Author Topic: 2nd gen TA aerodynamics and modifications  (Read 58999 times)

NOT A TA

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2nd gen TA aerodynamics and modifications
« on: August 02, 2015, 10:00:52 PM »
As part of the current rebuild on my 70 Esprit (with TA body parts) I'm doing several things which will hopefully make the car perform better for various high speed types of use. The car will spend a lot of time well over 90 MPH on road race courses, Land Speed Racing and open road racing. I've got several things I want to try and can't find much solid information on what actually works or doesn't and so I'll be doing a lot of testing, guessing, modifying, and more testing. If possible I'd like to get the car into the A2 wind tunnel for testing eventually but meanwhile I'll see what I can do with what I've got. I figured I'd document the process here for anyone interested now or in the future.

GM has has been using wind tunnels since the 50's.http://www.autoblog.com/2010/08/05/gms-wind-tunnel-turns-30/  I suspect the Pontiac engineers who designed the 2nd gen Trans Am used it to help design the new body style as well as the spoilers, flares etc. used on the Trans Am models. So my baseline is tuft testing the stock panels, spoilers, flares etc before modifications and then testing additional parts as well as modified factory parts.

 Here's a partial list of modifications. I welcome any comments, suggestions, etc.

Here's the plan

1. Extend air dam
2. Splitter
3. Belly pans
4. Side skirts & side splitters
5. Wicker bills in front of wheel openings
6. Rear diffuser, possibly two types
7. 3 different rear spoilers
8. Foilers behind wheel openings
9. Seal radiator support so only air allowed past is through radiator and brake ducts
10. Side window panels from cage to body to reduce chute effect on road courses
11. Roof fences?
12. Tire air dams
13. Front splash pan opening block offs
14. Modify fender vents
15 Rear wing

I'm a grassroots racer type guy. No engineering degrees, no supercomputer with CFD programs, no full size wind tunnel, no friends named Katz or McBeath, and don't have the math background to use Bernoulli's equation. However, I'll do as much testing as possible while building and then do track testing with video to see what actually works and how well in the real world.

The first modification is a taller rear spoiler. Lots of testing has been done on rear spoilers in general and for the shape of a 2nd gen the height after the first couple inches increases the downforce more so going from a 3" spoiler to a 4" spoiler doesn't increase the downforce as much as the change from say 4" to 5". The penalty is increased drag that will slow the car. Eventually I'll probably have 3 different rear spoilers and also full wing to test.

Although increased drag will lower the top speed capability the cars lap times on a road course may actually be reduced if the cornering grip is increased enough with the tall spoiler. I'll be making other spoilers for straight line top speed (less drag)and some for road course use so there will be several versions of aerodynamic prep I can set the car up with depending on what kind of race activity I'll be doing. At the same time I'll have most of the aero stuff removable so the car can look like a sort of stock bodied TA clone.







« Last Edit: August 03, 2015, 07:59:24 AM by NOT A TA »
John Paige
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NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #1 on: August 02, 2015, 10:43:05 PM »


Shown above is my rudimentary aerodynamic setup with very high speed additional wind provided by a Stihl leaf blower. Testing worked out surprisingly well to determine what I wanted to test for modifying fender vents.




The stock fender air extractor vent shown above (without screen) during base line yarn tuft testing at normal driving speeds shows the vent does work to help reduce air pressure underhood based on my crude testing. Even at normal driving speeds the vents pull air out of the engine compartment. As speed increases the vents pull more air. I have long strands of yarn inside the fender attached at various distances from the vent opening so I can see how much suction there is pulling air out.

Now the stock vent opening is about 15 Sq. In. and the stock screen blocks off about 5 Sq. In. of that. The air coming out is subjected to turbulence slowing it down which is caused by the screen itself. So anyone wanting to increase the breathing a quick 50% plus over stock can just remove the screens.

The vents help reduce underhood air pressure that causes the "floating" feeling that a lot of cars (including base 2nd gens) get at high speed. Having spent quite a bit of time over 120 MPH in my car I'll say it's very steady and stable feeling at speeds up to 150 MPH due to the stock TA aero parts I believe. Since I'm going to try and go a lot faster at Land Speed Races I want to make a set of vents that will optimize underhood evacuation with the least amount of drag. I also want to make a set that will help maximize usable downforce by reducing underhood pressure as much as possible and by design perhaps add some downforce by the exterior design of the vents themselves.

« Last Edit: August 03, 2015, 12:09:12 PM by NOT A TA »
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Casey

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Casey

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Re: 2nd gen TA aerodynamics and modifications
« Reply #3 on: August 02, 2015, 11:15:51 PM »
Also found this posted by one of our members on another forum: http://www.firebirdnation.com/forums/topic/490514-aerodynamics-of-a-trans-am/

Another interesting discussion that took place right here on this board: http://transamcountry.com/community/index.php?topic=42840.0

Well if I bothered going past the first post obviously you know about the first link, but I'll leave it for others.
« Last Edit: August 02, 2015, 11:35:19 PM by Box »

NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #4 on: August 03, 2015, 01:29:50 PM »
Interesting info about using Chevy's aero test results to develop the TA parts in that Muscle Car History book linked by BOX.

I posted in the parts wanted section here to get some extra expendable fender vents I wouldn't be worried about hacking up and then tossing if my plans didn't work. Our fearless leader Mike Barefoot donated a set to the project and i got another set from Jack in exchange for some modified early 2nd gen engine mounts I've been working on. So I stripped them of paint and this way I'd have my stockers along with two more sets to modify so I can see the difference changes make by just doing all my testing on one side of the car and not having to reshape one vent over and over to test different theories.

The first thing I tried was changing the exterior of the vents to change the airflow and increase the suction of underhood air. I made two different designs and it appeared to me that both designs drew substantially more air through the stock openings with the larger more radical angle design pulling more air than the more streamlined one.



Pic below shows the yarn tufts with no air movement and the more radical "just for the track Jack" concept mocked up with cardboard.



Pic below is the track Jack concept with high speed air moving over it. You can see how air close to the surface is actually drawn backward from the rear of the vent housing to join the air coming out the vent opening. Seems to me like this also shows increased drag.



The streamline barefoot version shown below with the wind speed the same as the track Jack version pic shown above. You can see some of the long strands of yarn have been pulled out from inside the fender and how the boundary layer air moves over the Barefoot vent opening as opposed to above and below it as seen in the pic above.







« Last Edit: August 03, 2015, 01:47:16 PM by NOT A TA »
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Re: 2nd gen TA aerodynamics and modifications
« Reply #4 on: August 03, 2015, 01:29:50 PM »

jonathonar89

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Re: 2nd gen TA aerodynamics and modifications
« Reply #5 on: August 03, 2015, 02:07:56 PM »
Very nice stuff John!  Always seeing good work from you online.  I would like to see what you'd do if you had a 79-81 body.  The later body seems like a better starting point if talking aero.

I'd imagine new rear spoiler ends that extend forward and don't let the air roll off the sides.  That might play a big role in keeping downforce out back.  The Camaro was better than the firebird in this area but there might be a better custom end to make.

NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #6 on: August 03, 2015, 05:12:00 PM »
Very nice stuff John!  Always seeing good work from you online.  I would like to see what you'd do if you had a 79-81 body.  The later body seems like a better starting point if talking aero.

I'd imagine new rear spoiler ends that extend forward and don't let the air roll off the sides.  That might play a big role in keeping downforce out back.  The Camaro was better than the firebird in this area but there might be a better custom end to make.


The first thing I'd try on a 79 would be a clear Lexan flat sheet that fit over the headlight openings. I had an 80 Monza Spyder with the dual square headlight openings similar to 79 TA's. I bought the car new and bought a kit to make headlight opening covers for it but could never bring myself to drill holes and what not to put mounting brackets on it.  Shoulda just done it as I ended up giving the car to the first ex-wife as a consolation prize/parting gift anyway. ahahaha

The Camaro rear spoiler end cap design does give more downforce supposedly. I tried reworking the end caps on my tall spoiler to be more  like the Camaro ones but they just didn't really look right so I extended the TA style caps so they stick out a bit wider at the outside corners to hopefully give a little more downforce being out in cleaner air on the sides even though the air rolls off the ends easier.  A fence of some type like is used on the sides of the rear extending aluminum pro stock style spoilers would probably help but look funny. The third gens pulled it off better with the wraparound style spoiler.

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Black Sheep

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Re: 2nd gen TA aerodynamics and modifications
« Reply #7 on: August 03, 2015, 06:12:38 PM »
Try blocking off your grilles so the only air going thru the radiator (and engine bay) is what's pulled in from under the bumper.  Pulling too much air thru the grilles makes the area underhood into a huge parachute.  Also, many high speed autos duct the air coming thru the radiator out thru the top of the hood, bypassing the parachute effect.

Bellypan and diffuser at the rear.

Suck in your bumpers

Really low ride height and side skirts.  If it don't scrape, it ain't low enough.

They do land speed racing about 20 minutes from me in Wilmington, Ohio.  Be happy to lend my shop if you wanna come and run :cool:
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Casey

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Re: 2nd gen TA aerodynamics and modifications
« Reply #8 on: August 03, 2015, 06:38:38 PM »
That Red Baron Pizza side extractor, should keep it like that.  Get some sponsorships and free pizza. :P

I too found it interesting Chevy did a lot of aero testing only for big wigs to turn it down because it wouldn't fit the Chevrolet image or what have you.

77 TA man

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Re: 2nd gen TA aerodynamics and modifications
« Reply #9 on: August 03, 2015, 08:03:48 PM »
Cool stuff! I never realized that aerodynamic testing was this intensive, thanks for posting!
As a side note, when I was doing the drivers ed course the instructor said a reason to not drive fast was that the cars areodynamics werent made to keep it pinned to ground; my thoughts were "you've obviously never have encountered a 2nd gen Trans Am, "Areodynamics of a stealth fighter".
« Last Edit: August 03, 2015, 08:08:49 PM by 77 TA man »
1977 HardTop T/A: 347 LSx Build,3.905" Wiseco 25cc dished pistons,forged rods, OE crank,BTR Stage 2 turbo cam, ARP Main+Head Studs,

1986 T-Top T/A:
Navy Blue Paint ,Grey/Black interior,140mph speedo,overhead console, LB9/Automatic, 2.77 Posi,  WS-6 suspension, All power options, UMI Wonderbar, UMI Rear LCAs, KYB Excel-Gs, Opened Formula hood,

jonathonar89

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Re: 2nd gen TA aerodynamics and modifications
« Reply #10 on: August 03, 2015, 08:27:02 PM »
Very nice stuff John!  Always seeing good work from you online.  I would like to see what you'd do if you had a 79-81 body.  The later body seems like a better starting point if talking aero.

I'd imagine new rear spoiler ends that extend forward and don't let the air roll off the sides.  That might play a big role in keeping downforce out back.  The Camaro was better than the firebird in this area but there might be a better custom end to make.

The first thing I'd try on a 79 would be a clear Lexan flat sheet that fit over the headlight openings. I had an 80 Monza Spyder with the dual square headlight openings similar to 79 TA's. I bought the car new and bought a kit to make headlight opening covers for it but could never bring myself to drill holes and what not to put mounting brackets on it.  Shoulda just done it as I ended up giving the car to the first ex-wife as a consolation prize/parting gift anyway. ahahaha

The Camaro rear spoiler end cap design does give more downforce supposedly. I tried reworking the end caps on my tall spoiler to be more  like the Camaro ones but they just didn't really look right so I extended the TA style caps so they stick out a bit wider at the outside corners to hopefully give a little more downforce being out in cleaner air on the sides even though the air rolls off the ends easier.  A fence of some type like is used on the sides of the rear extending aluminum pro stock style spoilers would probably help but look funny. The third gens pulled it off better with the wraparound style spoiler.

I haven't seen anyone a set but classic industries carries clear GTS headlight covers for 79-81 Firebird.  I have a few ideas myself but geared more towards 79-81.  Not trying to change your thread to 79-81 subjects/ideas so I'll stop here on that. 

Another crazy thought for you John is to form the front of your doors behind the fender.  You could also do this in the fender section somehow.  Herb Adams did that on his race car.  It would look somewhat like 1st generation Vipers in front of the door.

NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #11 on: August 03, 2015, 09:42:46 PM »
Try blocking off your grilles so the only air going thru the radiator (and engine bay) is what's pulled in from under the bumper.  Pulling too much air thru the grilles makes the area underhood into a huge parachute.  Also, many high speed autos duct the air coming thru the radiator out thru the top of the hood, bypassing the parachute effect.



Bellypan and diffuser at the rear.

Suck in your bumpers

Really low ride height and side skirts.  If it don't scrape, it ain't low enough.

They do land speed racing about 20 minutes from me in Wilmington, Ohio.  Be happy to lend my shop if you wanna come and run :cool:

I ran my car with the ECTA back when they ran races at Maxton NC. Haven't been to the new place in Ohio. We had a venue here in FL I've run my bird at.  The Dade/Collier airport that was built for the SST planes that were given up on. The strip is 2 miles long and perfectly flat. Temps were a little high to make good power naturally aspirated but the boosted cars just turned them up a bit. I may end up in Ohio if it's closer than the Texas mile when the car is back together.

The Dade Collier LSR strip.

John Paige
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NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #12 on: August 03, 2015, 09:56:33 PM »
Cool stuff! I never realized that aerodynamic testing was this intensive, thanks for posting!
As a side note, when I was doing the drivers ed course the instructor said a reason to not drive fast was that the cars areodynamics werent made to keep it pinned to ground; my thoughts were "you've obviously never have encountered a 2nd gen Trans Am, "Areodynamics of a stealth fighter".


While my car certainly won't be stealth by any stretch of the imagination with bright red paint and loud side pipes.  I'm hoping my efforts work out. The tuft testing I've shown is just the tip of the iceberg compared to what race teams do. For the vents I'm working on I'm just concentrating on the vent shape and openings now. Once I have the vents mocked up I'll be working on a sort of funnel shaped piece that will fit inside the fender to smooth the flow through the fender vent opening with the thought that increasing air speed through the opening will further reduce pressure under the hood thereby reducing lift more which will make available downforce more effective.
John Paige
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NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #13 on: August 03, 2015, 10:30:55 PM »

I haven't seen anyone a set but classic industries carries clear GTS headlight covers for 79-81 Firebird.  I have a few ideas myself but geared more towards 79-81.  Not trying to change your thread to 79-81 subjects/ideas so I'll stop here on that. 

Another crazy thought for you John is to form the front of your doors behind the fender.  You could also do this in the fender section somehow.  Herb Adams did that on his race car.  It would look somewhat like 1st generation Vipers in front of the door.

Everyone, please feel free to chime in with any ideas, mods you've done, or mods your considering no matter what year 2nd gen. I purposely worded the thread title in the hopes of a free discussion on the whole 2nd generation not just "NOT A TA's aero crap". The whole aerodynamic topic is like a black hole rarely discussed. Those in "the business" have to be careful not to divulge secrets so they don't/can't say much and there's only a few guys in the world who publish anything useful to the average guy. Anyway, please feel free to discuss any thing related to 2nd gens of any year here. There's plenty of info out there on 3rd and fourth gens and I'll be happy to point those interested in the right direction for 3rd & 4th gen aero info but I'd like this thread to concentrate on 2nd gens.

While I'm making a lot of modifications, I'm trying to keep them easily changeable back to stock looking or things that can't be seen when the car is assembled. As examples, when I made the tall rear spoiler I made it with a slightly smaller footprint than the stock spoiler which is also ready for paint. So I can always put the stock one on and no one would ever know the tall one had been on the car because the register marks in the trunk lid paint will be covered by the stock spoiler. The way I plan on sealing the core support so the only air entering the engine compartment from the front is through the radiator won't be seen with the hood closed. Something like spreading the fenders to be wider than the doors I won't do because it'll affect the look of the car more than I want to live with on a semi-permanent basis. Most of the aesthetically obvious things I'm doing will be able to be added/removed fairly quickly. Not saying the wider fender thing won't work. It may in fact, but I'm taking a slightly more conservative approach.
« Last Edit: August 04, 2015, 09:39:07 AM by NOT A TA »
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77 TA man

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Re: 2nd gen TA aerodynamics and modifications
« Reply #14 on: August 04, 2015, 07:36:05 AM »
Cool stuff! I never realized that aerodynamic testing was this intensive, thanks for posting!
As a side note, when I was doing the drivers ed course the instructor said a reason to not drive fast was that the cars areodynamics werent made to keep it pinned to ground; my thoughts were "you've obviously never have encountered a 2nd gen Trans Am, "Areodynamics of a stealth fighter".


While my car certainly won't be stealth by any stretch of the imagination with bright red paint and loud side pipes.  I'm hoping my efforts work out. The tuft testing I've shown is just the tip of the iceberg compared to what race teams do. For the vents I'm working on I'm just concentrating on the vent shape and openings now. Once I have the vents mocked up I'll be working on a sort of funnel shaped piece that will fit inside the fender to smooth the flow through the fender vent opening with the thought that increasing air speed through the opening will further reduce pressure under the hood thereby reducing lift more which will make available downforce more effective.
Did you notice any difference normally driving the car with out the fender cent screens vs with the screens in?
Not sure what hood you have, but if its a shaker hood you could try running w/o the shaker?
1977 HardTop T/A: 347 LSx Build,3.905" Wiseco 25cc dished pistons,forged rods, OE crank,BTR Stage 2 turbo cam, ARP Main+Head Studs,

1986 T-Top T/A:
Navy Blue Paint ,Grey/Black interior,140mph speedo,overhead console, LB9/Automatic, 2.77 Posi,  WS-6 suspension, All power options, UMI Wonderbar, UMI Rear LCAs, KYB Excel-Gs, Opened Formula hood,

Re: 2nd gen TA aerodynamics and modifications
« Reply #14 on: August 04, 2015, 07:36:05 AM »



NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #15 on: August 04, 2015, 09:16:48 AM »
Cool stuff! I never realized that aerodynamic testing was this intensive, thanks for posting!
As a side note, when I was doing the drivers ed course the instructor said a reason to not drive fast was that the cars areodynamics werent made to keep it pinned to ground; my thoughts were "you've obviously never have encountered a 2nd gen Trans Am, "Areodynamics of a stealth fighter".

I didn't do any tuft testing with screens in place. I can do easily do that though and will report my observations.


While my car certainly won't be stealth by any stretch of the imagination with bright red paint and loud side pipes.  I'm hoping my efforts work out. The tuft testing I've shown is just the tip of the iceberg compared to what race teams do. For the vents I'm working on I'm just concentrating on the vent shape and openings now. Once I have the vents mocked up I'll be working on a sort of funnel shaped piece that will fit inside the fender to smooth the flow through the fender vent opening with the thought that increasing air speed through the opening will further reduce pressure under the hood thereby reducing lift more which will make available downforce more effective.
Did you notice any difference normally driving the car with out the fender cent screens vs with the screens in?
Not sure what hood you have, but if its a shaker hood you could try running w/o the shaker?

I never drove my car without the screens in the fender vents. I have run my car at Road Atlanta and Sebring road courses without the Shaker. I did that because my shaker was pushed up high by carb spacers and the shaker blocked my view enough so that I was missing the apex of one turn on each track. Without the shaker I hit the apex more consistently but it felt like the rear of the car was a little looser in other turns and radiator temps were higher. On a day when on track temps were over 100 at Sebring I had to take a slow lap in the middle of each 20 minute session to get the engine temps down. I suspect that was due to high pressure air from the windshield bow wave being forced into the engine compartment through the shaker opening which was working against the engine fan and increasing the air pressure under the car.

One of the reasons I'm trying to maximize the airflow out the fender vents is because a lot of the area under the engine compartment will be blocked off by the splitter that will extend back to the cross member and a belly pan behind that. Because I have sidepipes most of the bottom of the car back to the rear axle will be covered by belly pans. With the engine compartment sealed up pretty well I'll need to have enough flow exiting somewhere for the radiator fans to keep things cool. Hopefully the modified fender vents will be enough.
« Last Edit: August 04, 2015, 09:20:51 AM by NOT A TA »
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NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #16 on: August 04, 2015, 09:36:54 AM »
Getting back to my testing, I added a small wicker bill (Gurney flap) to each of the cardboard mock up vents and tested. Adding the flap seemed to increase the suction of air out the vent while reducing turbulence and boundary layer reversion just aft of the vent. Notice in this pic the strands on the fender are all aimed rearward while in the pic above without the wicker the strand just behind the vent is pointing forward. both modified vents had similar changes with the track Jack vent appearing to pull a lot more air out of the engine compartment.

« Last Edit: August 18, 2017, 11:51:26 AM by NOT A TA »
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Re: 2nd gen TA aerodynamics and modifications
« Reply #17 on: August 04, 2015, 09:42:37 AM »
Really doesn't have much to do with aerodynamics as it does heat extraction, but do you still have the metal fender liners in place?  When I first looked at my brother's T/A there's no direct line of sight from the engine bay to the vents, so I always thought they were for looks more than anything but one day I noticed some air seemed to be coming out of them.  I'd imagine without the fender liners in the way they'd do a much better job.

Another thing I've heard of is people mounting PC fans or the like on the backside of the vent to forcibly pull air out, but with you spending most of your time at 100+ mph I'm not sure if they'd help or just be a hinderance.
« Last Edit: August 04, 2015, 09:46:36 AM by Box »

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Re: 2nd gen TA aerodynamics and modifications
« Reply #18 on: August 04, 2015, 09:50:07 AM »
My next change was increasing the size of the opening itself in the vent to allow more volume. It appeared that even with the stock vent exterior shape the volume exiting increased while the boundary layer airflow was smoother. This leads me to believe the stock shape was capable of pulling more air but stylists probably decided the opening size and use of a screen.

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jonathonar89

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Re: 2nd gen TA aerodynamics and modifications
« Reply #19 on: August 04, 2015, 10:55:09 AM »
Really doesn't have much to do with aerodynamics as it does heat extraction, but do you still have the metal fender liners in place?  When I first looked at my brother's T/A there's no direct line of sight from the engine bay to the vents, so I always thought they were for looks more than anything but one day I noticed some air seemed to be coming out of them.  I'd imagine without the fender liners in the way they'd do a much better job.

Another thing I've heard of is people mounting PC fans or the like on the backside of the vent to forcibly pull air out, but with you spending most of your time at 100+ mph I'm not sure if they'd help or just be a hinderance.

Why wouldn't the fender vent not have much to do with aerodynamics?  Seems like a good pressure relief area considering how much air passes through a grill at speed and maybe a reason why its installed. 

Small computer fans seem like the biggest waste of time.  It would push if anything but to each their own.

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Re: 2nd gen TA aerodynamics and modifications
« Reply #20 on: August 04, 2015, 10:58:36 AM »
Really doesn't have much to do with aerodynamics as it does heat extraction, but do you still have the metal fender liners in place?  When I first looked at my brother's T/A there's no direct line of sight from the engine bay to the vents, so I always thought they were for looks more than anything but one day I noticed some air seemed to be coming out of them.  I'd imagine without the fender liners in the way they'd do a much better job.

Another thing I've heard of is people mounting PC fans or the like on the backside of the vent to forcibly pull air out, but with you spending most of your time at 100+ mph I'm not sure if they'd help or just be a hinderance.

EDIT: Jon put it above using less words while I was typing.

I'm not a aerodynamics or fluid dynamics engineer but I can tell you from experience that running without inner fenders at high speed creates a LOT of under hood air pressure. In a straight line it may not be a really big deal (like a drag car) but for any activity involving turning you need them.  The gel coat on the  fiberglass lift off hood that was on my 74 Camaro drag car was cracked and ruined when it bowed up about a foot in the center at over 100 MPH when the previous owner was running it with just Dzus fasteners on the sides and tried removing the inner wheelwells to reduce weight.

The engine compartment becomes a pressurized box with an open bottom (think hovercraft). The pressure is basically equal on the sides and top of the box (not taking into account outside pressures)) and so any opening on the sides will allow air to escape with the air taking the path of least resistance. In our case of trying to evacuate as much as possible we want to choose a place with the least external air pressure to place the vent. This seems to be behind the wheel on the side of the fender for most cars. I considered running 6" hoses from the vents to just behind the radiator fans but have decided it's not worth the hassle. I will however be creating a funnel shape for inside the fender to smooth the flow as it enters the vent opening.

With the hovercraft image in mind this is why we want to reduce the pressure under hood. A hood is roughly 4' X 5' so any change in the difference between the pressure above and below the hood will change the amount of weight on the tires. More weight= more grip so the track Jack vents will be designed to pull as much air as possible for max cornering. The barefoot vents I'm working on just need to pull enough air to keep the engine from overheating during 1 mile land speed races with the least amount of drag possible.

The volume of air moved by a PC fan would have a negligible cooling affect even when parked, they simply don't move enough air and depending on placement would probably slow the air movement out of the vents at almost any forward speed.
« Last Edit: August 04, 2015, 11:02:43 AM by NOT A TA »
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Re: 2nd gen TA aerodynamics and modifications
« Reply #21 on: August 04, 2015, 11:15:13 AM »
The ones talking about them were mainly talking for around town getting heat out.  Maybe it was a small electric rad fan, but even the smallest would be too big I'd think.  I never really put much thought into what they were saying since I had closed off Firebird fenders so it didn't matter anyway.  If I ended up keeping mine I was looking towards T/A fenders and making a ducting of some type through the liners(didn't want to compromise crash safety on a street car by removing the liners, but good to know now about the aerodynamics effect) to the vents to let more heat out, since even with stock log manifolds my engine bay is an inferno.  Especially once I were to put on headers and redo the exhaust, something would have to be done.

Since you're going all race car maybe some heat extractors on the hood would help with downforce and letting heat out?  Sort of like the GT40, but obviously dialed down some given the space constraints.
« Last Edit: August 04, 2015, 11:18:10 AM by Box »

Casey

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Re: 2nd gen TA aerodynamics and modifications
« Reply #22 on: August 04, 2015, 11:33:36 AM »
Couldn't find as good of a picture but maybe could graft in an early 4th gen hood:

NOT A TA

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Re: 2nd gen TA aerodynamics and modifications
« Reply #23 on: August 04, 2015, 12:03:29 PM »
I'm not going all out race car although to purists it might seem like it. I'm simply trying to incorporate modern aero techniques to an old style body without altering the appearance with anything that can't be quickly changed back to stock looking. Kind of as if Pontiac's engineers could have modified a stock car  back in the early 70's for sports car and land speed racing using modern day aerodynamic knowledge.

To be most effective the hood radiator extraction openings would require other changes like switching to a bottom feeder and making a new radiator mounting. Neither of which I'm willing to do even though I have a spare hood although it might very well be advantageous overall for a better aero package. I believe most of the advantage on some of the newer cars is that by tilting the radiator they can make the front of the car more pointed and reduce the pile of air and bow wave before the bumper.
John Paige
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Re: 2nd gen TA aerodynamics and modifications
« Reply #24 on: August 04, 2015, 12:36:32 PM »
In the pic below I added the Barefoot cardboard with wicker and it appeared that the vent could pull more air than even the larger opening could provide as the yarn tufts at the rear of the vent flipped to a forward direction. Seeing this I skipped testing the Track Jack version and decided to open the vents more.

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jonathonar89

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Re: 2nd gen TA aerodynamics and modifications
« Reply #25 on: August 04, 2015, 12:39:35 PM »
If you do the under pan up, I think adding louvers with openings towards the rear would help pull out your engine bay pressure.  Hope to see some interesting stuff from you on that.  It's crazy to see a lot of the new cars having under trays made with condensed fabrics.  The only thing on your list I'm a bit at odds with regards to aero benefits is the foilers behind wheels. 

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Re: 2nd gen TA aerodynamics and modifications
« Reply #26 on: August 04, 2015, 12:50:50 PM »
I remember reading where the '79-81 at least are bottom feeders, I didn't think about earlier cars not being that way.

Look forward to the "cardboard" vents being opened up and the results they bring.  Plus I think as a finished product they'll look really cool too.

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Re: 2nd gen TA aerodynamics and modifications
« Reply #27 on: August 04, 2015, 03:29:58 PM »
You want as much air as possible to go around the car and not thru it.  For drag racing, just block it off and run it, turning on your cooling system as soon as the run is over.  For anything longer than a 1/4 mile, you need to figure how to get air thru the radiator and out from under the hood.

And leave your inner fenders in :wink:
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Re: 2nd gen TA aerodynamics and modifications
« Reply #28 on: August 04, 2015, 04:30:20 PM »
If you do the under pan up, I think adding louvers with openings towards the rear would help pull out your engine bay pressure.  Hope to see some interesting stuff from you on that.  It's crazy to see a lot of the new cars having under trays made with condensed fabrics.  The only thing on your list I'm a bit at odds with regards to aero benefits is the foilers behind wheels.

You're correct, the foilers probably won't do anything and may in fact may hinder but I bought them a loooong time ago, I like the look, and so I'm going to use at least the rear ones.
John Paige
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Re: 2nd gen TA aerodynamics and modifications
« Reply #29 on: August 04, 2015, 04:33:25 PM »
I remember reading where the '79-81 at least are bottom feeders, I didn't think about earlier cars not being that way.

Look forward to the "cardboard" vents being opened up and the results they bring.  Plus I think as a finished product they'll look really cool too.

I'm farther ahead on the vents than my posts and will get caught up to date over the next couple days. On my out to dinner with a TA buddy now but I don't get in too late I'll post some more later tonight.
John Paige
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Re: 2nd gen TA aerodynamics and modifications
« Reply #30 on: August 05, 2015, 09:30:01 AM »
I opened up the rear of the stock opening to the metal upright in the inner metal structure. Still seemed to be able to pull more air as seen in the pic below.



I decided to try cutting a slot in the fiberglass vent behind the metal support and was surprised to find yarn strands a few inches in from the slot were being sucked out the slot even with the stock exterior vent shape. Boundary layer flow seems good with very little drag. Perhaps something like this was what Pontiac's engineers wanted to make the vent look like before stylists got their hands on it?

John Paige
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Re: 2nd gen TA aerodynamics and modifications
« Reply #31 on: August 05, 2015, 10:10:23 AM »
With the more Barefoot cardboard installed (pic below without wicker) the drag increased apparently and the suctioning of yarn strands increased inside the fender.



Then I set up the track Jack cardboard setup (with wicker)and found I could really pull a lot of air out of the engine compartment pulling long strands of yarn 10" away taped by the hood hinge out the opening! However there appeared to be a lot of turbulence so I decided to try adding strakes to help smooth the flow and reduce turbulence.





The strakes seemed to straighten the flow coming out of the vent (pic below) so my thinking is that a little more air was being be drawn through with less turbulence. At this point my openings were limited in size by the metal inner structure and it appears the exterior vent shapes can still pull more air soooo the next step will be to start cutting the inner structure and open the vents up more!

John Paige
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Re: 2nd gen TA aerodynamics and modifications
« Reply #32 on: August 05, 2015, 10:44:29 AM »
After Box mentioned the hood vents I was trying to remember who's 2nd gen bird I'd seen them on. Then it came to me ! Bob Bertelsen's "Code Red". I don't know if it was done for aesthetics or function and whether or not any testing was done.




« Last Edit: August 05, 2015, 10:47:38 AM by NOT A TA »
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Re: 2nd gen TA aerodynamics and modifications
« Reply #33 on: August 05, 2015, 02:15:34 PM »
After thinking about it the Stabil 360 Camaro had some pretty wild stuff done to it as well:


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Re: 2nd gen TA aerodynamics and modifications
« Reply #34 on: August 05, 2015, 02:58:58 PM »
Great info I love what your doing, this is what makes racing/innovation fun. I so want to get a go-pro, string the car and see what the air is doing!!

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Re: 2nd gen TA aerodynamics and modifications
« Reply #35 on: August 05, 2015, 06:58:31 PM »
Wow... very interesting discussion.  Unfortunately that's about all I have to add....  Although I have solved Bernoulli's equation a time or two!

My uncle was a wind tunnel test engineer.... unfortunately he passed away a couple of years ago.  He would have been WWWaaaayyyy into this discussion!
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Re: 2nd gen TA aerodynamics and modifications
« Reply #36 on: August 05, 2015, 09:25:06 PM »
Wow... very interesting discussion.  Unfortunately that's about all I have to add....  Although I have solved Bernoulli's equation a time or two!

My uncle was a wind tunnel test engineer.... unfortunately he passed away a couple of years ago.  He would have been WWWaaaayyyy into this discussion!

Someone like your uncle would be an awesome resource to learn from.

A bud of mine was in town on business the past couple days. He's a fluids specialist and happens to be a Trans Am owner with a 70 Ram Air III who's always been interested in the modifications on my car. I asked him his opinion on several things I'm working on and discussed axial flow type pumps as a possibility for brake duct use. I explained most of the current aero upgrades and why I'm doing certain things certain ways. He agreed with pretty much everything I've planned and had a couple suggestions.

Surprisingly his first mention about fans to pull air out of the engine compartment were the computer type fans Box mentioned TA guys using with the stock fender vents.

Getting back to the fender vents. I removed a lot of the unnecessary metal inner vent mounting structure. Looking at the design I decided the vertical metal section was probably incorporated to keep the inner structure from bending or twisting before and during installation (spot welding) to the fender skin. So I cut it out and opened up the leading edges as well so I could make the vent opening as large as possible. With a stock fender vent in place no one could tell from the outside. With a modified vent you can see some of the inner structure if you look and are close. From any distance more than a few feet no one would notice.

 



I'd put a slot in the vents previously and decided that now that there is no support in the way I'd try opening up the vent even more. I won't bore you guys with a lot of different pics of the progression of tuft tests but the Track Jack design with wicker, strakes,  and wide opening seems to pull the largest volume of air through the vent. I kinda like the looks of the stock vent with the big opening and it seems to have the least drag.





The large opening of the Track Jack vent now has over 30 Sq. In. to draw air through which is more than 3 times the stock vent with screen. When combined with the increased angle, size, wicker, and strakes I'd imagine it can pull 4-5 times or more the volume of air that a stock vent can pull. I'm going to see if I can find someone with a flow bench I can test my theory and designs on. Meanwhile I'm going to modify the vents to be ready for paint. I'll be making a flow straightening piece to fit inside the fender vents the next time I have the fenders back off the car (which will be pretty soon).

Here's the difference between stock and modified size openings.



« Last Edit: August 05, 2015, 09:33:02 PM by NOT A TA »
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Casey

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Re: 2nd gen TA aerodynamics and modifications
« Reply #37 on: August 05, 2015, 11:39:32 PM »
Did some quick looking and there are pc fans capable of moving 300+ cfm.  Mounted into a sealed housing/ducting I'd think they'd be pretty effective, so 600 cfm being moved out even when stationary would be the bee's knees.

Liking the big vents, functional and look cool.  Kind of curious as to how much air they'll move at your average track speed and highest back straight speed, though not sure of a good way of testing that without a wind tunnel.
« Last Edit: August 05, 2015, 11:41:45 PM by Box »

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Re: 2nd gen TA aerodynamics and modifications
« Reply #38 on: August 06, 2015, 07:07:59 AM »
Someone mentioned extractors on the hood and that has been done before, but that would mean Jon would need two hoods for his plans.  Not that he couldn't, but hoods take up a lot of space.   :D

For the pic....

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Re: 2nd gen TA aerodynamics and modifications
« Reply #39 on: August 06, 2015, 07:34:08 AM »
I can't really offer any real world auto experience at this level, but I do have observations from the IT industry that I feel are applicable.  Over the past 20 years server internal layouts have evolved to seperate elements of the board as well as to direct air flow in a straight line thru the server case.  PC fans are laid out to pull air front to back.  With that in mind the PC fan would have to push\pull an equal or greater amount of air then your radiator fans to make a difference in my opinion. 

Also, are you going to modify the way air reaches the carb rather then using the cowl effect with the shaker?  If you utilized ducting to ram air in like a Olds W30 setup to the carb couldn't you use the shaker as a large extractor?  Maybe even make a low profile shaker to increase your track visibility?
« Last Edit: August 06, 2015, 09:12:34 AM by mrbandit »

Re: 2nd gen TA aerodynamics and modifications
« Reply #39 on: August 06, 2015, 07:34:08 AM »
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