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Very old bird gets updated aero

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  • Very old bird gets updated aero

    I found this site looking for info on aero stuff a while back and joined. I know most of the discussions here involve more modern cars but I thought some of you guys might be interested in this and perhaps have suggestions and/or answers to questions.

    Back in the late 60's when the General Motors 2nd gen F bodies were being designed the engineers at Chevrolet supposedly did some wind tunnel testing. While they chose not to use the information collected for racing applications, legend has it that the engineers over at Pontiac (racers) got a copy of the test files and put the information to use when designing the 70 Trans Am which would be used for road racing with the number of the original 70 production run of Trans Am's being enough to fulfill homologation requirements of the sanctioning body.

    So while the 70 Camaro only received a small rear spoiler the 70 Trans Am got a tall rear spoiler, functional fender vents, low front air dam, and flares in front of all the wheel openings. My car's a 70 TA clone I built from an Esprit and I've owned it about about 25 years. Although the car is street driven I've run it at several drag strips, 1 mile LSR's at Maxton and Dade/Collier, and HPDE's at Lime Rock, Road Atlanta, the old Moroso & new PBIR, as well as Sebring. Road courses are my favorite place to run the car and I'd like to try open road racing eventually.

    What I'm trying to do is incorporate some of the air flow management techniques for racing that have been used since the car was built as though the Pontiac engineers who were racing had them available to them back in the early 70's. I don't have to stay within any "rules" since I don't race in any particular class so things like rear diffuser tunnels that start forward of the rear axle are fair game. Hopefully the aero mods will improve the performance of the car. I know once I get the car back on track there'll be a lot of testing and tuning to get things right. I fully expect things like spring rate changes to be necessary.


    Here's the car before being stripped to the unibody for the current rebuild.




  • #2
    What started as a project to do a few upgrades went right down the slippery slope to a complete restoration stripping the car to a bare metal shell and putting it on the rotisseri. I figured as long as I'm in this deep I should do a lot of the little things I'd dreamed of and talked about.

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    • #3
      Subbed!

      Welcome to our little corner of the net. Interested to see how this turns out. Are you thinking about keeping all the aero mods stealth/invisible or letting it hang out time attack style? I think it would be cool to keep the aero low key, sleeper style. The diffuser could certainly be that way.

      What do you have for a powertrain?
      WWW.949RACING.COM
      SuperMiata

      Aside from their cost I never understood why people race them.
      But obviously I just dont get it. -fatbillybob

      Comment


      • #4
        Yes yes please god yes.
        2001 MR2-Eleven
        Experience Points: 21
        Youtube Channel.

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        • #5
          Originally posted by emilio700 View Post
          Subbed!

          Welcome to our little corner of the net. Interested to see how this turns out. Are you thinking about keeping all the aero mods stealth/invisible or letting it hang out time attack style? I think it would be cool to keep the aero low key, sleeper style. The diffuser could certainly be that way.

          What do you have for a powertrain?
          Thanks! While I appreciate the stealth approach for some cars you can probably guess that a guy running 5" side pipes and bright red paint probably isn't going to go for the stealth approach. Probably end up looking like a slightly subdued version of what a 70 Trans Am WTAC car might have looked like. I am trying to keep everything removable as well as adjustable so I can run different versions on the street, drags, LSR's , and on road tracks.

          Current powertrain is a mildly built Pontiac 400 with Canton RR pan and other goodies, T-400 with shift kit etc., and an 8.5" 10 bolt 2.41 posi with Moser tapered axles etc. I figured better to learn track skills by not having a lot of power so it's kinda like a big momentum car. After I get the aero and suspension set up I'm going to build a serious engine and swap to a 5 speed manual. Hopefully the driver will progress at the same time.

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          • #6
            Originally posted by SDSUsnowboards View Post
            Yes yes please god yes.
            I've read your home brewed aero thread a couple times and figured you'd like this! I've been making everything myself so far.

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            • #7
              Man that is awsome. I hope you post up more. Please consider a redesign on your doorbar. That doorbar setup is useless but the Full containment seat is about as safe as you can get.

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              • #8
                I was going to say the same thing about the door bar, not doing much as it is and should be revised.
                Otherwise I like this idea quite a bit and look forward to see what you're coming up with
                Moti

                Blackbird Fabworx - Quality Performance Fabrication

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                • #9
                  I'm curious why you guys would change the door bar. As with most things there's always compromises to be made. This car is not used in any wheel to wheel racing and I don't want to hollow the doors and climb over NASCAR door bars every time I go to the store. When the cage was designed we used the regulations from the SSCC, SCTA, NHRA. After discussing material options with tech guys from the various sanctioning bodies we decided on 1 3/4" 1020 DOM main tubes. Here's a thread on the safety upgrade project with the cage, fire systems, etc. I did back in 2008. The 14 Car safety thread, Roll Cage, Kirkey seats,Fire systems.

                  Here's the basic list of things on my aero adgenda.

                  1. Extend air dam
                  2. Splitter
                  3. Underbody pans from splitter to diffuser
                  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 (these may actually be detrimental and not used on track)
                  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 if needed

                  I'm a grassroots racer type guy. No engineering degrees, no supercomputer with CFD programs, no full size wind tunnel, no friends named Katz, McBeath, or Brilliant 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 probably 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 with the combined effects of splitter and underbody tray. 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 track 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 edited by NOT A TA; 11-17-2015, 08:33 AM.

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                  • #10


                    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.

                    Theoretically the vents help reduce under hood air pressure that causes the "floating" feeling due to lift 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 in part 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 under hood evacuation with the least amount of drag. I also want to make a set that will help maximize usable down force by reducing under hood pressure as much as possible and by design perhaps add some additional down force by the exterior design of the vents themselves.

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                    • #11
                      The three things that popped into my eye the moment I saw the door bar are -
                      1. Your body is completely exposed at bumper height.
                      2. There's no triangulation to keep the things from bending upwards.
                      3. It's just one tube.

                      I realize you built it to clear the factory door panel, but the safety aspect of it is compromised as a result.
                      Hope you take this all as constructive criticism, as it was meant to be that way
                      Moti

                      Blackbird Fabworx - Quality Performance Fabrication

                      Comment


                      • #12
                        In for DTM T/A
                        WWW.949RACING.COM
                        SuperMiata

                        Aside from their cost I never understood why people race them.
                        But obviously I just dont get it. -fatbillybob

                        Comment


                        • #13
                          Originally posted by Blackbird View Post
                          The three things that popped into my eye the moment I saw the door bar are -
                          1. Your body is completely exposed at bumper height.
                          2. There's no triangulation to keep the things from bending upwards.
                          3. It's just one tube.

                          I realize you built it to clear the factory door panel, but the safety aspect of it is compromised as a result.
                          Hope you take this all as constructive criticism, as it was meant to be that way
                          Appreciate the criticism. When using a street car as a track car there's going to be compromises and a certain level of what one considers an acceptable risk. This goes both ways and I've heard the roll cage on the street side often as well. Anyone who asks I tell them "Build a track car for the track and keep your street car a street car". It's a lot easier that way.

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                          • #14
                            Originally posted by emilio700 View Post
                            In for DTM T/A
                            AHAHAHA, now if I could shed 1300 lbs and get a carbon tub in the process that'd be awesome!

                            Comment


                            • #15
                              Originally posted by NOT A TA View Post
                              Appreciate the criticism. When using a street car as a track car there's going to be compromises and a certain level of what one considers an acceptable risk. This goes both ways and I've heard the roll cage on the street side often as well. Anyone who asks I tell them "Build a track car for the track and keep your street car a street car". It's a lot easier that way.
                              Would a bar going from the rear foot up to the diagonal to form a triangle fix most of the issues and still clear the door?

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