FRAM Ultra Bypass Valve Pressure Test

[ARCOgraphite]

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The 25% was just a rough visual estimation. The initial opening pressure is more important and should be more accurate.

There are four vertical plastic supports that hook onto the top of the spring and connect to the valve plate that gets pushed open by oil pressure. The area they take up on the top of the valve plate is area that the oil pressure won't be acting on, so I subtracted that area. Ignoring the supports, the calculated pressure ends up being a bit lower, 14.8-16.9 psi instead of 17.4-20.2 psi.

@ZeeOSix beat me to it, as I am just rejoining now. The resulting force vector calculation can get a bit involved here but you cannot ignore the leg area altogether. I would make an assumption that the correct spring rate was installed and then pick a method that approaches the advertised specification, +/-.going forward. Also, I would say as you stated, it is correct to assume that the poppet doesn't have to be far off the seat to flow near the max orifice value for the Dp to normalize. Fun engineering exercise.

 

[ARCOgraphite]

Actually, there is oil pressure acting on those legs as shown below, so the dP does put some force on those legs. The top area of the legs also see pressure vectors of the dP across the valve. What's the flat plane projected area in the vertical direction of those legs? What do you get if you don't subtract out the 4 legs on the top of the bypass valve, and just use the hole area in the leaf spring?

View attachment 209282

It appears you can ignore the spring retention hook part of the legs, as in a static situation there is an equal and opposite vector on the underside of the hook. 90 deg side vectors (not illustrated) are ignored.
Without much consideration in the past. I would have used just the open poppet orifice area - and that may actually be the way to go here.

 

[ZeeOSix]

It appears you can ignore the spring retention hook part of the legs, as in a static situation there is an equal and opposite vector on the underside of the hook. 90 deg side vectors (not illustrated) are ignored.
Without much consideration in the past. I would have used just the open poppet orifice area - and that may actually be the way to go here.

Yes, the leg portion of the hooks should be treated as part of the total dP acting area. Yes, the vertical force vectors from the dP on the hooked portion of the legs will basically cancel out - updated figure below. The hole in the leaf spring is rounded pretty good where the valve seats, to the effective dP acting area should be based on that diameter. Given all the possible +/- factors involved, the calculated opening pressure comes out relatively close to the advertised setting.

 

[ZeeOSix]

Here's another variable to consider - metal spring rates can change (become softer) as they get hotter - example below. What would the bypass spring be doing at 200F? Maybe it's right on target at 200F - 230F operating temperatures.

 

[Mewbs]

Just no.

why not? pretty sure some of us here want verify if that OEM 20+ PSI bypass setting is fact or myth.