| Type1 | 01-07-2006 05:35 PM |
Undercarriage diffuser/spoiler - serious input
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So ive been at my new job now for about 3 weeks (a ferrari/lamborghini/maserati dealership and shop and yes ive got to push alot of them) [url]http://www.bobileff.com[/url] and ive seen probably all types/years/models of these cars and what ive noticed is that starting from the early models all of the ferraris undercarriages are covered up. Espeically the new ones obviously with all the technology there is alot of R&D that goes into these underbody spoilers.
Anyway I know the new 06 STi has some new "covers" or whatever you want to call them but in my opinion they are really to small to make a difference, I know its there but I dont think its enough.
This monday im going to an steel/aluminum shop with one of the shop welders cause he has to pick up material to make a new table and since im there I was thinking of buying some sheets of aluminum to possibly make a full underbody cover/diffuser.
Im going to copy some designs of the ferraris and stuff where they leave the sections of the exhausts open to release heat, and cut slits where the engine bay is to further release heat, etc..
I was wondering if anyone has attempted this cause I could use some help. The other mechanics at the shop are willing to help me and ill probably do this before or after my shifts and I have access to all the tools in the world.
So if anyone can tell me anything before attempting this I will be really grateful. If you think this is a bad idea tell me too also but give me a reason...not just "thats ****s rice."
Thanks!
Anyway I know the new 06 STi has some new "covers" or whatever you want to call them but in my opinion they are really to small to make a difference, I know its there but I dont think its enough.
This monday im going to an steel/aluminum shop with one of the shop welders cause he has to pick up material to make a new table and since im there I was thinking of buying some sheets of aluminum to possibly make a full underbody cover/diffuser.
Im going to copy some designs of the ferraris and stuff where they leave the sections of the exhausts open to release heat, and cut slits where the engine bay is to further release heat, etc..
I was wondering if anyone has attempted this cause I could use some help. The other mechanics at the shop are willing to help me and ill probably do this before or after my shifts and I have access to all the tools in the world.
So if anyone can tell me anything before attempting this I will be really grateful. If you think this is a bad idea tell me too also but give me a reason...not just "thats ****s rice."
Thanks!
| racerjon1 | 01-07-2006 06:05 PM |
Other than the Formula cars I race.. I dont have experience with building a flat bottom for one.
But I will soon.
The issues I am coming up with is material, how to attach it, cooling, design.
Remember the Ferrari and such are designed on a program, soildworks run through fluidworks or something even more specailized. They also have moving ground wind tunnels to test stuff on.
My first thought was to just build a flat bottom for the car, with a basic diffuser (break where you want the most downforce, no more than 7' upsweep) The problem with this is, there is some optimum length for laminar flow and if its too long then you can have turbulance before the break point of the diffuser and it wont be as effective, so there are considerations there, and also, a pure flat bottom without tunnels is sensetive to pitch.
I will be seeing speeds in the 170-180 range at times, so I am slightly worried about that whole pitch issue. (I dont want no acrobatics)
The other thing i am trying to consider is method of attachment, my F2000 diffuser when i first put it on despite having brackets and attachment front and rear, flexed and pulled itself into the track. (it was a honycomb center carbon build as well) So we had to add another center attachment point. If things go well and you develop enough downforce, then there is a chance it all gets ripped out the bottom..
So.. thats where I stand.
Jon
But I will soon.
The issues I am coming up with is material, how to attach it, cooling, design.
Remember the Ferrari and such are designed on a program, soildworks run through fluidworks or something even more specailized. They also have moving ground wind tunnels to test stuff on.
My first thought was to just build a flat bottom for the car, with a basic diffuser (break where you want the most downforce, no more than 7' upsweep) The problem with this is, there is some optimum length for laminar flow and if its too long then you can have turbulance before the break point of the diffuser and it wont be as effective, so there are considerations there, and also, a pure flat bottom without tunnels is sensetive to pitch.
I will be seeing speeds in the 170-180 range at times, so I am slightly worried about that whole pitch issue. (I dont want no acrobatics)
The other thing i am trying to consider is method of attachment, my F2000 diffuser when i first put it on despite having brackets and attachment front and rear, flexed and pulled itself into the track. (it was a honycomb center carbon build as well) So we had to add another center attachment point. If things go well and you develop enough downforce, then there is a chance it all gets ripped out the bottom..
So.. thats where I stand.
Jon
| BIGSKYWRX | 01-07-2006 08:51 PM |
The STi has continued to add more and more in the way of under aero bits
[IMG]http://i7.photobucket.com/albums/y276/jpapania/Bottom2006STI.jpg[/IMG]
[IMG]http://i7.photobucket.com/albums/y276/jpapania/Bottom2006STI.jpg[/IMG]
| darksands | 01-07-2006 09:35 PM |
^^^
That doesnt look like a USDM STi.
That doesnt look like a USDM STi.
| godai | 01-07-2006 09:43 PM |
[QUOTE=darksands]^^^
That doesnt look like a USDM STi.[/QUOTE]
how so?
That doesnt look like a USDM STi.[/QUOTE]
how so?
| afpdl | 01-07-2006 09:44 PM |
[QUOTE=darksands]^^^
That doesnt look like a USDM STi.[/QUOTE]
In what way?
That doesnt look like a USDM STi.[/QUOTE]
In what way?
| MPME | 01-07-2006 11:02 PM |
I have a somewhat recent article that covers this exact topic--if it doesn't answer your questions, let me know and I'll gladly help. It has pictures of an '05 STi Cusco front splitter/aluminum floor install I did as well.
[url]http://www.tprmag.com/issue/13/13_aerodynamics.shtml[/url]
The part 2 of the feature is due out in a month or two months, and covers road racing aero for tuner/import car specifically, and might have more direct info for you.
[url]http://www.tprmag.com/issue/13/13_aerodynamics.shtml[/url]
The part 2 of the feature is due out in a month or two months, and covers road racing aero for tuner/import car specifically, and might have more direct info for you.
| Homemade WRX | 01-08-2006 12:35 AM |
it will make a difference with drag, if not with downforce...I've been looking into making one for my car and another local...it is actaully quite simple to do, I just need to time and money now...
I've only looked into doing the front bumper to the firewall (area) and under cabin area...the rear I imagine would be quite simple though.
I've only looked into doing the front bumper to the firewall (area) and under cabin area...the rear I imagine would be quite simple though.
| Patrick Olsen | 01-08-2006 01:07 AM |
No offense, Homemade, but there's absolutely nothing simple about designing any sort of aerodynamic device. You could just put a flat plate back there, and that would be simple, but it would also be completely ineffective and may actually hurt the airflow around/under the car.
Type1, I'd say your best bet is to start by duplicating what's been done on the '06 STi. The problem will be determining any effect of what you add to the car. At least if you roughly copy the STi bits you'll know that you're working in the right direction. Just be ready for it to be an iterative process - you may need to refine/redesign your parts as you go along.
Definitely has the potential to be a neat project. Keep us informed.
Pat Olsen
'97 Legacy 2.5GT sedan
Type1, I'd say your best bet is to start by duplicating what's been done on the '06 STi. The problem will be determining any effect of what you add to the car. At least if you roughly copy the STi bits you'll know that you're working in the right direction. Just be ready for it to be an iterative process - you may need to refine/redesign your parts as you go along.
Definitely has the potential to be a neat project. Keep us informed.
Pat Olsen
'97 Legacy 2.5GT sedan
| Homemade WRX | 01-08-2006 01:24 AM |
[QUOTE=Patrick Olsen]No offense, Homemade, but there's absolutely nothing simple about designing any sort of aerodynamic device. You could just put a flat plate back there, and that would be simple, but it would also be completely ineffective and may actually hurt the airflow around/under the car.
[/QUOTE]
trust me I know more than you think I do...just got done building and testing (8 different models) our 1/2 scale model for our Formula SAE car...I have also taken 3 400 level aerospace courses, one specifying in ground vehicle aerodynamics. I'm also lined up to get an internship at Langley full scale windtunnel...and when I said it's easy, I was referring to mounting...there are plenty of nuts, bolts and open spaces to mount to on the bottom of our cars.
as for the flat plate covering the spare, that actually reduces the turbulent flow of air (causing drag) coming from the back of you car...have the test numbers from a ford taurus where it was done.
-Micah
[/QUOTE]
trust me I know more than you think I do...just got done building and testing (8 different models) our 1/2 scale model for our Formula SAE car...I have also taken 3 400 level aerospace courses, one specifying in ground vehicle aerodynamics. I'm also lined up to get an internship at Langley full scale windtunnel...and when I said it's easy, I was referring to mounting...there are plenty of nuts, bolts and open spaces to mount to on the bottom of our cars.
as for the flat plate covering the spare, that actually reduces the turbulent flow of air (causing drag) coming from the back of you car...have the test numbers from a ford taurus where it was done.
-Micah
| bemani | 01-08-2006 01:35 AM |
[QUOTE=godai]how so?[/QUOTE]
Undercover for the transmission?
Undercover for the transmission?
| afpdl | 01-08-2006 02:35 AM |
[QUOTE=bemani]Undercover for the transmission?[/QUOTE]
Added in 06 along with the diffuser.
Added in 06 along with the diffuser.
| Imprezanator | 01-08-2006 03:31 AM |
[QUOTE=godai]how so?[/QUOTE]
The exhaust is coming down on the left side of the car and exiting out the right in the rear, instead of vice-versa for LHD cars.
Alot of those under-body panels are for sound dampening.
The exhaust is coming down on the left side of the car and exiting out the right in the rear, instead of vice-versa for LHD cars.
Alot of those under-body panels are for sound dampening.
| afpdl | 01-08-2006 03:35 AM |
No its not, the downpipe is on the left side and the muffler is on the right, the car is upside down. And LHD cars have the same exhaust set up anyway.
| Ver.III | 01-08-2006 04:29 AM |
Its JDM. That pic shows no mid-cat . Just 2 resonators.
| AUTOwrXER | 01-08-2006 05:49 AM |
[QUOTE=BIGSKYWRX]The STi has continued to add more and more in the way of under aero bits
[IMG]http://i7.photobucket.com/albums/y276/jpapania/Bottom2006STI.jpg[/IMG][/QUOTE]
So that's where all the extra weight comes from...
[IMG]http://i7.photobucket.com/albums/y276/jpapania/Bottom2006STI.jpg[/IMG][/QUOTE]
So that's where all the extra weight comes from...
| makofoto | 01-08-2006 10:06 AM |
What are you going to be doing with your car that you feel you would benefit from this project?
| BIGSKYWRX | 01-08-2006 11:27 AM |
That is a pic of the jdm car, but as has been pointed out now the same underside as the 06 usdm, 05 so the addition of the two side bits, 06 the rear diffuser (and evidently the tranny one as well- didn'ty know the 06 usdm got this one).
Several have added the rear diffuser w/o much hassle, a couple have added the side bits- requires drilling.
What I found interesting was that although no one could provide emperical data on downforce changes, etc- they did report a mile or two/ gallon improvement in fuel consumption :)
These are plastic bits, so there isn't too much in the way of increased weight.
Several have added the rear diffuser w/o much hassle, a couple have added the side bits- requires drilling.
What I found interesting was that although no one could provide emperical data on downforce changes, etc- they did report a mile or two/ gallon improvement in fuel consumption :)
These are plastic bits, so there isn't too much in the way of increased weight.
| Type1 | 01-08-2006 12:44 PM |
[QUOTE=makofoto]What are you going to be doing with your car that you feel you would benefit from this project?[/QUOTE]
Well I used to be really into rallying, actually I still am but the cost of replacing stock shocks and going through tires is starting to add up. I got a deal on some KYB's a while back and have them on now and from what I hear from everyone its super easy to blow them doing what I do and I cant afford those DMS rally shocks for 5 grand. I also recently got sponsored by dunlop and currently I only have 1 set of wheels and tires and I dont want to wreck them cause I need them for shows so basically the only thing im left with is autocrossing and track time. Since im in san diego im not too far from buttonwillow or other semi-local tracks and I just thought it would be a cool idea to make somethin like this for my car since I basically have all the tools, material, and knowledge in my hands. I was planning to make myself some skidplates anyway so why not just do this right? And im not concerned with downforce im looking for less drag.
I remember watching an old episode of car and driver about 2 years ago and at that time one of the lexus sedan cars I forget which one had the lowest drag coefficient compared to other cars and this was attributed to a full undercarriage cover. A freakin boat lexus had the lowest drag coef. can you believe that? And I know there is a lot of R&D that goes into it but I dont mind test fitting my car..its a work in progress. Maybe after this project if im still working at this gig Ill have my whole car stitch welded...rally style :D
Well I used to be really into rallying, actually I still am but the cost of replacing stock shocks and going through tires is starting to add up. I got a deal on some KYB's a while back and have them on now and from what I hear from everyone its super easy to blow them doing what I do and I cant afford those DMS rally shocks for 5 grand. I also recently got sponsored by dunlop and currently I only have 1 set of wheels and tires and I dont want to wreck them cause I need them for shows so basically the only thing im left with is autocrossing and track time. Since im in san diego im not too far from buttonwillow or other semi-local tracks and I just thought it would be a cool idea to make somethin like this for my car since I basically have all the tools, material, and knowledge in my hands. I was planning to make myself some skidplates anyway so why not just do this right? And im not concerned with downforce im looking for less drag.
I remember watching an old episode of car and driver about 2 years ago and at that time one of the lexus sedan cars I forget which one had the lowest drag coefficient compared to other cars and this was attributed to a full undercarriage cover. A freakin boat lexus had the lowest drag coef. can you believe that? And I know there is a lot of R&D that goes into it but I dont mind test fitting my car..its a work in progress. Maybe after this project if im still working at this gig Ill have my whole car stitch welded...rally style :D
| richde | 01-08-2006 01:15 PM |
[QUOTE=AUTOwrXER]So that's where all the extra weight comes from...[/QUOTE]
That's probably 20 pounds of plastic/fasteners, MAX. I'd think the extra weight comes from the tranny and misc chassis stiffening bits, like the part behind the rear seat.
All the info to do it, part #'s and basic instructions, is here: [url]http://forums.nasioc.com/forums/showthread.php?t=889855[/url]
That's probably 20 pounds of plastic/fasteners, MAX. I'd think the extra weight comes from the tranny and misc chassis stiffening bits, like the part behind the rear seat.
All the info to do it, part #'s and basic instructions, is here: [url]http://forums.nasioc.com/forums/showthread.php?t=889855[/url]
| richde | 01-08-2006 01:30 PM |
[QUOTE=afpdl]No its not, the downpipe is on the left side and the muffler is on the right, the car is upside down. And LHD cars have the same exhaust set up anyway.[/QUOTE]
I think the negative got reversed and nobody noticed along the way, since JDM engines are the same as USDM as far as exhaust routing goes.
Afpdl get's an "A" in Attention to Detail! :banana:
I think the negative got reversed and nobody noticed along the way, since JDM engines are the same as USDM as far as exhaust routing goes.
Afpdl get's an "A" in Attention to Detail! :banana:
| Calamity Jesus | 01-08-2006 01:37 PM |
[QUOTE=Type1]I remember watching an old episode of car and driver about 2 years ago and at that time one of the lexus sedan cars I forget which one had the lowest drag coefficient compared to other cars and this was attributed to a full undercarriage cover. A freakin boat lexus had the lowest drag coef. can you believe that?[/QUOTE]
Sure I can believe that. Drag coefficient is a 'coefficient' because it's only a part of the whole story. You need to multiply the coef. by the frontal area (the area of the car if you were too look at it from straight on as a silhouette) of the car to determine the actual amount of drag. Something like a corvette, with very little frontal area and a similarly low drag coefficient would produce much less actual drag than the 'freakin boat' of a lexus. ;)
Sure I can believe that. Drag coefficient is a 'coefficient' because it's only a part of the whole story. You need to multiply the coef. by the frontal area (the area of the car if you were too look at it from straight on as a silhouette) of the car to determine the actual amount of drag. Something like a corvette, with very little frontal area and a similarly low drag coefficient would produce much less actual drag than the 'freakin boat' of a lexus. ;)
| endeavor | 01-08-2006 03:26 PM |
One other thing too, race cars are designed to produce downforce, not just have low drag; downforce is created with drag. So a C6 Z06, Viper, or F1 car will have a higher Cd than a Lexus or other sedans. I'm not sure which would actually have the higher net drag. (i.e. does the smaller frontal area make up for the higher Cd.)
| speedyHAM | 01-08-2006 03:59 PM |
[QUOTE=endeavor]One other thing too, race cars are designed to produce downforce, not just have low drag; downforce is created with drag. So a C6 Z06, Viper, or F1 car will have a higher Cd than a Lexus or other sedans. I'm not sure which would actually have the higher net drag. (i.e. does the smaller frontal area make up for the higher Cd.)[/QUOTE]
Race cars that produce downforce typically have a horrible Cd and net drag ratings. A C5R corvetter for instance has a Cd of .37 vs. a Cd of .28 for the production Z06. An F1 car is setup purely for efficient downforce, drag is a secondary concern. Those things with almost 1000 Hp had a top speed of around 250 mph, with a much sleeker body and 375 less Hp a Mclaren F1 had a top speed of 245. The smaller frontal area makes no difference when you are talking about that much downforce.
A flat bottom to our cars would help the overall fuel economy, but not enough to be cost effective for Subaru. Those little plastic peices and fasteners + assembly time add up to a lot on a per car basis. I'd like to make one but don't have the money or the time.
As far as the laminar flow underneath the car- it stops at the end of your front bumper. To get it past the front wheels would be practically a miracle with a smooth bottom. If you are really interested in doing this pick up a book called "Race Car Aerodynamics" it is the best book out there on the subject from an overall standpoint. It has more usefull information than anyone here could spit out.
Race cars that produce downforce typically have a horrible Cd and net drag ratings. A C5R corvetter for instance has a Cd of .37 vs. a Cd of .28 for the production Z06. An F1 car is setup purely for efficient downforce, drag is a secondary concern. Those things with almost 1000 Hp had a top speed of around 250 mph, with a much sleeker body and 375 less Hp a Mclaren F1 had a top speed of 245. The smaller frontal area makes no difference when you are talking about that much downforce.
A flat bottom to our cars would help the overall fuel economy, but not enough to be cost effective for Subaru. Those little plastic peices and fasteners + assembly time add up to a lot on a per car basis. I'd like to make one but don't have the money or the time.
As far as the laminar flow underneath the car- it stops at the end of your front bumper. To get it past the front wheels would be practically a miracle with a smooth bottom. If you are really interested in doing this pick up a book called "Race Car Aerodynamics" it is the best book out there on the subject from an overall standpoint. It has more usefull information than anyone here could spit out.
| racerjon1 | 01-08-2006 05:18 PM |
There is another thing to consider in designing a bottom like this fro street car vs race car.. Heat buildup.
A Racecar that is going to run for short periods, and/or be rebuilt following an event doesn't have to worry about this in the same way that a street car that is going to plan ot be run for 100k+ miles. When you consider a Subaru with differentials and such, there is a lot of heat that can cause problems.
"Production" Flat bottoms such as Ferrari and Lamborghini and such are actually not flat, they have tunnels, and either channels that rout air out the side that is turbulant (such as that caused by the tires) or tunnels that rout it back out through the diffuser. (example, Ferrari 360)
The Lotus Elise actually has the kind of flat bottom that we are talking about (big sheets of aluminum) followed by a diffuser. It is probably pratical in terms of fuel economy, and aids in reducing lift, but actually producing downforce per se is going to be higly unlikely withough some serious expertise/computer/wind tunnel time.
This isn't bad of course, modern cars produce from 200-750lbs of lift at 120 mph, and a reduction of that would be good.
Jon K
A Racecar that is going to run for short periods, and/or be rebuilt following an event doesn't have to worry about this in the same way that a street car that is going to plan ot be run for 100k+ miles. When you consider a Subaru with differentials and such, there is a lot of heat that can cause problems.
"Production" Flat bottoms such as Ferrari and Lamborghini and such are actually not flat, they have tunnels, and either channels that rout air out the side that is turbulant (such as that caused by the tires) or tunnels that rout it back out through the diffuser. (example, Ferrari 360)
The Lotus Elise actually has the kind of flat bottom that we are talking about (big sheets of aluminum) followed by a diffuser. It is probably pratical in terms of fuel economy, and aids in reducing lift, but actually producing downforce per se is going to be higly unlikely withough some serious expertise/computer/wind tunnel time.
This isn't bad of course, modern cars produce from 200-750lbs of lift at 120 mph, and a reduction of that would be good.
Jon K
| Homemade WRX | 01-09-2006 01:01 AM |
I will have to post some of the numbers I have for F1 car downforce vs. Cd...ferrari stock downforce numbers etc...I'll have to get out my ground vehicle aero notes....oh and the daytona prototype we help set up placed second at its race but had fairly large Cd...
| racerjon1 | 01-09-2006 10:33 AM |
I think F1 cars (IndyCars/Champ Cars as well) have Cd in the .7+ range depending on wings from what I remember.
They are producing downforce (negative lift) though, and have the HP and other aerodynamic ability to do it.
some interesting facts: lift produced at speed..
2000 VW beetle: 742lbs of lift at 124mph
2000 Audi TT: 386lbs of lift at 150mph
2000 Porsche 911: 600 lbs of lift at 150mph
1999 Ferrari 360 Modena: 294lbs of downforce at 150mph
Porsche 962: 2971lbs of downforce at 150mph
1967 Ford GT40: 148lbs of lift at 150mph
200 Reynard Champ Car: 2750lbs of downforce at 150mph
Jon K
They are producing downforce (negative lift) though, and have the HP and other aerodynamic ability to do it.
some interesting facts: lift produced at speed..
2000 VW beetle: 742lbs of lift at 124mph
2000 Audi TT: 386lbs of lift at 150mph
2000 Porsche 911: 600 lbs of lift at 150mph
1999 Ferrari 360 Modena: 294lbs of downforce at 150mph
Porsche 962: 2971lbs of downforce at 150mph
1967 Ford GT40: 148lbs of lift at 150mph
200 Reynard Champ Car: 2750lbs of downforce at 150mph
Jon K
| BIGSKYWRX | 01-09-2006 10:39 AM |
I would have to say (guess :)) that w/ our rally heritage Impreza's and their fairly significant ground clearance- that lift for us is pretty significant.
| Homemade WRX | 01-09-2006 10:47 AM |
[QUOTE=BIGSKYWRX]I would have to say (guess :)) that w/ our rally heritage Impreza's and their fairly significant ground clearance- that lift for us is pretty significant.[/QUOTE]
not necessarily...we actually discussed why the TT, beetle and 911 have such bad lift/drag...it's all about the roof line...of course the 911 we spoke of was pre 996...
funny fact, the subie xt had aCd of .29-.31 and Cl of .10
mclaren F1 had cd of.32 and cl of -.15 (using two sucker fans to hit target downforce of 160 [email�protected]
95 rx7 R-2 had Cd.29 Cl front .10 and Cl rear of .08
not necessarily...we actually discussed why the TT, beetle and 911 have such bad lift/drag...it's all about the roof line...of course the 911 we spoke of was pre 996...
funny fact, the subie xt had aCd of .29-.31 and Cl of .10
mclaren F1 had cd of.32 and cl of -.15 (using two sucker fans to hit target downforce of 160 [email�protected]
95 rx7 R-2 had Cd.29 Cl front .10 and Cl rear of .08
| psyber_0ptix | 01-09-2006 10:57 AM |
*subscribed*
Homemade WRX, gonna be engineering something for our cars soon? :devil:
Homemade WRX, gonna be engineering something for our cars soon? :devil:
| Homemade WRX | 01-09-2006 11:00 AM |
[QUOTE=psyber_0ptix]*subscribed*
Homemade WRX, gonna be engineering something for our cars soon? :devil:[/QUOTE]
I'd like too...and I'd really like to see if my prof/future boss would let me put it in the tunnel for 2 pulls...before and after...
I'd realy like to do one more which would pull air from the front fender wells to the underside of the car...just to see what happens with the Cl...although not the favorable place it does prevent body work...
Homemade WRX, gonna be engineering something for our cars soon? :devil:[/QUOTE]
I'd like too...and I'd really like to see if my prof/future boss would let me put it in the tunnel for 2 pulls...before and after...
I'd realy like to do one more which would pull air from the front fender wells to the underside of the car...just to see what happens with the Cl...although not the favorable place it does prevent body work...
| racerjon1 | 01-09-2006 01:20 PM |
[QUOTE=Homemade WRX]I'd realy like to do one more which would pull air from the front fender wells to the underside of the car...just to see what happens with the Cl...although not the favorable place it does prevent body work...[/QUOTE]
So instead of doing slots over the wheels to vacate the air in the fender wells (LMP style) you would try to get it to go under the car?
I have seen some examples that have aero mods in front of the front wheels and then routing contours behind them to manage this, but I would think just dumping it under the car without some kind of plan would disrupt airflow under the car, causing more lift?
Jon K
[url]www.racerjon.com[/url]
So instead of doing slots over the wheels to vacate the air in the fender wells (LMP style) you would try to get it to go under the car?
I have seen some examples that have aero mods in front of the front wheels and then routing contours behind them to manage this, but I would think just dumping it under the car without some kind of plan would disrupt airflow under the car, causing more lift?
Jon K
[url]www.racerjon.com[/url]
| Homemade WRX | 01-09-2006 01:59 PM |
[QUOTE=racerjon1]So instead of doing slots over the wheels to vacate the air in the fender wells (LMP style) you would try to get it to go under the car?
I have seen some examples that have aero mods in front of the front wheels and then routing contours behind them to manage this, but I would think just dumping it under the car without some kind of plan would disrupt airflow under the car, causing more lift?
Jon K
[url]www.racerjon.com[/url][/QUOTE]
there of many ways of doing it, but like I said, I wanted to do it without doing body work...altering stock sheetmetal
and yes, allowing more air to be pulled under the car would reduce the amount of downforce you would get from the undertray but give downforce buy reducing the high pressure in the wheel wells...so I'd see the trade off
I have seen some examples that have aero mods in front of the front wheels and then routing contours behind them to manage this, but I would think just dumping it under the car without some kind of plan would disrupt airflow under the car, causing more lift?
Jon K
[url]www.racerjon.com[/url][/QUOTE]
there of many ways of doing it, but like I said, I wanted to do it without doing body work...altering stock sheetmetal
and yes, allowing more air to be pulled under the car would reduce the amount of downforce you would get from the undertray but give downforce buy reducing the high pressure in the wheel wells...so I'd see the trade off
| racerjon1 | 01-09-2006 02:12 PM |
I guess without doing bodywork and adding slots I was considering the wheel well air as a "given" and was going to concentrate on managing the air that is under the car.
My next question of course is, if you dump the air from the wells back under the car, then wouldn't you want to use some stepped, or sections of the bottom to dump the air back out from the sides, so that air under the center of the car can be used for reducing lift without being interupted.
The Ferrari 360 looking at it seems to collect this air from behind the front wheels and routs it through the tunnels exiting the rear.
This is where I get into the tunnels vs flat bottom quandry for simple construction methods.. yes I would love tunnels and of course it would work better, but I think because of the added level of difficulty in desiging, it could end up hurting worse if I messed it up.
Jon K
[url]www.racerjon.com[/url]
My next question of course is, if you dump the air from the wells back under the car, then wouldn't you want to use some stepped, or sections of the bottom to dump the air back out from the sides, so that air under the center of the car can be used for reducing lift without being interupted.
The Ferrari 360 looking at it seems to collect this air from behind the front wheels and routs it through the tunnels exiting the rear.
This is where I get into the tunnels vs flat bottom quandry for simple construction methods.. yes I would love tunnels and of course it would work better, but I think because of the added level of difficulty in desiging, it could end up hurting worse if I messed it up.
Jon K
[url]www.racerjon.com[/url]
| TheRipler | 01-09-2006 04:15 PM |
[QUOTE=MPME]I have a somewhat recent article that covers this exact topic--if it doesn't answer your questions, let me know and I'll gladly help. It has pictures of an '05 STi Cusco front splitter/aluminum floor install I did as well.
[url]http://www.tprmag.com/issue/13/13_aerodynamics.shtml[/url]
The part 2 of the feature is due out in a month or two months, and covers road racing aero for tuner/import car specifically, and might have more direct info for you.[/QUOTE]
Thanks for the article. I recently purchased the Cusco lip and underbody panel, but haven't installed it yet. From my armchair aerodynamicist seat, it looked like the most functional body kit out there. I need to find someone to paint the lip first, and I'm putting it off until the next season starts in March, since it looks like oil changes will get more complicated with that thing.
Anyhow, I have yet to see a full pic of the underbody panel installed. The one in the article cuts off, and I was wondering about airflow out of the engine bay, cooling, and all that. I also have an aftermarket DP that comes down a little lower than stock, and was wondering if I was going to need to do some cutting there. Any clues as to how that's going to work? full pic on the car?
Also, I found the idea of the temp rear diffuser with aluminum tape fairly interesting. I've been thinking about fabricating something, but I was going in a more permanent aluminum direction. My question is about the exhaust temps. The muffler gets pretty warm. What keeps plywood or plastic from lighting up underneath the car. That would be bad, methinks.
Last year I ditched the rear wing for a CF trunk lid, and picked up over 3mph on the top end with no other modifications. ([url]www.texasmile.com[/url]) I'm just looking to see if I can improve things a little more before I start dumping tons of money into power mods, moving me into a higher class, taking on lightly modified Cobras and Vettes.
...and yes, I realise (after spending a year reading about aerodynamics), that I don't know what I'm doing. Still, I think that even something crude could help with the rear bumper situation.
Thanks,
Scott.
[url]http://www.tprmag.com/issue/13/13_aerodynamics.shtml[/url]
The part 2 of the feature is due out in a month or two months, and covers road racing aero for tuner/import car specifically, and might have more direct info for you.[/QUOTE]
Thanks for the article. I recently purchased the Cusco lip and underbody panel, but haven't installed it yet. From my armchair aerodynamicist seat, it looked like the most functional body kit out there. I need to find someone to paint the lip first, and I'm putting it off until the next season starts in March, since it looks like oil changes will get more complicated with that thing.
Anyhow, I have yet to see a full pic of the underbody panel installed. The one in the article cuts off, and I was wondering about airflow out of the engine bay, cooling, and all that. I also have an aftermarket DP that comes down a little lower than stock, and was wondering if I was going to need to do some cutting there. Any clues as to how that's going to work? full pic on the car?
Also, I found the idea of the temp rear diffuser with aluminum tape fairly interesting. I've been thinking about fabricating something, but I was going in a more permanent aluminum direction. My question is about the exhaust temps. The muffler gets pretty warm. What keeps plywood or plastic from lighting up underneath the car. That would be bad, methinks.
Last year I ditched the rear wing for a CF trunk lid, and picked up over 3mph on the top end with no other modifications. ([url]www.texasmile.com[/url]) I'm just looking to see if I can improve things a little more before I start dumping tons of money into power mods, moving me into a higher class, taking on lightly modified Cobras and Vettes.
...and yes, I realise (after spending a year reading about aerodynamics), that I don't know what I'm doing. Still, I think that even something crude could help with the rear bumper situation.
Thanks,
Scott.
| Homemade WRX | 01-09-2006 04:56 PM |
for an undertray you are working on suction though air velocity...you want to limit any amount of air flowing under the tray hints skirts (standard, virtual and dragging). Also why front splitters ("lips") are used to help...having vents on the side would actually allow air to come under the car as apossed to flowing out...
The whole theory behind and undertray is bernoulli's equation.
It is really basic fluids with aero tidbits thrown in to improve it. Some F1 teams actually use vortex generators to seperate the flow in there venturis/tunnels.
the venturis and tunnels are really used to control flow out of the back and are used to allow for higher velocity on the flat part of the tray creating more suction.
this is just a quick sum up on an undertrays operation
ripler...post up a pic of your car...please...I'm sure there are several quick things that could be improved...
The whole theory behind and undertray is bernoulli's equation.
It is really basic fluids with aero tidbits thrown in to improve it. Some F1 teams actually use vortex generators to seperate the flow in there venturis/tunnels.
the venturis and tunnels are really used to control flow out of the back and are used to allow for higher velocity on the flat part of the tray creating more suction.
this is just a quick sum up on an undertrays operation
ripler...post up a pic of your car...please...I'm sure there are several quick things that could be improved...
| AndyRoo | 01-09-2006 05:46 PM |
[QUOTE=Homemade WRX]I will have to post some of the numbers I have for F1 car downforce vs. Cd...ferrari stock downforce numbers etc...I'll have to get out my ground vehicle aero notes....oh and the daytona prototype we help set up placed second at its race but had fairly large Cd...[/QUOTE]
I have a bunch of these numbers as well...unfortunately they are all at school. i'll put them up monday when i get back. pretty interesting stuff.
- andrew
I have a bunch of these numbers as well...unfortunately they are all at school. i'll put them up monday when i get back. pretty interesting stuff.
- andrew
| TheRipler | 01-09-2006 05:48 PM |
[URL=http://www.landracing.net/cgi-bin/pro/emAlbum.cgi?c=show_image;p=Texas%20Mile/2005/October%2022,%202005;i=22;in=IMG_2077.jpg]October 05 meet pic[/URL]
Right now the car is just an '04 STi with a wingless CF trunk lid. I actually thought the car felt more stable without the trunk towel rack. We usually have some stiff crosswinds, gusting 15-20mph in the afternoon. Without the wing, the car was much more predictable, and didn't get pushed around as much.
That pic was from the first morning, when I was running in "street" form. 93octane, nothing special, turn in the side mirrors, and that's about it. When all was said and done, I had the front seams taped up, and the lower grill covered. This helped some, but I couldn't do back to back runs due to heat soak. There was some weight reduction the second day as well.
Removing the mirrors is an obvious choice. I'm also considering removing the hood scoop, and replacing it with a flat cardboard or aluminum plate. Since I cover the TMIC with 15lbs of dry ice for a run, the air coming in is just warming things up, assuming the scoop is even catching anything at 150mph. Covering the vent between the hood and windshield is another option, and of course, removing the wipers.
[edit] I've also considered fabricating a front air dam that would bolt in between the lip and undertray. ...lowering the car, etc..[/edit]
Like I said, I haven't even put the Cusco parts on yet. I'm still wondering how to jack up the front of the car once that thing is on. I was hoping to talk to someone who had one before I made the leap. It doesn't have drain holes, which would be required under certain sactioning bodies. Lots of little questions like that.
Thanks,
Scott.
Right now the car is just an '04 STi with a wingless CF trunk lid. I actually thought the car felt more stable without the trunk towel rack. We usually have some stiff crosswinds, gusting 15-20mph in the afternoon. Without the wing, the car was much more predictable, and didn't get pushed around as much.
That pic was from the first morning, when I was running in "street" form. 93octane, nothing special, turn in the side mirrors, and that's about it. When all was said and done, I had the front seams taped up, and the lower grill covered. This helped some, but I couldn't do back to back runs due to heat soak. There was some weight reduction the second day as well.
Removing the mirrors is an obvious choice. I'm also considering removing the hood scoop, and replacing it with a flat cardboard or aluminum plate. Since I cover the TMIC with 15lbs of dry ice for a run, the air coming in is just warming things up, assuming the scoop is even catching anything at 150mph. Covering the vent between the hood and windshield is another option, and of course, removing the wipers.
[edit] I've also considered fabricating a front air dam that would bolt in between the lip and undertray. ...lowering the car, etc..[/edit]
Like I said, I haven't even put the Cusco parts on yet. I'm still wondering how to jack up the front of the car once that thing is on. I was hoping to talk to someone who had one before I made the leap. It doesn't have drain holes, which would be required under certain sactioning bodies. Lots of little questions like that.
Thanks,
Scott.
| Homemade WRX | 01-09-2006 07:11 PM |
[QUOTE=AndyRoo]I have a bunch of these numbers as well...unfortunately they are all at school. i'll put them up monday when i get back. pretty interesting stuff.
- andrew[/QUOTE]
yeah, I have several pages of them...all in my race car aero book
- andrew[/QUOTE]
yeah, I have several pages of them...all in my race car aero book
| racerjon1 | 01-09-2006 10:39 PM |
Ok, I have been doing more research, (actually this has been ongoing for me for the last month now) and in an article by the Chalmers University of Technology, a point is brought up in relation to flat bottoms and stability under braking from high speed.
In the article it describes that the car while running at speed has a set Center of Pressure (CoP) and that when the brakes are applied and the car pitches forward, the CoP moves forward causing an instability at the rear, inducing rear lockup sooner because of the lack of weight on the rear wheels.
The McLaren F1 roadcar overcomes this by having a spoiler/wing pop up under braking from high speeds. It is also counteracted by higher spring rates to minimize pitch, though with too high a spring rate you of course give up lower speed mechanical grip.
Now getting to my question.. will a car without a flat bottom though not producing an abundance of negative lift possibly duplicate this behavior? In the AMS Evo we are experiencing severe rear instability characterized by lockup when under braking above 155mph, and in once case below 150mph but braking while going uphill.
Until I discovered this point in the article I was thinking it was an ABS brain issue that only showed after the factory speed limiter was exceeded, or possibly just incorrect spring rates for the speed. Now I am forced to consider that it could have an aero cause.
Homemade, have you run across this in any of your experience?
(also, changing the break from the flat bottom to the diffuser from a sharp break to a curved can help with pitch sensitivity)
Jon K
[url]www.racerjon.com[/url]
In the article it describes that the car while running at speed has a set Center of Pressure (CoP) and that when the brakes are applied and the car pitches forward, the CoP moves forward causing an instability at the rear, inducing rear lockup sooner because of the lack of weight on the rear wheels.
The McLaren F1 roadcar overcomes this by having a spoiler/wing pop up under braking from high speeds. It is also counteracted by higher spring rates to minimize pitch, though with too high a spring rate you of course give up lower speed mechanical grip.
Now getting to my question.. will a car without a flat bottom though not producing an abundance of negative lift possibly duplicate this behavior? In the AMS Evo we are experiencing severe rear instability characterized by lockup when under braking above 155mph, and in once case below 150mph but braking while going uphill.
Until I discovered this point in the article I was thinking it was an ABS brain issue that only showed after the factory speed limiter was exceeded, or possibly just incorrect spring rates for the speed. Now I am forced to consider that it could have an aero cause.
Homemade, have you run across this in any of your experience?
(also, changing the break from the flat bottom to the diffuser from a sharp break to a curved can help with pitch sensitivity)
Jon K
[url]www.racerjon.com[/url]
| Homemade WRX | 01-09-2006 11:02 PM |
I have actually designed the brake system for our formula car this year and weight transfer is an issue with braking when your range of speeds vary a good deal...ideally you will have a range of speeds and deceleration rates (g's) this will give your weight transfer and from that you can get how much torque the tires can take without locking up...the undertray will initially help fight this...but when the pitch overcomes the downforce you start to lift the rear end...when you rake a car with an undertray it can actually gain downforce (as seen testing a daytona prototype)...but if the front bumper/air supply get's pinched off you loose all downforce created by the undertray (why DTM anbd other low touring cars have a center section of there lip raised up)...
another thing that is paid attention when designing an undertray for downforce is where the peak vacuum (most downforce) is...many prototype racecars actually will eleviate the vacuum in some cases because it is too much in the wrong place...generaly in the front half of the car and will thus put in vents to suck heat out from the engine bay.
just some food for thought...in the AMS evo case it is most likely just too much rear brake pressure/bias for the weight transfer (caused by G's) you are seeing...either go with lighter braking, heavier front springs, anti-dive geometry, get some rear downforce, or a brake bias tuned for that braking...
another thing that is paid attention when designing an undertray for downforce is where the peak vacuum (most downforce) is...many prototype racecars actually will eleviate the vacuum in some cases because it is too much in the wrong place...generaly in the front half of the car and will thus put in vents to suck heat out from the engine bay.
just some food for thought...in the AMS evo case it is most likely just too much rear brake pressure/bias for the weight transfer (caused by G's) you are seeing...either go with lighter braking, heavier front springs, anti-dive geometry, get some rear downforce, or a brake bias tuned for that braking...
| Patrick Olsen | 02-02-2006 10:40 PM |
[QUOTE=Homemade WRX]trust me I know more than you think I do......and when I said it's easy, I was referring to mounting...there are plenty of nuts, bolts and open spaces to mount to on the bottom of our cars.[/quote]
Yeah, I can see that now. ;) Your initial post just seemed a bit cavalier, but I understand now what you were saying.
[quote=Homemade WRX]as for the flat plate covering the spare, that actually reduces the turbulent flow of air (causing drag) coming from the back of you car...have the test numbers from a ford taurus where it was done.[/QUOTE]
So there are legitimate gains to be had from the "ghetto" rear undertray that is mentioned in the article MPME posted? Seems like a pretty easy thing to try, I'll probably give that a shot in the near future. I also think it would be pretty easy to add the side undertray bits that the STi has - same reasoning as the rear part, plenty of locations to bolt/rivet something to under there. Probably wouldn't provide a huge gain, but should help smooth flow under the car, which is generally good, right? I don't think I'll be trying the engine/tranny undertrays, though, as my car wasn't designed for those (as the STi obviously has been) and I don't want to cause cooling issues by blocking off too much air flow.
[quote=Homemade WRX]I'd realy like to do one more which would pull air from the front fender wells to the underside of the car[/quote]
Is there something inherently bad about trying to pull air out the wheel wells to the sides of the car? I've seen on race cars (and apparently on the C6 Z06, as the pic below kind of shows) that you can put a lip on the leading edge of the fender opening, which creates a little low pressure area behind it (so in the opening of the wheel well) to suck air out of the wheel well. At some point I vaguely recall reading this could even improve brake cooling, as you're helping get air through the wheel well. Anyway, here's a view of the Z06 wheel well from the front, and you can see the black plastic lip extending out a bit:
[img]http://superdork.net/horsepower/auto/houstonautoshow05/images/DSC_0040.jpg[/img]
I would think it would be pretty easy to use some aluminum sheet or maybe some tough plastic mud flap material to experiment with this on the front wheel wells.
Edit: I haven't read any of these yet, so I don't know which articles cover which topics, but these apparently have some good aero tech in them - [url]http://www.advantage-cfd.co.uk/Newsletter/Articles-inline.htm[/url] .
Pat
Yeah, I can see that now. ;) Your initial post just seemed a bit cavalier, but I understand now what you were saying.
[quote=Homemade WRX]as for the flat plate covering the spare, that actually reduces the turbulent flow of air (causing drag) coming from the back of you car...have the test numbers from a ford taurus where it was done.[/QUOTE]
So there are legitimate gains to be had from the "ghetto" rear undertray that is mentioned in the article MPME posted? Seems like a pretty easy thing to try, I'll probably give that a shot in the near future. I also think it would be pretty easy to add the side undertray bits that the STi has - same reasoning as the rear part, plenty of locations to bolt/rivet something to under there. Probably wouldn't provide a huge gain, but should help smooth flow under the car, which is generally good, right? I don't think I'll be trying the engine/tranny undertrays, though, as my car wasn't designed for those (as the STi obviously has been) and I don't want to cause cooling issues by blocking off too much air flow.
[quote=Homemade WRX]I'd realy like to do one more which would pull air from the front fender wells to the underside of the car[/quote]
Is there something inherently bad about trying to pull air out the wheel wells to the sides of the car? I've seen on race cars (and apparently on the C6 Z06, as the pic below kind of shows) that you can put a lip on the leading edge of the fender opening, which creates a little low pressure area behind it (so in the opening of the wheel well) to suck air out of the wheel well. At some point I vaguely recall reading this could even improve brake cooling, as you're helping get air through the wheel well. Anyway, here's a view of the Z06 wheel well from the front, and you can see the black plastic lip extending out a bit:
[img]http://superdork.net/horsepower/auto/houstonautoshow05/images/DSC_0040.jpg[/img]
I would think it would be pretty easy to use some aluminum sheet or maybe some tough plastic mud flap material to experiment with this on the front wheel wells.
Edit: I haven't read any of these yet, so I don't know which articles cover which topics, but these apparently have some good aero tech in them - [url]http://www.advantage-cfd.co.uk/Newsletter/Articles-inline.htm[/url] .
Pat
| drees | 02-02-2006 11:01 PM |
The lip in front of wheels is designed to push the air over the wheels, not to try to suck air through them, the wheels of a car are a major source of drag.
| Homemade WRX | 02-02-2006 11:06 PM |
for the rear diffuser, I won't make any claims about it although I would love to test it...the smoother the flow under the car the better and that ends up resulting in noticeable downforce and lower drag
for the wheel well pressure (which cause lift), I would love to pull it out of the fender(rear or top of the wheel well) but can't think of how to do it without it looking goofy/ugly on our cars...this also helps keep brake and residual temps in the well down...
as for the little black lip/front splitter on the z06, that covers the front tire and seperates the air flow from the spinning wheel. Spinning wheels cause lift and drag....
haven't looked at your link yet....just now opening it ;)
edit:yeah, kinda basic flow and turbulence stuff from what i breezed through...I will read in more in depth later when my brain is fully functioning ;)
as for doing it on your car...go for it...you will see several cars (generally higher end) have them...and a lot of weird plastic things on the undersides of lots of cars are there for reasons(even the flat black plastic piece under Saturn bumpers)...
for the wheel well pressure (which cause lift), I would love to pull it out of the fender(rear or top of the wheel well) but can't think of how to do it without it looking goofy/ugly on our cars...this also helps keep brake and residual temps in the well down...
as for the little black lip/front splitter on the z06, that covers the front tire and seperates the air flow from the spinning wheel. Spinning wheels cause lift and drag....
haven't looked at your link yet....just now opening it ;)
edit:yeah, kinda basic flow and turbulence stuff from what i breezed through...I will read in more in depth later when my brain is fully functioning ;)
as for doing it on your car...go for it...you will see several cars (generally higher end) have them...and a lot of weird plastic things on the undersides of lots of cars are there for reasons(even the flat black plastic piece under Saturn bumpers)...
| BIGSKYWRX | 02-02-2006 11:24 PM |
Pat- I put the STi side under aero pieces on- wasn't too bad- the pieces lined up nicely (just had to drill several holes-posted a tutorial on scoobymods). Working on the rear piece hopefully this weekend :)
| Patrick Olsen | 02-03-2006 07:01 AM |
[QUOTE=drees]The lip in front of wheels is designed to push the air over the wheels, not to try to suck air through them, the wheels of a car are a major source of drag.[/QUOTE]
I understand that, I'm just saying that the lip is going to create at least a small low pressure area behind it, which will help pull the high pressure out of the wheel wells. I imagine it's a secondary effect, but I know I've read that somewhere, and it makes sense to me.
Pat
I understand that, I'm just saying that the lip is going to create at least a small low pressure area behind it, which will help pull the high pressure out of the wheel wells. I imagine it's a secondary effect, but I know I've read that somewhere, and it makes sense to me.
Pat
| Homemade WRX | 02-03-2006 11:25 AM |
[QUOTE=Patrick Olsen]I understand that, I'm just saying that the lip is going to create at least a small low pressure area behind it, which will help pull the high pressure out of the wheel wells. I imagine it's a secondary effect, but I know I've read that somewhere, and it makes sense to me.
Pat[/QUOTE]
that could be very possible and would work in theory...so long as the windtunnel testing got it dialed in to that, it can...
Pat[/QUOTE]
that could be very possible and would work in theory...so long as the windtunnel testing got it dialed in to that, it can...
| davis10 | 02-03-2006 02:25 PM |
[QUOTE=speedyHAM]R
A flat bottom to our cars would help the overall fuel economy, but not enough to be cost effective for Subaru. Those little plastic peices and fasteners + assembly time add up to a lot on a per car basis. I'd like to make one but don't have the money or the time.
[/QUOTE]
I was thinking it would improve gas mileage too, it may not be cost effective for subaru but maybe it would be for us :). Even just having a piece to prevent the parachute effect of the rear bumper might make a difference.
A flat bottom to our cars would help the overall fuel economy, but not enough to be cost effective for Subaru. Those little plastic peices and fasteners + assembly time add up to a lot on a per car basis. I'd like to make one but don't have the money or the time.
[/QUOTE]
I was thinking it would improve gas mileage too, it may not be cost effective for subaru but maybe it would be for us :). Even just having a piece to prevent the parachute effect of the rear bumper might make a difference.
| Homemade WRX | 02-03-2006 02:30 PM |
[QUOTE=davis10]I was thinking it would improve gas mileage too, it may not be cost effective for subaru but maybe it would be for us :). Even just having a piece to prevent the parachute effect of the rear bumper might make a difference.[/QUOTE]
well, sean (speedyham), rob (rbehny) and I have talked about making one for a while...just a matter of time and money...
well, sean (speedyham), rob (rbehny) and I have talked about making one for a while...just a matter of time and money...
| davis10 | 02-03-2006 02:37 PM |
[QUOTE=Patrick Olsen]
I would think it would be pretty easy to use some aluminum sheet or maybe some tough plastic mud flap material to experiment with this on the front wheel wells.
Pat[/QUOTE]
Yea I was thinking the same thing about the mudflap material I think that the WRC uses similar material to cover some stuff for some rallies. I think ive seen it covering like control arms and stuff, thats more for protection then areo but I still think it would be good to look at. The material is similar to Ultra High Molecular Weight Polyethelyne. I worked with it when I made some ski boxes last summer its very strong, impact resistant, and not too heavy. You can order it off the internet in sheet form, it mildly expensive though.
for a picture of what im talking about gor to [url]www.swrt.com[/url] and go to the gallery of 2005 pics, then go to sweden the look at the picture in row 2 in the middle.
I also have a picture of the bottom of a WRC car
[IMG]http://img70.imageshack.us/img70/8332/kresta040tn.jpg[/IMG]
**thanks for the help hosting i didnt know you could do it w/o an account
However now that I see this i realise WRC cars are the wrong place to look if you want you car more areodynamic, in the pic I posted you can see that there is not diffuser on the bumper and you would have the parachute effect just like a road car, but if you look at the back of a ferrari f430 you can see that the rear bumper doesn't form a parachute, but bottom is smooth right to the back of the car.
I would think it would be pretty easy to use some aluminum sheet or maybe some tough plastic mud flap material to experiment with this on the front wheel wells.
Pat[/QUOTE]
Yea I was thinking the same thing about the mudflap material I think that the WRC uses similar material to cover some stuff for some rallies. I think ive seen it covering like control arms and stuff, thats more for protection then areo but I still think it would be good to look at. The material is similar to Ultra High Molecular Weight Polyethelyne. I worked with it when I made some ski boxes last summer its very strong, impact resistant, and not too heavy. You can order it off the internet in sheet form, it mildly expensive though.
for a picture of what im talking about gor to [url]www.swrt.com[/url] and go to the gallery of 2005 pics, then go to sweden the look at the picture in row 2 in the middle.
I also have a picture of the bottom of a WRC car
[IMG]http://img70.imageshack.us/img70/8332/kresta040tn.jpg[/IMG]
**thanks for the help hosting i didnt know you could do it w/o an account
However now that I see this i realise WRC cars are the wrong place to look if you want you car more areodynamic, in the pic I posted you can see that there is not diffuser on the bumper and you would have the parachute effect just like a road car, but if you look at the back of a ferrari f430 you can see that the rear bumper doesn't form a parachute, but bottom is smooth right to the back of the car.
| BraveUlysses | 02-03-2006 03:32 PM |
^^^^ [url]www.imageshack.us[/url] or photobucket.com can be used for your image hosting needs.
| davis10 | 02-03-2006 05:49 PM |
this is something you may want to look at. I don't know how much you want to do with this, but it would be cool if you could cut out some of the back bumper and professionally wrap around some fiberglass or somthing to make the underbody and the bumper a continuous shape like ferrari does on cars like to enzo as you see here
[IMG]http://img217.imageshack.us/img217/4792/picfetch0hb.gif[/IMG]
[IMG]http://img217.imageshack.us/img217/4792/picfetch0hb.gif[/IMG]
| subber | 02-03-2006 09:52 PM |
[IMG]http://www.gruppe-s.com/Subaru/subext/kansai_FRP.jpg[/IMG]
Here's a rear diffuser being sold by gruppe-s.. anybody have firsthand info on its effectiveness? It seems simple enough and can be 'home-made' although maybe not with as good fit quality. To me it seems it at least reduces the 'parachute' effect caused by the rear bumper.
Here's a rear diffuser being sold by gruppe-s.. anybody have firsthand info on its effectiveness? It seems simple enough and can be 'home-made' although maybe not with as good fit quality. To me it seems it at least reduces the 'parachute' effect caused by the rear bumper.
| Patrick Olsen | 02-03-2006 11:18 PM |
Wow, that's a nice-looking piece. Looks much more "complete" than the stock diffuser.
Pat
Pat
| LastResort | 02-03-2006 11:23 PM |
[QUOTE=Patrick Olsen]Wow, that's a nice-looking piece. Looks much more "complete" than the stock diffuser.
Pat[/QUOTE]
I *think* that is the HKS diffuser, and APS is coming out with one real shortly.
Pat[/QUOTE]
I *think* that is the HKS diffuser, and APS is coming out with one real shortly.
| Homemade WRX | 02-04-2006 12:08 AM |
I like it...too bad they don't make one for my car...they don't make any of the good stuff for my car :(
| TheRipler | 02-04-2006 12:24 AM |
[QUOTE=LastResort]I *think* that is the HKS diffuser, and APS is coming out with one real shortly.[/QUOTE]
I think you're right. I was looking at that before I decided (after seeing the price) to try and make one myself.
I think you're right. I was looking at that before I decided (after seeing the price) to try and make one myself.
| Homemade WRX | 02-04-2006 12:29 AM |
[QUOTE=TheRipler]I think you're right. I was looking at that before I decided (after seeing the price) to try and make one myself.[/QUOTE]
for our cars I wouldn't worry to much about making one with directional venturis...so much as just the venturi itself (if one at all)...just flaring the back up with the bottom of the bumper will give some effect in itself...
for our cars I wouldn't worry to much about making one with directional venturis...so much as just the venturi itself (if one at all)...just flaring the back up with the bottom of the bumper will give some effect in itself...
| TheRipler | 02-04-2006 01:03 AM |
I agree. I wasn't going to try to duplicate the venturis so much as just try to smooth things out with the bumper. I can see how the venturis might help with downforce if designed properly, but I don't know that I could do that with my "agricultural engineering" (read: raised on a farm) background. :) My plan was to leave them out.
Seeing this picture again, I wonder about the cutout sections on the side, and if that might not be releasing some air trapped above the diffuser. Thoughts?
Seeing this picture again, I wonder about the cutout sections on the side, and if that might not be releasing some air trapped above the diffuser. Thoughts?
| Homemade WRX | 02-04-2006 01:12 AM |
[QUOTE=TheRipler]I agree. I wasn't going to try to duplicate the venturis so much as just try to smooth things out with the bumper. I can see how the venturis might help with downforce if designed properly, but I don't know that I could do that with my "agricultural engineering" (read: raised on a farm) background. :) My plan was to leave them out.
Seeing this picture again, I wonder about the cutout sections on the side, and if that might not be releasing some air trapped above the diffuser. Thoughts?[/QUOTE]
I can't know for sure, but looking at it, I'd say it is for air to escape, especially seeing the wheelwell right there...
Seeing this picture again, I wonder about the cutout sections on the side, and if that might not be releasing some air trapped above the diffuser. Thoughts?[/QUOTE]
I can't know for sure, but looking at it, I'd say it is for air to escape, especially seeing the wheelwell right there...
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