Oil filter bypass settings?

[AuthorEditor]

Big Dave O did a nice chart a while back summarizing FL-1A equivalents: https://bobistheoilguy.com/forums/posts/345366/

By any chance did anyone ever do one like that including bypass valve settings? In my limited research it seems that there is a variation between manufacturers for filters listed for the same application. For example, the Wix 51515 lists 8-11 psi, the PureOne is 8-16 psi, a Fleetguard LF3313 lists at 10 psi, and the Donaldson P550008 is 7-10 psi.

My suspicion is that these small distinctions don't really mean anything and the valves are probably not all that accurate anyway. Why the ranges on some filters? Thoughts?

 

[bepperb]

I'm sure there's a pretty big "range" on all of them, regardless of whether they print it as such or not. Even when they have a quality spring and design, like a WIX, it's still a roughly cut piece of steel "sliding" across a nitrielle rubber surface which will have large amounts of variance in resistance from one unit to another.

Really, I think the bypass pressure is of very little concern anyway. And if it is a concern to you, I assume you would just want a filter that bypasses early and easily and before the filter element?

 

[labman]

A few years ago I could buy an ST with a thread end bypass and as much media as anything but an AC. My Wal-Mart doesn't stock an Ecore with a 20 mm thread. All the cheaper stuff now has dome end bypasses. There is a lack of documentation of problems with dome end bypasses, but I am still looking for a cheaper filter on the shelf with a thread end bypass. I do have a Motorcraft number now.

 

[Corvette Owner]

Are those bypass pressures ? They seem low.

The Corvette 5.7 liter has a bypass in the engine block that is set at 72 psi. Rarely do I see over 55 psi.

 

[AuthorEditor]

Those are settings for the bypass valves within the oil filter itself. The engines also have a pressure relief valve that blows if the engine pressure gets too high. The oil filter valve relates to the differential pressure within the filter. In other words if 50 psi oil is coming in and the psi drops to 40 on the way out, theoretically the 8 psi valve should open to let the oil temporarily bypass the filter until the pressure difference equalizes. That will usually only happen with cold oil, too heavy a weight oil, a very dirty (plugged) filter, or very high-revving engine.

 

[Pete C.]

Originally Posted By: AuthorEditor
My suspicion is that these small distinctions don't really mean anything and the valves are probably not all that accurate anyway. Why the ranges on some filters? Thoughts?


I can't say for others but ours list the cracking pressure and the full open pressure at a specified spring preload. Oh, there is no rough metal in contact with our rubber gaskets in the UFV.

 

[SuperBusa]

Originally Posted By: AuthorEditor
Why the ranges on some filters? Thoughts?


Most likely due to a couple of design criteria: a) filter media flow resistance, and b) media loading factors. If the media is a little more restictive to flow, you would want to design the bypass valve setting a little higher to give adequate pressure drop "headroom" before it opens.

Same goes with media loading. If you design a filter to be used for releatively long OCIs, then you would expect it to load up a little more, and therefor the bypass would be set a little higher to ensure oil is filtered (instead of going into bypasss) as the media loads (which causes a slightly higher pressure drop).

 

[SuperBusa]

Originally Posted By: Corvette Owner
Are those bypass pressures ? They seem low.

The Corvette 5.7 liter has a bypass in the engine block that is set at 72 psi. Rarely do I see over 55 psi.


The oil pump's pressure relief valve is built into the pump ... the filter bypass valve is in the filter mount in the engine block ... and it's set to around 8~10 psi I believe on the LSx Vette engines.