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Old 04-21-2022, 11:35 AM   #171 (permalink)
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upper trailing edge

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Originally Posted by Phase View Post
Is that in a 3D all 4 sides shape or just the side flares?
1) I recommend losing the wickerbill. It's a downforce device, intended to create separation, not attachment. Especially not 're-attachment.'
2) I recommend that you not create a backwards-facing-step, ending the upper trailing edge at the taillight location. Aerodynamically, you couldn't possibly do anything worse to the car!
3) And as I've stated, since the IONIQ is already a 'fit' under the AST-III, the rear upper trailing edge ought to just follow the AST contour.
I can only guarantee 100% flow attachment.
4) The 'diffuser' should also follow the AST.
5) I don't have access to an IONIQ. I haven't a clue about the rear quarter-panel camber, or any vestigial OEM boat-tail tapering. If there is some preliminary tapering, it should take off from there, while following a 'french-curve' contour of the AST, as is present on the roof.
6) This is the most important thing you're going to be working with.

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Old 04-21-2022, 12:46 PM   #172 (permalink)
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Quote:
Originally Posted by aerohead View Post
1) It's never been done.
2) Two surfaces of the body will be experiencing pressure increase, while two surfaces will be in separated flow.
3) The wake is going to take on the low pressure of the separation line at the sides, not at the rear of the spoilers. It's explained in your book, "Modifying the Aerodynamics of........................, Figure 4-14, page 80.
4) Hyundai's OEM diffuser is an unknown quantity. Without a full belly pan in front of it, by default, it cannot be effective, and may just be serving as an aerodynamic 'styling cue.'
The new Elantra has the top and bottom spoilers slightly going inwards and out without a side taper. In person it looks more extreme and jagged.

Also the Ioniq doesnít seem to have a rear diffuser at all. Itís just a flat bumper. The parachute effect underneath is very strong. I actually have to take the bottom rear bumper off every few months to clean out all the rocks and gravel that gets stuck in it
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Old 04-21-2022, 12:48 PM   #173 (permalink)
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Quote:
Originally Posted by aerohead View Post
1) I recommend losing the wickerbill. It's a downforce device, intended to create separation, not attachment. Especially not 're-attachment.'
2) I recommend that you not create a backwards-facing-step, ending the upper trailing edge at the taillight location. Aerodynamically, you couldn't possibly do anything worse to the car!
3) And as I've stated, since the IONIQ is already a 'fit' under the AST-III, the rear upper trailing edge ought to just follow the AST contour.
I can only guarantee 100% flow attachment.
4) The 'diffuser' should also follow the AST.
5) I don't have access to an IONIQ. I haven't a clue about the rear quarter-panel camber, or any vestigial OEM boat-tail tapering. If there is some preliminary tapering, it should take off from there, while following a 'french-curve' contour of the AST, as is present on the roof.
6) This is the most important thing you're going to be working with.
I will film an Ioniq walk around video and upload it on here soon and point out the area that need focusing. Searching online for Ioniq images doesnít have much high definition detail Iíll admit
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Old 04-21-2022, 01:05 PM   #174 (permalink)
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Elantra

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Originally Posted by Phase View Post
The new Elantra has the top and bottom spoilers slightly going inwards and out without a side taper. In person it looks more extreme and jagged.

Also the Ioniq doesnít seem to have a rear diffuser at all. Itís just a flat bumper. The parachute effect underneath is very strong. I actually have to take the bottom rear bumper off every few months to clean out all the rocks and gravel that gets stuck in it
1) What is the Elantra's drag coefficient?
2) The diffuser ( or lack thereof ) figures. Without a full belly pan, it wouldn't function.
3) While the tires may be slinging debris into the cavity of the bumper, it's not evidence of a 'parachute effect.'
4) It may 'tremble' as the Lincoln Town Car did, but that was due to turbulence, and an under-engineer rear valence which couldn't deal with the cyclic pressure pulses it was exposed to.
5) According to Subaru research on the 1985 XT, the IONIQ's rear bumper is actually reducing drag just as it is.
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Old 04-21-2022, 02:20 PM   #175 (permalink)
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Quote:
5) According to Subaru research on the 1985 XT, the IONIQ's rear bumper is actually reducing drag just as it is.
If the extrapolation is valid, then an overlay with box extension, skegs and fences [respecting departure angle] should improve things.
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Old 04-21-2022, 02:34 PM   #176 (permalink)
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box extension

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Originally Posted by freebeard View Post
If the extrapolation is valid, then an overlay with box extension, skegs and fences [respecting departure angle] should improve things.
1) Are we talking about underneath the car, in the rear axle region?
2) Or behind the car?
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Old 04-21-2022, 02:47 PM   #177 (permalink)
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<iframe width="560" height="315" src="https://www.youtube.com/embed/6LToz2JIcyY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

if the embedding doesnt work---


https://youtu.be/6LToz2JIcyY



heres a full walk around with my car! up close, even go under the car, showing underside of the rear, showing the back bumper. everything in detail!
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Old 04-21-2022, 02:57 PM   #178 (permalink)
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Quote:
1) Are we talking about underneath the car, in the rear axle region?
2) Or behind the car?
Why not both?

Box behind, skegs and fences beneath.
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Old 04-21-2022, 03:37 PM   #179 (permalink)
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YouTube IONIQ

Thanks! That's helpful.
1) The VG on the mirror is for acoustics. Noise showed up the aero-acoustic wind tunnel and the aerodynamic engineers were able to shift the resonant frequency of the mirror unit by adding the VG ( a very cheap modification to the tooling ) to kill off the offensive noise source.
2) Wheel covers won't be improved upon at any cost.
3) the forwards portion of the belly looks good up to the rear wheel region, then is compromised on account of the exhaust, heat, and carbon-monoxide.
4) Additional heat-shields could be placed strategically.
5) Fiberglass racing exhaust wrap could solve some heat flux issues.
6) Sheet aluminum would be a natural for this area.
7) The 'diffuser' isn't a 'diffuser'. It's just styling.
8) A 'real diffuser should follow where the bottom of quarter-panels project. If it can be worked out around the muffler issue.
9) Aerodynamically, with any tail extension, only the portion of the taillights, up to their burst-edges, would remain visible.
10) The existing rear spoiler would remain in place, just as it is.
11) A new tail upper would integrate to the spoiler's trailing edges.
12) New side extensions would integrate to the existing burst edges .The rear DOES have some existing boat-tailing, so you'd take advantage of that, and add to it, respecting the same contour as you have on the roof, if you can. No more. No less.
13) New diffuser would rise and extend along the path already established by the bottom of the rear quarter panels.
14) New taillights would have to be added, along with relocation of the license plate.
15) If you could relocate the backup camera, and extend the harness, you could maintain that function.
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Old 04-21-2022, 03:49 PM   #180 (permalink)
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both

https://patentimages.storage.googlea.../US8590961.pdf
Quote:
Originally Posted by freebeard View Post
Why not both?

Box behind, skegs and fences beneath.
Both is good!
1) The diffuser area does need to be a solid surface. Fences are okay because of transverse contamination.
2) A box-cavity could be constructed. It's rear perimeter would need to fall exactly where the AST-III would otherwise project to.
3) From the rear, be an exact, scaled-down replica of the OEM perimeter.
4) 'Stringers' would span between original architecture 'starting points', and curve down to the new trailing edges, along the AST contour. Top, sides, and bottom, as if it were a proper tail, hitting 'zero' at they marry onto the new transom ( it could all be 'skinned' later to create a boat-tail ).
Kinda like this, but without the skin ( see at top of page )

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Last edited by aerohead; 04-21-2022 at 03:53 PM.. Reason: add patent
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