Would they all flow the same?

[MarkC]

I'm not sure I can verbalize what I'm thinking, but here goes.
If oil pumps are positive displacement, they're going to pump oil through the filter anyway, or through the bypass valve. The lowest flow ratings I've seen on a filter are about 3 gpm, which is probably more than the pump will move. So, won't the flow be about the same out of the filter, no matter what filter it is?

 

[Gary Allan]

Unless the internal relief settings of the oil pump are reached, every filter moves the same amount of oil. The stuff crawls through the filter. If the visc is too high ..the bypass opens ..but this, I truly think, is only for a brief moment since once the system is pressurized, the differential pressure is within the bypass limits (the high visc oil is producing higher pressures downstream as well).

I think the difference between a high flow filter and a low flow filter is just the velocity that the oil is subjected to passing through the media. The gpm should be identical. Just stretch out the media and look at how the oil must slow to fill all the square inches (think toll booths 150 lanes wide for a 1 lane highway).

Two 13/64 holes passed so much oil through my Permacool adapter that it had no differential after warm up. This is with a start up pressure of 82 psi and 32 psi after warm up. When I went straight up, so to speak, with an unmodified adapter, the pressure was 82/80. Granted this was across a very large fitler ..but it was 1um filtration.

After this revelation in flow characteristics (albeit of imperical nature), I would have no reservations using the finest of media (most "restrictive"). I would naturally seek out the largest filter available just for capacity overkill. This too, I dont' think is a real concern.

The only sad part about it is that the really fine filters (M1 for example) cost 3-5 times the amount of our ST types ..that are just grand in the bang for the buck dept.

[ February 10, 2005, 11:26 AM: Message edited by: Gary Allan ]

 

[MarkC]

Kinda what I thought.
I found Pure One's for $3.50 yesterday.

 

[T-Keith]

Theoretically the system will flow the same. The difference would be how much is going through the media and how much is going through the bypass valve. If you referring to a filter with a built in bypass then you would be correct. I haven't seen anyone prove how much or how often the bypass valve is open during typical operation, so how much it matters is up to some debate.

Bottom line is that a more restrictive filter will NOT flow less then a less restrictive one. If you believe otherwise you do not understand the principle of a positive displacement pump.

-T

 

[Gary Allan]

quote:

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Many filters have drasticly different flow rateing!

---

Not really, James. Although it is true that, for example in Grease's flow test, different medias showed different "flows" ..that was at a given pressure. It would be JUST as true to say that the same filters rated at a given flow rate would result in different differential pressures. Since your oil pump is a positive displacement pump ..the flow dictates the pressure drop across the media at a given viscosity. The flow, unless the internal relief springs are breached, always remains the same. Now, as I said, the filter itself may be in bypass ..but I would think that this would be brief since the fully enveloped oil system would also raise the downstream pressure. The oil can is a BIG chamber compared to the (maybe) 1/2 square inch pickup tube in the sump ..or the return line that you thread the filter to. 5 gpm is not a radical flow to produce out of a 1/2" hose ...try thinking of standing there for 1 min holding a hose to fill a 5 gallon bucket ..you'ld get bored doing it. And that is about the max flow the pump can produce. I think that my HV pump is rated around 8 ..or maybe 10 gpm.

 

[3000GT VR-4]

quote:

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Originally posted by Razl:
In the event you have a faulty bypass that’s closed, the media is going to fail regardless of its "restrictive" value.

---

Then won't particles of the media be pumped through the oil galleries? Wouldn't be a good situation IMO.

 

[ZR2RANDO]

Bottom line is that a more restrictive filter will NOT flow less then a less restrictive one. If you believe otherwise you do not understand the principle of a .


I side with using a less restrictive filter personally. Just because a pump is a "positive displacement pump" does not mean it is a 100% efficient pump. As resistance to flow builds up the pressure relief valve at the pump opens up to limit the pressure being delivered to the system. At this point the flow is being decreased by diversion, the pump can also have flow loss at the impeller as it encounters increased resistance above the pump. A filter that provides a higher efficiency at filtering smaller particles may provide sufficient flow when it is clean, but by definition it will clog quicker as well..gradually causing more back pressure. As long as it is changed before that point is reached- no problem, but a "finer filter" is definitely NOT a "long lifer" unless it really has additional sq inches of media to give it some extra time at the clean filter flow rate...
Any increased restriction will cause a decrease in flow rate as compared to an alternate lesser restriction choice (rough surface pipe over smooth/small bearing clearances over large/thick oil over thin/fine filter over a less fine one..)

Using a less restrictive filter will provide higher flow for a longer service life than a more restrictive filter will....and as that filter ages it gradually starts filtering out smaller particles anyway....works out pretty well because that new oil starts out relatively clean when that filter/oil is changed out.....

 

[3000GT VR-4]

quote:

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Originally posted by Gary Allan:

quote:

---

Many filters have drasticly different flow rateing!

---

Since your oil pump is a positive displacement pump ..the flow dictates the pressure drop across the media at a given viscosity. The flow, unless the internal relief springs are breached, always remains the same.

---

I think this depends on the tolerances and seal quality of the pump. The higher the pressure, the more oil will leak past the seals and/or through the tolerances of the pump, reducing flow rate. So, for a given engine (oil pump) RPM, the higher the backpressure the less the flow to the bearings will be, even if the bypass is closed.

 

[Razl]

I think what you are saying is that if a filter is "too" restrictive, the oil pump's own pressure tolerance will be exceeded and thus not capable of delivering oil to the bearings, etc. Right?

In reality, this doesn't happen. The bypass in the filter is mechanically kept close so the oil will flow only through the media when media flow is adequate. If the flow through the media is too restrictive, the bypass will open relieving the pressure built up thus allowing oil to flow through the bypass opening.

Depending on resistance to flow thru the media, the amount of oil going thru the bypass may a little flow or a lot of flow. But in either case, you end up with the same amount of flow. This is what Gary is saying. Even with a fully clogged media, the opening of the bypass is large enough to deliver the proper flow (look how small the opening is in a Permacooler design).

The relief pressure on the bypass is extremely low compared to the relief pressure on the oil pump.

In your scenario, the only way possible to starve the engine of oil (flow) is using a filter designed with no bypass where a bypass is required (some engines have an internal bypass, most don’t).

Then and ONLY then does the filter's media have the potential of becoming too restrictive because it has no alternative path (bypass) to travel.

MarkC, are you having fun (confused) yet?

[ February 10, 2005, 04:52 PM: Message edited by: Razl ]

 

[T-Keith]

A restriction of around 8 psi(typical bypass setting) will not cause a major change in the volumetric efficiency of a pump that generates 60+ psi of pressure.

-T

 

[ZR2RANDO]

T is right, 8 psi(typical bypass setting) probably will not cause a major change in the volumetric efficiency of a pump that generates 60+ psi of pressure, (also depends on the health/age of that pump ) but that 8psid would be in addition to other pressure drops through the engine...it wouldn't help either.

Another side effect of a more restrictive filter is that the bypass would open a little more often..I'd rather that oil go through the paper than through that bypass. ..and if that bypass is open, then flow has already been reduced because of that psid..

I'd say, more restrictive filters just start filtering more efficiently right out of the box (when the oil and filter are new and relatively clean anyway)...just not a good choice for extended interval oci's.

That's a WHOOPS on my previous post above, I didn't mean to accidently cut/paste that first line at the top, not sure how I did it, sorry bout that..

Rando

 

[Filter guy]

Well just for fun..

A new filter regardless of the least efficient media being used or the most efficient media ( Mobil M1, Pure One, etc)...will have an initial pressure drop of less than 1 psi, usually in the range of .3 to .5 psi.

What you as a consumer don't know is, what is the restiction on your used filter when you change it. Regardless of how dirty you think it is. It might only be 3-5 psi..

As for stretching out media in order to claim you have something the other guy doesn't...

Look at the filter before you do that. The more pleats, the more restriction if the pleats are to "bunched" together. The only way to have more pleats is to have less basis weight media (thinner). Jam them in the same area of the endcap and you end up restricting flow at the center tube area. Your looking at the "outside" where the pleats can fan out but in the center tube area the pleats bunch and restrict flow. Sometimes more isn't better.

 

[ZR2RANDO]

Those are some very good points, and it is good to see some numbers too (I need to invent a pressure differential gauge that all the major auto makers would actually install on vehicles..

)
Back when I compared the AC filter for my trucks, (Ac-PF52)I compared a Delphi and Champ version to each other. They both had the same sq inches, but the Delphi had fewer,deeper pleats (had gaps). The Champ version had more,shallower pleats and was much more evenly spaced- and was my choice from then on until I ran in to the Black Can Supertechs...(not a bad thing here, I'm saying the Champ version had a much better arrangement for pleat number/depth)

And sometimes more IS better....like whiskey in my glass!

Rando

[ February 10, 2005, 07:09 PM: Message edited by: ZR2RANDO ]

 

[Razl]

Filter Guy, I have the feeling you have some insight to our questions. You are hush about the new Mobil Ext filters

That's just cruel bringing it up. So how about it?

How frequently do FFs go into bypass?

On average, how much containments is released in the auto per 1,000 miles? Or on average, how many miles before a filter's media becomes clogged?

 

[Razl]

Once again Gary nails it! You will not starve you engine for oil using more restrictive media. The flow to your engine will be the same. In the event you have a faulty bypass that’s closed, the media is going to fail regardless of its "restrictive" value. A high flow filter isn’t going to buy you any insurance in this situation.

My ideal filter is one that removes the smallest particles most efficiently and has enough capacity to continue filtering until the next filter change. The latter part is still an unanswered question for me

 

[JohnBrowning]

I do not agree with this at all! Many filters have drasticly different flow rateing! WHile it is true that exceeding your oil pumps flow ragteing may not help you at all a filter that flows less then you pump is able to flow can hurt you. We have see many instances prior to "BOB" geting sick were oil flow through the filter was more important then filtering ability in preventing wear. We also saw a lot of difference in flow rate through their test system and a large difference in restriction from brand to brand.

Most engines are not pumping that much oil at idle but as RPM reachs between 2000 and 3000 RPM's rest assured your engine oil pump is pumping a large volume of oil!

 

[MarkC]

I'm thinking that if you take the lowest flkow rate published for a filter--which I think is 3gpm--you won't find a pump that moves that much oil anyway.
Anyone have any numbers about that?

 

[Ugly3]

quote:

---

Originally posted by MarkC:
I'm thinking that if you take the lowest flkow rate published for a filter--which I think is 3gpm--you won't find a pump that moves that much oil anyway.
Anyone have any numbers about that?

---

I contacted an oil pump maker and they reported that my pump 3800 V6 put out 3.5 gallons of oil per minute per 1000 RPM. They also indicated that most engines reach maximum PSI somewhere between 2000 and 3000 RPM at operating temps meaning that the max flow will normally be between 7 and 10.5 gallons per minute.

I checked a viscosity / temperature table that indicated raising the temp of an oil from 70 degrees to 200 degrees will result in a 10 fold increase in flow thru a media due to reduced viscosity.

A poster reported that he had a vehicle that had a light on the dash that indicated when the oil filter was in bypass mode. He said that other than right at cold start the filter was almost never in bypass mode. As I recall, he has some foreign car and the accuracy of the bypass light was not tested so take it for what you will.

My conclusion is that even the most restrictive filter will almost never be in bypass mode under normal driving conditions once the engine is up to a reasonable temp. I figure the oil is going throught he filter at a rate of about 5 or 6 times a minute (28 quarts a minute flow and a 5 quart sump), even if 1/2 the oil were being bypassed all the time the flow rate of filtered oil would be 2 or 3 times a minute, not a problem in my view.

 

[Ugly3]

quote:

---

Originally posted by Razl:
Filter Guy, I have the feeling you have some insight to our questions. You are hush about the new Mobil Ext filters

That's just cruel bringing it up. So how about it?

How frequently do FFs go into bypass?

On average, how much containments is released in the auto per 1,000 miles? Or on average, how many miles before a filter's media becomes clogged?

---

Given that car makers are now recommending filter changes every 15,000 miles (my 98 Van has that recommendation) and the filters are not monster size, one might believe that the car makers feel a filter will not be 80% clogged in 15,000 miles under non severe service.

 

[ZR2RANDO]

"Given that car makers are now recommending filter changes every 15,000 miles (my 98 Van has that recommendation) and the filters are not monster size, one might believe that the car makers feel a filter will not be 80% clogged in 15,000 miles under non severe service. "

Or they may just not be as interested in you keeping that vehicle forever as you are...
They really push "leasing", and they know lots of people switch vehicles routinely and mainly care about reducing maintenance costs..
But some of us (BITOGRS !!!) care more about longevity instead.