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Old 09-30-2013, 10:13 PM   #11 (permalink)
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You might want to look into a drag actuated airdam. Someone on here has the air dam flip up out of the way at low speeds via gravity, the air flips it back down at speed.

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Old 09-30-2013, 10:32 PM   #12 (permalink)
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I think the kind of testing you are doing to establish the best height is the way to go. Then a full lower pan fitted will give you the lower support you need.

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Old 09-30-2013, 10:46 PM   #13 (permalink)
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Originally Posted by whatmaycome14 View Post
Ok, well. This thing is too low I think. It keeps scraping on stuff. I'm going to make a new one that isn't quite as low.
It is self-adjusting!
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Old 09-30-2013, 10:55 PM   #14 (permalink)
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It is self-adjusting!

X2!!! Let the ground do the work for you. That way its as low as possible for the driving that you do on a regular basis. Pair with side skirts to maximize benefits.

Can you share how its attached? Plan to make a plow for my Saturn in the future...
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Old 10-01-2013, 12:43 AM   #15 (permalink)
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Quote:
Originally Posted by spacemanspif View Post
... Pair with side skirts to maximize benefits...
Going to hit search on this. What are your thoughts spaceman? Will the sides add as much as the front does? If so, I'm in. About to add front to my saturn. Did on previous CRX with the good old garden edging.

Back to OP.. I would let it scrape on those steep driveways. What can it hurt? Lower is better.
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Old 10-01-2013, 09:08 AM   #16 (permalink)
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From what I have read, it kind of depends on how smooth the bottom of your car is. If it is smooth, the strategy is to get the air to flow smoothly between the wheels. If it is not smooth, then you try to get it outside the wheels and around the car. Then the challenge is getting the air to come back together smoothly with minimum drag at the back. That kind of depends on what you did at the front, and the shape of the rear. I would like to hear others' thoughts on this.

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Old 10-01-2013, 11:48 AM   #17 (permalink)
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Quote:
Originally Posted by Sam Powell View Post
From what I have read, it kind of depends on how smooth the bottom of your car is. If it is smooth, the strategy is to get the air to flow smoothly between the wheels. If it is not smooth, then you try to get it outside the wheels and around the car. Then the challenge is getting the air to come back together smoothly with minimum drag at the back. That kind of depends on what you did at the front, and the shape of the rear. I would like to hear others' thoughts on this.

Sam
I have read repeatedly on here that only minimal improvements to aerodynamics can be achieved with the front, while the greatest difference can be had through the back. Grill blocks and air dams work. People think that nosecones will make a car more aerodynamic. They just make things worse in a cross-wind. A Kamm-back or better yet a boat-tail will allow the air to stay attached longer, leave a smaller wake, resulting in less drag.
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Old 10-01-2013, 12:57 PM   #18 (permalink)
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An air dam is going to increase front area. The benefit of an air dam (from my interpretation) is to stop the air from going underneath. So if your underbody is terrible, an air dam would be good. If you are totally smooth and looking good, I would not do an air dam, as one does increase frontal area- and there is not much benefit. When I completed my final underbody (all the way back, and into the diffuser), I was done with the air dam. I'd say I removed it, but I didn't get a chance to- a giant puddle did lol.

I first suggest an air splitter, easiest to build/install, live with day to day while still helping.
Then an air dam, pretty easy to install, and only a bit difficult to live with (bumps/hills/pot holes).
Finally, a total underbody is easiest to live with, had the lowest drag w/o increasing frontal area, but is definitely the most difficult to do well.

This is all subjective to my experience, and may vary vehicle to vehicle. I am not doing a total air dam on the Insight because the underbody is so good already, and when I make it totally flat & sealed, the frontal area increase won't be worth it (in my mind).

I would note the tires are a rough spot, and including those could skew my mental calculations. It also depends what you can make work, ease/cost, and what it is worth to you. For me, Mustang vs Insight really varies the project- Insight must be dirt cheap, doesn't matter how it looks. Mustang must look decent to good, and be cost effective/worthwhile for the adventure/learning experience.
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Old 10-01-2013, 02:01 PM   #19 (permalink)
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Sam Powell basically has come to the same conclusions I have from reading on this board.

Basically a full smooth belly pan is the best but takes a lot of time and material to build and I don't think its worth removing panels every time you want to jack the car up or change the oil.

Air dams aren't as good as belly pans but effectively eliminate the amount of air that can become turbulent under the car and induce drag. But just a dam on the front only blocks a certain amount of space behind it as air then enters the underside of the car behind the front wheel. Adding side skirts keeps most of the air from coming back under the car until behind the rear wheel.

Its kind of a game of numbers. Air dam scraping the ground keeps 80% of the air out that a non-dammed car would allow in and has a "shadow" of 4ft. By adding skirts you keep out another 80% (80% of the previous 80%) and increase the dam's "shadow" by the length between the tires. These numbers are for argument's sake only and have no science to support them.

So the dam does most of the work, the skirts help to maximize the effort and bring you ever so slightly closer to the benefit of a full belly pan. Dam and skirts will never be as good as a belly pan but when you weigh time, materials and maintenance hassles to the mix I think its the best compromise.

Like UltArc said though, depending on each car's underside, a dam will have varying degrees of benefits.

At least that is the way I understand it. Please speak up to tell me I am dumb when I start giving bad advice lol.
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Old 10-01-2013, 09:19 PM   #20 (permalink)
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Quote:
Originally Posted by UltArc View Post
An air dam is going to increase front area. The benefit of an air dam (from my interpretation) is to stop the air from going underneath.
Right now my underbody is horrible. I'm doing ABA testing tomorrow on the front dam, so I'll post results on the effect it had on my car.

Ultimately, I've been cringing at the increase in frontal area and do intend on a full underbody pan when I get access to a lift. Jack stands in the driveway just won't give me the kind of clearance I need to build such a thing!

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