FRAM Ultra Bypass Valve Pressure Test

[twX]

I decided to test the bypass valve opening pressure of a FRAM Ultra XG3593A (original wire-backed) after I cut it open. It has the typical FRAM leaf spring bypass. I was curious if the bypass pressure rating was for initial, average, or fully-open pressure.

I measured the diameter of the valve, subtracted the area of the plastic supports, and used a kitchen scale to see how much force was required to open it.

Bypass valve spec: 12 psi
Initial opening pressure: 14 psi
~25% open: 16.5 psi
100% open: 22 psi (extrapolated, since my scale maxed out)

It seems that when FRAM gives the spec as a single value, it's for the initial opening pressure. It measured a bit higher than its rating, but some of that could be measurement error.

 

[Rand]

sounds about right.

 

[fantastic]

Great work & it's neat to see how a certain filter ticks via diy.

 

[ZeeOSix]

I measured the diameter of the valve, subtracted the area of the plastic supports, and used a kitchen scale to see how much force was required to open it.

Was that the same as the diameter of the hole in the metal leaf spring that the valve seals on?

Any good way to check the accuracy of the kitchen scale?

 

[Mewbs]

I decided to test the bypass valve opening pressure of a FRAM Ultra XG3593A (original wire-backed) after I cut it open. It has the typical FRAM leaf spring bypass. I was curious if the bypass pressure rating was for initial, average, or fully-open pressure.

I measured the diameter of the valve, subtracted the area of the plastic supports, and used a kitchen scale to see how much force was required to open it.

Bypass valve spec: 12 psi
Initial opening pressure: 14 psi
~25% open: 16.5 psi
100% open: 22 psi (extrapolated, since my scale maxed out)

It seems that when FRAM gives the spec as a single value, it's for the initial opening pressure. It measured a bit higher than its rating, but some of that could be measurement error.

Now try it on a subaru oil filters.

 

[ARCOgraphite]

I decided to test the bypass valve opening pressure of a FRAM Ultra XG3593A (original wire-backed) after I cut it open. It has the typical FRAM leaf spring bypass. I was curious if the bypass pressure rating was for initial, average, or fully-open pressure.

I measured the diameter of the valve, subtracted the area of the plastic supports, and used a kitchen scale to see how much force was required to open it.

Bypass valve spec: 12 psi
Initial opening pressure: 14 psi
~25% open: 16.5 psi
100% open: 22 psi (extrapolated, since my scale maxed out)

It seems that when FRAM gives the spec as a single value, it's for the initial opening pressure. It measured a bit higher than its rating, but some of that could be measurement error.

Cool!
Curious how you calculated 25% open? And why subtract the area of "plastic supports"? I am unsure what you include as "plastic supports". Just trying to back into your calculation, as you "didn't show the math"

Not being too critical here, I do appreciate this thread you started

 

[twX]

So, there was a calculation error in my spreadsheet. I'll show my updated calculations here so somebody can double check them, but I think it's correct now. I rechecked the measurements and included what I estimate to be the measurement uncertainty.

I checked the calibration of both the scale and digital calipers I used. Both have <1% error, but there's some judgment involved on my part, especially with the scale measurement.

So the initial opening pressure of the bypass seems to be in the range of 17.4 psi to 20.2 psi, quite a lot higher than the 12 psi rating. Considering this filter was used on my Subaru, the high bypass pressure is nice to see.

Was that the same as the diameter of the hole in the metal leaf spring that the valve seals on?

Yes, it's the diameter of the hole.

Cool!
Curious how you calculated 25% open? And why subtract the area of "plastic supports"? I am unsure what you include as "plastic supports". Just trying to back into your calculation, as you "didn't show the math"

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]

Yes, it's the diameter of the hole.

Did you remove the bypass valve from the leaf spring to get a good measurement on the hole in the leaf spring? Much easier and more direct way of getting that hole diameter.

 

[ZeeOSix]

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.

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?

 

[twX]

Did you remove the bypass valve from the leaf spring to get a good measurement on the hole in the leaf spring? Much easier and more direct way of getting that hole diameter.

No. I considered doing that, but decided to hold off, just in case I wanted to redo the scale measurement for some reason. I'll provide an update with a more accurate measurement at some point.

 

[ZeeOSix]

No. I considered doing that, but decided to hold off, just in case I wanted to redo the scale measurement for some reason. I'll provide an update with a more accurate measurement at some point.

The legs of the valve can be disconnected from the spring pretty easily to dissemble the system.

 

[twX]

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

Good point. There would also be pressure acting upward on the hooked part, so I think it's best to just ignore the legs altogether. Initial opening pressure is 14.8 to 16.9 psi ignoring the legs.

 

[ZeeOSix]

Good point. There would also be pressure acting upward on the hooked part, so I think it's best to just ignore the legs altogether. Initial opening pressure is 14.8 to 16.9 psi ignoring the legs.

But the vertically projected area on the bottom of part of that hook is less than the top projected area. So overall, there's still some force being put down through the legs.

 

[ZeeOSix]

I had a Fram leaf spring sitting in the garage (out of a PH7317), so disassembled it and measured the hole diameter. Camera battery was low on the phone, so didn't get a good photo (slightly blurry) of the caliper, but it's just shy of 0.530 inch.

 

[twX]

But the vertically projected area on the bottom of part of that hook is less than the top projected area. So overall, there's still some force being put down through the legs.

Yeah, I agree. What I meant by ignoring the legs is just pretending they don't exist and using the full area of the bypass hole.

I measured the hole in the leaf spring with calipers after disassembling the valve and measured 13.47 mm, which puts the initial bypass pressure at 16.0 to 17.0 psi, ignoring the legs and using the full area of the bypass hole.

 

[ZeeOSix]

Yeah, I agree. What I meant by ignoring the legs is just pretending they don't exist and using the full area of the bypass hole.

I measured the hole in the leaf spring with calipers after disassembling the valve and measured 13.47 mm, which puts the initial bypass pressure at 16.0 to 17.0 psi, ignoring the legs and using the full area of the bypass hole.

Got ya. You got the same diameter I got on the hole (13.47 mm = 0.53 inch).

 

[ZeeOSix]

If you want to really get into the hair splitting, look closely at the hole in the leaf spring. The edge that is on the flat valve side of the valve is actually rounded pretty good, so I think the effective diameter the dP acts on is actually slightly larger than the 13.47 = 0.53 inch diameter.

If I take into account that rounded edge on the hole, I get a diameter of 0.59 inch.

 

[twX]

If you want to really get into the hair splitting, look closely at the hole in the leaf spring. The edge that is on the flat valve side of the valve is actually rounded pretty good, so I think the effective diameter the dP acts on is actually slightly larger than the 13.47 = 0.53 inch diameter.

If I take into account that rounded edge on the hole, I get a diameter of 0.59 inch.

Yeah, mine's looking like 14.6mm=0.575", for an initial opening pressure of 13.6-14.4 psi. Final answer.

 

[ZeeOSix]

The calculation is pretty sensitive to F and A. Just using an effective hole diameter of 0.590 vs 0.575 changes the crack open dP from 14.0 to 13.3 PSI.

 

[SubieRubyRoo]

Now try it on a subaru oil filters.

Just no.