Purolator dome-end bypass pics

[AuthorEditor]

Since everyone loved the thread about the Motorcraft thread-end bypass valve I thought I would share some pics of a Purolator dome-end bypass valve from a recently cut PureOne PL24651 (equivalent to a FL820S). Three things struck me. First, the spring is really hard to open--couldn't pry it up with my fingertips alone--required sticking a screwdriver blade under and then I could pry it open with force. Second, that thing doesn't open very wide ever I imagine. There isn't a lot of travel available. Probably just opens a sliver once in a great while in real-world use. Third, there would have to be a lot of sludge in the can before it would ever get close to the opening. It's hard to imagine there is any significant advantage to a thread-end bypass valve.

 

[mazdamonky]

If they are so hard to open, maybe requiring higher PSI than recommended for the application, that could be the reason they were tearing.

 

[CarbonSteel]

I have always thought the same about the PL14610 filter I used to use on my Brute Force 750 which has the same type of bypass. The bypass does not really seem to function, but in reality, I am sure that it does or at least one would hope so.

 

[CT8]

The bypass opens every time you start the engine. If you don't think so see if you can find a filter that fits with out a bypass and see what happens.

 

[tig1]

It's not like Pure doesn't test these things.

 

[CarbonSteel]

Originally Posted By: CT8
The bypass opens every time you start the engine. If you don't think so see if you can find a filter that fits with out a bypass and see what happens.
Jim Allen tested this long ago and debunked this. The only time the bypass would open at start-up is running high RPMs at startup or using a heavy viscosity oil in cold weather. Otherwise, bypass events are far fewer in a normally running engine than is assumed. Do a search and you can find his results.

 

[AuthorEditor]

Here's a link to the classic Jim Allen thread on differential pressure and bypass events being rare. http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3198369/1

And here's a great Jim Allen quote from that thread about bypass valve location (thread-end vs. dome-end):
Quote:
As to the bypass location, if you recall, I argued that even if it occurs with frequency, it's still not that big of a deal. Also, Go back and look at the pics of all the autopsied filters that contained a lot of gunk, particularly those with base end bypass valves. If regular bypassing had a major washing effect that would blow the gunk thru into the clean lube oil flow, there would have been little to no gunk left to look at!

 

[goodtimes]

They specify the opening force, so 14 psi on one to open will be 14 psi on another brand regardless of design. The Fram type also feels hard to open prying on the opening cover. Good pics it looks like metal to metal sealing. That's the best kind.

 

[AuthorEditor]

Quote:
Good pics it looks like metal to metal sealing.

Good point--I forgot to mention that. There is no rubber (nitrile or whatever) gasket in there. It is metal to metal.

 

[HerrStig]

Originally Posted By: mazdamonky
If they are so hard to open, maybe requiring higher PSI than recommended for the application, that could be the reason they were tearing.
--Another clairvoyant. ^

 

[ZeeOSix]

I always felt a bit skeptical about the flat spiral spring in this bypass valve design. It is super stiff, but if you measure the surface area and the force to crack it open it should come out close the the PSI rating of the valve. This subject has come up a few times over the years, and I think someone did measure the force and valve surface area and verified it looked correct.

For a given PSI setting, the smaller the surface area, the softer the spring will be. So if a valve is pretty large in size, then it will seem to have a pretty stiff spring.

F = P x A
lbs = (lbs/in^2) x (in^2)

P = F/A

If P is constant, then F goes down as A goes down.

 

[AuthorEditor]

I set up a crude test to measure the force required to open the bypass valve. I measured the opening as about 3/4 of an inch in diameter giving an area of .442 square inches. My wife had some small lifting weights of five pounds each that I attached to the valve cover with some copper wire. When I hung the 5lb weight from the valve it was just opening a bit--maybe not all the way, but a good bit. So flipping your formula around
Pressure = Force/Area, Pressure = 5lbs/.442^2, Pressure = 11.2 lbs/in^ or 11.2 psi. It matches up pretty well with Purolator's specs. on the bypass of 8-16 psi.

 

[ZeeOSix]

^^^ AuthorEditor - nice job and the test to verify the valve setting.

 

[AuthorEditor]

Quote:
^^^ AuthorEditor - nice job and the test to verify the valve setting.

Thanks! Now that I have looked at this thing closely I understand better why the range is quoted, which is more accurate than the single number you get from say Fram of 12psi. I imagine that 12psi is either the minimum pressure to crack the valve or else possibly the median pressure--note how it is halfway between 8 and 16 that Purolator specs.

Also, these Purolator valves look pretty simple, rugged, and foolproof. I can't imagine anything going wrong other than possibly the rivet failing.

 

[WellOiled]

Originally Posted By: AuthorEditor
Quote:
^^^ AuthorEditor - nice job and the test to verify the valve setting.

Thanks! Now that I have looked at this thing closely I understand better why the range is quoted, which is more accurate than the single number you get from say Fram of 12psi. I imagine that 12psi is either the minimum pressure to crack the valve or else possibly the median pressure--note how it is halfway between 8 and 16 that Purolator specs.

Also, these Purolator valves look pretty simple, rugged, and foolproof. I can't imagine anything going wrong other than possibly the rivet failing.

I think the manufacturer may be stating the threshold of starting to open (8) and fully open (16). Not a range for the starting to open number.

Nice cut & post as well as the test on the relief valve. Thanks.

 

[AuthorEditor]

Quote:
I think the manufacturer may be stating the threshold of starting to open (8) and fully open (16).

Agreed.

 

[jhellwig]

Originally Posted By: AuthorEditor
I set up a crude test to measure the force required to open the bypass valve. I measured the opening as about 3/4 of an inch in diameter giving an area of .442 square inches. My wife had some small lifting weights of five pounds each that I attached to the valve cover with some copper wire. When I hung the 5lb weight from the valve it was just opening a bit--maybe not all the way, but a good bit. So flipping your formula around
Pressure = Force/Area, Pressure = 5lbs/.442^2, Pressure = 11.2 lbs/in^ or 11.2 psi. It matches up pretty well with Purolator's specs. on the bypass of 8-16 psi.

It is going to take far less weight to open the valve the way you have it hooked up than if you made it pull squarely from the center. If you drilled a small hole through the rivet and then stuck the wire through you would get the correct weight required to open it.

 

[Sayjac]

AE, glad you did a practical test of the Puro flat spring design to debunk the idea that because it's difficult to push open with ones finger it may not open as spec'd. Basically you put Zee's math formula to the test and confirmed the bypass psi. I've used many filters with that type bypass in both the P1 and BD+ many times on Hondas mostly, and never had an issue as viewed from dissection.

That's not the only type bypass design they use. Also use the more common coil spring type dome bypass shown below in some applications. The last PL14459 made in late 2013 used that type. Not sure how they determine which filter gets which, but as long it works as designed, makes no difference to me.

 

[AuthorEditor]

Quote:
The last PL14459 made in late 2013 used that type. Not sure how they determine which filter gets which, but as long it works as designed, makes no difference to me.

My guess would be that some engine manufacturers spec a coil spring for their filters for some reason, and the filter company goes along in order to be able to supply OEM filters off of the same line. We have all seen how most OEM filters are simply rebranded or slightly modified filters we could purchase off the shelf in an independent parts store.