[Alext]

Just wondering if anyone has any feedback on this drop-in?

[jzchen]

I actually like the dry filters for forced induction engines. (I actually look for it for any of my cars.) I worry about the little cotton fibers being sucked in... There is a little less performance gain as I understand, but better filtration.

[SV Concepts III]

aFe offers both options, a Pro5R oiled and Pro Dry S. The main difference is the Pro5R oiled version offers better flow but does require that you reoil it with the included recharge kit.

The dry version does not require reoiling and offers better filtration but not as much flow.

AFE Pro Dry S

• Off-White Air Filter
• Average of 50% air flow over stock filter element
• 99.2% filtration

AFE Pro 5 R (oiled)

• Blue Air Filter
• Average of 75% air flow over stock filter element
• 98.6% filtration

And here is a break down on the various materials available on drop ins across the market.

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.