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Old 06-01-2008, 05:14 PM   #1
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Default Choosing an air filter

I'm tired of my current self-destructive pre-turbo intake setup. Yeah it doesn't like heat. Also I like to hear the turbo spooling. It gets nice cool air but I don't want to find out if a turbo likes deteriorating rubber. Please excuse the dirty engine bay.
DSC_0107.jpg
DSC_0108.jpg
DSC_0109.jpg
DSC_0110.jpg

So I've been looking at the K&N filters, nice big selection, but amazingly I don't see a filter that has a 60mm flange that is angled. So that seems to leave me with 57mm and 62mm, specifically one of these...
http://www.knfilters.com/search/prod...x?Prod=RU-1720
http://www.knfilters.com/search/prod...x?Prod=RU-1770

Do I get the 57 or the 62?
Are these filters big enough to support 250ish HP?

I don't care about hot air from the radiator.
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Old 06-01-2008, 05:20 PM   #2
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I would say anything is better than the current setup. I take it you plan on going turbo-AFM-filter in a straight line? Depending on the size of the filter you might have clearance issues between the hood and near the radiator fan.

If you could, take the time to measure things and make a sweep back toward the firewall like alot of people do. But realistically, anything is better than what you have right now.

Vash-
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Old 06-01-2008, 05:23 PM   #3
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Air filter is going straight on the turbo. I should prolly add something to my sig. I can't for the life of me find any 60mm pipe.
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Old 06-01-2008, 05:39 PM   #4
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Is that like the tubing that they use for washers or dryers?
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Old 06-01-2008, 05:44 PM   #5
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Quote:
Originally Posted by compy View Post
Is that like the tubing that they use for washers or dryers?
Nah, you can get this stuff from Autozone, Orielly's, whatever your local auto store is in the ricer section. It definitely doesn't stand up to turbo applications.
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Old 06-01-2008, 05:57 PM   #6
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Im sorry but I LOLd at the tin foil/kragen intake pipe set up. It may sound crazy but I personally see merit in a plastic intake tube(like the company that used to make iceman inkaes used) plus PVC type tubing isnt expensive and comes in a huge amount of sizes and shapes. Idk though, metal seems to be how most people do it
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Old 06-01-2008, 06:11 PM   #7
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Quote:
Originally Posted by J.T. View Post
Im sorry but I LOLd at the tin foil/kragen intake pipe set up. It may sound crazy but I personally see merit in a plastic intake tube(like the company that used to make iceman inkaes used) plus PVC type tubing isnt expensive and comes in a huge amount of sizes and shapes. Idk though, metal seems to be how most people do it
Adhesive insulation tape ftw. I had to do that to keep it from melting.

PVC will get brittle with heat and I've never seen it in the right size. I can't say I haven't used it for a cold air intake on my old Eclipse gs though.
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Old 06-01-2008, 06:41 PM   #8
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Well its prob not PVC, i dont know my plastics very well lol.
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Old 06-01-2008, 07:12 PM   #9
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A mom and pop exhaust shop will bend you some tubing for your intake if you want a single piece crazy intake setup like that. If you want to do a intake with a cold air box heatshield i suggest getting a pretty small filter like what you see on Saml01's car and the filter offered in the BEGI kits.

PVC is not a good option, it doesn't withstand that kind of heat very well and it emits some kind of vapor that is bad for O2 sensors I believe.
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Old 06-01-2008, 07:14 PM   #10
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Ah thanks. Well the question now is... My turbo inlet is 60mm, should I get a filter with a 57mm flange or a 62mm flange?
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Old 06-01-2008, 07:44 PM   #11
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Looks like AC and PS is out, I'd clock the compressor and mod the charge piping to fit. Leaves plenty of room for an intake when you're done.
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Old 06-01-2008, 11:16 PM   #12
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Look at dwights car. I think you will like the airfilter he is using. We can get some piping and make something of it
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Old 06-01-2008, 11:38 PM   #13
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If it were me, id do a 45* coupler at the turbo, length of pipe, 90*, then the filter tucked up over the lower rad hose in the wheel well.
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Old 06-02-2008, 12:19 AM   #14
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The turbo intake is about 2.5" so a coupler and this should bring it over to the shock tower and than add filter.

http://store.summitracing.com/partde...5&autoview=sku


PS: nice intercooler.
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Old 06-02-2008, 12:36 AM   #15
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I used to have that same hose
DSC00487Medium.jpg

I currently use a K&N RU-5111 and route it to the wiper cowl via 2.5" tubing.
0e5bc851.jpg
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Old 06-02-2008, 12:48 AM   #16
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https://www.miataturbo.net/forum/showthread.php?t=16531
My cowl CAI setup. Very similar to what SamS did above.
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Old 06-02-2008, 02:08 AM   #17
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OP asked about a filter supporting 250whp...
Does/can the size of the filter affect anything??? I'm using a pretty damn small one, its KNN but I think its for a MC or snowmobile or something....
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Old 06-02-2008, 02:24 PM   #18
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Quote:
Originally Posted by tvalenziano View Post
OP asked about a filter supporting 250whp...
.
I know he did, and there are two K&N filter part numbers listed in the link I posted, the one I used and the one Sam used. Here is the one I am using
http://www.knfilters.com/search/prod...x?Prod=RD-0720

According the the K&N sizing guide this is large enough for 250 HP.
If the filter is too small, there will be a higher pressure drop across the element that will effectively choke the turbo. It is not an all-or-nothing thing, but gradual. Go here for sizing formulas:
http://www.knfilters.com/filter_facts.htm#SELECT
The way I did it is I doubled the engine displacement to simulate doubling the volumetric efficiency under boost.

Short answer is, get the biggest one you can fit in the available space WITH room around the outside so the air can flow into the filter. See my CAI thread for an example of what NOT to do with allowing space around the filter.

Last edited by ZX-Tex; 06-02-2008 at 02:50 PM.
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Old 06-02-2008, 03:54 PM   #19
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Thanks for the show of pics and info. I did the math on the sizing and found that even the small filters I listed can support the power, barely.
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Old 06-02-2008, 04:15 PM   #20
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97.7 x 7000 / 20,839 = 32.8 sq in. required for minimum surface area.

RU-5111, 4.5" x 5.75", slight taper to 3.5" at tip.

4.5 x 3.14 x 5.75 = 81.24 -.75 = 80.49 sq in.

this is not factoring the small taper, but I doubt it will lower 48 sq in of area.
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