Aftermarket Oil filter for HD Twin cam

[ZeeOSix]

I've calculated the pressure drop across the centre tube of a louvered PurolatorOne filter using an online pressure drop calculator. It worked out to be on the order of 1% of the total filter dP. The inlet holes on the filter base were a bit more restrictive at 2% of total dP. So almost all of the restriction is from the media, and the centre tube is hardly going to restrict flow unless maybe it's defective and most of the louvers are closed, which can happen.

I played around with the dP on-line calculator (using the thin perforated plate configuration) and wanted to see how the dP across the center tube changed as the flow area became choked down - ie, as in badly formed "choked down" louvers. What happens is if they are choked down pretty good (like 20% or below their normal fully opened area, the dP increases pretty dramatically - see the Series 1 curve.

So for example, the nearly closed louvers shown in the post #20 above could cause the dP across the filter to increase quite a bit (ie, dP goes from near zero at 8 GPM to ~10 PSI at 8 GPM. That's 10 PSI closer to the bypass valve setting compared to what well formed louvers would be. The bottom line is people should inspect the louvers, and don't install an oil filter that looks to have barely opened up louvers.