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Discussion Starter #1
Interested in opinions/experiences with dry air filters and which brand people think is the best. Concerned after finding air filter oil all over the bottom of my stock air box. Worried about the MAF so I'm switching. AEM seems the least expensive and the AFE seems the most expensive.
 

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I had an AEM dryflow filter on another project once. the dust where I am at in AZ is super fine. Shows up in PM2.5 EPA testing, generaly considered as fine as diesel exhaust soot. Very fine. That AEM filter had the inside of the ductwork coated in 2k miles as if there were no filter at all.

The coated factory filters I have found do a really good job. They are the same ones used with the 5.6 so I feel they are large enough to feed the little 4.0 we have.
 

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Discussion Starter #3
I get more performance out of my oiled KN filter than stock filter so I expect the same from a dry filter but with easier maintenance. Like that I can use a shop vac with them instead of using a cleaner, let dry THEN put in oil.
 

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I get more performance out of my oiled KN filter than stock filter so I expect the same from a dry filter but with easier maintenance. Like that I can use a shop vac with them instead of using a cleaner, let dry THEN put in oil.
I run an AEM dry filter in the Volant enclosure. I've been happy with it. I shop-vac it twice a year and fully clean it once a year. So far its been very clean. My intake tubes are still clean plastic. Though I think this is mostly a function of the Volant enclosure. If you are running an exposed or semi-exposed CAI I would not run a dry filter. They are more exposed to the elements. The stock box would be fine for a dry filter.

That said, your last sentence (in bold) confused me. You don't need to oil a dry filter. You do need to clean them, which consists of a vacuum, and a washing. I used the K&N cleaner and a hose as low pressure. Then let dry. There are videos online showing how to clean a dry filter. Basically the same as a K&N filter minus the oil step.
 

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But honestly, if you are going to spend the money on a dry filter, in the stock air box, how much of an improvement are you going to see?

I'd look over prices. $10 every 12k miles on a paper filter vs. $XX for a re-usable?
 

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Buy a wix or stock part. Cleaning a dry filter with water will expand the fibers, increase pore size, and reduce the filtering capabilities. They are inexpensive, get a new one when its dirty.
 

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Buy a wix or stock part. Cleaning a dry filter with water will expand the fibers, increase pore size, and reduce the filtering capabilities. They are inexpensive, get a new one when its dirty.
What do you base this on? (Genuinely would like to know, as I run a dry filter.)

Wouldn't the same apply to any air filter, as water is used to clean it as well? You are supposed to use water at low pressure, either out of the sink or a garden hose with no nozzle.
 

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It happens with any paper getting wet. Take a sheet of paper from your printer, look closely, even use a magnifier if you want. The fibers are densely packed. Of course your air filter is not so dense, its engineered to have a specific pore size.
Now wet the sheet of paper in the center, and let it soak in. The paper will curl or warp because the in the center of the sheet, the fibers are absorbing the moisture and its spreading the fibers apart.

I'm sure you've had a book get wet and seen that the pages curl. They don't fit the binding any more.

When dry you've essentially changed engineered the porosity, as the paper won't go back to being perfectly flat.

Other reusable filters are engineered differently, the oiled ones at least (think k&n, etc). They usually have a gauze substrate that has a certain porosity, and they use a sticky oil to trap dirt particles. My 47 Willy's has an oil bath filter, a metal mesh that's bathed in an inch or so of oil 30W to (try) and capture the dust on its way to the carb. (We've come a long way!)
 

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Why don't you just keep the K&N and clean the MAF from time to time? Generally, I clean my MAF every time I clean my K&N.

Also, I don't use the K&N brand cleaner, I use a shallow loaf pan with a small amount of gasoline in the bottom. It dissolves the old oil instantly, washes out the dirt, and it's dry in a few minutes. Then I re-oil and reinstall.


Sent from AutoGuide.com App
 

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. . . My 47 Willy's has an oil bath filter, a metal mesh that's bathed in an inch or so of oil 30W to (try) and capture the dust on its way to the carb. (We've come a long way!)
Actually, an oil bath air cleaner is as or more efficient than most paper filters.

I had the honor when I was a young teenager (many,many decades ago) to get a summer job working for an elderly gentleman up the road who, it turned out, was generally credited with inventing the oil bath air cleaner for agricultural equipment sometime around 1916. He patented his designs, which made him a wealthy man, as did the government contracts to produce oil bath air filters for tanks and armored personnel carriers during WWII and the Korean War.

I still remember his reaction to my attempt in the mid 1960s to ditch the oil bath air cleaner on my VW and replace it with a paper filter. He had me accompany him to the lab at his company's plant where he showed me reams of test results and then had me test the filtration of my stock oil bath filter and the AC/Delco paper filter I wanted to use. The oil bath filter showed superior filtration. I didn't want to believe it, but the test results didn't lie. There was a time that I could explain the physics, but that was 45 years ago. I do remember that the change to paper filters in the late 1960s had more to do with reduction in production costs by the auto manufacturers (paper filter for pennies vs. dollars for an oil bath filter), marketed to the public as ease of maintenance.

All that being said, I'm sure that paper filters have evolved since then, but how much I haven't a clue.

Now back to our regular programming - a discussion of the "best" drop in "dry" air filter for an Xterra.
 

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It happens with any paper getting wet. Take a sheet of paper from your printer, look closely, even use a magnifier if you want. The fibers are densely packed. Of course your air filter is not so dense, its engineered to have a specific pore size.
Now wet the sheet of paper in the center, and let it soak in. The paper will curl or warp because the in the center of the sheet, the fibers are absorbing the moisture and its spreading the fibers apart.

I'm sure you've had a book get wet and seen that the pages curl. They don't fit the binding any more.

When dry you've essentially changed engineered the porosity, as the paper won't go back to being perfectly flat.

Other reusable filters are engineered differently, the oiled ones at least (think k&n, etc). They usually have a gauze substrate that has a certain porosity, and they use a sticky oil to trap dirt particles. My 47 Willy's has an oil bath filter, a metal mesh that's bathed in an inch or so of oil 30W to (try) and capture the dust on its way to the carb. (We've come a long way!)
Hmmm, I get where your thought process is coming from, but DryFilters aren't basic paper based products. Have you seen a dry performance filter in person? The AEM dry filter starts it's life as a K&N: http://www.aemintakes.com/dryflow_air_filters.htm

Really its just a K&N that's less porous. Yes, an oiled filter will likely flow better, as it can be more porous and rely on oil to provide additional protection while allowing more air in.

I had a very high flow oiled filter that came with my Volant (a PowerCore). There is such a thing as too much air. The powercore (in certain environments) would blow codes. Plus its pretty noisy. I went to a dryfilter and its really the same material used in the powercore. Hell, I cleaned my filter and my wife's K&N system from her car. Both are practically the same. The dry filter is quiet(er) and protects well, with no noticeable difference in performance over the higher flowing PowerCore.

Really a CAI (by itself) doesn't do much for performance anyway. In the end it all comes down to preference. Do like the noise and the absolute most airflow? Get an oiled filter. Are you fine with better than stock flow, but not the most - and less maintenance? Get a Dry filter.

And actually - if you have a stock box anyway, keep using regular paper and replace it. It'll provide the most protection, its cheap, and in stock form new square filters ain't gonna make a difference.
 

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Best dry filter? Not sure, but the WIX 46213 is a very good one. I'm a big fan of Wix filters.

The OEM filter has 55 pleats and the WIX has 87 pleats. That is almost 60% great filtration area for the WIX filter. It is made in the USA and the foam gasket material seems very comparable to the OEM filter.

Check out this post from 2007: http://www.thenewx.org/forum/showpost.php?p=30994

OEM on the left, Wix 46213 on the right.


regards,
 

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I ran into an article where a guy on another (to remain nameless) forum ran an air filter test using oiled, dry and standard paper filters. He ran particulate tests, time to clog, total airflow, etc. It was quite comprehensive. What I got out of it all is that a paper filter does the best job and although it flows (generally) slightly less than the other "performance" filters, the added airflow is far in excess of what the engine requires. What was surprising to me was the amount of particulates that got through these "performance" filters. More airflow = bigger holes... Not a good combo for something driven in dirt.

Because of that article, I've decided not to buy into any of these high flow performance filters and stay with paper ones. IIRC, the Purolator filters were the top performing ones he tested. This topic comes up in forums ad naseam. You'll probably find all sorts of opinions on which is "best"...
 
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Discussion Starter #16
Originally asked this question cause of excessive oil filter oil collecting at the bottom of my stock airbox. I also hate the maintenance and time it takes to clean and re oil filter. I know with the AFE synthetic filter I can wash it out and throw it back in even if its wet or use a shope vac to clean it out. Hell of a lot easier up keep that my current oiled KN. Was wondering if anyone noticed any difference as far as performance between oiled vs non oiled filter. Was considering either AMSOIL, AFE or AEM. I noticed a difference (albeit small) in performance goin from paper to KN. Would go full blown aftermarket CAI but dyno results for the manufacturers show gains more at the top end than low end and am more concerned with keeping low end performance than the top end UNLESS it improves throttle response.
 

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Ran OEM in my wife's '08 Altima (hear me out) drives 80mph+ 60 miles a day commuting.
Mileage 29 1/2 Replaced with K&N after 1st year, mileage is steady at 31 mpg. For grins I
checked MAF sensor last week (@90K) clean as a whistle. Now to my Xterra...w/the OEM 19.4
with the K&N 20.6 combined for last 2000 mi. (mix of 45-80 mph) Next 1000 using the AEM
and it's lookin' like 20.4 so performance almost as good as the oiled K&N. Box and MAF
clean as can be. Question: are you guys drowning the K&N in oil after cleaning?? Been
using them since '78 in crotch rockets thru super trucks. Somethin's fishy...just sayin'
 

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Most people use way to much oil on a K&N(or any oiled filter). But the good news is, as far as the MAF, the intake flow will pull the extra oil into the motor. If you have oil in the airbox clean it and the filter, use less oil this time around!
 
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