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boosted79 boosted79 is offline
Join Date: Jan 2015
Posts: 1,430
See the attached. If the filter ( paper or oiled gauze or foam) can flow the SCFM required by the engine at max rpm then a less restrictive filter (meaning more dirt gets thru it into the engine) is not going to make ANY measurable difference. In this test the K&N had an initial pressure drop of 4.54" H2O vs. 6.23 " H2O for the AC Delco. Both of those points are at 350 SCFM. 4.54 " WC = 0.164 psi, 6.23" WC = .225 psi. So in a turbo engine running at sea level ( filter sees 14.7 psia) at 1 bar boost (29.4 psia) the K&N will give a PR across the compressor of 2.02 ((14.7 + 14.7 / 14.7 - .164). The AC Delco will give a PR of 2.03 ((14.7 + 14.7 / 14.7 - .225). To see exactly how much difference that makes in airflow depends on the PR vs. flow curve for the compressor but I can guarantee you will not see the difference on a dyno.

I question the flow capability of those small round filters sitting right on top of the flow meter, whether they are paper or oiled gauze.. Look at the surface area of those vs. the stock 930 flat filter.

K&N Air Filter Review - Debunking the Myths (and why OEM is better)
Old 01-16-2017, 09:34 AM
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