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.
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.
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.
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:
If someone would mind double checking my angle, it would be a huge help, thank you!
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.