K&N Air Filter
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I took a look at the way the filter fits into the box. the foam layer seems to be more for noise cancelation than filtration. air can easily be drawn into the sides of the pleats thus circumventing any added filtration properties of the foam layer.chan said:
the foam layer may add to filter life. the theory is that the foam layer will trap larger particles, preventing them from getting stuck in the paper filter and plugging it.
anyway, the foam layer version is the one for E46. if the number of pleats is the same then the one without the foam layer will have more surface area (less restrictive). this is because the over all heighth of both filters is the same and the foam layer takes up about 10mm of that. see the picture below from shawn fogg's web site to see what I mean.
here's shawn fogg's article on the subject relavent to a 2.3 Z3:
http://ackthud.com/shawnfogg/2_3lairbox.htm
Brought the non-foam version to try on my E46 over the weekend.
The paper is not as dense and smooth compared to the ‘with-foam’ version.
Dealer was telling me that the foam is carbon coated thus engine breaths better, prolong service interval and it’s meant for topical specs. HA!
Anyway, the car does response swifter. Didn’t hear any hissing or increase engine noise. Maybe the filter is still fresh.
Puzzling though, the E46 318 (1998-2001) has the same engine as the Z3 1.9l but yet they don’t use the same filter.
The paper is not as dense and smooth compared to the ‘with-foam’ version.
Dealer was telling me that the foam is carbon coated thus engine breaths better, prolong service interval and it’s meant for topical specs. HA!
Anyway, the car does response swifter. Didn’t hear any hissing or increase engine noise. Maybe the filter is still fresh.
Puzzling though, the E46 318 (1998-2001) has the same engine as the Z3 1.9l but yet they don’t use the same filter.
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