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

[SV Concepts II]

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 S65 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.

Please note that on a flow bench test, the stock paper filter produces approximately 310 CFM. (Source: aFe)


Active Autowerke "Green Filter"


Filter Element Type : Oiled Dual Layer Woven Cotton
Approximate Surface Area: Unknown
Filtration Efficiency (Average): Unknown
Air Flow Bench Test (Cubic Feet/Min): Unknown
Warranty : Unknown
Price: $70-80

K&N


Filter Element Type : Oiled Cotton Gauze
Approximate Surface Area: Unknown
Filtration Efficiency (Average): 98.69%*
Air Flow Bench Test (Cubic Feet/Min): 343 CFM
Warranty : Signature 1 Million Mile / Limited Lifetime
Price: $55-$65
*Source : K&N


BMC

Filter Element Type: Oiled Cotton Gauze
Approximate Surface Area: Unknown
Filtration Efficiency (Average): Unknown
Air Flow Bench Test (Cubic Feet/Min): Unknown
Warranty: Unknown
Price: $98-$110

Macht Schnell


Filter Element Type: Oiled 8-Layer Cotton Gauze*
Approximate Surface Area: Unknown
Filtration Efficiency (Average): ~99%*
Air Flow Bench Test (Cubic Feet/Min): Unknown
Warranty: Unknown
Price: $99-$110
*Source: eas


AFE Pro-5R


Note- Filter shown above is for 2008-2009 NA Spec models.

Filter Element Type: Oiled Progressive 5-Layer Cotton Gauze
Approximate Surface Area: 598.5 In. Squared
Filtration Efficiency (Average): 98.6%
Air Flow Bench Test (Cubic Feet/Min): 480 CFM
Warranty: Limited Lifetime
Price - $90-100

*Fig. 1 - Flow Bench Test of aFe P5R S65 Drop-In Filter vs. OEM Paper


AFE Pro-Dry S


Note- Filter shown above is for 2010+ NA Spec & EURO models

Filter Element Type: Multi-Layer Synthetic Media Gauze
Approximate Surface Area: 598.5 In. Squared
Filtration Efficiency (Average) 99.2%
Air Flow Bench Test (Cubic Feet/Min): 432 CFM*
Warranty: Limited Lifetime
Price - $90-100
*Note - Values calculated by aFe claims that 10% (on average) 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, M&S)
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).

Multi Layering of Filter Elements - Basic Technical Explanation
Most aftermarket performance drop in filters utilize several layers of mesh gauze, stacked on top of each other in order to maximize filtration efficiency while retaining optimal air flow. The depth loading of dust onto multiple layers provides for high dust holding capacity and cumulative filtration efficiency while also providing for longer service intervals.


Example of multiple layers of constant mesh gauze with 4 layers of same thread count in a "stacked" fashion.



Example of "progressively" layered mesh gauze. 5 layers of progressively higher thread count gauze. Higher thread count equates to smaller and smaller openings upon each added layer.


A good explanation in layman's terms is outlined below.

Imagine airflow as a stream of water, and that dust particles as different sized fish. Think of the progressively laid gauze layers as nets with smaller and smaller grid sizes.



The largest of the fish will be caught in in the first net, allowing smaller fish to go through. This process repeats itself until the fish goes through all the net "layers". The smallest of the fish will be caught in the last net but the water is allowed to flow freely thruout the layers as the biggest of the fish were already caught in the beginning few layers.

However, when all the nets are the same grid size (ie: not progressively layered), the small fish are only caught when enough large fish are caught in the nets to trap the small fish, this also hinders the flow of water (ie: air).

To put it simply, progressively layered filter elements leave less "dead space" in the filter media, which would drop overall filtration efficiency.



I will periodically maintain this thread with updates as they come in as new information is gathered on the specifics.

Comments, concerns, questions, etc. are welcome and appreciated.

[SV Concepts II]

reserved

[BimmerRob08]

Good thread, just learned a few things. Glad I went M&S, I like the filter and cleans easily IMO.

cheers,

[punksterz626]

Is there any increase in sound with these filters?

[shendrick]

What about oiling? Seems like it would be easy to apply too little or too much. Advice?

[SV Concepts II]

Originally Posted by punksterz626

Is there any increase in sound with these filters?

Yes, a bit more throaty engine tone coming from on the engine bay is to be expected at WOT. Difference isn't that major but it should be noticeable.

Originally Posted by shendrick

What about oiling? Seems like it would be easy to apply too little or too much. Advice?

Proper re-oiling of filters is key to make sure you don't run the risk of fouling the mass air flow sensors. I'll draft up a detailed post soon on the proper servicing of oiled filter elements soon, and touch base on the issue of MAF fouling due to overoiling.

[tom @ eas]

Originally Posted by Cal@Jlevi SW

Yes, a bit more throaty engine tone coming from on the engine bay is to be expected at WOT. Difference isn't that major but it should be noticeable.




Proper re-oiling of filters is key to make sure you don't run the risk of fouling the mass air flow sensors. I'll draft up a detailed post soon on the proper servicing of oiled filter elements soon, and touch base on the issue of MAF fouling due to overoiling.

The S65 does not have a MAF.

Oil should be used as only to change colors on the gauze, evenly coating without dripping.

[SV Concepts II]

Originally Posted by tom @ eas

The S65 does not have a MAF.

Oil should be used as only to change colors on the gauze, evenly coating without dripping.

Thanks for the clarification Tom.

Yes, the S65 engine utilizes a Manifold Absolute Pressure (MAP) sensor instead, so it is a non-issue for E9X M3 owners.

Nonetheless, If anyone were to be interested in getting performance oiled filters for their other BMWs, they should be aware of the ill effects of an improperly re-oiled filter element on the MAFs, (ie: shendrick's E46 330i ZHP).

[N8dawg]

sticky that shit!

[BruinE90]

does bmw service replace the air filter often as part of maintenance? service I or II?

do you guys tell the service advisor not to touch the air filter then?

[shendrick]

When I went to BMW for my 15K oil change they didn't want to change the air filter - either because they didn't know to do it or were following their own SOP. After I pointed out to them that the owner's manual says to change the air filter when you change the oil - they agreed.

[alefcole]

Which is better Macht Schnell or AFE Pro-5R?. If basically the same, is there a reason why choose one vs the other?? Help please

[SV Concepts II]

Originally Posted by alefcole

Which is better Macht Schnell or AFE Pro-5R?. If basically the same, is there a reason why choose one vs the other?? Help please

All the info you need is compiled in the OP.

It's up to you to decide which filter is right for you.

[Dave07997S]

Originally Posted by Cal@Jlevi SW

All the info you need is compiled in the OP.

It's up to you to decide which filter is right for you.

I think that means the AFE....

Do you think there would be an improvement over a 2010+ OEM filter due to the fact the carbon insert is already removed with the 2010+ filters?

Dave

[SV Concepts II]

Originally Posted by Dave07997S

I think that means the AFE....

Do you think there would be an improvement over a 2010+ OEM filter due to the fact the carbon insert is already removed with the 2010+ filters?

Dave

Given the stock paper filter element is quite restrictive, I'm positive there will be an improvement even though this insert is no longer present on the 2010+ models. Granted, the difference won't be as pronounced on the pre-2010 models due to the lack of the charcoal filter.

In any event, one could justify the cost of a new aftermarket drop in performance filter solely on the fact that you'll never have to replace it again.

[tom @ eas]

Originally Posted by alefcole

Which is better Macht Schnell or AFE Pro-5R?. If basically the same, is there a reason why choose one vs the other?? Help please

Layer count for some reason isn't discussed in this thread, in which the Macht Schnell units have a 8 layer count, while the aFe and K&N units has only 5 layers for filter media.

We were one of the first to receive the S65 filters when released by aFe and immediately noticed a very soft polyurethane is used on the lid of the filter, which can cause distortion when the centering pin places pressure on the filter. This cause be contributed to the "fluttering" sound some have reported on the forums.

Filters like the Macht Schnell & BMC (and presumingly K&N) units use a more rigid construction to prevent seal distortion. BMW OEM for instance, uses a plastic lid - evidenced by the CNC tooling marks on the lid itself.

[SV Concepts II]

Originally Posted by tom @ eas

Layer count for some reason isn't discussed in this thread, in which the Macht Schnell units have a 8 layer count, while the aFe and K&N units has only 5 layers for filter media.

Good suggestion in regards to the layer count. OP updated with new info.

[Malek@MRF]

Originally Posted by Cal@Jlevi SW

Yes, a bit more throaty engine tone coming from on the engine bay is to be expected at WOT. Difference isn't that major but it should be noticeable.




Proper re-oiling of filters is key to make sure you don't run the risk of fouling the mass air flow sensors. I'll draft up a detailed post soon on the proper servicing of oiled filter elements soon, and touch base on the issue of MAF fouling due to overoiling.

We don't have Mass Air Flow senors, we have MAP.

[SV Concepts II]

Originally Posted by Malekreza11

We don't have Mass Air Flow senors, we have MAP.

See Post #9. Thanks for the reiteration though.

[dhoggm3]

With the MS filter you will hear a staccato engine note coming from the hood snorkel at 75%+ throttle - not a low rumble. It's a nice complement to the exhaust - kinda like enabling the rear speakers on a surround sound system. Not overwhelming or annoying at all. No difference at civilian commuting throttle openings.

[mdosu]

do you need a tune after a drop-in to realize the performance gain?

[SV Concepts II]

Originally Posted by mdosu

do you need a tune after a drop-in to realize the performance gain?

The increased air flow from a drop in filter alone does not require a tune, performance gains from ANY drop in filter alone will be minimal. Primary benefits of a drop in filter include slight performance increase, improved throttle response, throatier engine noise and the fact you'll never have to replace the filters again.

However, if one were to upgrade the stock system with (for example) AFE's STG II Performance Intake system , coupled with AFE intake scoops...a tune will most definitely help maximize the realized gains.