Let's Talk Aero

Discussion in 'Road Racing Forum' started by antman450, Oct 21, 2017.

  1. AJ Hartman

    AJ Hartman TMO Intermediate

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    Glad this thread opened back up. To put it simply, just because something works for one car, doesn't mean it will automatically work for another. But there are some easier basics that hold true in just about every case.
     
  2. AJ Hartman

    AJ Hartman TMO Intermediate

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    Also, there are certain constraints everyone must work around. When this thread was locked up for a few days, it was centering around splitter tunnels. If you open up a straight tunnel directly into a tire, its not the greatest in terms of performance. but if you open up a straight tunnel into the wheel well, and that wheel well is vented, that tunnel will work pretty good. If you have to put a tunnel in front of a tire, try and curve it so there is an outwash across the tire. Thats better then dumping straight into the tire straight. Couple that outwash with something like canards, side plates, and/or flaps to help that outwas and lower the pressure in front of the tire, and you will gain Df. Hope that clears up some stuff.
     
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  3. flyhalf

    flyhalf TMO Race

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    Allright
    Let's bring back attention on the splitter please.
    So this the 2018 mustang splitter.
    Now
    I know plastic is not the best because the material can bend but
    The splitter is hold at the chassis with 8 screws.
    In addition i added a big lip in thr front
    Which is bigger than the PP2.
    So. Pp2 splitter generates extra 24lbs.
    Am I assuming this will generate more?

    I have 2 tunnels. Those are for "cooling the brakes. So they aim the inside of the wheel.
    AJ. Is your principle applied to those tunnels too?( i mean do they generate DF?)

    LAST. 2 things
    1. following kylie pic
    It seems the majority of DF comes from the lip and the tunnel
    So it is not optimal to have the splitter made in plastic JUST because the LIP bends?
    2. Is the lip angle important?
    Kylie mentioned in theory a positive angle will allow more air to go under the car speeding up it for increasing DF.
    While someone said a negative angle will create more vortex = more DF. where is the true?[​IMG][​IMG][​IMG][​IMG]

    Sent from my LG-H932 using Tapatalk
     
  4. blacksheep-1

    blacksheep-1 TMO Addict

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    from a rules perspective, you have to be careful of plastic aero devices because they can bend, that would make them " moveable aerodynamic devices" and get you thrown right out of the tech shed.
     
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  5. Bill Pemberton

    Bill Pemberton TMO Addict

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    Nice shop ---look how clean the floor is?? Heh, just an off the cuff observation , that those of us that are anal , really appreciate!
     
  6. AJ Hartman

    AJ Hartman TMO Intermediate

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    Kinda hard to see from the pictures but since the tunnels open up to the wheel well they have to do something. I'm assuming that 24lb is from Ford but at what speed? It looks like there is a little bit of an air dam (opposite of a tunnel) in front of the tire, too. Looks like a drag reduction device there, but could also cause a slight low pressure behind it allowing the tunnel to flow into it a little better. Also, the highest ground clearance we tested in CFD was 4" on splitters and diffusors. between 2"-3" saw the best Df numbers. 4" was crap compared to 3" so with yours are 5.5" you are pretty much out of ground effect at that point. As for splitter angle, don't get confused between an actual profiled splitter (underside basically looks like a wing shape and the very tip is higher then the main body at the lowest point like an LMP or GTLM car) vs just a flat splitter (like a piece of plywood) at an angle where the very leading edge would be the lowest point.
     
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  7. flyhalf

    flyhalf TMO Race

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    Got it. Thank you AJ
    Yes ford declares 24lbs DF at 80mph

    So lower even more the car or the splitter should be my #1 thing.
    #2 better strong material

    Thanks AJ



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  8. JDee

    JDee Ancient Racer

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    I know nothing about aero, as can be seen by my bone stock car. My question is how does the following splitter help? It seems to be fairly common now, the splitter going up not down.

    2019_iwsc_scuderiacorsa63_teampage_1280x626.jpg
     
  9. AJ Hartman

    AJ Hartman TMO Intermediate

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    The easy thing would be to lower the car as long as you don't get into destroying suspension geometry. Thats a whole nother issue. But lowering just the splitter would be the next option. You will need some sort of air dam to fill the space between the bumper cover and the now lower splitter tho.
     
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  10. AJ Hartman

    AJ Hartman TMO Intermediate

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    The splitter is not going up. The throat, or inlet of the splitter is going up, but the exit area has a larger volume then the inlet usually. This is for 2 reasons but both take advantage of Bernoulis principal. It squeezes more air under the splitter, which forces the air to speed up. When air speeds up, you get a dynamic pressure drop across a surface. So you can get more downforce with a raised splitter throat like that. Keep in mind this air needs to go somewehre. So there has to be some sort of tunnels in that splitter and/or is channeling more air to the diffusor. This will allow the diffusor to work better. We can assume the car pictured probably has a higher rear weight bias so more Df is needed in the rear then the front. Its also only a GTD car and they are limited on what they can do aero wise.
     
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  11. blacksheep-1

    blacksheep-1 TMO Addict

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    It's simple, if you have an S197 you use the IMSA splitter and wing for some aero downforce, if you want more you use the PWC splitter and wing, if you want to go beyond that, call AJ Hartman
     
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  12. flyhalf

    flyhalf TMO Race

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    So AJ
    BIGGER INLET increases OVERALL DF
    If there are not tunnels to exit air innthe front.
    With tunnels DF is more focus anteriorly?

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  13. AJ Hartman

    AJ Hartman TMO Intermediate

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    ehhhh to an extent but not always. It could easily get to the point of to much, but the trend in the past few years has been seeing them get bigger and bigger.
     
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  14. Boone

    Boone TMO Advanced

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    I get that forcing more air under the splitter will increase the speed of the air and make any tunnels or ducts on the bottom side of the splitter more effective. For race cars with intricate splitters and flat bottoms, this makes sense. For the weekenders among us (like me) with flat splitters and no clean air under the car after the splitter, does it make more sense to take advantage of the "racing brick" aspect of the front of our Mustangs creating high pressure on the top of the splitter that extends in front of the bumper? It would appear the mid-engine Ferrari in the picture has much lower frontal area than our cars, and it can take advantage of the air that is forced under the car.
     
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  15. AJ Hartman

    AJ Hartman TMO Intermediate

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    All good points I may have missed. Yes, the Ferrari has a complete package around the size of the throat of the splitter. As you mentioned, most of us, myself included, would probably not benefit with that agressive of a splitter inlet. And you hit on a good point. The "brick" face of the average mustang would probably build up a larger high pressure zone in front of the car and get more "spillage" of that high pressure to under the splitter, where as a very small nose of a Ferrari wouldn't get that effect as much, so making the splitter throat much larger is a trick to get more mass flow under the splitter.
     
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  16. JDee

    JDee Ancient Racer

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    Nah, S550. I know nothing about this stuff, just generalities. I probably should have just shut up and read. I couldn't help but wonder about the FRONT EDGE of the splitter going up and what that did. I'm purely a mechanical grip guy, but would like to know more about aero, especially front downforce because that's where this car needs help IMHO. I think better venting in the hood, or a totally new vented hood is a good start since it also could stand some more cooling, also just MHO.
     
  17. carver

    carver TMO Intermediate

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    Hmmm, I see an impending rabbit hole on the horizon!!....:D
     
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  18. JDee

    JDee Ancient Racer

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    Started down that rabbit hole a couple of years ago, aero is probably just a branch off the main tunnel....
     
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  19. Bill Pemberton

    Bill Pemberton TMO Addict

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    I leave the Aero to experts and take their recommendations, since watching F1 over the years I see all these goofy little additions, weird shaped wings and more , and just view myself in the mirror and say, " Duh, I don't get it !" The complexity of Aero on vehicles today, not only takes the skill of an Aerodynamicist , he/she needs to be a structural Engineer with an advanced degree in Computer Design ---- you lost me at ......Aero!

    Thanks to Jonathan Blevins at Chicane 23 for my hood, wing endplates and more from Dean Palmer Racing Development- car runs cools and seems stuck and neutral at my skill level. When you are basically stupid like me, the Aero you do is based more on your friends, acquaintances and competitors that are fast , and if that is what is working you go with the flow.

    The cool thing about TMO , is many of us can do just this, base our thoughts on Aero by getting data from friends, acquaintances and current or future competitors on this site , and doing what fits our psyche or degree of knowledge/talent?

    So plenty of good stuff here , and like many items , if you glean just a tiny bit of knowledge reading through the various threads on TMO, then you have found another reason to contribute yourself, tell your friends about this site, and enjoy the camaraderie that is damn good for a Forum today. I like this place as the tone and comments are largely positive and even when there is a bit of disagreement , the level is palatable and not full of crash and foul language like so many others.

    Continue and as usual , I know I will learn something ..................
     
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  20. AJ Hartman

    AJ Hartman TMO Intermediate

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    Dont forget to duct the front side of the radiator. Was just at the wind tunnel with a BMW that had no front rad ducting and the smoke test was very interesting seeing how much slipped around it. The car had a monster splitter and canards (prior to some other aero tweaks we did in the tunnel over the course of several runs) the car had front lift. Thats with some fairly large hood louvers installed as well.
     
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