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Bigger Air Filter = Better?

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49 minutes ago, grannyknot said:

@AlbatrossCafe, is that the Amsoil EaAU air filter we were talking about?  Very interested to hear what you have to say about it.


Sure is. Got it here: https://www.amsoil.com/shop/by-product/filters-and-by-pass-systems/air/amsoil-ea-universal-air-induction-filters/


Though TBH it won't be much of a review... I bought my Z last fall, put about 60 miles on it driving it home, took off all the suspension, and it has been on jackstands ever since waiting for coilover parts to arrive and welding to be done. So I don't really have a benchmark to judge it against haha

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  • 2 months later...

As a rule of thumb the filter flow, in cfm at standard pressure drop, should be ~1.5x the hp it is supporting.  This means for 500hp you want a filter to flow 750cfm.  That doesn't mean you can't make the same hp with a smaller filter, but you will have a higher pressure drop.  Whether turbo or NA, pumps don't like restrictions on the suction side.  K&N doesn't list flow numbers on their site, but if you call they will provide.

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  • 8 months later...

Dealing with centrifugal air compressors daily, the general rule of thumb is you can not got too big. What everybody is missing here is HOW the gauze filters work!
The bigger the filter, the slower the air passes through the media, the slower the air passes through the media, the more efficient it becomed in recovering and filtering out micronic and sub-micronic particulates... As most will know or argue the K&N Mesh filters do NOT clean the air as well as a pleated paper OEM unit does, BUT if the filter sizing is increased appropriately then they WILL start recovering to an OEM absolute standard.

Sure, pumping losses are part of it... but in the end, the bigger the filter the better the filtration recovery you will get. This goes for whatever media you choose. We used to run Oldsmobile 455 filter housings, with elements double-stacked up on the roof of "Mud Buggies" that we ran throug the northwoods of michigan. We NEVER had ring and cylinder problems like the guys using cone filters on top of their carbs, or even guys with cone filters remotely mounted up high like ours. Those Olds filters were well constructed AC-Delco Parts, and could be loaded filled with mud and sticks and STILL breath fine with our little 1600cc beetle engines.

That taught me long ago, fit the biggest filter you can into wherever you can, because you never know what's going to get sucked up inside there!


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  • 1 month later...

Rule of thumb I use is multiple engine hp you want to support and multiply by 1.5 to get CFM needed.  If you call K&N they will give you the CFM rating of a filter at standard pressure drop (can't remember what that drop is).  So, if you want to support 500hp@engine then get a filter that flows 750cfm at standard pressure drop.  I like running larger inlet filters and use a velocity stack.  You can run a filter smaller than what I recommended, but this will only increase the pressure drop across the filter.

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