2007 Focus Front Air Dam
 

OK, time to stop lurking and show what I'm doing.

First, my 07 Focus usually returns about 30 mpg in my commute. The current tank is going a LOT farther (412 miles on it with almost a quarter left) so my EOC'ing and other techniques I learned here are most definitely helping.

Anyway, here's the how the front end air dam is progressing.

The stock front end includes a smallish air dam and partial front end belly pan, as shown here:
http://i306.photobucket.com/albums/n.../lhs_stock.jpg
Not bad, but it's not as far down as some of the chassis parts farther back, and being that bigger is ALWAYS better :) (just kidding -- I know -- but easier to start a bit larger and trim than to add on later) I thought it could be improved.

I stopped by a local sign place and ordered a 6' x 2' piece of black coroplast. It's supposed to be available on Monday, so today I mocked up what I had in mind out of cardboard.

The left side was easier for me to reach, and taking a good look at it I thought I could also shield the exposed face of the front tires, too. Anyway, here's the left side.

From the front:
http://i306.photobucket.com/albums/n...nly_front2.jpg

Under:
http://i306.photobucket.com/albums/n.../rhs_under.jpg

Detail at the fender where it curves up the tire:
http://i306.photobucket.com/albums/n...tail_front.jpg

From the back:
http://i306.photobucket.com/albums/n...etail_back.jpg

Not too bad. I took it off, flipped it over and made a mirror image template for the right side:
http://i306.photobucket.com/albums/n...s_template.jpg

This went on:
http://i306.photobucket.com/albums/n...tail_front.jpg

With both sides on:
http://i306.photobucket.com/albums/n...ides_front.jpg

I just had to fill in the gap, pull it off carefully and wait for the coroplast:
http://i306.photobucket.com/albums/n...ate_on_car.jpg

And for next week:
http://i306.photobucket.com/albums/n...e_template.jpg

There we have it. I'll likely screw the coroplast into the face of the existing air dam and under the fender lips (all plastic).

Hopefully I'll have enough left to play with grill blocking, too. Oh, and I'm going to have to figure out some way to put smooth covers over those fog lamp cutouts. Maybe some flexible plastic stuff (suggestions?)

I'll add on to the thread when I get the plastic and start cutting.

Good luck with the Focus :)

My trip in my 1.8 Tdci Diesel achieved 67.2 mpg today.... without any mods!

I'll be getting better than that with the mods I have planned ;)

Looks good so far, think it'll stay on?

Looks alright. I'd be concerned with the top of where is is for the wheel wells. I don't think that you want it to stick out that far, at least not a sharp straight edge. To me that looks like it would create more drag. And also make sure you not going too much lower then the lowest suspension/drivetrain part. I'm quite familiar with exteriors of Fords from the past few years and i'm pretty sure the stock air dam is as low as it needs to be across the middle in the front.
I don't know, i mean it is just my 2 cents. Good work and i'd like to see the results

i think you will have better luck with lawn edging under the front of the bumper. that looks to me like it will hit the dam then get stuck there because of the factory undertray. then it would cause lift, letting more air under the car and you dont want that. i thought the rule was that airdams should be at the front most part of the bumper. if you put a kink in the middle so its like a triangle and pushes the air out from under the car to the sides, i think you might get more out of it then having it flat down like that.

When my wife saw it she said, "Uh, is it going to stay that white?" :D

I only drove as far as the end of the driveway with the cardboard on it to see if it would hit the street if driving out front-first. It doesn't, barely. Mostly I back out so that shouldn't be a problem.

As for the coroplast holding up, I think I'll add some tabs to the dam by folding it and screw it in with the screws vertical, like this:
http://i306.photobucket.com/albums/n..._under_rev.jpg

That will hopefully make it more resilient and the screws won't be as visible from the front of the car. The existing dam will back it up and ought to prevent if from unfolding and acting too much like a scoop funneling air down to the ground. I may have to add some thickness to the 'plast, maybe another layer glued on partially to help make it stand straight. I'll have to wait and see on that, I guess.

I first bought lawn edging but the stuff is so flimsy that I thought a 30 mph ride would just fold it right back. Maybe I should have bought better stuff. :p

As I mentioned, above, I'm planning on folding the 'plast over and screwing it UP into the tray. That ought to hold on pretty well and keep it vertical.

Interesting thought about the need for a dam to be in the most forward part of the vehicle (leading edge of the bumper). I'll do some more research and get back to the group on that.

As for making it into a VEE shape, I could do that. There's plenty of room on that tray to screw the thing onto, I'd maybe back it up with aluminum angle to keep it straight down. I had thought about doing that but figured I'd follow the factory's original direction.

Oh, and regarding bringing it up in front of the tire, the pics don't make it clear but the front edge of the tire IS exposed to the oncoming airflow. The fender wraps in and leaves the oncoming tread cutting the air. I thought that making the whole thing into a combo. air dam and tire spoiler (running up as high as needed to fully block the tire) could only help.

Yeah, that projection out the side looks a bit crazy but I have to come out that far to shield the tires. I'd originally thought of separate tire spoilers, but seeing as how the front edge of the fender's tire cutout was only a few inches behind the stock air dam I figured I'd just make it one piece. The fender really does wrap that far in, exposing quite a bit of the tread to the oncoming air. I will radius the bottom of the thing, though, once I settle on a height.

As for spoiler height, it's not quite as low as the lowest chassis parts farther back (by at least half an inch). Like I said, I can much more easily make it shorter if I want than add on.

I do want to find out, though, if it makes a big difference on where the air dam is relative to the front edge of the bumper. If it's supposed to be up front, I'll change plans accordingly.

ohh ok. I guess it depends on the rims the car comes with, as the 15's or 16's aren't as wide as some of the other ones.
And with the placement of the air dam, i'd say front. Reason being is, it is supposed to keep air from going under the car, with it in place where you have it mocked up you letting air to go back already, and then hit a straight wall. the air can't go up, and if it's straight across the air would struggle deciding which side to exit to

I think those folding tabs are a good idea. If you could install 90deg angle iron brackets along the folds, it should make it pretty sturdy.
I've made some RC airplanes out of the stuff.
http://i46.photobucket.com/albums/f1...OR/th_ec3c.jpg

Coroplas is like corrugated cardboard and is pretty easy to fold along the lines of the corrugations and folds with great difficulty sideways to the grain of the corrugation tubes.

A lot of people find it so hard to fold, even just to 90 deg, they cut along one side of a corrugation tube. I don't recommend that.
Lay the coro out flat on a hard flood and take a dull screwdriver and use it to
compress a line down one of the corrugated tubes. That will allow you to make a clean fold. Sometimes it takes a few passes with the tool to bend the plastic into the tube enough to get a clean fold.

If the wind load is high, the coro will bend. So, for wings, we install steel rods inside the some of the tubes. (Music wire from a hobby shop).
If you make the L brackets (or angle iron brackets) large enough, they might do the job of keeping the coro from flexing under with the wind.

You could do a small test install and have someone drive in front of you at 65mph take a look (or video) under your bumper.

New to this. Do you totally want to block the air under the car? Don't your want the high pressure air under the car to meet the low pressure air in the rear?

If you have a smooth belly pan covering up the under-body, you don't need
a large air dam. (Just some shorts ones for the wheels).

But normally, the underbodies of cars have all kinds of non-aerodynamic
junk hanging down in the air-flow..

So, sometimes, there is a need to keep the air flow off that junk..

http://fullmonte.smugmug.com/Other/2...97_mQhqv-M.jpg

I don't see how the parts on the sides can possibly reduce drag!

You're "shielding the tires" but you're doing it with flat sheets. The Cd of a flat plate is 1.0. You're also redirecting all the sideways flowing air from the bumper straight out to the sides. Hold a flat knife under a faucet-- it's just like that.

Okay, your right! They don't work.. Guys use air dams because they look Cool..

http://ll.speedhunters.com/u/f/eagam...om_Snap/86.jpg

And, that's how they get the hot chicks!!

http://ll.speedhunters.com/u/f/eagam...fdseattle3.jpg


And, I'm never wrong about these things!! :rolleyes:

Neither of those air dams extends to the side of the vehicle where they act as air brakes, which is what I was talking about.

I recently put a lawn edging type air dam on a 2003 Focus that doesn't have that stock dam back from the front edge. I found that it tends to hit when entering driveways and will be an issue in winter for sure.

The poly lawn edging is tuff stuff and is ideal for an air dam....and putting it back on that OEM dam would be ideal in that you wouldn't have the scraping issue. For stiffness you can insert a metal rod into the hollow part at the bottom....and shape it how you want.

Home Depot 20 ' ...for $7.


I have noticed a lot of women crowding around and people thinking I'm driving for NASCAR though.

Your dam is so much rearwards under the front end that I have doubts it will improve something. The air can flow only sidewards, with difficulty... I would focus first on this :http: //imageshack.us/photo/my-images/189/focusonthis.jpg/
I have the same problem with my Astra G

Im thinking that due to its location, it might not be a bad idea to have it angled down towards the meeting point of the tires/asphalt.
this would have the benefit of redirecting the air away from the under body, but not acting as a wind plow.

sort of like this:
---\
___|
-/

i have a few remarks. you may not want the dam to reach to cover the whole width of your tires as you'll increase your side wake. i flat plate will have a very broad wake so even if it's smaller than the wdith of the tire behind it it will still send the air around in a clean path,
http://i77.photobucket.com/albums/j5...efficients.jpg

second you may not want the central dam to be so low, nascar cars have a front ends that coupled with a full airdam will send all oncomming air over the car, where you have the dam it'll send the air around the car.

this graph althoug generic and incomplete sugests that an airdam can be to low and that beyond a certain point, only downforce will decrease but drag will increase again.
http://i77.photobucket.com/albums/j5...rdamheight.jpg
(Katz, "Race Car Aerodynamics", p.208)
reasearch on the ople calibra found that raising the center of the airdam also reduced drag (A)
http://i77.photobucket.com/albums/j5...ay/calibra.jpg
sketch (b) however sugests that the area in front of the tires can should be as low as possible although there's a point where the improvements are minimal so ground clearance is likely more important to keep them in one piece

i don't want to come across negative or as if i know it all, And by all means test what you have because it might just work, but it seems to me that you're puttin a lot of effor into something that might be a dissapointment. and if you have that much plastic you may as well start a modest undertray ;), but again, just my thoughts...

there is something off on your first graph, majorly off
the first cylinder shows a CD of 1.2, the teardrop and the 2nd cyl shows the same, but then the last cyl shows a CD of 0.6

looking at the "wake" pattern flowing behind each object shows no discernible reason for the #1 & #2 cyl object and teardrop to have the same CD, while cyl #3 has a less than CD and a smaller wake behind cyl #3 than behind #1 & #2.

re @ OP
trial and error are going to allow you to find the best combination, but I do agree with what others have posted about it being too far from the actual to make much of a difference, if any, or even the opposite effect.

well it's just a graph i got somewhere of the web to illustrate a generic wake as it might come of a flat plate. so i make no claim as to the accuracy of anything pictured

i don't know all that much about aerodynamics, but the main difference i see is the R value i have no idea what that stands for in this graph (reynolds number perhaps?) but it might explain the different numbers

but it doesn't matter all that much, the point i wanted to make is that the fact a flap plate has a large wake is an advantage, as you can have a smaller dam send the air around the larger tire behind it. but if you make it to wide you may actually add drag.

For the latter cylinder the Reynolds number is 100 times higher, and the air's separation point is well aft of the center / greatest width as seen by the air.

that still doesnt explain why the variance in air flow, a cylinder is a cylinder (or a circle a circle) which will have the same dynamic affect on the flow pattern.
unless #1/2 are cylinders and #3 is a ball, which of course will have a huge impact on flow. :)
either way, the teardrop should have the lowest CD on the chart according to the flow pattern itself.

@ lunar, sorry, I didnt mean to imply it was your chart specifically, just that you posted it so as such are responsible for it ;)

you still with us??
 

any updates to this? just wandering how it all came out? I have the same car and I'm thinking about doing the same thing. Thanks!