1 Oil filter bypass valve specifications Thu May 31, 2012 8:57 am
Dennis
Platinum member
I've used the Ryco Z418 oil filter for quite some time, both on the K100 and now on my K12LT. I finally got around to contacting Ryco with a technical inquiry regarding the oil filter bypas valve. Yesterday I received an answer, details are as follows - BMW OEM oil filter (which is by Knecht or Mahle) is stated in the workshop manual as opening at 1.5 Bar (21 psi). The Ryco Z418 bypass valve opens at 1 Bar (15 psi). What does this mean for us ? Well, 2 things really - when the oil is cold the bypass valve opens to allow the full flow from the oil pump to pass through at the required flow and pressure. Then, as the oil warms up and the pressure drop across the filter paper reduces, the bypass valve closes and we have "full flow" filtering through the paper. The second issue is related to filter contamination, when the BMW filter gets loaded up sufficiently, it will take a higher pressure drop to cause the bypass valve to open than with the Ryco filter. This means that not all the oil is filtered all of the time. Moreso with the Ryco filter (in theory). So it comes down to how dirty the oil gets, which then contaminates the filter paper, so causing the bypass valve to open. Just some tech info for those interested parties to ponder. Cheers, Dennis.