03-27-2012, 06:11 PM
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#1 (permalink)
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Mechanical engineer
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Drag reduction modifications in wind tunnel: Audi A2 from Cd 0.288 to 0.204
Hi,
Thanks to Ausias who tipped me off with this Cd study:
http://wwwm.coventry.ac.uk/researchn...%20Vehicle.pdf
Lupos 0.25 Cd target starts to feel pretty plausible without chopping the roof  .
Enjoy.
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SUMMARY...
(added by MetroMPG, because these online files have a bad habit of disappearing...)
- START: MIRA wind tunnel showed a stock co-efficient of Drag (CD) of 0.288
- COOLING: vents, intakes, panel gaps taped on front end - Total Contribution: 9% of total Drag
- Underfloor:-Foamboard and tape -All components covered -Total Contribution: 7% of total Drag
- MIRRORS - door mirrors removed: -Total Contribution: 5% of total Drag
- Wheels and Wheel arches: Wheel Spoilers / spats; smooth wheel covers; Wheel Arch Blanking (rear fender skirts); Underfloor Wheel Arch Blanking
- Base pressure recovery (tailgate "box cavity")
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The Following 37 Users Say Thank You to Vekke For This Useful Post:
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03-27-2012, 07:11 PM
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#2 (permalink)
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Master EcoModder
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0.25
Quote:
Originally Posted by Vekke
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Cd 0.25 should be a walk in the park.I'm certain of it.Even lower if you like.  |
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03-27-2012, 08:58 PM
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#3 (permalink)
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Master EcoModder
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Awesome paper. Makes it easier to quantify every mod accordingly.
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03-28-2012, 12:56 AM
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#4 (permalink)
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EcoModding Lurker
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Good simple paper to guide mods. I'm a wind tunnel engineer at work and like seeing studies like this with measured data.
Thanks for sharing. 
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03-28-2012, 09:27 AM
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#5 (permalink)
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Ultimate Fail
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I had seen mention of the " box cavity" method of reducing drag at the rear in an old paper* from the UCDavis " future car " hybrid Ford Taurus .
It's good to see results quantified here .
* no longer online.
Last edited by Cd; 03-28-2012 at 01:13 PM..
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03-28-2012, 11:21 AM
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#6 (permalink)
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Batman Junior
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Vekke - nice find! I added the summary to post #1, since these files often disappear from the web after a while.
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03-28-2012, 01:35 PM
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#7 (permalink)
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Ultimate Fail
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If you notice the caption on the bottom of the picture of the A2 at the top of the paper, there is mention of the A2 being introduced at .25 Cd .
This number is often given as the official Cd in published literature ( I've also seen .27 )
This makes me wonder what would have caused such a drastic rise in drag to .288 .
The only visible changes are the style of wheels, and surely this would only account for a count or two .
( And it also makes me wonder if they did the same mods to the .25 version, just how low of a Cd they would have achieved ! )
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03-28-2012, 02:24 PM
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#8 (permalink)
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Batman Junior
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Quote:
Originally Posted by Cd
there is mention of the A2 being introduced at .25 Cd .
This number is often given as the official Cd in published literature ( I've also seen .27 )
This makes me wonder what would have caused such a drastic rise in drag to .288 .
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The A2 was available in several different trim levels/models , one of which was a high-efficiency version ("3 L" diesel). That's what the .25 figure refers to. It had a different grille, wheels, tires (size) and partial underbody panels (if memory serves), and possibly also a lower ride height.
Ride height is one mod our experimenters didn't attempt here. |
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03-28-2012, 03:13 PM
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#9 (permalink)
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aero guerrilla
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Too bad those slides didn't give more info about the effects of the rear box cavity versions.
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[Old] Piwoslaw's Peugeot 307sw modding thread
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03-28-2012, 04:13 PM
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#10 (permalink)
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Mechanical engineer
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Quote:
Originally Posted by MetroMPG
The A2 was available in several different trim levels/models , one of which was a high-efficiency version ("3 L" diesel). That's what the .25 figure refers to. It had a different grille, wheels, tires (size) and partial underbody panels (if memory serves), and possibly also a lower ride height.
Ride height is one mod our experimenters didn't attempt here.
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A2 3l Had 0.25
145/80R14 tires
Lower ground clearance
smooth hubcaps
almost fully blocked front grille
smooth underside to some extent
plus lots of small modifications
Lupo 3L has smaller mirrors I am not sure if A2 has them on also
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