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Performance "Drop-In" Air Filter Technical Information & Comparison Thread

10K views 5 replies 4 participants last post by  Bryan@Jlevi SW 
#1 · (Edited)
Gentlemen,

I’ve started this thread in an effort to compile information in regards to the various performance “drop-in” filters that are available on the market today for the S85 engine, in addition to providing some information in regards to air filters in general.

Let’s make an effort to keep this a purely technical thread.

In regards to “Unknown” or missing data, I welcome fellow board members to chime in and help out where they can (ideally by providing measurements of the filter pleats in order to calculate surface area )- [in general] more filter element surface area = more airflow.

K&N


Filter Element Type : Oiled Cotton Gauze
Filter Type: Flat Panel
Approximate Surface Area: Unknown
Filtration Efficiency (Average): Between 96-99%*
Air Flow Gains Over Stock (CFM): Unknown
Warranty : Signature 1 Million Mile / Limited Lifetime
Price: $80-$90/set
*Note - Claim as per K&N website on Filtration Efficiency
K&N Air Filter Efficiency Testing

BMC

Filter Element Type: Oiled Cotton Gauze
Filter Type: Flat Panel
Approximate Surface Area: Unknown*
Filtration Efficiency (Average): Unknown
Air Flow Gains Over Stock (CFM): Unknown
Warranty: Unknown
Price: $160-$165 for the set
*Note- Judging purely from the appearance of this filter, it appears the surface area would most definitely be greater than that of the K&N filter.

AFE Pro-5R


Filter Element Type: Oiled Multi-Layer Cotton Gauze
Filter Type: Inverted
Approximate Surface Area: 224 In. Squared
Filtration Efficiency (Average): 98.6%
Air Flow Gains Over Stock (CFM): 110 CFM (25%)
AFE Bench Air Flow Test on S85 Pro-5R Performance Filter

Warranty: Limited Lifetime
Price - $150-$160 for the set

AFE Pro-Dry S


Filter Element Type: Dual Layer Synthetic Media Gauze
Filter Type: Inverted
Approximate Surface Area: 224 In. Squared
Filtration Efficiency (Average) 99.2%
Air Flow Gains Over Stock (CFM) : 99 CFM (22.5%)*
Warranty: Limited Lifetime
Price - $150-$160 for the set
*Note - Values calculated by aFe claims that (AVG) 10% more flow is realized on the P5R (Oiled) filter element versus the PDS (Dry) filter element.


Basic Comparison of common filter medias (paper, foam and gauze).


Paper (OEM)


Tightly compressed cellulose fibers bonded together provide very small pores. Dust is captured on the surface as air flows through these pores. Restriction increases as dust accumulates on the surface. Very good filtration but relatively poor airflow. Very limited service life, not reusuable.

Foam (ie: ITG)


Synthetic foam provides larger pores than paper and compensates with thicker materials. Often utilizes a tackifier to capture dust. Restriction increases as dust accumulates on the surface. Good airflow until dirt builds up on the surface. Limited service life due to no depth loading. Washable but difficult to clean.

Oiled Cotton Gauze (K&N, AFE P5R, BMC)
Cotton gauze media provides large pores with microfibers extending into these pores. Multiple layers of gauze increases filtration as they overlap. Oil is generally used as a tackifier, lubricating the microfibers and as a result - captures dust particles as they come in contact. Retains excellent airflow thruout the service cycle with improving filtration efficiency as more dust accumulates. Washable, easy to clean and reoil/service.

Dry Synthetic Gauze (AEM Dryflow, AFE Pro-Dry S)
Utilizes oil free media with several layers of different porosity synthetic materials. Requires no oiling and dries quicker because it retains little moisture. Retains excellent filtration efficiency thruout the service cycle. Airflow generally remains excellent until huge amounts of dust accumulates towards the end of service cycle. Washable, easy to clean and requires no re-oiling or re-charge kits (only soap & water).

Advantages of Inverted Filter Type vs. Flat Panel
Inverted filters (AFE) are designed to fit into the same stock airbox that the standard flat panel filter goes into, but utilizes an inverted "cone type" design which allows for more filter media surface area to be fitted into the OEM airbox when compared to flat panel type filters. This, in short, translates to increased air flow in comparison to flat panel type filters.


That's all I got for now. :D

Comments, concerns, questions, etc. are welcome and appreciated. :M5thumbs:
 
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#2 · (Edited)
How to measure a filter for surface area.

1. Pleat Depth


*Note - About .1" of "dead space" on this particular ruler

AFE Filter: Approximately 0.5"

2. Height

Measure height of the pleats.
AFE Filter : Approximately 3.5"

3. Number of pleats

AFE Filter: 64 pleats

To calculate surface area:
Multiply pleat depth measurement by 2 (each pleat has two sides).
0.5 X 2 = 1
Multiply above number by number of pleats & height
1 X 64 X 3.5 = 224 Inches Squared



I encourage board members to chime in with these measurements on their own preferred brand of performance filter :byebye:
 
#3 · (Edited)
To calculate surface area:
Multiply pleat depth measurement by 2 (each pleat has two sides).
0.5 X 2 = 1
Multiply above number by number of pleats & height
1 X 64 X 3.5 = 224 Inches Squared
Truthfully the surface area is more, because:

  1. The pleats are slanted... we measured the depth but not the true length. Think of a triangle, pythagorian theorum. The hypotenuse is longer than the longest side (it's a right triangle). This may be negligible but could count for as much as 20 square inches.
  2. there is a rounded top of about .1" on each pleat... that's .1"x3.5" tall x 64 pleats = 22.4 square inches

So, conceivably, it could be a lot more surface area, nearly 275 square inches. The only way to truly find out will be to have the factory workers at aFe tell us exactly how much cotton is laid out into each filter. If anyone is interested in knowing EXACT surface area, I am sure we could contact aFe and inquire.

Otherwise, it's always best to under-rate and say 224 inches, squared. That's why BMW lets you think your E46M3 is 333 horsepower when it's generally more like 350 :byebye:

Fun fact about surface area, for those of you who don't believe how something so small can have SO much surface area:
Did you know that a piece of carbon graphite the size of a pin-head has so much complexity to the surface that it has more surface area than 5 foot by 5 foot floor? That's why carbon is used for odor trapping, etc.
 
#5 · (Edited)
I have tried these filters and they do not make any difference in power. The air flow charts used by AFE does not tell us anything about how the filters will actually perform when installed because the filters are tested on a flow bench. To properly test performance of a filter translated into hp, you will have to test the flow rate and flow characteristics of the filter based on the engine CFM and flow characteristics of the intake system. Putting a filter on a flow bend and showing a flow chart doesnt tell consumers anything and is yet another attempt at selling a product based on marketing hype. Its really sad..........
 
#6 · (Edited)
I agree for the most part Eloy. The gains from any drop in filter alone will be minimal. And yes I do agree that a flow bench test is not a realistic indicator of improved performance in the real world on the actual vehicle.

However, I feel that flow bench numbers are better than NO data at all. At least with a flow bench, you get some indication of what to expect from an aftermarket "performance" filter.

As for the "marketing" reference...K&N would take the cake on this one. If you take a single look at their website, it's filled with tons of data, tests, scientific procedures, etc. from everything to filtration efficiency to air flow...and it's very detailed and very well put together. But they have yet to publish actual data on this specific filter for the S85 application.

Now the real question is, what type of filter would work better with Intake Air Scoops...flat panel or inverted?

In any event, I've contacted K&N directly in the hopes of attaining the missing data...but I may have access to a K&N filter soon, at least that way we can calculate the surface area. :cheers:
 
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