Hopefully picking up an '82 Supra P-type tomorrow. Regardless, I'm curious - what's everyone's favorite material for quick & cheap front air dam additions? Basically looking for something I can run underneath the stock front bumper for cosmetic/trash-ramming purposes. Considering this is a $500 beater Supra, I plan to give it a faux-Group B kind of look. Should be fun!
Garden/brick edging from Home Depot
.125 Black ABS from your friendly local plastic supplier works good too.....
I use the home depot lawn and garden edging too. $5 for a 20' roll is pretty cheap. It's just cable tied to the front bumper.
Old conveyor belting. The rattier the better :)
I used that for years on a couple of autox cars it looked pretty good and was about 1 inch of the ground. Gave an Fx16 a pretty hot look
mw wrote: I use the home depot lawn and garden edging too. $5 for a 20' roll is pretty cheap. It's just cable tied to the front bumper.
The brick/paver edging works well if you need to mount to a horizontal surface. If it's vertical, you'll want the lawn/garden edging or other flat materials.
Here's the former on my E39 - I've actually seen about a 2% fuel economy improvement on the highway with this.
i like the edger stuff from HD as well. can shape it with a utility knife and i used self tapping sheetmetal screws to mount it under the bumper, then some nuts to keep them from backing out. gets scraped daily on my miata but doesn't budge.
Garage door weather stripping will work in some cases.
02Pilot wrote: The brick/paver edging works well if you need to mount to a horizontal surface. If it's vertical, you'll want the lawn/garden edging or other flat materials. Here's the former on my E39 - I've actually seen about a 2% fuel economy improvement on the highway with this.
I'm shocked at the difference that makes... I would think that a larger frontal surface area would increase the CoD, and therefore decrease economy.
Can someone give me the high-school physics level reasoning behind the increase of aerodynamic efficiency with the added air dam?
It keeps air out of the aerodynamically dirty undercarriage
Anything to direct air around the car cleanly helps. You can see in my pictures the small factory tabs in front of the tires, for example. More manufacturers are using these to make incremental efficiency improvements to help meet CAFE standards. Check out the hypermiler sites for more examples, such as grill blocking. Of course, lowering the frontal area helps as well.
You;re not increasing the frontal area - most of that air would have hit something underneath the car which would then have tumbled about fairly randomly and created high pressure areas under the car for the rest of the air to hit and find a way around. Air dams typically force air through the radiator, and at least around the car to the left or right. If it creates enough force to produce lift on the car, that's generally a fair amount of drag. Eliminating that lift generally reduces the drag substantially.
Or something like that.
Plus, they look cool when done right. 
My understanding is that the undercarriage's aerodynamics is one of the areas that can be cleaned up the most. Look at those hypermilers http://blogs.insideline.com/straightline/2007/12/hypermiler-builds-95-mpg-aero-civic.html. http://www.japanesenostalgiccar.com/forum/viewtopic.php?p=49208&sid=16de6e91d44ca646b16e1bd74dd45fab They close up the undercarriage as much as possible so that it is as clean as the top side of the car. Second to that is an airdam, which diverts the air.
the lawn edging is pretty stable when you use the fat tubular part at the bottom It adds a lot of stiffness, so there is no flapping.
yes, the lawn edging does wonders. I know on my ti, I am missing the underbumper tray that closes up the area behind the bumper to direct most of the air towards the radiator. I have to wonder what a difference in stability and efficency I will see by closing up that big hole under the car
tuna55 wrote: You;re not increasing the frontal area - most of that air would have hit something underneath the car which would then have tumbled about fairly randomly and created high pressure areas under the car for the rest of the air to hit and find a way around.
Ah! Okay, this makes sense to me. You're not increasing the frontal area, you're just moving it around a bit.
I have an old Ford van that sits on 16 inch wheels, it's an E-250 and it has a large gap between the bottom of the front bumber and the ground. I had a piece of plastic I bolted to a piece of angle steel that was bolted to the bottom of the bumper. It helped so I went to look for something better. I found it at Menard's! They sell exterior trim made of plastic. I found a piece that measured 1/2 inch thick by 8 inches wide by 8 foot long. I cut it to length and was even able to heat the ends with a heat gun and bend the ends back about 70-80 deg. I bolted to the angle steel bracket from the old air dam. The only thing is it only comes in white! I just used Rustoleun Plastic paint on it and it looks almost stock.
ReverendDexter wrote:02Pilot wrote: The brick/paver edging works well if you need to mount to a horizontal surface. If it's vertical, you'll want the lawn/garden edging or other flat materials. Here's the former on my E39 - I've actually seen about a 2% fuel economy improvement on the highway with this.I'm shocked at the difference that makes... I would think that a larger frontal surface area would increase the CoD, and therefore decrease economy. Can someone give me the high-school physics level reasoning behind the increase of aerodynamic efficiency with the added air dam?
I guarantee that the margin of error is over 2%. It may help, but not enough to show up in any home testing. Just too many variables.
2% is over a fixed route run in both directions multiple times. It isn't perfect, to be sure, but it's not a completely random claim.
In other words build a homemade air dam to look cool or to improve airflow through your radiator, not to get better mileage.
(Of course I'm not really concerned with a 2% change in mpg - that would get me an 'extra' 4 or 5 miles per tank or so.)
I have used black vinyl wall base. Don't get the self adhesive kind! It has a lip that makes installation easier.
I want on this bandwagon. I've never made an air dam. I will take a look at the fleet and find the best candidate and go from there. Not sure I want to make extra holes in any of my three choices though, but two of them are old enough with enough other body problems that it's really a non-issue to sink in a few sheet metal screws.
Old conveyor belt material is great. It also makes great side skirts.
We used to use it on the MR2's all the time. The Lawn edging is also a good option but did not seem to stand up as well to off track excursions as well.
http://www.cmwraceparts.com/proddisp.php?pn=CAP93081-10
High density polyethylene plastic 22" wide x 10' long .070" thick. comes in about 10 different colors too. Pop rivets to match the plastic are available too.
Conveyor belting works the best we used it on Mark's Fiesta and wrapped it around the side right to the wheel well. It made a great snow plow in the winter.
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