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USDM > *
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Discussion Starter · #403 · (Edited)
This is another FD2 that inspires me.


I love how aggressive this car looks and I decided to fabricate a splitter/front diffuser this weekend. Made a quick stop to Home Depot for supplies:


Made some measurements and trimmed the plywood:


Coated the underside with epoxy:


And a coat of black primer and epoxy on the top (visible) side:


For the side strakes, I will go with a design that has been wind tunnel tested:




Some might wonder why I cut the center out of the front diffuser. The main reason is to cut down on weight. Another reason is that an optimally designed front diffuser should NOT be flat. I know this is going to be shocking, so brace yourself....there is a lot of misinformation on the internet.

Whew, now that we have that out of the way we can clarify some terms. A "splitter" is the leading edge, usually (and preferably) on the bottom of an airdam. A "front diffuser" is the entire panel that extends behind the splitter. This figure illustrates the difference between the two...splitter on the left, diffuser on the right. Importantly, notice that the rear of the diffuser gradually curves upward. This is to allow the air to slowly expand.


This last figure shows that the middle, rear third of the diffuser is particularly prone to air separation (turbulence).


These images are from Simon Macbeath's technical articles on the subject in Racecar Engineering. I did not want to ignore the critical area. By removing this section, I can make a modular panel out of carbon fiber and play with different design elements.

Fortunately, there is a hybrid version of the 8th gen civic and Honda has already developed aerodynamic underpanels:




And the rear panels from the 9th gen hybrid can be modified to work on the 8th gen:
 

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USDM > *
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Discussion Starter · #408 ·
Well, it's kinda funny you ask. That is not the planned update, but it is something I have been researching lately. Unfortunately, the closest enclosed wind tunnel large enough for a full scale passenger car - and most importantly open for public reservations - appears to be in North Carolina (#becauseNASCAR).

Once the car and aero mods are complete, I would like to trailer it NC and rent an hour or two for wind tunnel testing...if for nothing else, to get some epic pictures:shades:
 

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Arouse the DAMPFHAMMER!
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Would a simple metall plane like the Elise has it also fit to the Civic underbody?

Not mine, I would be scared to drive an yellow Elise :D

Just two thoughts, which popped up reading your nice post about, among others, underbody paneling:
  • What would your aim to measure at the wind tunnel (downforce, cW, ...)?
  • Did you integrate the released heat from the exhaust system in your considerations towards the undertray closing?
 

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USDM > *
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Discussion Starter · #410 ·
Would a simple metall plane like the Elise has it also fit to the Civic underbody?

Not mine, I would be scared to drive an yellow Elise :D

Just two thoughts, which popped up reading your nice post about, among others, underbody paneling:
  • What would your aim to measure at the wind tunnel (downforce, cW, ...)?
  • Did you integrate the released heat from the exhaust system in your considerations towards the undertray closing?
Greetings, always happy to have your input and critique.

The lotus under paneling is probably a lot more expensive than the OEM civic hybrid underpanels. I can get all the underpanels for around $400 with little to no modification required. I think I would have to make custom (extended) side skirts to give the extra clearance to run a completely flat under panel. I have been brainstorming custom side skirts, however, it's not high on the priority list at the moment.


What would your aim to measure at the wind tunnel (downforce, cW, ...)?
I have spent so much time developing my radiator duct project, I would love to actually visualize how well it works (or how much it fails). The prices I've seen per hour are around 2x to 3x what a dyno tuning session would run. For that price, I think it's worth the experience (road trip, learning, feedback for improvement, etc).

I'm not a race car driver so this is just a strange hobby/obsession.

Did you integrate the released heat from the exhaust system in your considerations towards the undertray closing?

If you look on the OEM underpanels, the exhaust tunnel remains open.
 

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Discussion Starter · #411 ·
On a separate note, I recently bought a well known k-swapped Spoon themed EG civic from a friend (Eric). I don't deserve to post a "build thread" on this car because I didn't build it, however, my buddy Preston is helping perform some upgrades before the car is delivered.


He is installing a set of DC 2.2 cams and a valve train upgrade. I took advantage of the Labor Day sale to save a couple hundred bucks. The k20a2 is otherwise stock with a R crew header and RBC manifold.
 

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Wait, I remember this car, you lucky man you... hell of a build/restoration.

Glad to see it hasn't been turned to scrap.
 

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Discussion Starter · #413 ·
Yes, this was an epic rebuild. Unfortunately, the build thread is gone due to Photobucket. A couple pics that survived:







My plans for the car are pretty simple. A bump in power with the DC 2.2 cams and I want to complete the Spoon look with Spoon calipers and a cf hood.
 

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Arouse the DAMPFHAMMER!
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...I'm not a race car driver so this is just a strange hobby/obsession.
We are in the same boot :D. I would love to read about your experience if you went through that wind tunnel project.

On a separate note, I recently bought a well known k-swapped Spoon themed EG civic from a friend (Eric).
Maybe just a chance to see how small the world could be a question, was it that guy's car, named Eric, who did run the tuning session for katman's intake manifold shoot out? It also would be too much of a coincidence if that friend of you, named Preston, is the guy who cames from South Dakota and his member name at K20a.org is preston...would be to far away from your place.

...He is installing a set of DC 2.2 cams and a valve train upgrade...
Good to see your DC 2.2 cams find their way in a very nice project :up:! Like a Legend! Would you mind to share the tuning result afterwards?
 

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We are in the same boot :D. I would love to read about your experience if you went through that wind tunnel project.

Maybe just a chance to see how small the world could be a question, was it that guy's car, named Eric, who did run the tuning session for katman's intake manifold shoot out? It also would be too much of a coincidence if that friend of you, named Preston, is the guy who cames from South Dakota and his member name at K20a.org is preston...would be to far away from your place.

Good to see your DC 2.2 cams find their way in a very nice project :up:! Like a Legend! Would you mind to share the tuning result afterwards?
haha i am that Preston ;) Brian only lives about 3 1/2 hours from me so i also delivered the car to him.
 

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Arouse the DAMPFHAMMER!
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haha i am that Preston ;) Brian only lives about 3 1/2 hours from me so i also delivered the car to him.
Very nice coincidence. Seems like the world is really small in some way :). Was it Eric's or katman's car before you owned it?
 
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