Aerodynamics for high speeds

racebronco2

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Not very effective,
1. The angle you need the diffuser to rise with no turbulence is around 15 degrees.
2. You must have clean air channeled to the diffuser.
3. The diffuser need to start at the lowest rear portion of the car.

I had one on my car which i designer properly. It started slightly lower than the exhaust and was flat with the bottom of the car. At the rear of the car i made a piece that extends the rear of the bumper cover a few inches so that the diffuser was only 15 degrees. I removed it because it was really hard to work on the suspension, load the car on the trailer without the fins hitting the ground. Did it make a difference, i couldn't tell because the underside of the car was not paneled in.
 

FoMoCo01

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That is a show piece. If you were going to run a rear diffuser like that, you would want the front of the diffuser to be completely sealed to the body and you would want a 7-10 degree angle in the diffuser instead of the large angle of the one shown. Better yet would be to make the underside of the car completely smooth and flat. It also depends on how fast you're going. If you're 120+ you want to start looking into reducing drag and adding some downforce to keep the car stable at higher speeds. Look into the rear spoilers that drag racers or nascar use use. Stay away from wings as they will add too much drag. They will offer the most benefit along with some some rear to front rake.
 

iismet

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Not very effective,
1. The angle you need the diffuser to rise with no turbulence is around 15 degrees.
2. You must have clean air channeled to the diffuser.
3. The diffuser need to start at the lowest rear portion of the car.

That is a show piece. If you were going to run a rear diffuser like that, you would want the front of the diffuser to be completely sealed to the body and you would want a 7-10 degree angle in the diffuser instead of the large angle of the one shown. Better yet would be to make the underside of the car completely smooth and flat. It also depends on how fast you're going. If you're 120+ you want to start looking into reducing drag and adding some downforce to keep the car stable at higher speeds. Look into the rear spoilers that drag racers or nascar use use. Stay away from wings as they will add too much drag. They will offer the most benefit along with some some rear to front rake.

+1

diffusor2-jpg.79345


You can just see the bottom of the exhaust - that is how low the floor is. I have checked mine several times with a level. We plan to build the ceiling @ 8 degrees. At 8 degrees from the floor there is a gap between the bottom of the bumper and the ceiling of the diffuser - that is how low the diffuser has to be. If he were to to sheet the bottom, lower the diffuser, correct the ceiling angle, he would want to push it back so it's trailing edge intersected the vertical plane established with the trailing edge of the spoiler. Also the outer strakes are too far inboard. Their job is to seal wheel well pressure out out of the diffuser.

The goal is to build a venturi with the area between the ground and bottom sheeting acting as the venturi throat.

With a dirty bottom he is dragging dirty air which creates lift.

Stolen for reference

Rear%20Diffuser%20Aston.jpg


Diffuser.jpg


air-flow-under-car.jpg
 

WHT03SVTCOLO

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This one is from Maier Racing.

1brr.jpg


gthTSv.jpg


We had to build the dam and figure out how to attach it. We got down force as soon as we installed it. It is currently configured < 3" off the pavement. It is not a big shelf. I believe it works because we have accelerated the air under the car specifically at the axle line - we run a fully sheet-ed engine. The pressure is much lower there than stock. The rest of the air is directed above and around the front bumper cover. As you can see we have away to go on the sheeting - the work we have, made a significant difference in handling. Turn 9 at Portland is off camber and the car wanted to drive off (around 110). Our first shot with the splitter and we were driving it flat out which lead to MM3 components and bump steering the car.

Tuck exhaust up high

ksqeFB.jpg


Splitters are not recognized as adding drag. The sill splitters extend into the sub-frame connectors. You do not want to drag air under the car. Rather force it thru a venturi with speed . You wish you could run the air faster under the bottom than over the top.

We run 1/8 inch of slope rear to front this gives us a venturi in side view (ours is weak without more sheeting). It is evolution for us. We modify it, run it, and check lap times and feel. The more you can sheet the better. We originally ran the Cobra hood with the vents punched out, but have since changed to a more free flowing hood and the cooling is boxed. This is another aspect of getting control of the air.

tgaA6g.jpg


Meir has a shallow and a deeper one for flairs. Ours is shallow and we run trip fencing on the fenders because of the offset of the Enkeis.

At the rear the Terminator spoiler could be used as a baseline. As stated, I would try to get rid of it, but it may be that a Gurney attached to the spoiler could work well. Gurneys are not recognized for adding drag, but do help clean up the air - dirty air causes drag. Pretty sure Maiers spoiler is not what you want, but it all takes testing. A Maier spoiler could be purchased and cut down.

On a speed car I would lower the front splitter down to 2" off the ground. This will complicate your effort because you will need to remove it for transport. We are too lazy. I would space the bottom panels down. I would try to get slope with suspension setup, but would consider building additional slope into the floor if needed. I have seen studies where bottoms less than 2" lessened ground affect. You can really see the slope on current F1 cars.

I recently acquired this

ypN3sn.jpg


It comes from the factory with a sheet-ed bottom. It is sheet-ed from the front bumper to the back of the engine.

Aston_Martin_V8_Vantage_Sport_Cat_X_Pipe_Install_1  __31456.1430934064.1280.1280.JPG


Top speed claimed 175 - 3600 lb - 380 bhp. No splitter, no spoiler, no diffuser. Intake is boxed cold air, cooling is boxed, bottom is sheet-ed. I smiled when we put it on the rack because it increased my confidence we are headed in the right direction on the Cobra. It won't hang with a stock SVT on the street, but out of the box pretty sure it would get one on the track. (It will not hang with my Cobra on the track - it's not quick enough) The engineering, execution, and balance are beautiful and it is much easier to drive at the limit (49/51 with lower cg).

Our stuff is crude - it has been an experience in learning how to keep it attached.

If you have to turn at speed all bets are off :-D - I would think wing and enough HP to drag it. The air under this car is ripping - not fast enough :eek: Notice how close he is drafting. Is it possible he lost flow to the bottom?

[video=youtube;8snP33Ga3X4][/video]

chr

How does the apr stuff stack up for aerodynamics for high speeds? I'm looking to improve my 11 top speed. Maier racing doesn't have anything for us 10-12 mustang.

http://aprperformance.com/racing-product/widebody-aerodynamic-kits/
 

racebronco2

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Diffusor are not street or working on the car friendly. I built one with the correct specs. I could not tell any improvement in the car with it installed. I think there was no improvement because the whole under body needs to be smoothed out to direct the air correctly. The fins were so low it was hard to adjust the rear suspension. i could barely rear the toe links. The car would scrap sometimes on steep driveways. I used to open track alot and sometime i had to be towed home. There is no way the car could be put on a flatbed backwards, putting the car on a flatbed front first we had to use 2 x 4's in front of the rear wheels so that the diffusor wouldn't scrape so much.
 

noldevin

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Sounds like a lot of pain in the ass for little or no gain.
Sadly the underside of these cars is just too messy to get a good rear diffuser set up.
I have wondered if those RTR vented inserts next to the rear license plate actually make any difference.
 

N/Angel

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blowing the light dust of this thread... been working on the engine a bit more and got it to 496hp at the crank, 500hp is the limit in my class.
Last event was great, got second place in front of Golf 7R, AMG C63, M2, M3 Competition, Alpina... only the one C7 Vette was faster.
I passed the line at 246,59kph, he is at 249,71kph. Cars in my class going faster than the 250kph limit automatically are moved to the next higher class.

So I'm trying to find the missing 3kph for the next event in July, the M3 got really close in the last run!
My mods sofar: Coyote engine, Magnum 6-speed, 3.73 IRS, Racebronco hood, gutted interior with rollcage (dash, door panels and corbeau seats), battery moved to the trunk, 18" Wedsport wheels.
Things I already have on the to do list:
- run with below half tank of gas! (full the last time)
- tape up my Agent47 Side window scoops
- fold in the mirrors

Any other suggestions?
I would like to get rid of the stock door panels but can't seem to find a carbon fiber replacement. Probably not much for weight savings but every little bit helps.

Here is a pic of the car at the last event
IMG_3542_small.jpg
 

03 DSG Snake

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blowing the light dust of this thread... been working on the engine a bit more and got it to 496hp at the crank, 500hp is the limit in my class.
Last event was great, got second place in front of Golf 7R, AMG C63, M2, M3 Competition, Alpina... only the one C7 Vette was faster.
I passed the line at 246,59kph, he is at 249,71kph. Cars in my class going faster than the 250kph limit automatically are moved to the next higher class.

So I'm trying to find the missing 3kph for the next event in July, the M3 got really close in the last run!
My mods sofar: Coyote engine, Magnum 6-speed, 3.73 IRS, Racebronco hood, gutted interior with rollcage (dash, door panels and corbeau seats), battery moved to the trunk, 18" Wedsport wheels.
Things I already have on the to do list:
- run with below half tank of gas! (full the last time)
- tape up my Agent47 Side window scoops
- fold in the mirrors

Any other suggestions?
I would like to get rid of the stock door panels but can't seem to find a carbon fiber replacement. Probably not much for weight savings but every little bit helps.

Here is a pic of the car at the last event
View attachment 1489602

Ultra-Carbon '99-'04 Ford Mustang Parts | Ultra-Carbon

SN95 99-04 Doors
 

BlackStripes

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I would like to get rid of the stock door panels but can't seem to find a carbon fiber replacement. Probably not much for weight savings but every little bit helps.

I'd cover the area where the pony is, our cars can get all the air from the bottom opening.


I spoke with AJ (rhrperf) several months ago and his doors are for RACING.... they are only a little piece of carbon :) ( I have their trunk)

And I also was talking to Greg Shampine (Ultra Carbon owner), since I heard from friends that his products are outstanding, but he raised his price from $2800 to $3800 in matter of 3 months ... I stopped talking right there ;)

Seems like you want only the panels, which, you are right, I can't see that saving more than a couple of lbs. The doors though, they save over 65lbs (both). I am getting a set, but waiting to find the right time/company.
 

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N/Angel

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Inflate your tires to the max, If you radiator is boxed in remove the bottom panel.

I usually run 3 bar tire pressure front and back. Even higher?
I'm also looking at a set of semislicks for my 9x17 Wedsports. Maybe run 245/40/17 all around if traction is no issue.

Radiator is not boxed in
 

N/Angel

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is covering the area where the pony is really not hurting cooling? I remember the FR500 had the hood extended to cover this area, but it wasn't a production car.

I would love to get a set of doors, but the cost is insane and it will never be TÜV approved, I'm in Europe. This is why I'm looking for the panels only, something like Agent47 had a couple of years back, just in carbon fiber.

Cost is a real issue as I'm trying to put money aside for a sequential transmission and maybe a supercharger setup next year.

and just to make things more interesting, a Ferrari F430 signed up for the July race and sits at the same powerlevel as mine. How on earth can I beat a Ferrari!?!? LOL!
 

BlackStripes

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1174655_616945858396751_5602956704531435672_n.jpg
AJFrontEnd.jpg
is covering the area where the pony is really not hurting cooling? I remember the FR500 had the hood extended to cover this area, but it wasn't a production car.

A lot of American Iron (X) cover the front area, as long you open up the bottom, you should be ok. You have a real water/oil temp gauge?
 

racebronco2

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I'd cover the area where the pony is, our cars can get all the air from the bottom opening.

I did a test years ago with yard and a camera because i heard the same thing. The results is that our cars do not get any air from the boom below the bumper cover. Think about it, you are doing 100mph, the air is not going to slow down to make a 90 degree turn up and another 90 degree up from 2 inches to 14 inches to the top of the radiator. Our bumper cover forces the air down to clear the radiator support.
 

BlackStripes

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I did a test years ago with yard and a camera because i heard the same thing. The results is that our cars do not get any air from the boom below the bumper cover. Think about it, you are doing 100mph, the air is not going to slow down to make a 90 degree turn up and another 90 degree up from 2 inches to 14 inches to the top of the radiator. Our bumper cover forces the air down to clear the radiator support.

Not sure about that, there is air that touches the car for first time at the bumper (i guess around 4 or 5 inches) but there's also air that touches the car for first time right at the pony height, and that air will try to go to the radiator instead going up the hood, if you have enough opening at the low side I think you should be ok. If it's a car that is not concern about street driving, i'd cover that section. I've seen enough cars that cover that area in AI/X.

Possibly the best aero company in my opinion that works on Mustang sells this for that reason:

SN95 99-04 Cobra R Bumper

edit: ooops I referenced this a post ago :)
 

302blown

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This post is a little old but the key to any sort of rolling top speed event is lowering drag. Now if the speeds are up there a little bit to downforce, a little, may help with stability at speed. As mentioned in a previous post sealing up the entire grill opening where the pony is will certainly help reduce drag and increase top speed. These extractors are designed to allow reducing the front grill opening, this reduces drag while still maintaining cooling. This was confirmed in wind tunnel testing. www.racelouvers.com
 

N/Angel

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My hood has this kind of louvers.

I bought another Mustang so budget on this one is tight, currently searching for semislicks for my 9x17 Wedsport wheels, narrowing the tire width should help a bit with top speed.
 

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