| civicstealth | 08-15-2006 11:30 PM |
Aerodynamic Aids
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I've done about a dozen searches in the exterior section of the forums, and in the forums in general, and I learned about the different types of wings there are for Subarus, along with air dams, spoilers, body kits and their costs and availabilities. There was also some information on repairing and attaching them.
But no where did I find an in-depth discussion on their actual aerodynamic properties, in theory or in fact.
Now, I know that increased downforce increases traction because your car is being pushed down onto the road, allowing a vehicle to corner better at higher speeds. By observation, this is worth the added weight and drag costs the aerodynamic aids incur on the car--see F1, WRC, etc etc.
And I've read that Subaru and other manufacturers actually do design their air dams, wings, and other bits and pieces with this in mind, and actually test them in wind tunnels.
Some aerodynamic aids create downforce directly, others are used to create low or high pressure zones, others are used to channel air to brakes and coolers, and some are used to create a "slot effect" that reduces frictional drag.
I've come across two schools of thought on the forums here:
1. Aero aids and body kits look cool. I want one.
2. All these wings and other crappola are just added weight that makes you look like a ricer--rip 'em off and throw 'em away, you'll go faster.
There must be some kid of balance here somewhere (hopefully in the design).
Any other ideas? Also, any technical data on this subject in regards to Subarus? What do you all think? I'm open to anything and any kind of discussion. :p
But no where did I find an in-depth discussion on their actual aerodynamic properties, in theory or in fact.
Now, I know that increased downforce increases traction because your car is being pushed down onto the road, allowing a vehicle to corner better at higher speeds. By observation, this is worth the added weight and drag costs the aerodynamic aids incur on the car--see F1, WRC, etc etc.
And I've read that Subaru and other manufacturers actually do design their air dams, wings, and other bits and pieces with this in mind, and actually test them in wind tunnels.
Some aerodynamic aids create downforce directly, others are used to create low or high pressure zones, others are used to channel air to brakes and coolers, and some are used to create a "slot effect" that reduces frictional drag.
I've come across two schools of thought on the forums here:
1. Aero aids and body kits look cool. I want one.
2. All these wings and other crappola are just added weight that makes you look like a ricer--rip 'em off and throw 'em away, you'll go faster.
There must be some kid of balance here somewhere (hopefully in the design).
Any other ideas? Also, any technical data on this subject in regards to Subarus? What do you all think? I'm open to anything and any kind of discussion. :p
| rkramer | 08-15-2006 11:40 PM |
most, if not all, aero aids only come into effect at high speeds, 80+ mph or alot higher in some cases. the exception are air redirectors, like the ones that channel air to the brakes (and obviously the scoop) beyond that, lots of high performance cars do not have much for aerodynamics, so keep that in mind.
| 05wrxmatt | 08-15-2006 11:44 PM |
In terms of the front end, the only lip that I know of actually being tested is the STi V-Limited lip. Subaru designed it in a wind tunnel to reduce front end lift. It is also supposed to create a 36% increase in Cd (reduces drag).
| motohead125 | 08-16-2006 12:03 AM |
High performance cars dont have much for aerodynamics? wtf....Take one look at a ferrari F430 and tell me that thing wasnt designed around the aerodynamics, or the Enzo for that matter. NO SPOILER. Cmon now.
| TeRonde | 08-16-2006 12:10 AM |
A 36% increase in coefficient of drag is an increase in drag...not a decrease. You can't get increased downforce for free.
| Pocon | 08-16-2006 12:12 AM |
Prodrive intervened with the front redesign of the MY06 WRX. There's a diagram of an air tunnel comparison between the STi and Evo. Guess who's got the better profile?
| t3hWIT | 08-16-2006 12:40 AM |
[QUOTE=TeRonde]A 36% increase in coefficient of drag is an increase in drag...not a decrease. You can't get increased downforce for free.[/QUOTE]
TeRonde, meet the F430. ;) Sport Compact Car described it better, but I think this article explains it a bit.
[url="http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html"]http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html[/url]
TeRonde, meet the F430. ;) Sport Compact Car described it better, but I think this article explains it a bit.
[url="http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html"]http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html[/url]
| civicstealth | 08-16-2006 12:46 AM |
Great article on drag coefficient in general and in cars on particular, with a long list of past and present models at:
[url]http://en.wikipedia.org/wiki/Drag_coefficient[/url]
CD for WRX STi is listed as .33. Check out some of the other cars. And is there a comparison between the STi vs. WRX vs. RSi?
I agree that most of these aerodynamic aids don't start to help until 80+ mph, and they're cutting down on fuel econmy all the time--drag and weight. As someone pointed out, downforce comes at a cost.
How often do you drive at 80 mph? Well, it depends on what section of Interstate 95 you're on, I guess.
I've always thought a front lip is worthwhile, to keep the front end from getting light at highway speeds.
But are there any actually specs on this stuff anywhere?
[url]http://en.wikipedia.org/wiki/Drag_coefficient[/url]
CD for WRX STi is listed as .33. Check out some of the other cars. And is there a comparison between the STi vs. WRX vs. RSi?
I agree that most of these aerodynamic aids don't start to help until 80+ mph, and they're cutting down on fuel econmy all the time--drag and weight. As someone pointed out, downforce comes at a cost.
How often do you drive at 80 mph? Well, it depends on what section of Interstate 95 you're on, I guess.
I've always thought a front lip is worthwhile, to keep the front end from getting light at highway speeds.
But are there any actually specs on this stuff anywhere?
| civicstealth | 08-16-2006 12:49 AM |
[QUOTE=mi_cistemz_loudr]TeRonde, meet the F430. ;) Sport Compact Car described it better, but I think this article explains it a bit.
[url="http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html"]http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html[/url][/QUOTE]
Well, that's definitely not shaped like a brick....
[url="http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html"]http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html[/url][/QUOTE]
Well, that's definitely not shaped like a brick....
| civicstealth | 08-16-2006 12:51 AM |
[QUOTE=rkramer]most, if not all, aero aids only come into effect at high speeds, 80+ mph or alot higher in some cases. the exception are air redirectors, like the ones that channel air to the brakes (and obviously the scoop) beyond that, lots of high performance cars do not have much for aerodynamics, so keep that in mind.[/QUOTE]
Has anyone ever driven their WRX or STi at high speeds with a wing and aero-kit, then removed them all and done the high speed? If so, did you notice a difference?
Has anyone ever driven their WRX or STi at high speeds with a wing and aero-kit, then removed them all and done the high speed? If so, did you notice a difference?
| TeRonde | 08-16-2006 09:38 AM |
That article was discussing the ratio between coefficient of downforce and coeficient of drag. I'd pull out Aerodynamics For Naval Aviators but I don't think you guys want to sit through that discussion. I stand by my previous statement.
[QUOTE=mi_cistemz_loudr]TeRonde, meet the F430. ;) Sport Compact Car described it better, but I think this article explains it a bit.
[url="http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html"]http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html[/url][/QUOTE]
[QUOTE=mi_cistemz_loudr]TeRonde, meet the F430. ;) Sport Compact Car described it better, but I think this article explains it a bit.
[url="http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html"]http://www.italiaspeed.com/new_models/new_models_2004/f430/aerodynamics.html[/url][/QUOTE]
| BurtonCR | 08-16-2006 09:47 AM |
[QUOTE=civicstealth]Has anyone ever driven their WRX or STi at high speeds with a wing and aero-kit, then removed them all and done the high speed? If so, did you notice a difference?[/QUOTE]
I noticed a HUGE difference when I lowered my car (in 03). At 80+ the car was floaty, lowered on whiteline springs (1.5" drop) it was much more planted. On my coilovers its even better.
As for wing info. There was a large discussion back in the day with regards to the 02-03 OEM kits, STI front lips, and STI wings. IIRC someone from prodrive or data from prodrive chimed in and let us know how well the stuff worked. Now that I mentioned it, the discussion may have included the UK300 kit, thus the Prodrive input.
Itll take some digging, but I know the thread is out there somewhere in 02-03.
- Chris
I noticed a HUGE difference when I lowered my car (in 03). At 80+ the car was floaty, lowered on whiteline springs (1.5" drop) it was much more planted. On my coilovers its even better.
As for wing info. There was a large discussion back in the day with regards to the 02-03 OEM kits, STI front lips, and STI wings. IIRC someone from prodrive or data from prodrive chimed in and let us know how well the stuff worked. Now that I mentioned it, the discussion may have included the UK300 kit, thus the Prodrive input.
Itll take some digging, but I know the thread is out there somewhere in 02-03.
- Chris
| civicstealth | 08-16-2006 11:37 AM |
[QUOTE=TeRonde]That article was discussing the ratio between coefficient of downforce and coeficient of drag. I'd pull out Aerodynamics For Naval Aviators but I don't think you guys want to sit through that discussion. I stand by my previous statement.[/QUOTE]
Hey, I'm game for the Naval Aviators handbook, although I think there are some differences between aerodynamics for aircraft and for ground vehicles (ground effects, speeds, two vs. three dimensions, etc).
CD is only one factor at work here, theres also frontal profile, surface area, etc. Although I'm interested in theory, I'm also interested in what people have found to work on imprezas--sort of real world experience--what's worth doing and what's not.
Lowering the car would have the effect of allowing less room beneath the car for a high-pressure area to form at speed, thus decreasing lift (in addition to lowering the Center of Gravity). A front air dam and rear diffuser would have the same effect, yes?
Hey, I'm game for the Naval Aviators handbook, although I think there are some differences between aerodynamics for aircraft and for ground vehicles (ground effects, speeds, two vs. three dimensions, etc).
CD is only one factor at work here, theres also frontal profile, surface area, etc. Although I'm interested in theory, I'm also interested in what people have found to work on imprezas--sort of real world experience--what's worth doing and what's not.
Lowering the car would have the effect of allowing less room beneath the car for a high-pressure area to form at speed, thus decreasing lift (in addition to lowering the Center of Gravity). A front air dam and rear diffuser would have the same effect, yes?
| STiShawn | 08-16-2006 03:29 PM |
go to local book store and pick up a copy of "Race car aerodynamics" by Robert Bentley Publishing. Read, reread and enjoy. This book explains it all, drage vs. lift/df,ride heights, splitter length to ride height ratios, etc
| nhmtns | 08-16-2006 03:57 PM |
[url]http://www.urbandictionary.com/define.php?term=ricer+wing[/url]
Not that this helps or anything.
Not that this helps or anything.
| civicstealth | 08-16-2006 04:43 PM |
[QUOTE=STiShawn]go to local book store and pick up a copy of "Race car aerodynamics" by Robert Bentley Publishing. Read, reread and enjoy. This book explains it all, drage vs. lift/df,ride heights, splitter length to ride height ratios, etc[/QUOTE]
Thanks. I'll check it out.
Thanks. I'll check it out.
| civicstealth | 08-16-2006 04:46 PM |
[QUOTE=nhmtns][url]http://www.urbandictionary.com/define.php?term=ricer+wing[/url]
Not that this helps or anything.[/QUOTE]
Here's something that might:
[url]http://www.okcupid.com/tests/take[/url]
Not that this helps or anything.[/QUOTE]
Here's something that might:
[url]http://www.okcupid.com/tests/take[/url]
| AbACUZ | 08-16-2006 04:59 PM |
[QUOTE=civicstealth]Has anyone ever driven their WRX or STi at high speeds with a wing and aero-kit, then removed them all and done the high speed? If so, did you notice a difference?[/QUOTE]
I do that every weekend, i usually drive without the hood first
then i remove the doors a,d put the hood back , then i remove the rear window, and put the doors back in . I also carry a lit candle in the car to see which way the wind is blowing when i drive over 120 mph.
powerd by honda yo!!!
I do that every weekend, i usually drive without the hood first
then i remove the doors a,d put the hood back , then i remove the rear window, and put the doors back in . I also carry a lit candle in the car to see which way the wind is blowing when i drive over 120 mph.
powerd by honda yo!!!
| rukkie | 08-16-2006 05:22 PM |
[QUOTE=motohead125]High performance cars dont have much for aerodynamics? wtf....Take one look at a ferrari F430 and tell me that thing wasnt designed around the aerodynamics, or the Enzo for that matter. NO SPOILER. Cmon now.[/QUOTE]
Right, no spoilers on those cars; but you're comparing cars that they spent countless hours and time to develop and their entire car's body shape serves the purpose of beauty & aerodynamics all together, and on the other hand 4 door family sedan inspired AWD vehicles that can sit 5... A little logic please?
Right, no spoilers on those cars; but you're comparing cars that they spent countless hours and time to develop and their entire car's body shape serves the purpose of beauty & aerodynamics all together, and on the other hand 4 door family sedan inspired AWD vehicles that can sit 5... A little logic please?
| Oldfart Racer | 08-16-2006 06:25 PM |
I can tell a different on the wagon with the LNR lip. The car feels much more stable at speeds. I had the coilover on the car before the lip came in. The Top Serect, Chargerspeed, APR and Bombex kits are designed to work at speed. But if this not a track car, you will be hard pressed to see the difference.
| civicstealth | 08-16-2006 10:35 PM |
[QUOTE=AbACUZ]I do that every weekend, i usually drive without the hood first
then i remove the doors a,d put the hood back , then i remove the rear window, and put the doors back in . I also carry a lit candle in the car to see which way the wind is blowing when i drive over 120 mph.
powerd by honda yo!!![/QUOTE]
Werd! You rock! w00T!
then i remove the doors a,d put the hood back , then i remove the rear window, and put the doors back in . I also carry a lit candle in the car to see which way the wind is blowing when i drive over 120 mph.
powerd by honda yo!!![/QUOTE]
Werd! You rock! w00T!
| civicstealth | 08-16-2006 10:38 PM |
[QUOTE=Oldfart Racer]I can tell a different on the wagon with the LNR lip. The car feels much more stable at speeds. I had the coilover on the car before the lip came in. The Top Serect, Chargerspeed, APR and Bombex kits are designed to work at speed. But if this not a track car, you will be hard pressed to see the difference.[/QUOTE]
Thanks--sounds like info that can be used and has been proven in reality.
Good point on the track car--I assume you mean the cost in money and drag isn't worth it unless your going at a high rate of knots pretty often. :)
Thanks--sounds like info that can be used and has been proven in reality.
Good point on the track car--I assume you mean the cost in money and drag isn't worth it unless your going at a high rate of knots pretty often. :)
| FWD WRX | 08-16-2006 10:50 PM |
i noticed a huge difference in handling and lane changing at high speeds on my way back from vacation where i just swapped my wrx wing with someone with the STI spoiler
| Oldfart Racer | 08-17-2006 08:50 AM |
civicstealth, yes that was my point. If you are going to be a show car,put the all the kits and wing on you want. If you are looking for perfromance the kits and wings could hurt more than help.
One thing that might help is to install the 06 STI under car areo bits. Big Sky install them and said he saw a diffference at speed. If you can control the air under the car, the car will handle better, and have more down force.
One thing that might help is to install the 06 STI under car areo bits. Big Sky install them and said he saw a diffference at speed. If you can control the air under the car, the car will handle better, and have more down force.
| shaw169 | 08-17-2006 09:37 AM |
Just my point of view, dealing with aerodynamics and such. (Race) cars can benefit from good testing and use of such aids, in safety as much as performance... especially very light ones at very high speeds.
Rally cars can use these devices for similar purposes and additionally, for more/better control during jumps and such times when the suspension no longer controls the car.
That being said, for the average/daily driver to a amature racecar/rally person. Considering the costs of developing said aerodyamic aids and testing them would raise the costs of such kits, personally with a car I would spend my tightly budgeted $$$ on suspension upgrades and such, considering that better control at the wheels is easier/ better cost to improvement, than modifying the aerodynamic handling of the car.
C.N. Useful, especially for pros, but average person might consider other upgrades first.
Rally cars can use these devices for similar purposes and additionally, for more/better control during jumps and such times when the suspension no longer controls the car.
That being said, for the average/daily driver to a amature racecar/rally person. Considering the costs of developing said aerodyamic aids and testing them would raise the costs of such kits, personally with a car I would spend my tightly budgeted $$$ on suspension upgrades and such, considering that better control at the wheels is easier/ better cost to improvement, than modifying the aerodynamic handling of the car.
C.N. Useful, especially for pros, but average person might consider other upgrades first.
| civicstealth | 08-17-2006 11:53 AM |
Thanks for both the empirical data on the use of aerodynamic aids and the advice. Here's what I gather so far:
1. Spend money on upgrading suspension first--more handling bang for the buck.
2. Aerodynamic aids really only come into effect at high speeds, say 80 mph or so, so you may notice a difference in handling on say, I-95, when traffic is moving at that speed or higher--more stability and surer handlling.
3. At track speeds, say 80+, aerodynamic aids are almost reguired and worthwhile. Not as much of an issue for amateur race/rally speeds, however.
4. Controlling the air flowing under the car is more important than generating direct down force with wings (this has me thinking that for most driving situations--road and track--a front air dam is MUCH more important than any read deck spoiler or wing).
[B]And another question:[/B] I know that the Honda Civic Hybrid has modifications to it's underside to REDUCE DRAG. Hybrids are looking for the best fuel economy, after all, not downforce. Are these the same sort of measures that are taken on the STi, or does the STi use underside pieces to speed up the flow of air beneath the car, creating a low pressure zone that will suck the car down onto the road.
I just read that last question, and it appears that the two objectives might be the same thing. What do you think? :huh:
1. Spend money on upgrading suspension first--more handling bang for the buck.
2. Aerodynamic aids really only come into effect at high speeds, say 80 mph or so, so you may notice a difference in handling on say, I-95, when traffic is moving at that speed or higher--more stability and surer handlling.
3. At track speeds, say 80+, aerodynamic aids are almost reguired and worthwhile. Not as much of an issue for amateur race/rally speeds, however.
4. Controlling the air flowing under the car is more important than generating direct down force with wings (this has me thinking that for most driving situations--road and track--a front air dam is MUCH more important than any read deck spoiler or wing).
[B]And another question:[/B] I know that the Honda Civic Hybrid has modifications to it's underside to REDUCE DRAG. Hybrids are looking for the best fuel economy, after all, not downforce. Are these the same sort of measures that are taken on the STi, or does the STi use underside pieces to speed up the flow of air beneath the car, creating a low pressure zone that will suck the car down onto the road.
I just read that last question, and it appears that the two objectives might be the same thing. What do you think? :huh:
| STiShawn | 08-17-2006 01:22 PM |
the hybrids have smooth underpanels to reduce the drag caused by the air turbulating over the chassis bits, lines, hoses etc. It cleans the airflow up for improved fuel economy. Now the same principles apply to an developed undertray and diffuser combo. Smooth faster flow to the diffuser which creates suction hence downforce.
In the past I've noticed mileage gains after lowering the car and installing a deeper spoiler (not a body kit or a splitter, but an air damn type spoiler), I attribute this ti the reduction of under car airflow and hence under car drag.
From my readings aerodynamics come into play more around 65 then 80, proper aero is effective on street,rally,track,etc not just highspeed uses, look at WRC and Groupe B Rally cars..aero was very much needed.
In the past I've noticed mileage gains after lowering the car and installing a deeper spoiler (not a body kit or a splitter, but an air damn type spoiler), I attribute this ti the reduction of under car airflow and hence under car drag.
From my readings aerodynamics come into play more around 65 then 80, proper aero is effective on street,rally,track,etc not just highspeed uses, look at WRC and Groupe B Rally cars..aero was very much needed.
| Donzo | 08-17-2006 01:31 PM |
I didn't bother reading the entire thread but I can contribute in one small way. A friend of mine has an STi with around 700whp if not more. He recently took his wing off and on a straight strip at an old airport, where he would test his speed and shifting, (he always went straight with his wing) he actually began to drift sideways and fishtail once he got to around 100mph. Luckily he regained control of the vehicle and didn't crash. The first thing he said was "I have to put that wing back on or I'm going to die."
| BurtonCR | 08-17-2006 02:36 PM |
[QUOTE=TheDon427] friend of mine has an STi with around 700whp if not more. [/QUOTE]
If you are gonna quote ridiculous amounts of power like that you better show a dyno graph - otherwise Id keep it to "with alot of power".
If you are gonna quote ridiculous amounts of power like that you better show a dyno graph - otherwise Id keep it to "with alot of power".
| Donzo | 08-17-2006 02:44 PM |
It even sounds ridiculous when I hear myself say it but it's true. I've seen the dyno chart. He's also a member on these boards but keeps very low key
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