05' focus zx3 partial kamm

[tru]

I want to start out this thread by quoting my girlfriend when she saw me mocking this up. "its a good thing i love you" lol

anyway, i bought some coroplast and abs plastic last week on a day off and they gave me a large 4x8 sheet of cardboard to go with it. a nice bonus

ive used the abs plastic to mold/smooth over the non existant fog lights location and will continue forward with it later.

anyway onto the pics


car in profile, anyone care to lay the template for my reference?


close-up detailing construction, not seen are 2 interior supports that are taped to the glass to keep the shape under driving conditions.


from the back to show the flaw in my design. i simply cut cardboard to desired shape and "wedged" it between the tail lights and the glass of the hatch, simple and effective. However the hatch bows outwards as it goes toward the ground leaving an angle in the opposite direction of the desired direction.

I did a prelimminary test this afternoon but couldnt get any real numbers b/c of strong winds. I typically can cruise right around 50 with engine fully warmed and get 49-51 mpgs, so i will use that as my reference.

[TXwaterdog]

That actually looks good too. I'm interested In your results.

[tru]

aww, the power of search

[Arragonis]

That looks really good, look forward to the results. Not clear from the pics, but do you have any support under the centre ? You may want to take a loot at AeroModder's similar mod on his Aspire.



I'm contemplating a similar mod to my Aygo, when I can work out how to attach it as I only have a glass rear hatch.

[tru]

yes, the center has 2 supports set about 1/4 of the way in on each side that matched the shape of the black coroplast. today is the first "run" of the cardboard didnt get saturated.

[tru]

well initial drive to work avg dropped from 40-41 down to 39. there was less traffic but average at 50mph was lower than normal. I think this mod maybe toast.

[Nevyn]

The fact that it's not the whole width of the car may be creating vortices and increasing wake - just a guess.

[AeroModder]

I also worried about vorticies in my design, but yours looks like it has far larger "steps" from the side of the car to the Kammback.

What you could probably do is have the top panel wide enough to cover the entire side, and add some side supports that just sit on the ends of the taillights. Those might need to be made of Lexan or other polycarbonate sheeting so others can still see your brake lights.

But what is most important that you factor out things such as weather changes. If you can, make a test run with it on, then quickly remove it and go for another run. The more trials, the better your results.

It's cooler here, and I'm seeing about a 3 MPG drop from usual. I might need to re-route my intake tubing to suck in some warmer air for the coming winter.

[aerohead]

Originally Posted by tru

well initial drive to work avg dropped from 40-41 down to 39. there was less traffic but average at 50mph was lower than normal. I think this mod maybe toast.

Top performance of the roof is contingent upon a smooth,radiused edge where the top and sides meet.Ford has provided a special challenge with respect to the tailights on the Focus.
Unless this area can be 'blended' into the extension,there is a low probability for success.I wish it weren't so,but we just can't trick the air.
One option for proof of concept,is to wire the car for a trailer,purchase a trailer light kit and temporarily attach the lights,while covering over the O.E.M. light package.
If you see results you like from the rough prototype,then you know it's worth the trouble to pursue the project.
My gut feeling is that you'll need to fully 'Kamm' at least 18-inches of additional length onto the car for remarkable results.

[tru]

Originally Posted by aerohead

Top performance of the roof is contingent upon a smooth,radiused edge where the top and sides meet.Ford has provided a special challenge with respect to the tailights on the Focus.
Unless this area can be 'blended' into the extension,there is a low probability for success.I wish it weren't so,but we just can't trick the air.
One option for proof of concept,is to wire the car for a trailer,purchase a trailer light kit and temporarily attach the lights,while covering over the O.E.M. light package.
If you see results you like from the rough prototype,then you know it's worth the trouble to pursue the project.
My gut feeling is that you'll need to fully 'Kamm' at least 18-inches of additional length onto the car for remarkable results.

interesting, i removed the extension last night, we are expecting some heavy weather the next day or so. im going to modify the extensions to flow towards the center of the car with the tail lights and perhaps extend it longer if i like the results.

Also wanted to add that on my return trip home i noticed higher mileage across the board with a bit of a tailwind, its possible the wind skewed my results in the morning on the way into work. I didnt notice much wind but its possible.

Thanks for the replies so far