Neon Aeromod coastdown testing Results
 

Hello everyone, sorry I don't post very often, I mostly just hang back and read, but my turn to contribute a bit, and hopefully get some feedback. :thumbup:

My car is a 2000 Dodge Neon, which you can see what I've done here:

http://ecomodder.com/forum/showthrea...ods-20741.html

For testing, I did 120-70 km/h coastdown testing, the road was not totally flat (none in southern Ontario are), but I figured that since I am only using it for comparison sake it should be okay since it is consistent. A friend of mine started and stopped the stopwatch, and didn't tell me any numbers during the testing just to try and keep this is objective as possible.

Anyways, my new mods that I tested were a vertical (Nascar style) spoiler at the very back of the car, which extended vertically above the trunk lid. Although it was not quite meeting up with the template line, I didn't want to go higher due to visibility concerns and also lack of material.

http://i282.photobucket.com/albums/k.../Image0073.jpg

http://i282.photobucket.com/albums/k.../Image0070.jpg

On it's own, this spoiler had an increase in drag of 4.3%. However when tested with version 1 of the kammback (see below), it was only a 3.4% increase in drag. In the pursuit of gas mileage, it is needless to say that this spoiler did not stay on long.

Next was my "bonneville" style spoiler. Which extended straight off the back of the trunklid. For this, I only went back about 6" because this allowed the back of the spoiler to be flush with the rear bumper, the final version will most likely extend a little bit farther out.

http://i282.photobucket.com/albums/k.../Image0086.jpg

I would also greatly appreciate any input as to whether I should try an upward or downward slope to it, as well as any comments about overall length.

After doing some reading, I understand that going upwards with it could be beneficial to help it reach the template line, although sloping it down could reduce drag farther if it's long enough. I wanted to test these but I ran out of time.

Based on the coastdown testing, this spoiler alone gave a decrease in drag of 3.9%.

Tested with version 2 of the kammback gave a total of 7.1% decrease in drag (compared to only 4.56% drag reduction from kammback alone)

Here is the partial kammback, sorry I only have pictures of version 1. It got too dark by the time I revised it for any decent pictures. It will be going back on the car and can get updated pictures if you would like. I built it as you see for visibility, trunk access and the length was because that was how big of a piece of coroplast I had leftover.
Here it is:

http://i282.photobucket.com/albums/k.../Image0067.jpg

http://i282.photobucket.com/albums/k.../Image0066.jpg

If someone would mind double checking my angle, it would be a huge help, thank you!
http://i282.photobucket.com/albums/k.../Image0068.jpg

This first version of the kammback, I know that I made the sides taper in too quickly, which was made a bit better in the second version, which I added 4" to it, allowing the side pieces to attach a better angle. I measured it to be 21*, so still too sharp, but better than before, and better than stock.

The first version of the kammback had an improvement of only 3.1% drag reduction, and the second (revised) version had a total drag reduction of 4.56%. I think that if I make it a bit longer, and keep working on the side angles I can get a little more from it.

So there we are, I still have a ways to go yet but this at least gives a good starting point, and some numbers for comparison as I revise these mods and keep testing.

If anyone has any questions or comments I am open to feedback, Im sure that you guys know a LOT more than me.

i've been considering a bonneville style spoiler myself, i didnt even consider the idea of sloping down, kicked around the idea of sloping up, but am thinking that i would try something flat. which when i thought about it, thats how they do it at bonneville, so it kinda made sense. likewise with the length, i think what you see on the cars at bonneville might be the best for aero, but i think at that length and limited profile (hard to see at certain angles) i could see issues arise in parking lots, backed into, walked into, door opened into, so i dont think i would extend it very far past the edge of the bumper.

Thats exactly what I was thinking too, if I go past the rear bumper, it wont be much mlre than 1" or so, Luckily the neon bumper extends quite far out from the edge of the trunklid.

I should mention, my bonneville spoiler has metal rod beneath the cardboard giving it strength, it did not flap at all.

yea, i'm interested to see how your later versions are made / attached / look also... so i can copy it :p

I have some aluminum sheet that I can use, although it is a very thin gauge so a frame of some sort will be necessary. As for attachment, since this car is very rough already, I might just bolt it on through the trunk lid, although Im debating some other mounting options.

2000neon -

I'll let others chime in, but here is my overlay :

http://ecomodder.com/forum/member-cf...0-template.jpg

CarloSW2

guess i'd probably go with bolts or something simmilar too ,since i'd be replacing my stock spoiler and already have holes. alum. sheet plays on my parking lot issues, if you could do a rolled edge might give it strength, while making it less of a blade to passers by.

Thanks cfg!

As for the aluminum, i did some of my belly pan with the aluminum around my exhaust, I did a double "factory fold" on the edges, it was amazing how much of a difference in strength it made. I might even do a piece of roundbar along the edge of it, although that adds more attachment problems, lol.

thanks cfg83
where my imagination put the traditional length of bonneville spoiler is about where the template would intersect.

i think one of the problems with the nascar style, or sloping a bonnevile type up is that, even though they fit in the template, the template is 2d while the car is 3d. so if youre not just extending part of the body back to meet it, air coming around the sides of the car causes additional drag when it hits the spoiler. i wonder if a nascar type spoiler tapered off at the sides would do better, but kinda doubt its even worth testing

As for the nascar spoiler, i think that you are right. From the increase in drag that I got, even if there is room for slight improvememt, I dont think it would be enough to even break even, let alone decrease drag any substantial amount.

So do you have any real world MPG numbers for before and after?

I have a ton of before numbers, I am hoping to get the real version of the bonneville spoiler installed tomorrow to get some after numbers. Unfortunately I am stuck with tank-tank averages.

Interesting project, keep up the good work.

You gotta have some tank to tank by now?
I am looking into this for my neon, but wanna see how yours turned out.

I only actually have one tank so far, last week I had a surgery to fix a hernia and so I havent been driving at all for a little while. The last half of a tank and one full tank I have on it seem promising though, the full tank came in as 44.2 mpg US compared to an average of 43.1. I will be driving again tomorrow and will have more numbers coming in.

I will also get pictures of the finished product. Sorry for the delays.

Filled up again, 43.82mpg, a little bit more city driving on this tank and still higher than previous averages. More time will tell, but it seems to be a ~ 1 mpg improvement. I painted it today so I will get the finished pictures in the morning.

1MPG, thats pretty good. I have my little Neon at about 40-41 mpg. I had been carpooling with a guy and now I am not. I seem to be getting about 1 to 2 mpg better with the less weight. Now, if I do the aeromods, I hope to get another MPG hopefully. I have to go get the material and try this out. I am just going to duct tape the stuff on for initial testing, then I will perform a permanent attachment.

Depending on the aero mods, you can easily get more than 1 mpg. Keep in mind that my car is an automatic, with decent aero I would think 45+ should easily be possible for you.

What did you use fpor the Kammback and where did you get it? I was looking at lowes for some plexiglass and they have lexan (I think). Anyway, a sheet large enough to do the kammback is about $50. That just seems like a lot of cash. Anyway, let me know what you did! Thanks.

The kamm is actually just corrugated plastic. I didn't bother making it clear since at the distance it goes down the back window, there is still decent visibility out of the back window.

what are the smooth wheel covers made of (green) in your first post?

Also just corrugated plastic, and some zip ties :D

A few more tanks, one at 41.7 - More city driving than normal.
43.4 - Slightly better than "before" average.
44.0 - Same deal, bit higher than previous average.

Oh and dohcsvt, I got the corrugated plastic at home depot. A 4 x 8 sheet of it was $19, I got two and have done the majority of a belly pan, wheel covers and wheel skirts with it as well.

Considering you somehow coerced a friend into stop watch duty, it shouldn't be too hard to tuft test your kammback. This will tell you if the angle is right- and perhaps allow you more improvement.

I would also encourage you to tuft test the rear of the car without any aero aids. If you can figure out where the air starts to get turbulent behind the C Pillar, you can find where to end the NASCAR spoiler. If the air is clean and attached, no spoiler needed. You just want to trap a vortex behind your turbulent window to act as a virtual kammback.

Should this work, you can use a piece of stiff, clear acrylic instead of coroplast. This will allow you full vision while taking advantage of the aero benefits and Coventry data on base plates.

I do not know how big or in what shape you should build a spoiler. You might, however, be able to rig up a test apparatus to find out. Instead of tuft testing only on the surface, you could try another technique the professionals use- 3D tuft testing.

Looking through some old Car Styling issues, I found these photos. Issue 2009.1, page 16.

From a square framework, they strung cables vertically behind the vehicle. From the cables are attached tufts about 5cm apart from each other in a careful array. You can see that the ones going straight back are "good" flow and those that are fluttering exhibit turbulence. By attaching a frame like this to the top of your trunk you may be able to see where to build a spoiler, or even kammback.

http://farm9.staticflickr.com/8154/7...d5443101_b.jpg

I don't know if this will work in real world situations or if it's purely a closed-environment test. Maybe aerohead can weigh in on this; it might be a fun thing to try.

PS- I'm also interested in seeing the raw data. 3-4% isn't much, and if the data varies a bit those kind of changes may not be conclusive.

frame
 

If the frame could be examined at a number of locations from the backlight header rearwards,in the absence of smoke,you could visualize what the flow was doing.
As to a 'kicker' type spoiler,without a force balance it would be tough to know if you had gone too far with the angle or sizing.
The K-form roofline is a known quantity,so it's easier to predict the outcome of that kind of mod,whereas spoilers would be more of a challenge.
Re-attachment would be part of the problem,but just getting 'enough' would be the tough part.
Longitudinal vortices would be the boogaboo.This is where the frame might allow their visualization and tailoring of the spoiler.Tough assignment!

Thanks, Phil. Clearly Mazda has done something screwy to keep attachment over that steep rear window, so I don't recommend that. I was thinking of a sort of base plate as in the Coventry thing, combined with the NASCAR approach.