In the November issue of JP magazine (jeep mag) they did a controlled study on aftermarket air filters. The International Organization for standardization set up a uniform testing procedure,conditions,and equipment so that test results could be reproduced.What they found is pretty interesting. All testing was done with a 9"x6" cone filter which is similiar to the one run on our h3's. Here are the companies tested

AEM - Dry flow filtermade of a single layer of pre-pleated polyester synthetic filter media with a nylon reinforced internal cage for support.

AIRRAID - made of multiple layers of cotton synthetic gauze nylon reinforced internal cage for support

AMSOIL - made of wire mesh construction with synthetic nanofibers overlaying cellulose fibers. Claims to highest efficiency and dust capacity rating on the market (not!)

K&N - made of four to six layers of cotton fiber sandwiched betwen mesh, oiled

S&B - made of six to eight layers of oil impregnated cotton gauze construction.


Two main tests were done, dust capacity which basically tests how many grams of dust particles the filter can hold until theengines performance is negatively affected.
Heres how they stacked up from best to worst:

K&N 167 Grams of dirt
AIRRAID 126 grams of dirt
S&B96.8 grams of dirt
AEM 73.6 Grams of dirt
AMSOIL39 Grams of dirt..............In anther study I read online a cotton sock scored 46 grams of dirt!!!!


Second test was a efficiency test, basically the numbers given for each filter was a percentage out of a hundred that the filter actually traps in dirt grams. so if a filter got a score of 90% then 10% of the dirt grams got through the filter into your engine, seven grams of dirt equals one four ounce wheel weight worth of dirt passing into your engine. scores again are from best to worst.

AEM 99.41%
AIRRADE 98.43%
AMSOIL 98.29%
S&B 98.05%
K&N 96.13%

So if your looking for the best filter all around AIRRADE would be your choice, K&N Can handle a ton of dirt on the filter and still allow the motor to breath but also allowes more particles through to the motor than any other filter tested.

Thought this might help tp clear up the confusion over which air filter is best.

 

OMG.........Hummerguy is gonna have a ball with this info.

 

That is interesting..But K&N is still nothing to sneeze at..Because like all filters..the dirtier they get the better they trap dirt and less gets through...So it's important to take these sort of tests with a grain of salt..because they can be skewed and only a snap shot over the long haul of use...Now if a graph could be put together over a 10,000 mile period and look at each of these tests above at say a 1 month interval and plot each filter against each other you'd see significant differences between them at different stages of their life of the 10,000 mile time frame...In other words, what may seem bad numbers at first, become excellent numbers later in the tests or visa versa.

 

I am using a "pre-filter" over my K&N on my WRX. I had some leftover from my dirtbike, and figured, why not?!! It seems to trap the real fine dust particles before they get to the K&N, so I figure that they can't be bad.I don't know if they make them big enough to cover a cone filter longer than about 6" though.

 

the foam pre-filters are made by K&N and others, in another study they found that the K&N with the pre-filter filtered down to 5 microns and was water resistant.

 

actually Dennis, thats not really true. On the dust capacity test the filters were ran until they didn't flow enough air to keep the motor running. Doesn't matter if it took an hour under these controlled test conditions or 10,000 miles on a car on the road, the numbers given are the accurate numbers as far as how much dust and dirt the filters could hold before the motor was starved for air. And teh oiled filtered did prove to hold teh most with K&N leading the pack.

As far as the efficiency test, yes I could see where a slightly dirty oiled filter would improve on the numbers listed because as you said they do filter better once they get a little dirt on them. Unfortunetly they didn't give any indication as to how long the filters were run under the dusty dirty conditions when they took the flow rate numbers.

I was totally shocked by the Amsoil filter though, only to hold 39grams of dirt particles is terrible!! Like I said a plain cotton sock was scored in the 40's in another test I read about.

The efficiency numbers aren't the real big thing for me, they are all close enough that none of them really stand out compared to the others, anything over 96% is considered safe by the "experts" but the dust/dirt capacity test is what is shocking to me, and is why K&N is such a good filter. You also have to remember that under normal driving conditions alot of dirt and dust will be knocked off of the filter, so for a K&N to get up to the 167 to actually stall the motor will take a very very long time. That explains why the K&N on my Grand Cherokee has been on for 7 years now without ever bieng cleaned or re-oiled and I have never had a problem with it. I will stick to K&N

 

That has to be total BS! From the independent testing the Amsoil Nano fiber filters are a copy of the same air filters that the M1 Abrams uses in conditions in Iraq. A plain sock......LMAO

 

I don't know I didn't run the test myself, all I can go by is what the study showed and I copied it word for word. And all testing was done at an independant ISO certified test facility.

 

I just put on a pair of pantyhose on my K&N..wonder if that will help?...I know they kept meout of a lot of tight spots in my day..[sm=smiley2.gif]

 

ummm...what kinda tight spots are you talking about Dennis? That can be taken a few different ways.