Air Filter Comparison
 Courtesy of: Mance Etheredge

 

I managed to pick up 4 air filters today. Below are the names and physical specifications of each. All of the elements use pleats that are EXACTLY 7.875" wide.

All pleat heights (depth) are measured in 5 places randomly and numbers averaged. This average is then used when figuring total length and surface area. Each "pleat" is multiplied by 2 as it takes two identical depths of paper element to equal 1 pleat.

FRAM LX422
Pleat Width: 7.875"
Pleat Depth: 1.775"
Pleat Count: 67
Total Length of Filter Media: 19.826ft
Toal Filter Surface Area:: 11.67sq ft

Purolator A47039
Pleat Width: 7.875"
Pleat Depth: 1.775"
Pleat Count: 68
Total Length of Filter Media: 20.12ft
Total Filter Surface Area: 13.20sq ft

MANN C26168
Pleat Width: 7.875"
Pleat Depth: 1.790"
Pleat Count: 98
Total Length of Filter Media: 29.24ft
Total Filter Surface Area: 19.17sq ft*

MAHLE LX422
Pleat Width: 7.875"
Pleat Height: 1.73"
Pleat Count: 88
Total Length of Filter Media: 25.37ft
Total Filter Surface Area: 16.65sq ft

K&N
Pleat Width: 7.375"
Pleat Height: .700"
Pleat Count: 27
Total Length of Filter Media: 3.15ft
Total Filter Surface Area: 1.94sq ft

AUDI 058 133 843
Pleat Width: 7.875"
Pleat Height: 1.800"
Pleat Count: 89
Total Length of Filter Media: 26.70ft
Surface Area: 17.32sq ft

I'm going to try and get a Bosch filter tomorrow but may give up on it as they're rare in my neck of the woods. I'll also pick up my Audi filter tomorrow from Will-Call. I was running late today and didn't want to be caught in rush hour.

I'm going to try and get a Bosch filter tomorrow but may give up on it as they're rare in my neck of the woods. I'll also pick up my Audi filter tomorrow from Will-Call. I was running late today and didn't want to be caught in rush hour.

* Indicates clear winner so far in surface area.

Ok K&N/oiled gauze filter owners, here's where it gets ugly...
 


First pic is my K&N. 621 miles total. In a minute your're going to see why it's really really bad filtration.

I took this pic so you can see what I placed the camera up against to shoot the 3rd pic in this series.

Pic 2: My kitchen light...
 

Hey don't shoot me I didn't pick it. Just got lucky with the home purchase I guess.

Anyway it's important to note this pic and the following one were done with flash turned off and all mechanical settings used on the camera with no changes made whatsoever... NONE!!

I stood in the same spot in this one as the next one. Only thing that changed is I picked the K&N off the counter beside me to hold over the camera lense for the next shot.

These last two pics were not altered in any way. Nor were they cropped or anyadjustments made for brightness or contrast. They were uploade directly from the camera without benefit of any editing tools.

Pic 3: My kitchen light thru the K&N...
 


Ok, here it is. The same light 10 seconds later thru the K&N filter elements dirtiest spot. The "sweet spot" on the back of the filter where the airbox inlet is aimed.

If you can see the kitchen light, lense and mounting plate I guaranf'ingtee you dirt is getting in.

I also shot the MANN and MAHLE paper elements as well but just got black rectangles with no image whatsoever.

Now just wait till you see the cup of dirt fall thru this thing. It leaks dirt thru the filtration media like a sieve!!

Audi air filter is now listed in "Air Filter Comparison"...

and the plot thickens...

Weird! Box says "Audi/made in Slovenia." Mahle says made in Germany while MANN says made in Austria. Sealing material is same color, consistency as the MAHLE filter but thicker, tighter fit as the MANN. Paper element is identical appearing to MANN but closer pleat-count to MAHLE at 89. Adhesive strip is top & bottom in the same amounts, ie; 1-top/4-bottom as MANN.

Biggest surprise is the pleat count is 9 less than the MANN and only 1 more than the MAHLE. Be interesting to see the differences in flow rates as the Audi paper element is easier to blow thru with breath pressure than all except K&N yet is identical color/thickness as MANN.

Also makes me wonder if even with the greater surface area of the MANN that the fewer pleats and easier "blow-thru" might favor the Audi. Maybe 98 pleats is too densely packed?

Are MANN/MAHLE in cahoots? Maybe a MANLE filter? "MANLE yes, but I like it too" in my best Irish brogue.

Keeps gettin interestinger and interestinger ;-)
Air filter flow testing...

This turned out to be easier than I thought. All of the air filters except the K&N were self-sealing under vacuum. I just sat them upside down, centered over the flow bench inlet and the vacuum would pull them flat and seal them against the bench top. The K&N required a small bead of silicone around it's rubber sealing edge and a big dictionary (true!) placed on it til the silicone cured to seal it as it's rubber is less compliant/resiliant than the type used on the others.

Testing started at 280CFM and was slowly cranked up until first depression was noted. Then the process was repeated 3 times for each filter and their numbers averaged.

While the K&N is "very slightly" used it has been cleaned per manufacturer's instructions with their cleaning/recharging kit. Then excess oil wicked out with paper towels pressed tightly into pleats on both sides overnight.

In order of best-to-worst:

K&N: 732CFM (521 miles)
AUDI: 728CFM (0 miles)
MANN:678CFM (0 miles)
MAHLE: 662CFM (0 miles)
FRAM: 622CFM (0 miles)
PUROLATOR: 618CFM (0 miles)

Bear in mind these numbers are pure "flow"... nothing more, nothing less. They don't address or speak to any pressure differentials once mounted in the airbox tho they are a very accurate representation of what I'll find once I get to that aspect of testing which could take weeks to conclude as it's done with repetitive 2nd gear-to-100 mph road-tests. And I have to drive 22 miles out in the country-side to do them comfortably.