Wings / Drag / Downforce
07-03-2006, 08:41 AM
#1
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Wings / Drag / Downforce
Further to my comments in the v-max thread:
Those in the know explained the destruction of my splitter was due to removing the top part of my rear spoiler. They explained it as such that the removal of the piece will have reduced the rear down force, hence meant the front end would be angled further down. This change in angle would cause the splitter to feel more force from the air than before, and hence cause it to break.
A friend there with a standard turbo wing plus GT2 front splitter also sadly found his (brand new) splitter had leanings to try to detach itself from the car.
So, as you may imagine, I wish to reduce drag to get higher speeds, but not at the expense of down force and the health of my front splitter. The GT2 front splitter is a must at these speeds IMHO, so I am alittle lost to what options I have for the rear spoiler considering its effect on the front.
Turbo S rear spoiler is an option, though I assume it still produces a lot of drag given its shape? Certainly more than the standard melted cheese type, which as shown seems not be a happy companion with the GT 2 front splitter.
Can anyone offer any help please?
Those in the know explained the destruction of my splitter was due to removing the top part of my rear spoiler. They explained it as such that the removal of the piece will have reduced the rear down force, hence meant the front end would be angled further down. This change in angle would cause the splitter to feel more force from the air than before, and hence cause it to break.
A friend there with a standard turbo wing plus GT2 front splitter also sadly found his (brand new) splitter had leanings to try to detach itself from the car.
So, as you may imagine, I wish to reduce drag to get higher speeds, but not at the expense of down force and the health of my front splitter. The GT2 front splitter is a must at these speeds IMHO, so I am alittle lost to what options I have for the rear spoiler considering its effect on the front.
Turbo S rear spoiler is an option, though I assume it still produces a lot of drag given its shape? Certainly more than the standard melted cheese type, which as shown seems not be a happy companion with the GT 2 front splitter.
Can anyone offer any help please?
07-03-2006, 12:26 PM
#2
Nordschleife Master
Mod55,
Sorry to hear about that front splitter. I'm anxious to hear what people might have to say. I'm wondering if there are any secrets to share... it seem like a pretty simple tradeoff... if you want downforce, you pay with drag. The only secret would be determining how little downforce you can use in a straight, high speed run (as opposed to downforce required for cornering).
Sorry to hear about that front splitter. I'm anxious to hear what people might have to say. I'm wondering if there are any secrets to share... it seem like a pretty simple tradeoff... if you want downforce, you pay with drag. The only secret would be determining how little downforce you can use in a straight, high speed run (as opposed to downforce required for cornering).
07-03-2006, 03:54 PM
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You will have absolutely zero problems with the stock wing even at 200+mph.
Ask Ruf or Auto Motor Sport magazine that test drove the 993 turbo R with stock wing at 328kph.
Buy a used set of stock wings and front just for the Vmax and drive your GT2 style else.
Ask Ruf or Auto Motor Sport magazine that test drove the 993 turbo R with stock wing at 328kph.
Buy a used set of stock wings and front just for the Vmax and drive your GT2 style else.
07-03-2006, 07:07 PM
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every pro driver that has driven my car (normal TT front-rear spoiler) has said there is not enough front end down force for good turn-in on a track.
What front setup do you guys think works if the gt2 splitters do not stay on.
What front setup do you guys think works if the gt2 splitters do not stay on.
07-03-2006, 07:57 PM
#5
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Rob,
Mod55 was having trouble with his GT2 splitter at very, very high velocity, and with no rear wing, which may have added to a nose-down attitude. For more normal track speeds, the GT2 splitter should be fine... but perhaps a bit much for the stock rear wing. The trick is balance between the front and rear wings. With the stock rear wing (or the turbo S rear wing), you may want to add the S spoiler lip to your stock front bumper. IMHO.
You may also want to consider changing your alignment, using wider front wheels/tires, or adjusting your swaybars to get better turn-in. The aero aids work best at higher speeds.
Mod55 was having trouble with his GT2 splitter at very, very high velocity, and with no rear wing, which may have added to a nose-down attitude. For more normal track speeds, the GT2 splitter should be fine... but perhaps a bit much for the stock rear wing. The trick is balance between the front and rear wings. With the stock rear wing (or the turbo S rear wing), you may want to add the S spoiler lip to your stock front bumper. IMHO.
You may also want to consider changing your alignment, using wider front wheels/tires, or adjusting your swaybars to get better turn-in. The aero aids work best at higher speeds.
07-03-2006, 08:45 PM
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The turbo S front spoiler will work well with the GT2 wing as long as the setting is at the least aggressive setting.
Thanks to Dr. Larry Armi, who did the calculations the GT2 wing will produce 6 mph of drag at 150 mph at 6 deg which is the max adjustment for the wing. We confirmed this at Willow Springs inconjunction with the GT2 front spoiler. The key is to balance thats why the rear wing is adjustable.
Jimmy the fugitive
Thanks to Dr. Larry Armi, who did the calculations the GT2 wing will produce 6 mph of drag at 150 mph at 6 deg which is the max adjustment for the wing. We confirmed this at Willow Springs inconjunction with the GT2 front spoiler. The key is to balance thats why the rear wing is adjustable.
Jimmy the fugitive
07-04-2006, 08:34 AM
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MOD, you certainly get affected by your GT2 wing at higher speeds.
I think there are 2 approaches to this very interesting and vague topic
Practical Approach:
The practical approach to determine this is by doing an actual drag test with a tool like the AX22. You simply let the car decelerate between 2 high speeds (for drag calculation) and two slow speeds (for rolling drag). The software will tell you what sort of CD you have.
The other practical approach is by comparing 2 runs, one with the wing and the other without it on the same stretch of road using the Ax22 as well. One right after the other preferably (JJayB?).
Other example, we saw a 2-3 mph top speed reduction (from 154mph if I recall correctly) by the addition of this (see arrow) small CF guerney or lip to the rear spoiler of a Supercup car as datalogged by the factory Motec system, check out how small it is. The downforce gained is worth it however on certain tracks (In Bahrain here).
Theoretical approach:
I asked TB993TT if he had any drag data of our cars, which he kindly sent me, the drag coefficient of the stock 993TT is Cw 0.34 and the area is 1.93sq.m. This gives you a CDA of 0.656 for a stock TT.
A 993RS has a CDA of 0.614, (0.33 x1.86) being NB with aerodynamic improvements and smallish wing.
The addition of the Clubsport wing to an RS at 0 degrees increased the Cw to 0.34 from 0.33, and at 9 degrees to 0.36. The RS CS wing is quite similar to the GT2. At 4 degrees it might be safe to assume a Cw of 0.35 approx.
Applying this to the 993TT, one can asusme that the GT2 wing will add the Cw from 0.34 to 0.36 at about 4 degrees slope.
To the calculation of power needed to move the car:
P= 0.5 X Air Density X Area X CD X Speed^3 (use a software, it is faster)
and assuming sea level and barometric conditions,
Then the HP loss for the 993TT stock at 183mph is: 289HP
HP loss for a GT2 winged (4 degrees) 993TT at 183mph: 306HP
Net difference: 17HP. A difference of about 2-3 seconds to reach 183mph at around 70meters (230ft.)/second!
A loss of 5-6mph as mentioned by JJayB is very realistic.
Disclaimer: Please take all the above as directional only! I am not an engineer.
I think there are 2 approaches to this very interesting and vague topic
Practical Approach:
The practical approach to determine this is by doing an actual drag test with a tool like the AX22. You simply let the car decelerate between 2 high speeds (for drag calculation) and two slow speeds (for rolling drag). The software will tell you what sort of CD you have.
The other practical approach is by comparing 2 runs, one with the wing and the other without it on the same stretch of road using the Ax22 as well. One right after the other preferably (JJayB?).
Other example, we saw a 2-3 mph top speed reduction (from 154mph if I recall correctly) by the addition of this (see arrow) small CF guerney or lip to the rear spoiler of a Supercup car as datalogged by the factory Motec system, check out how small it is. The downforce gained is worth it however on certain tracks (In Bahrain here).
Theoretical approach:
I asked TB993TT if he had any drag data of our cars, which he kindly sent me, the drag coefficient of the stock 993TT is Cw 0.34 and the area is 1.93sq.m. This gives you a CDA of 0.656 for a stock TT.
A 993RS has a CDA of 0.614, (0.33 x1.86) being NB with aerodynamic improvements and smallish wing.
The addition of the Clubsport wing to an RS at 0 degrees increased the Cw to 0.34 from 0.33, and at 9 degrees to 0.36. The RS CS wing is quite similar to the GT2. At 4 degrees it might be safe to assume a Cw of 0.35 approx.
Applying this to the 993TT, one can asusme that the GT2 wing will add the Cw from 0.34 to 0.36 at about 4 degrees slope.
To the calculation of power needed to move the car:
P= 0.5 X Air Density X Area X CD X Speed^3 (use a software, it is faster)
and assuming sea level and barometric conditions,
Then the HP loss for the 993TT stock at 183mph is: 289HP
HP loss for a GT2 winged (4 degrees) 993TT at 183mph: 306HP
Net difference: 17HP. A difference of about 2-3 seconds to reach 183mph at around 70meters (230ft.)/second!
A loss of 5-6mph as mentioned by JJayB is very realistic.
Disclaimer: Please take all the above as directional only! I am not an engineer.
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07-04-2006, 08:41 AM
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OK, my post above was totally OT 
To be on topic, If you want to keep your GT2 wing, you certianly need to have a good front lip, you need to make sure you don't have any lift at high speeds, it is very dangerous especially in winter conditions with aquaplanning.
It is very likely that your front lip broke because of the removal of the rear wing, however, I would bet that it is a defective unit, if both you and your friend (with stock TT wing) had the same issue?
Check out the wing that Leon has on if RUF, that is a beautiful addition and seems to have very good aerodynamic qualities, certainly much less drag that the GT2 wing.
To be on topic, If you want to keep your GT2 wing, you certianly need to have a good front lip, you need to make sure you don't have any lift at high speeds, it is very dangerous especially in winter conditions with aquaplanning.
It is very likely that your front lip broke because of the removal of the rear wing, however, I would bet that it is a defective unit, if both you and your friend (with stock TT wing) had the same issue?
Check out the wing that Leon has on if RUF, that is a beautiful addition and seems to have very good aerodynamic qualities, certainly much less drag that the GT2 wing.
07-04-2006, 08:13 PM
#10
Why do I feel so left out!
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Slightly O/T!
GREAT!! 
Now that I have FINALLY tracked down a GT2 wing for my car and had gone through all of the justification in my head AND have obtained full WAF (wife approval factor) this thread comes along and makes me think that I actually shouldnt get one......for real reasons - rather than cosmetic.....
Is there any reason, considering I cant do V-MAX in this country and on the straight at "the Creek" I cant recall ever seeing over 250km/h (if actually that fast
) that I shouldnt get it??
Yes I want it, Yes I like it just for the look, Yes I NEED it.... but if it is going to do bad things to the car.... I will just have to suffer?????
I have the TT "S" front lip on my car - does this make a difference?
Eternally upset.....
Simon
Now that I have FINALLY tracked down a GT2 wing for my car and had gone through all of the justification in my head AND have obtained full WAF (wife approval factor) this thread comes along and makes me think that I actually shouldnt get one......for real reasons - rather than cosmetic.....
Is there any reason, considering I cant do V-MAX in this country and on the straight at "the Creek" I cant recall ever seeing over 250km/h (if actually that fast
) that I shouldnt get it?? Yes I want it, Yes I like it just for the look, Yes I NEED it.... but if it is going to do bad things to the car.... I will just have to suffer?????
I have the TT "S" front lip on my car - does this make a difference?
Eternally upset.....
Simon
07-05-2006, 01:34 AM
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Rob,
From the pictures posted a while back, it seemed to me like Leon's wing was flat on the sides, while looking like a 993TT stock wing, it was not. It was really nice in fact.
Simon,
the GT2 wing will certainly not help fuel consumption or acceleration. On the track it has big advantages, and then you have the looks, if you like it. I would not worry much about it. The GT2 flares and fat tires will be worse than this provided you keep the wing at decent slope level.
These speed and acceleration nutheads we have in this forum are just too picky
OTOH, do you know many people who are willing to pay money to loose HP?
From the pictures posted a while back, it seemed to me like Leon's wing was flat on the sides, while looking like a 993TT stock wing, it was not. It was really nice in fact.
Simon,
the GT2 wing will certainly not help fuel consumption or acceleration. On the track it has big advantages, and then you have the looks, if you like it. I would not worry much about it. The GT2 flares and fat tires will be worse than this provided you keep the wing at decent slope level.
These speed and acceleration nutheads we have in this forum are just too picky
OTOH, do you know many people who are willing to pay money to loose HP?
07-05-2006, 10:59 AM
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I'm going to stick my neck out and venture a guess that the reason the splitters came off is because they weren't mounted properly and/or have been loosened from kerbs and driveway entrances and the like. The higher speeds with the RS Tuning engine just put more load on them. While removing the upper portion of the GT2 rear wing will reduce downforce generated by the wing I can't help but think that you would get greater changes in the car's rake from undulations in the driving surface and from squat and dive in the (relatively) soft suspension.
Put another way, how much does several hundred pounds of weight placed over the engine compress the rear springs? And what's the resulting change in front ride height?
I freely admit I don't have any hard data to back up the above and am happy to be shown the error of my ways. And I'm not trying to wind anyone up, just posting my thoughts.
Put another way, how much does several hundred pounds of weight placed over the engine compress the rear springs? And what's the resulting change in front ride height?
I freely admit I don't have any hard data to back up the above and am happy to be shown the error of my ways. And I'm not trying to wind anyone up, just posting my thoughts.