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Originally Posted by ijaz_97  Anyone have experience with these drop-in filters? I was thinking of investing in these for my G35 but they're quite pricey for just simple air filters and was wondering if they're even worth it. What are the Pros and Cons of them and do they REALLY give any real world gains? |
A bit of background before I answer: I worked product development and technical support for an aftermarket performance company for five years. One of my responsibilities was creating air intake systems for own brand, private label customers and OEM customers. As part of the OEM work, I had to get into air filter testing via the SAE, ISO and ASTM standards for air filter testing. I won't bore you with the details, and it was ten years ago so I don't recall the exact results (as in measurement of particles passed through). Basically the tests involve placing the filters in a protected environment, and sucking carefully measured air that has a "certified dust" product added to it. Literally I bought vials of scientific approved dirt for this.
1) The best
filtering and protection for your engine is an OEM style paper filter. It traps the most dirt and dust.
2) Didn't find much, if any difference between OEM brand and aftermarket paper style filters.
3) Cotton Gauze filters such as K&N and others allow more dirt through, but also flow better.
4) An oiled cotton gauze filter can be made to meet OEM filtering requirements.
5) NEVER use an un-oiled cotton filter. You'd be surprised at how many unoiled filters are sold in the aftermarket.
6) You need to clean oiled-cotton filters more often than usually recommended.
6b) Everytime you clean and re-oil a cotton filter, the filtering capabilities go down slightly...but the flow goes up!
I remember the flow rate between the paper and oiled cotton filter not being worth it for a stock engine (in my opinion). The crazy horsepower numbers you see on filters and air intakes are due to a couple of vehicles being extremely restricted. The "air intake" numbers, for instance, are all based on a Chevy S-10 which has a ridiculously restrictive air intake system. Everyone who makes "up to 15hp" (or whatever the number is) has had that S10 system in their product line so they aren't lying.
Basically my personal conclusion was that if you're using the stock air intake system on the car you would be wise to keep a stock paper filter in there. You're not going to gain anything noticeable by going with a replacement panel filter. Whenever the intake system is swapped out for a non-OEM design, thats when the increased dirt intake becomes a negligible factor and an oiled-cotton filter makes sense. The company I worked for never made drop-in panel filters, for any application. We stuck to making cone filters for intake
systems.
On my cars I use K&N filters on the Rally Bug. You can actually see a noticeable difference in the filtering between the K&N and no-name brand filters available to fit my webber 44's. If Green filters were available to fit the Webers I would us them over the K&N. For vehicles where I use a cone filter, I buy a Vibrant Performance Classic filter as they filter just as well as the K&N, are cheaper, and stocked by Lordco.
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