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Discussion Starter #1
Been running the Napa 6637 filter for a little while but decided that I did not like the loud intake drone it produces while towing so I started looking for a AIS system which I found used locally with 2,000 miles on it. Looks brand new. Anyway me being me I wanted to know which one was really better, so before installing the AIS I installed a vacuum guage in the intake tube pre turbo and after filter. Since the 6637 was lightly used I cleaned it out as best as I could with compressed air and did the same with the AIS filter before the test. Here are my results, the truck is a early 99 basically stock with 4" exhaust and a PHP chip.

6637 at wot = 15" of vacuum
AIS at wot = 18-19" of vacuum

6637 cruising at 70 mph averaged 5" of vacuum
AIS cruising at 70 mph averaged 3-4" of vacuum

Also test was done on the same stretch of road 20 miles out and 20 miles back. Wot was done from a stop and I used PHP's 80dd and 100performance settings which did not have any difference between the two as far as vacuum numbers. Based on my test on my truck the 6637 does flow a little better at wot but not a huge difference. I was surprised to see the AIS flow a little better a cruising speed though. I suspect this may be do to the ram air effect since my truck does have the zoodad mod. Since I like the quieter AIS over the 6637 I will be keeping it on but figured I would share my results.
 

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cool comparison
 

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The reports I've seen are rated in CMF (I see the logic in your vacuum test too) and the AIS out flows the 6637 by quite a bit. The biggest advantage to the AIS is how "clean" it looks (all the DIYs seem like something a teenager would do to me...)

Also, do the "Fender Sleeve" if you're looking for the best performance ;)
 

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The biggest advantage to the AIS is how "clean" it looks (all the DIYs seem like something a teenager would do to me...)
exactly why I got the AIS... Well, the good flow over the stock was important too.
 

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Discussion Starter #5
The reports I've seen are rated in CMF (I see the logic in your vacuum test too) and the AIS out flows the 6637 by quite a bit. The biggest advantage to the AIS is how "clean" it looks (all the DIYs seem like something a teenager would do to me...)

Also, do the "Fender Sleeve" if you're looking for the best performance ;)
I've seen flow charts favoring both as king, that is why I wanted to do my own test on a real truck and not just a machine in a lab. My test showed me the flow and restriction of both in their installed state. AIS filter in the box and the 6637 with the obstructions around it. I am reluctant to do the fender sleave mod even though my early 99 has the ducting in the fender for it because I remember all the fine sand grit that would get sucked into the original filter box using this method. I think Ford changed this for a reason. The grit that got flung up from the tire into the box combined with the crappy sealing lid on the early99 box dusted alot of these early engines.
 

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What brand of intake system did you get?
 

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I've seen flow charts favoring both as king, that is why I wanted to do my own test on a real truck and not just a machine in a lab. My test showed me the flow and restriction of both in their installed state. AIS filter in the box and the 6637 with the obstructions around it. I am reluctant to do the fender sleave mod even though my early 99 has the ducting in the fender for it because I remember all the fine sand grit that would get sucked into the original filter box using this method. I think Ford changed this for a reason. The grit that got flung up from the tire into the box combined with the crappy sealing lid on the early99 box dusted alot of these early engines.
Well, of course, there is the inner fender well between the tire and that hole (although certainly not air-tight sealed) and not directly sucking air from what comes off that tire. Plus, the draw there is supplementary to the snorkel (especially going down the hi-way with a ZooDad). I guess if you live in a very dusty environment, drive a lot on dry dirt roads, it might be an issue. Otherwise, I'm sure the AIS media can handle the dirt quite well ;)

As you state, the only disadvantage might be slightly shortened filter changes, Not "dusting" as caused by a poor seal that actually bypasses the media.

As for the potential flow differences, I don't think it could make "one lick" of difference to any of us :) Freeing the engines ability to breath with free-flowing intake & exhaust is the important thing we're gaining.
 

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Discussion Starter #9
Well, of course, there is the inner fender well between the tire and that hole (although certainly not air-tight sealed) and not directly sucking air from what comes off that tire. Plus, the draw there is supplementary to the snorkel (especially going down the hi-way with a ZooDad). I guess if you live in a very dusty environment, drive a lot on dry dirt roads, it might be an issue. Otherwise, I'm sure the AIS media can handle the dirt quite well ;)

As you state, the only disadvantage might be slightly shortened filter changes, Not "dusting" as caused by a poor seal that actually bypasses the media.

As for the potential flow differences, I don't think it could make "one lick" of difference to any of us :) Freeing the engines ability to breath with free-flowing intake & exhaust is the important thing we're gaining.
You are right I have full confidence that the AIS will stop the dirt and do a heck of alot better job of sealing than my original fender draw box did. I have not ruled out doing the mod just don't know if I need to, one of the reasons that I did the flow comparison. You are also right about probably shorter filter life being a drawback of the fender mod.
 

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Thank you for this write up! I was just wondering this same question the other day. When i got my truck i thought i had a factory air box in it so i did the 6637 mod and then i got to wondering why the factory would put such a huge filter in the stock truck. Found out it came with the AIS system!
I have not put it back in mainly cause i really like the sound of the turbo but im sure once i get more seat time in and do so more hauling i will want to put it back in. Glad i didnt toss it!

Thanks again!
 

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Discussion Starter #12
Thank you for this write up! I was just wondering this same question the other day. When i got my truck i thought i had a factory air box in it so i did the 6637 mod and then i got to wondering why the factory would put such a huge filter in the stock truck. Found out it came with the AIS system!
I have not put it back in mainly cause i really like the sound of the turbo but im sure once i get more seat time in and do so more hauling i will want to put it back in. Glad i didnt toss it!

Thanks again!
No problem. I figured the information would be appreciated. Never minded the 6637 driving around solo but towing heavy loads for a few hundred miles the intake drone is too annoying.
 

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Put in the 6637 just a couple weeks ago. Towing our camper I was getting some seriously dirty looks from the wife.

I was thinking some acoustic foam right behind the filter may soak up some sound.:please:


We'll see.

ETA: When I researched the 6637, I never ran across the noise issue.:doh:
 

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Discussion Starter #14
Put in the 6637 just a couple weeks ago. Towing our camper I was getting some seriously dirty looks from the wife.

I was thinking some acoustic foam right behind the filter may soak up some sound.:please:


We'll see.

ETA: When I researched the 6637, I never ran across the noise issue.:doh:
I think the only way to quiet it would be to build a box around it, but if you do this then you might as well do the AIS :dunno:.
 

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The ammount of noise is going to varry from truck to truck... I have 6637 filters on all 3 of ours, put one on the wife's Excursion the first day we had it, and due to the addtional sound deadening material in the firewall the Excursion comes with in the first place, it is noticably quieter than the other 2 trucks, I don't even notice it now. On the other hand, the yellow truck, with the foil removed from the CAC pipe, 6637 filter, and a hole in the fire wall (Duh, that's what's doing it!) that I need to tape/cover in some way, is rather loud.

It's all a compromise, cost vs noise vs ducting, etc. For me, the cost and ease of install of the 6637, it's a great way to go. I will admit, I have not see a FORD AIS in person to evaluate it...
 

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Discussion Starter #16
The DIY 6637 filter is a great mod for the dollar but you can also get a new AIS for under $200 now. Just depends on what you want. I do like the clean factory look of the AIS and its quietness though.
 

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Anyone have an installed picture of the Ford AIS, I'd like to see it...
 

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Thanks for posting the pic!

So it's like the stock air box, only designed to flow more air? Same drop-in style filter as stock? One of the issues the stock air box has is the bail-clips that hold the box together, is the fastening method better on the AIS?

Do you have a picture of it 'open', of the filter?
 

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Thanks for posting the pic!

So it's like the stock air box, only designed to flow more air? Same drop-in style filter as stock? One of the issues the stock air box has is the bail-clips that hold the box together, is the fastening method better on the AIS?

Do you have a picture of it 'open', of the filter?
This is the kit layed out


Starting at the rear
Housing
Filter (made by Donaldson)
Cover
Battery blanket
Snorkel
Battery tray

It's seal better... These were designed for trucks going to the middle east working in sandy condition.

Honestly, I never had ssuse with the stock box not sealing (I ad the one with the amgr filter), but I coud see he if you were in a rush or careless that the cover coud easily be put on out of alignment or with one of the tabs ear the fender out of place.
 
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