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Old 10-01-2013, 10:58 PM   #21 (permalink)
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Originally Posted by whatmaycome14 View Post
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!
I thought the same- theres not enough space!

After I got under it and measured (lift), then got under and built one on a lift, I found that I really could do it underneath (on my ramps). As it gets colder, I will spend less time on the ground, but while it's nice out, I won't sweat as much.

And design, design, design! Mine is three pieces, rear to front. This is so there can be reasonable overlap, and the wind doesn't catch it.

At the very rear, I have the diffuser. Tucked into/out of/into/out of/into/out of/into, and attached every few feet at different points, is the rear panel. Air shouldn't be getting in my rear bumped from underneath, rather flowing along the panel. This goes from under my rear bumper to the mid of my cabin. The next piece covers that (by over 6 inches) and connects to a bar right before my front wheel wells, this is also just before I get to the engine drain plug. The final piece connects at this bar, not really overlapping but connecting to the bar so it can drop and hang from it. The beginning attaches at the very front, inside the bumper. The bumper hangs a bit lower, and I also have an air splitter helping keep the air apart (what is supposed to go underneath, and what should be pushed to the sides). The part that is attached to the bar works like a swing. So for an oil change, only the front zip ties need to be cut, the front drops down while the rear hangs up, and oil drain plug and filter have easy access.

It's been a while since my most recent build, and I don't change my own oil- but it made sense when I built it. The Ford techs have never had an issue with it, as long as they are aloud to rip out my SC&UG (EVERY F___ING TIME!!!), and remove my front seat and sit in the back (I literally fall backwards every time I get back into the car. Every time.).

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Old 10-01-2013, 11:49 PM   #22 (permalink)
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It is interesting to study what newer OEM rear treatments are doing. In general I would say the Germans are taking this more seriously than the Japanese. The American designers are somewhere in between. Some designers are incorporating something like a kammback effect on the lower edge of the bumper face in an attempt to carry the bottom air past the rear flat. Others are doing just the opposite and including molded ridges that run parallel to the air flow to help it move smoothly up the back side. This would be similar to the vortex generators that are getting press these days. The kammback design is nearly universal on the upper trailing edge these days. Once you start looking at these details it gets to be sort of an obsessive habit.

Has anybody here played with the vortex generators?

Sam
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Old 10-01-2013, 11:54 PM   #23 (permalink)
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Quote:
Originally Posted by Sam Powell View Post
It is interesting to study what newer OEM rear treatments are doing. In general I would say the Germans are taking this more seriously than the Japanese. The American designers are somewhere in between. Some designers are incorporating something like a kammback effect on the lower edge of the bumper face in an attempt to carry the bottom air past the rear flat. Others are doing just the opposite and including molded ridges that run parallel to the air flow to help it move smoothly up the back side. This would be similar to the vortex generators that are getting press these days. The kammback design is nearly universal on the upper trailing edge these days. Once you start looking at these details it gets to be sort of an obsessive habit.

Has anybody here played with the vortex generators?

Sam
I don't know anything about those.

I also don't know how much help it is to work on the underside of the rear if it isn't smooth and clean leading up to those parts.
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Old 10-02-2013, 12:06 AM   #24 (permalink)
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Those are good thoughts. It would be useful to have access to testing data on how the air does flow under a car. I cannot imagine. My car has deep cross members that stick down. Does static air just hang up there or does it flow up into and out of those spaces?

There are several types of vortex generators. The most common ones are showing up just above the rear window on the roofs of most BMW sedans. I will do a search and find others and post them. Somehow or other they make the air flow more smoothly down the rear window without creating eddies and separation.

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Old 10-02-2013, 07:28 AM   #25 (permalink)
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Quote:
Originally Posted by UltArc View Post
The Ford techs have never had an issue with it, as long as they are aloud to rip out my SC&UG (EVERY F___ING TIME!!!)
I understand them unplugging it, if they need to run diagnostics, but mechanics always remove mine, too. With the 3M tape that I use now, they would need to forcibly rip of my Ultragauge, and I am pretty sure that I would complain about that afterward, as I would need to scrape off the old tape and redo it.

Quote:
Originally Posted by Sam Powell View Post
Has anybody here played with the vortex generators?
It is not listed under Car MPG Efficiency Modifications Main - EcoModder or 65+ Vehicle modifications for better fuel economy - EcoModder.com. My understanding is that they actually create vortices in order to control airflow (Vortex generator - Wikipedia, the free encyclopedia seems to verify that), but they are not really DIY things, unless you have access to a wind tunnel. A Kamm-back would control airflow without creating vortices, yielding a larger difference

According to the Wikipedia page, they are actually installed on the front of a wing, not the back.
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Old 10-02-2013, 08:50 AM   #26 (permalink)
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UltArc, Could you post a photo or two of your lower treatment please? I would like to see what you have done.

Sam
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Old 10-02-2013, 08:55 AM   #27 (permalink)
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Quote:
Originally Posted by Xist View Post
I understand them unplugging it, if they need to run diagnostics, but mechanics always remove mine, too. With the 3M tape that I use now, they would need to forcibly rip of my Ultragauge, and I am pretty sure that I would complain about that afterward, as I would need to scrape off the old tape and redo it.



It is not listed under Car MPG Efficiency Modifications Main - EcoModder or 65+ Vehicle modifications for better fuel economy - EcoModder.com. My understanding is that they actually create vortices in order to control airflow (Vortex generator - Wikipedia, the free encyclopedia seems to verify that), but they are not really DIY things, unless you have access to a wind tunnel. A Kamm-back would control airflow without creating vortices, yielding a larger difference

According to the Wikipedia page, they are actually installed on the front of a wing, not the back.
There is an interesting web page I will try to re-find where a guy used pieces of yarn taped to the back window to find the best placement for a vortex generator. As i understand it the goal of the kammback and vortex generator are just the opposite.

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Old 10-02-2013, 11:20 AM   #28 (permalink)
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Quote:
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UltArc, Could you post a photo or two of your lower treatment please? I would like to see what you have done.

Sam
I second this.
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Old 10-02-2013, 12:29 PM   #29 (permalink)
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UltArc, I would also lik to see pics of the undertray you described.

If you do an EM search for vortex generators, you will find multiple accounts about their inability to show any real MPG gains. Even if one does the tuft test to find the best placement, they still find them to not be useful. I don't remember where, but I saw a guy who took some CDs and bent a third on the left and right side to make his own VG, pretty cool.

Quote:
Originally Posted by Sam Powell View Post
As i understand it the goal of the kammback and vortex generator are just the opposite.
Yes, if you have a kammback, the VGs are useless to you, because the kamm will allow air to stay attached for longer and force it to leave further out and down. The VGs are designed to slow down the air so that it will wrap around the back of a car easier.
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Old 10-02-2013, 02:46 PM   #30 (permalink)
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Quote:
Originally Posted by whatmaycome14 View Post
What do you guys think?

*I* think that nose looks familiar...



Yes, very familiar.

My air dam is shorter, far more rigid, and just as cheap. More pics in the link in my signature (as well as other stuff I did to my car). At first, mine only occasionally scraped anything, now it does more often since I lowered it a couple inches. But, it's so durable that it will take a long time to grind down and then I can get a new one for $8...

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