Teach me about dome vs. thread.

[hardcore302]

Tried doing a search, to no avail.

Keeping in mind the MC fl820S, but also in general, what is the difference between dome and thread end bypass?

Thanks!

 

[SuperBusa]

The bypass valve located at the base or threaded end of the filter allows oil to bypass the filter element without the oil traveling past the dirty filter media.

The dome end bypass is located on the opposite end of the base, so if the bypass valve opens, the oil that is in the dome end has already flowed past the outside of the dirty filter media, and could potentially (in theory) carry debris from the media into the bypass valve and then directly into the engine.

But realize that if the dome end bypass valve opens, there is still oil pressure and flow still going on throughout the entire media area ... so this should keep the trapped debris in the media pleats and nothing should come off and go down the bypass valve.

The only time I could see a dome end bypass valve potentially flowing crud from the filter is if for some reason there was a "dead zone" of flow in the dome end, and there was slug of crud waiting for the bypass valve to open and flow through it. Personally, I don't think there is much of a flow "dead zone" because the flow inside a filter at higher engine RPM is going to be somewhat turbulent and full around the filters media cartridge due to some pretty good oil volume flow.

 

[labman]

When, if ever, would a filter bypass? Most likely on start up with a cold engine. Engineers commonly specify dome down orientation. When the engine is shut off, larger particles are free to settle down to the dome end. There they could be swept through a open bypass and directly into the engine on start up.

GM defeats cost cutting filter manufactures by putting the bypass inside the engine before the debris in the filter. Ford specifies thread end bypasses in their Motor Craft filters. Most of your higher end filters such as Wix, NAPA Gold, M1, Clarcor have thread end bypasses. Champs improved Ecores have it. It is mostly the cheap, conventional filters with dome end bypasses including Fram, Purolator, and older design Champs. The only higher end ones I know of with it is the Pure 1 and the Bosch clone.

 

[Bruce T]

The filter bypass is supposed to open when the filter becomes clogged, so there will always be oil flow/lubrication to the engine. Clogging is why they don't recommend running the very efficient filters (like Purolator PureOne) past 5,000 miles. Other filters like Amsoil EaO are designed for long intervals, but might sacrifice a little in ultimate filtering.

If the bypass opens and there is still enough pressure to hold debris against the media, some of the debris on the surface will still flow through the bypass into the engine due to the turbulence that SuperBusa mentions. I agree that most of it will probably remain trapped against and inside the media.

I haven't heard of this objection by labman about dome bypasses in the thread-up position. Fallen debris at the bottom could be an issue if the oil filter goes into bypass on startup.

Is it assumed or known that the typical oil filter goes into bypass on startup? If the bypass does open this often, then dome vs. thread does matter. On the other hand, the thread below refers to a test where Gary couldn't get the bypass valve to open on cold engine startup (couldn't find the test itself):

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1467448&page=all

 

[labman]

Tons of unknowns. While Gary has suggested bypasses seldom open, I have heard horror stories about the oil filter blowing off the first time after driving off with other than the specified filter. Could happen if somebody put a non bypass filter on a non bypass application. I never had a problem using a PF 52 in place of a PF 47, but it could be a problem in place of a PF 1127. I forget whether Gary's tests included near the end of an OCI when a filter might be loaded up.

 

[Bruce T]

Yes, I think I understand. There are a lot of variables, but locating the bypass on the dome end can add several new risks. How much risk will there be in the real world? It's hard to say.

 

[gouda]

I just finished cahanging oil and filter in my 2008 Ford escape.
Installed a Carquest blue premium filter,made by Wix in the U.S.A. It has a dome bypass. I also changed oil and filter in my 2002 Ford Windstar with a Caequest premium blue made by Wix U.S.A, it has a base bypass.

gouda

 

[gouda]

P.S
The escape is a v6

gouda

 

[defektes]

Does the wix made proselect also have a dome bypass system?

 

[ThirdeYe]

Originally Posted By: defektes
Does the wix made proselect also have a dome bypass system?


In the 1040 I've cut open, it does. They have a coil spring on the dome end.

 

[Gary Allan]

Quote:
Is it assumed or known that the typical oil filter goes into bypass on startup? If the bypass does open this often, then dome vs. thread does matter. On the other hand, the thread below refers to a test where Gary couldn't get the bypass valve to open on cold engine startup (couldn't find the test itself):


The most likely time for anyone to encounter anything other than marginal PSID is at start up if the pump goes into relief. Otherwise, there's no PSID of merit for just about any operating mode in MOST engines. There can and will be unicorns. Herds of them for some.

I'd say that as soon as you're off of PEAK pressure (you have no idea of how much flow is being shunted when the gauge is peaked) then you have very little chance to have a bypass event occur since you have little PSID across the media. As the filter loads, this static and highly compressed PSID will gain in amplitude and duration, but will still be rather low ..at MOST sensible volume levels. There can and will be unicorns ..herds of them even ..but the average stroke driving MOST cars will not see a bypass event except at cold start. There it will probably still be just a transient event where fluid can't go from standing totally still COLD and accelerate to the required flow without the oil pump spinning its tires trying to move an effective solid mass instantaneously to a given rate.

You can also (perhaps) see it at startup where the galleries are empty and there is no "back pressure" to shore up the media on the engine side. The flow is identical ..and the visc can be anything up or down, but without the (let's say) 40-80psi of "back pressure" that the engine would kick back to the engine side of the media, then you may actually see the 8-16 (covers most of them) differential where most bypass valves operate. Once the engine is fully enveloped, then the only time AT MOST SENSIBLE VOLUMES FOR MOST ENGINES where you'll see high PSID will be when the pump is in relief. Where you have attenuated pressure pressure from the pump, but reduced volume to produce (near) matching back pressure from the engine.


Side note for comparison: Some LS(?) owner put in a high volume pump that had something like a 48lb relief limit. Same owner insisted on using 5w-40 ..which produced 40-45psi at hot idle. The reading was well downstream of the filter.

The result would be absolute assured pump relief off idle. That is, he would never see 100% of the sensible output of the pump "fitting" through the engine. The same engine did manage 50+ psi at some rpm level, but that merely proves that his relief port could not shunt enough volume to maintain the pump's relief setting. He even saw idle pressure differences between one filter and a PureOne. Since the filter effected flow (lower pressure) then the pump HAD to be in relief ..or seriously leaking by design. Here you may be able to understand that the only reason that the engine saw that reduced flow ..and the obvious pressure differential that it caused, was due to the relief event. He had to be seeing higher pressure above the filter. He could not possibly be seeing lower pressure below the filter without a reduced flow. The flow can't be reduced unless the pump is in relief.

round and round it goes.

 

[Nick R]

The NAPA Golds we put on the expedition and mustang (1372s I believe) had Dome end bypasses on them.

 

[defektes]

Originally Posted By: ThirdeYe
Originally Posted By: defektes
Does the wix made proselect also have a dome bypass system?


In the 1040 I've cut open, it does. They have a coil spring on the dome end.



excellent thank you!

 

[ronrackley]

Originally Posted By: ThirdeYe
Originally Posted By: defektes
Does the wix made proselect also have a dome bypass system?


In the 1040 I've cut open, it does. They have a coil spring on the dome end.


Does the coil spring on the dome end make it a dome bypass? I thought it was there to let the filter element move and allow the oil flow around it at the threaded end. If this is ignorance, and it might very well be since I have never been a filter cutter, someone please correct me.

 

[Sayjac]

You see what one needs to understand is that the incessant sniveling about dome end bypass has as much (or likely more) to do with a foreign ownership agenda, as it does bypass location

After one has read this board for a while it easy to see the constant complaining about Purolator's ownership, makes the opinion regarding dome bypass extremely suspect by that member. Those who have read this board have seen that horse beaten dead, dug up, then buried only to be dug up again....ad inifinitum!

Being as the Pure One is one the best, if not the best, bang for the buck, high quality, high efficiency oil filter's, it's difficult to find any negative. For those not familiar with the agenda....ad inifinitum, of not liking Purolator's German ownership, it can be disguised by the bypass location contention. Nevermind the fact that Purolator oil filter are made in America.

As said here, while the thread end may be preferable, in truth, bypass location makes little difference in overall filtration and oil filter function.

So buy an oil filter that you are comfortable with, just don't be confused by the....ad infinitum...

 

[labman]

So why buy from a German company when you can get the same thing for the same price from an American company? STP by Champ is identical to the Purolator Classic. So I will keep on sniveling about buy American.

I have also switched from Pennzoil to Mobil.

 

[ThirdeYe]

Originally Posted By: ronrackley
Originally Posted By: ThirdeYe
Originally Posted By: defektes
Does the wix made proselect also have a dome bypass system?


In the 1040 I've cut open, it does. They have a coil spring on the dome end.


Does the coil spring on the dome end make it a dome bypass? I thought it was there to let the filter element move and allow the oil flow around it at the threaded end. If this is ignorance, and it might very well be since I have never been a filter cutter, someone please correct me.


I'm pretty sure that means it's a dome-end bypass. I thought a thread-end bypass had the spring mechanism right by the threads whereas dome-end have a leaf spring or a coil spring or something like that right at the dome of the filter... someone correct me if I'm wrong though.

 

[labman]

You need to look at the dome end end cap. If it is solid, any bypass is at the thread end. You can easily see the dome end bypasses looking in the outlet. There are many different styles, a circle of holes, Champ uses a blue plastic button. Others use sort of a metal plate held by a spring outside the element.

I think all filters I ever cut open had a spring of some kind in the dome end holding the element against the base plate.

 

[river_rat]

Originally Posted By: sayjac
As said here, while the thread end may be preferable, in truth, bypass location makes little difference in overall filtration and oil filter function.

That's pretty much how I feel about it. Even when it goes into bypass, I doubt anything significant washes back out of the filter.

 

[Gary Allan]

Originally Posted By: labman

I think all filters I ever cut open had a spring of some kind in the dome end holding the element against the base plate.


Every filter that I've seen except an Ecore. The others may use a coil or a (sorta) leaf spring, but they've all had it.