worked with the scientists, researchers, engineers and staff at the university to develop a system and process that takes all the science and gives us net aero force data that racers can understand and use. All of the down force, lateral force and drag values were actual forces recorded by the system rather than calculated and inferred data.
The car with the restricted air intake in the front did gain front down force while still maintaining adequate cooling. The car does have vents in the hood and will most likely get more. We ran a tufted version of the car a few weeks ago in the tunnel and got to see where the flow and high/low pressures areas were at race speeds.
We were testing three different cars, each over a number of different configurations and all over a range of speeds so we did not have time to do any tests in yaw. The dyno plate/floor in the tunnel at ACE/UOIT can rotate so that is something we would like to look at. The tunnel climate is also controlled and can actually be programmed to simulate any temperature and any humidity.
first of all, thanks for the discussion and sharing the data that doesn't give away any competitive secrets
I don't know why there is so much push back for the things I am suggesting. im taking very valid wind tunnel data of similar wings and the the GF effects on those wings, and transferring the basic data/info to our GT3 cup wings.
This is for the quest for answers, based on what would be best for my car
you had all the engineers, scientists, etc etc, and yet, the one thing that the wing does, is provide downforce in the turns, yet you didn't even check how the turning (or side angled/ yaw) air flow would effect downforce. why are my assumptions or theories any less valid?
I know you don't want to share wing angles and actual data, but for the discussion here... and the main point and question is : Gurney flap or not for low wing angles (angles of incidence). however, all you have told us is that you used the wing at a more neutral position (which could be 2-4 degrees) and added the GF and found it had less drag than the "angled wing " for same downforce. GREAT info and we all knew this from the discussion for wings that were at or over max lift potential of the wing without GF. (10-12 degrees for GT3 cup wing) However it would be interesting to know if that more neutral position was 0 or something higher.
what we know:
1. The GT3 cup car wing has a max lift at 10-12 degrees. after that, drag continues to increase , while lift slowly falls off.
2. we (I) suspect the GT3 cup car wing at 0 AoA with a gurney flap will produce more drag than the same downforce (lift) than a clean wing at 7-8 degrees AoA.
3.The roofline of a 911 (like a cayman) is 15 degrees and the air deflection is 12.5 degrees . the roofline air deflection of the 928 is 8 degrees (both based on capturing air flow stream pictures and measuring the angle)
4. Based on #3, a "0" angle setting of the wing, still puts it above max lift, where drag and jumps almost double in most all wind tunnel test of all wings.
So, based on what we know from the GF wind tunnel tests and simulations, you can be in your own wind tunnel , testing a wing at 0, and have it be over max lift....by several wing degrees... while the drag might be 1-200% higher than optimum. you can then put a gurney flap on that wing set at 0 and find that the downforce is much higher and the drag is lower as the GF puts the wing out of the stall zone at lower AoAs and thus it would produce a lot less drag.
Now, couple all this information, including the air deflection from roof line, and realize all cars are a little different, as well as wing height, and look at the turning of the car..... folks , this is where you want the downforce. but what happens. most of the wing is getting air from the side of the car where there is no roof line to defect it.... this means when you want or need the downforce most, you will effectively have less AoA. the rear lifts up, the front gets even more downforce and the car now is more unstable than you would want it to be.
This brings me to my point of all this..... all the above doesn't matter if the car is driving well. however, by knowing how wings react, you might be able to get the same downforce with less wing angle, especially if you were way in the stall zone. Maybe not... maybe because the car is turning much of the time , and the AoAs are changing, maybe the GF gives a more usable range of downforce with overall less drag due to a wider range of high downforce use.
Ill go out this afternoon with some streamers off the roof line and take some video of how much deflection the roofline makes to my car, as well as in a turn, how much angle is changed laterally, and see if the deflection angle changes as well. (im going to pull a Jack Olsen again)
Again, the point of all this is to optimize what you have... if the car is running well, you are not gong to change anything that is going to change the balance of the car, I most cases. however, if you can make it better, like if you had a push and now you were able to gain more frontal downforce by closing off the air inlets, then that's what you do. at the track, it might make the car unstable and require more rear downforce, and that's what the on track testing is all about. BUT, If you are able to keep things the same and reduce drag, (my goal), then by gaining knowledge of how these wings react to certain angles and flows, you might be able to save 8-10 hp down the straight and not change anything... that is my goal and that could have been the result of Mikes Ferrari at RA, when he wanted to run 0 AoA with a GF.... in his case and maybe mine as well, his car might have had much less drag for the same downforce with wing angle alone.
none of the data so far presented shows otherwise. clean wings all seem to produce much less drag up to 7-8 degrees AoA vs 0 AoA for a wing with GF. the caveat here is, are you really at 0 AoA after roofline deflection? From the windtunnel video , the ferarri sure seems like it.... my car is at 8 degrees and the cayman/911 seems to be more like 12.5 degrees.
Also don't forget Mark that you're kinda talking in absolutes. As in a 911 has X roof angle, 928 Y...etc but as you yourself have said, what happens during a turn? (Turns and downforce go hand in hand) As the cars in question aren't wedged shaped in the rear quarters there are curves involved which are going to have an effect on the wing edges. This is also dependent on how wide the wing is plus all the the other aero going on at the front and middle of the car that has an effect on the wing. Canards/dive planes being a prime example that can disrupt the rear wing adversely. This is why a lot of cars have had these removed more recently. Wind tunnels are great but they can be somewhat 2 dimensional. Track testing might be anecdotal, but they would be able to fine tune this just a tad more than your 'Washed car' simile. Teams put a lot of time and money into testing which bears fruit.
Yep, I totally agree with you. ill do some tests today that might be telling for what happens to the airflow in a high speed turn. all the things you say are true. testing on track gives the result, but you never know if you are wall over the range of a given wing, if you don't test its full range. I would bet many haven't tested their cup car wing on a 911 with negative 2 degrees (to give near 11 degres true AoA) and then compare it to a gurney flap at negative 7 degrees. it just seems counter intuitive, but, its the kind of testing that might prove to be valuable at high speed tracks, where most might be running wings on a 911 , well past max lift, and not know it. (having set a wing at 5-7 degrees, puts the GT3 wing at near 20 degree AoA. lift might still be the same as 10 degrees, but the drag might have gone up 500%........ that's really my point here.
on a Ferrari.....Totally different, just as my 928 is as well. add some turns to the equation and all sorts of things change. when you turn, what does that wing look like to the air????? well, its cord is lengthened, and its width is shortened.
there is no doubt after seeing the roofline deflection that the 911 needs the GF to give downforce at a lesser drag than the wing alone MAINLY because the wing alone at low to 0 wing angles is still in the stall range (past max Cl)
my car??? its debatable...... if my wing was good set at 8 degrees plus a roof line deflection of 8 degrees , that's 16 degrees.... since the Cl doesn't change that much, but drag does, I can back the wing out 5 degrees and get the same downforce but less drag. (and operate at 3 degrees angle of incidence)...... the question is where with a GF would equal that downforce? it might be negative 3 degrees and it probably would have slightly more or the same drag..... as the graphs show at max Cl vs GF at the same downforce.
[QUOTE=chartersb;11776375]
The car with the restricted air intake in the front did gain front down force while still maintaining adequate cooling. The car does have vents in the hood and will most likely get more. We ran a tufted version of the car a few weeks ago in the tunnel and got to see where the flow and high/low pressures areas were at race speeds.
We were testing three different cars, each over a number of different configurations and all over a range of speeds so we did not have time to do any tests in yaw. The dyno plate/floor in the tunnel at ACE/UOIT can rotate so that is something we would like to look at. The tunnel climate is also controlled and can actually be programmed to simulate any temperature and any humidity.
QUOTE]How do you determine that the cooling is adequate? I see that you ran tufts on the hood. Just to clarify terminology, on a rear engine car where is the hood in this context? Are all the cooling cores in the front of these cars? I assume they are but excuse the ignorance.
That would be great if you can run some similar tests in Yaw conditions.
Originally Posted by mark kibort
Yep, I totally agree with you. ill do some tests today that might be telling for what happens to the airflow in a high speed turn. all the things you say are true. testing on track gives the result, but you never know if you are wall over the range of a given wing, if you don't test its full range. I would bet many haven't tested their cup car wing on a 911 with negative 2 degrees (to give near 11 degres true AoA) and then compare it to a gurney flap at negative 7 degrees. it just seems counter intuitive, but, its the kind of testing that might prove to be valuable at high speed tracks, where most might be running wings on a 911 , well past max lift, and not know it. (having set a wing at 5-7 degrees, puts the GT3 wing at near 20 degree AoA. lift might still be the same as 10 degrees, but the drag might have gone up 500%........ that's really my point here.
on a Ferrari.....Totally different, just as my 928 is as well. add some turns to the equation and all sorts of things change. when you turn, what does that wing look like to the air????? well, its cord is lengthened, and its width is shortened.
there is no doubt after seeing the roofline deflection that the 911 needs the GF to give downforce at a lesser drag than the wing alone MAINLY because the wing alone at low to 0 wing angles is still in the stall range (past max Cl)
my car??? its debatable...... if my wing was good set at 8 degrees plus a roof line deflection of 8 degrees , that's 16 degrees.... since the Cl doesn't change that much, but drag does, I can back the wing out 5 degrees and get the same downforce but less drag. (and operate at 3 degrees angle of incidence)...... the question is where with a GF would equal that downforce? it might be negative 3 degrees and it probably would have slightly more or the same drag..... as the graphs show at max Cl vs GF at the same downforce.
You're probably right although we have no proof of this. We could guess that 'they' assume that the wing has been tested thoroughly by the factory at extreme AoA and therefore the teams run within more acceptable positions.
On a side note, when I first started looking at Aero some years ago I used to wonder why the factory came out with the wing that went on some later 944s. It appeared to be mounted in a upward position and I then concluded that it mustn't do anything and just be purely cosmetic. Of course that demonstrates quite clearly the point about the slope of the hatch in relation to the wing and therefore it is at a positive angle of attack despite contrary appearance from side on. (Couldn't find a better pic but in the flesh the front of this wing appears to be higher than the rear)
The proof of the pudding is in the eating. In other words, CFD and wind tunnels only give you so much data. The data you must rely upon ultimately is the data you get actually driving the car on the track.
The last test: we removed the wickers, the wings, the uprights, the big mirrors and found no measurable change in the drag, it's still slow but hard to pass.
The car with the restricted air intake in the front did gain front down force while still maintaining adequate cooling. The car does have vents in the hood and will most likely get more. We ran a tufted version of the car a few weeks ago in the tunnel and got to see where the flow and high/low pressures areas were at race speeds.
We were testing three different cars, each over a number of different configurations and all over a range of speeds so we did not have time to do any tests in yaw. The dyno plate/floor in the tunnel at ACE/UOIT can rotate so that is something we would like to look at. The tunnel climate is also controlled and can actually be programmed to simulate any temperature and any humidity.
QUOTE]How do you determine that the cooling is adequate? I see that you ran tufts on the hood. Just to clarify terminology, on a rear engine car where is the hood in this context? Are all the cooling cores in the front of these cars? I assume they are but excuse the ignorance.
That would be great if you can run some similar tests in Yaw conditions.
You're probably right although we have no proof of this. We could guess that 'they' assume that the wing has been tested thoroughly by the factory at extreme AoA and therefore the teams run within more acceptable positions.
On a side note, when I first started looking at Aero some years ago I used to wonder why the factory came out with the wing that went on some later 944s. It appeared to be mounted in a upward position and I then concluded that it mustn't do anything and just be purely cosmetic. Of course that demonstrates quite clearly the point about the slope of the hatch in relation to the wing and therefore it is at a positive angle of attack despite contrary appearance from side on. (Couldn't find a better pic but in the flesh the front of this wing appears to be higher than the rear)
yep the S4 stock wing was much bigger... same thing. it was actually looking like it was providing lift. I put on some 3 " risers and made it provide some good downforce. a real wing (GT3) provided twice the downforce at much less angle.
Kibort, do you purposely try to **** everyone off, or are you really that clueless?
Hey, coming from someone that is only here to be a Troll. Hmmm . You obviously haven't been reading the exchanges or understand even what im questioning or saying...... I think you have a little projection going on here!
I just contacted NASA about their FoilSim program, as I was finding some conflicting data there as well. I was more than surprised and was actually starting to second guess myself a little on why I was so concerned. But, just a few moments ago, THE author of the air foil simulator wrote me this very polite note. I also had an other exchange with the NASA folks about what I was concerned with, and basically they said I was dead on track... lots of variables to consider, many of which only draw more questions, even when gaining data from the wind tunnel as baselines and contrasts are hard and take time to determine:
see below >>>>>>>>>>> Hey Mark,
Your question was forwarded to me .. I'm the author of FoilSim.
I think you've found an error in the program.
As you mention (and as aerodynamicists know) the drag should increase with angle of attack after stall .. even though the lift decreases. I have done some checking on this .. very preliminary. The code is currently showing the drag decrease with angle of attack after stall. The drag is being calculated by some curve fits of experimental data. The data was obtained in a wind tunnel here at the lab. I have gone back and checked the original data ... and it shows (correctly) that the drag increases. So there must be some error in the curve fits of the data. I had a summer student obtain the data and produce the curve fits .... he used a feature in Excel to produce the curve fits. It looks like some error has crept in there. I'll have to do some further investigating and then correct the problem.
I just got back from testing with some streamers on the road at very high speed.
rolled into curve where it was perfect for a very high speed entrance and exit.
interesting output. I took two videos. one from the inside of the car pointed to the wing. the other from the side of the car (go pro) where you could see the angles of the streamers at speed.
1st...... the angle of roof line deflection is 8 degrees, just as I had seen on wind tunnel output.
2nd ... the angle didn't change, nor the direction of the air going over the roof and to the wing. both at a tight 60mph turn 270 degree turn, and at a high speed turn 90 degree.
3rd. the most interesting thing was that even during a straight line, the air flow off the side edges of the roof, ended up about 6" inward to the wing, and it stayed like that regardless of speed or turning. It was the dominant factor that didn't seem to vary much in turns, if at all.
the center string stayed straight , but the sides bowed in significantly inward....
what does this mean..... well, I don't think much changes in turns for AoA, so the yaw testing might not provide much data. The fact remains, I think, and I bet most here, have grossely underestimated the roof line deflection and max lift points (in degrees) of our wings.
It makes perfect sense that the cayman wind tunnel tests found the data that they did.
This doesn't me it fits for all cars, it fits for that wing and that car.
That car could have started out at well over max lift, as I think mind did as well, even at low wing angles because of the characteristics of the wing and the roof line flow deflection.
If you look at the Ferrari vs the 911 video tests, you can see the difference. Ferrari almost no defection by the time it hits the wing area. 911... pretty significant deflection. 0 angle of incidence equals near 12 degrees, which is at max lift point. based on the GF findings, there is no downside in using a GF with the same downforce at that point, with about 6 degrees negative angle of incidence. certainly, If higher angles were used without the GF, it would be so deep above max lift that the drag would be off the chart and lift would actually be lower than if the wing was horizontal.
on wings that have a true horizontal air flow into them... like the ferarri, if you wanted a flat wing with gurney flap downforce, it would be better to angle a clean wing up to about 7-8 degrees true AoA. This is my only point and is my concern as well for my set up.
I don't want to be right here, I just want the answers and to understand.
11-04-2014, 01:30 AM
