Civic sedan rear spoiler
 

So I've been thinking about splashing some cash on a rear spoiler to reduce drag for a while. More recently I started thinking it would give the car a more balanced look, this was especially after i saw a civic like mine with a big spoiler, see pic.

So i spent $40 on a suitable spoiler, I spent ages hunting for it btw. I never get my money back on it but may increase the value of my car since it becomes more unique and desirable lol

The main purpose I hope will be to reduce drag, if it increases drag, I should see it on my mpguino, then ill take it off.

What do you guys think of it?

This one is my car [attach]Attachment 23212

This is the one that inspired me somewhat Attachment 23213[/attach]

As you can see it is only sitting on the trunk,
it'll need some custom mounting plates to fit nicely Attachment 23214

For fuel economy think differently. Instead of lift reduction (which is what race spoilers are about), which induces drag, try for drag reduction. Go for flat spoilers or trip spoilers like you see on fuel economy cars, such as the Prius or Civic hybrid. Like this, maybe: https://www.autocar.co.uk/sites/auto...?itok=Dq-1iGJ7

Looks nice, but I'll be surprised if the effect of the spoiler shows up definitively on the MPGuino in day to day use.

I think the best way to try testing this would be repeated sets of coastdown tests: more controlled, more sensitive to small changes.

I know a guy with a 2006 Civic who took his rear spoiler off (very similar to yours) for drag reduction. Who's right? Who knows!

I told him to get a 2006 Civic Hybrid style decklid lip spoiler.

Which purpose?

Fuel Economy = Small spoiler; something to minimize airflow disruption.

Down Force = Large spoiler; something to convert horizontal airflow into downward force.

The top of the wingy-thingy is about right (~12°), the tumble-home of the sides is good.

I'd stretch a black mesh over the opening to make a perforated base plate. Easily undone for A-B-A testing.

this one
 

With so very little actual data in the public domain,we have only scant information from which to predict your wings performance.
When KAMIE introduced the first commercial add-on spoiler,in the early 1980s,it was simply an non-ventilated upswept kicker style device.
During the development of the 1982 Pontiac Trans AM and Camaro,the aerodynamicist involved commented that the simple upswept spoiler (as would be used on the Camaro) was superior to the basket-handle,wing-type which ended up on the Firebird.Pontiac chose the latter for it's 'look',rather than it's performance.
Recent production cars chosen for Bonneville speed records (Fusion,Sonic,Jetta) have all chosen non-aspirated spoilers.There's probably a lesson for us there.
Your wing might have an advantage as to rear vision when backing the car into a parallel parking space.

So you mean close of the bottom, underneath the top surface of the spoiler, to prevent air exiting thereby causing a high pressure area that the air stream sees as similar to being a kamm back of 12 degrees?

Ikr I'll see what happens, so many variables.

Pretty much.

I was thinking of a half-tonneau in a pickup truck. It isn't like just having the tailgate up instead of down because there is a recirculation in the front half of the bed that moderates the flow (some how). It could be a sock that fit's over the hoop front and back.

The perforated part would be for rearward visibility, and perforated base plates are a thing so why not?

aerohead and I saw an example at the Darko wind tunnel where a wall of welded wire mesh affected the laminar flow in the tunnel, around a corner.

Take a good profile picture of your car and then put it on the template. I cannot imagine the spoiler would come near the airstream.

Create some spacers from a 2x4! :D

I had to make some from 12mm marine ply just to fit it! And To complicate things This spoiler has to be flush fitted. Makes it all very hard.

Is it merely fettled or permanently attached? Are there holes drilled yet?

It looks like it could move back about 3" to align with the bumper. Then you have two sides of a box.

It does attach to the lid, doesn't it?

It is permanently attached but not hard to move back, I did think about moving it back further.
I've actually been thinking about using the spoiler as an integral part of a full kaam back.
I'm holding back on extreme aeromods because I live in this car so i don't want to stand out too much. Also my gearing sucks and I can make a huge gain with a vx gearbox if i can find one, so i want to do that mod first.

K-a-double m. Perhaps you see the problem with putting a Kammback on a car with a trunk. I can't find the original build thread, but 2000neon did this:

http://i282.photobucket.com/albums/k.../Image0208.jpg
http://ecomodder.com/forum/showthread.php/2000-dodge-neon-aero-mods-20741.html#post326693

They haven't posted since 201608, but the thread should still exist. In case you can't make it out, it's a Watts linkage. You can't see the connecting arm in this view. The Kammback swings on a long arc and the decklid swings on a short one.

My guess is this might help you, I doubt it will hurt. Either way I don't see it having much effect on MPG.

Here's how I see it, In this pic we can see your trunk lid is below the Aero Template, which is not good.

http://i67.tinypic.com/wgzr7l.jpg

By adding the spoiler, it brings it up to being a bit above the line, which is Good. (BTW, I took great care to be sure the spoiler is proportional to the rest of the car, the white civic seemed just like yours but is a better picture to use for analysis)

http://i67.tinypic.com/vgu9s1.jpg

Now the "Maybe/Maybe Not" point. Since we don't know what effect this will have on the rear corners of the car, we don't know if it really helps, or hurts. If your car were only a 2 dimensional shape on paper, like it is here, this would be a definite improvement. But cars are 3D so it get's real complicated due to the whole "Cars have Sides on them" issue.

I tend to guess that Honda has not designed the sides of the trunk to taper in, so It stands to reason that the non-spoiled car has a sort of deep low over the trunk that the air from the sides wants to climb into, and that's really bad. So by adding the spoiler to lessen the deep low above the trunk, or maybe eliminate it, you'll keep the side air from wanting to climb....which is Excellent.

I'd say the odds are 15% big improvement, 45% small improvement, 30% nothing happens, and 10% small decrease.

So there.

Thanks a lot for your analysis, you saved me the work. Whether it is relevant or not the sides of the spoiler are nicely tapered inwards as the spoiler gains height.

As has been previously mentioned in this thread, I may trial closing in the spoiler. Blocking air from bleeding out the bottom and possibly creating a high pressure zone so that the airstream rides on it and separates at the spoilers rear most edge. Of course I could easily box in the sides with coroplast to prevent of negate the side in spilling in.

Idk much about aeros to be fair so my theory may be off. I have some testing to do, I like to follow the test protocols and get some solid data.

VGs
 

I don't ordinarily recommend them,but Wheeler Air Tabs were designed to help with notchback issues.The Mitsubishi Lancer Evo is an example of a car which was tested,and found to benefit a little.
Also,the Mercedes-Benz 190 2.3 received a backlight header air deflector and rear wing to help mitigate notchback-related issues.

^air tabs, very cool.
Well my first tank with spoiler on and it is my best tank ever, and I didn't try hard at all. It is too early to say what the spoiler has achieved but at the minimum it doesn't appear to be hurting things. I really like the look of it too so for now it is staying, no regrets so far on this $40 mod.

Try to find some foam you can use to fill the area under the spoiler and see if things get even better