Bypass Pressure depends on?

[TallPaul]

Does an oil filter bypass valve opening pressure depend on the engine spec, the materials and construction of the filter, or both? Seems there is some variation between companies on the bypass valve pressure for filters of the same application, which suggests to me that the engine spec may be a range and within that range the manufacturer has some leeway to fine tune the pressure to the filter components.

 

[Ken2]

The engine designer determines the specifications for the oil filter. Filter companies have told me that the engine makers do not publish oil filter specs...the filter companies reverse engineer OEM filters. Often compromises are made so an existing filter can be used for multiple engines. Those multiple engines may have slightly different OEM filters and full-line filter companies like WIX or Baldwin/Hastings will have filters just about for each. Short line filter companies will have a much smaller number of filters that fit the same engines, although with compromises. If one of these filters causes an engine failure (very unlikely), the owner's claim would be against the filter maker, not the engine maker.

Look to the OEM filter for the engine designer's spec. Baldwin's web site has the best on-line reference for filter specs that I've found. Their crossreferences to the OEM filter number will be very close to OEM specs.

Why does the engine maker specify particular bypass valve setting, filter flow rate, filter filtration efficiency, filter media size, filter media type, etc.? Very good questions.


Ken

 

[TC]

Between the "stock" replacement Wix, Baldwin, and Hastings filters for my 2002 car (just to name a few brands), the bypass settings range from 8 psi to 22 psi. By chance, except for racing filters this range encompasses the extreme ends of the bypass setting spectrum (aftermarket filter bypass settings typically range anywhere from 8-22 psi).

Needless to say, in light of this I don't pay much attention to bypass settings on aftermarket filters I buy, assuming they're in the typical range. Especially for oversize filters where the frequency of bypass is reduced (less total media resistance and less clogging effect), I suspect the significance of bypass setting is reduced -- the less bypass is likely, the less significant the bypass setting is. The oversize PureOnes I chose have a middle setting (supposedly 12-15 psi), so I saw no need to investigate that further.

Ken2 has some good insight. Personally I believe settings are often manufacturer and filter-specific. In other words, if Wix steers you towards 12 psi for an OEM filter for your ride, go with that for a Wix filter IRREGARDLESS of what setting your original factory filter may have had. If Baldwin suggests 20 psi, then go with that should you choose Baldwin. If you think of a filter as an overall engineered "package," rather than just an assemblage of parts bin components, this approach makes sense -- the Wix engineers may have seen a need for 12 psi for that particular package.