How critical is the bypass setting?

[Filter guy]

Ken..your right again above about the function of the oil pump and pressure regulating valve.

The oil pump is positive displacement as you noted. Viscosity of the oil when at ambient temperatures is also important as to resistance to flow.


I'm trying to keep thing simple for many who are not technically as gifted as others in this forum. This is my first day, be kind..lol
I don't know if this forum is full of chemical engineers or automotive engine designers or basic consumers just lurking for answers in laymans terms. I guess it's a learning curve for me as I tend to answer more in laymans terms. I've perused some of the threads and it seemed to me a lot of the posts were from general comsumers with basic questions. That's the avenue I took.

427Z06..chill..

No disrepect was intended with my comment about visiting with filter engineers. That's who have guided me the last 20 odd years. Obviously you have a grasp on filtration as it relates to engines. My expertise is on the manufacture and construction of the filters themselves, design and testing, and the basics of engines as they relate to filters. I'm not an engine expert /engineer by any stretch.

If your down in Dallas, i'll buy you a bevvy of your choice.

 

[XS650]

quote:

---

Originally posted by JDP:

Does any one know of information on the cracking pressures versus full flow pressures for any of the pressure regulators used in the engine lube pumps? I have wondered for a long time about the amount of oil being bypassed at the regulator when a new engine is idling. Guess maybe I’ll have to set up some kind of a test using a common engine oil pump.

---

JDP, the cracking vs full flow pressure characteristics are going to vary quite a lot between different models of pump and by manufacturer.

Cracking pressure is determined by how hard the spring presses against the valve when it is seated. That force is a function of how hard the spring is pressed against the seat when it is installed. That in turn is function of spring rate and how much it is compressed when it is installed.

A long soft spring and a short stiff spring can have the same force on the valve when the valve is seated. Therefore, same cracking pressue. As the oil lifts the valve off the seat, the short stiff spring will require more pressure to go to full open than the long soft spring will.

 

[JDP]

XS650

Thats how I've understood the operation too.

It's been my understanding that there is always some oil being bypassed at the regulator valve whether at idle, cruise or WOT.

Probably not though in the 76 Ford pickup w/390 that I once ran for 15k mile w/0 hot idle psi.

Was glad when I could afford a better one!!!

Always has intrigued me as to where the influences of oil temp/viscosity and engine clearances/oil pump wear/regulator spring fatigue converged as an engine wore out. All those factors affect the indicated oil pressure at a given engine RPM.

 

[Hirev]

quote:

---

So it is critical not to monkey with the oil filter by-pass valve settings when determining should I use this filter or that one because of different pressure relief settings. In otherwords, don't use a VW filter ( usually 30-35psi valve) on a Ford ( usually 8-11psi) or vise/versa.

---

Filter guy ~ I am not a Engineer by any stretch. But why is it critical not to monkey with oil filter bypass settings? I have owned, wrenched, and ran 2 different 11 second street/strip cars with NO oil filter bypass at all!

Why do you think VW and some other European cars use 30 - 35 psi oil filter bypass pressure relief settings as opposed to 8 to 16 psi?? Special motors? Or perhaps they want to see more oil filtered with each cycle?

 

[Hirev]

quote:

---

Grumpy was a genious ..no two ways about it ..but I think that I'd have to actually see his words in print to take them in context. Was he speaking as "Grumpy" the reknowned engine builder in terms of a racing application with a heavily dead headed pump with rapid and abrubt surges in oil flow using racing oil or did he say this as a mechanical engineer in regard to common hokey-pokey passenger cars using 20w-20???

---

Its in print in his book The Chevrolet Racing Engine. So yes it was in terms of racing applications.

However those small block Chevys don't need that much oil compared to some motors. In Smokey's book he commented that the loosest small block he ever assembled for testing only required 8.0 GPM oil flow.

 

[jsharp]

quote:

---

Originally posted by Hirev:

quote:

---

So it is critical not to monkey with the oil filter by-pass valve settings when determining should I use this filter or that one because of different pressure relief settings. In otherwords, don't use a VW filter ( usually 30-35psi valve) on a Ford ( usually 8-11psi) or vise/versa.

---

Filter guy ~ I am not a Engineer by any stretch. But why is it critical not to monkey with oil filter bypass settings? I have owned, wrenched, and ran 2 different 11 second street/strip cars with NO oil filter bypass at all!

Why do you think VW and some other European cars use 30 - 35 psi oil filter bypass pressure relief settings as opposed to 8 to 16 psi?? Special motors? Or perhaps they want to see more oil filtered with each cycle?

---

I'd like to hear an answer to this too since it's hard to believe that the bypass pressure is something that isn't related to a lot of other factors.

For instance, I can understand why it might be bad to use a filter with a bypass setting that's too high. That would end up being effectively a larger pressure drop in the oiling system since the bypass valve acts somewhat like a differential pressure regulator though it's really only a regulator in the sense that it limits the maximum pressure drop across the element in normal use.

But what about using a filter that has a lower bypass setting than was specified from the factory? All other things being equal that would mean less oil gets filtered as it passes through the filter and more is bypassed around the element as flow rate increases because of the lower bypass pressure.

But, if we increase the flow rate of the filter element by using a different media or larger filter element then it's possible we could have a filter with a lower bypass setting, yet have it actually filter more completely than one with a higher setting.

So, IMO the setting is "critical" only in the sense that we want to make sure the maximum practical amount of oil gets filtered with the minimum pressure drop across the filter.

In the case you listed, German manufacturers, I have to believe their high bypass settings are at least partially realted to their use of oils that are quite heavy compared to say the Japanese or American manufacturers...

[ November 01, 2004, 01:28 AM: Message edited by: jsharp ]

 

[Gary Allan]

quote:

---

But, if we increase the flow rate of the filter element by using a different media or larger filter element then it's possible we could have a filter with a lower bypass setting, yet have it actually filter more completely than one with a higher setting.

---

Do you mean velocity? The "rate" should be the same for any filter media as you sorta said here.

quote:

---

That would end up being effectively a larger pressure drop

---

quote:

---

Why do you think VW and some other European cars use 30 - 35 psi oil filter bypass pressure relief settings as opposed to 8 to 16 psi?? Special motors? Or perhaps they want to see more oil filtered with each cycle?

---

Well, I would kinda turn that around on you and ask "why don't US autos use 30-35 psi bypass settings? Special engines? or do they perhaps want very limited amounts of oil filtered with each cycle?

It would seem to me that VW obviously factors this into their oil volume/pressure and filter media component scheme ....and "we" do too. For all we know it's due to their extended drain program and the disapation of that higher bypass setting is part of the program ...as may oil shearing in a 7500 OCI with a common dino for a US man.


I think that we over 'guesstimate' the pressure drop over the media. Bob's filter study and Grease's filter study didn't use any heated fluid ..and I don't believe either of them used something that had a CST of 10-12 @ room temp ..nor did either test it, IIRC (I may be wrong in Grease's study). I think ATF would have a higher visc than 40 weight @ 200 F.


I have a Greshen hydraulic filter right in front of me. #K22001. This filter has NO bypass valve. I, btw, just went out and groped through my garage since I did have this filter sitting at my computer for about a year with it's mount ..often pondering putting it inline in my transmission. I cleaned my computer room ...and it got piled with all my other "fine junk" in the garage. It's 6:45 a.m. and rather cool.

I'll give you all the spec's list on the side just to show you have "good" the media is:

ISO 4572-1981 (I don't know what paper trail this would lead to)
TWA and TYP are assumed to mean time weighted average and typical where indicated.
TWA Beta10=2 TYP
TWA Beta20=20 TYP
TWA Beta22=75 TYP
Capacity 8 gms TYP

Delta P @ 10 gpm 150 SSU = 4 psid


So, if I read this correctly ..at a 10 gpm flow ....this filter will pass 10 weight oil @ 100 F with only a 4 psid. I'm assuming the lower scale ..if this is the upper scale ...then the fluid tested is probably a 70 SAE weight ..which I doubt.

What auto filter is this "tight" and will see any higher delta P ...at a 10 gpm flow rate? How many will ever see a 10 gpm flow rate? How many have a Beta10=2? None virtually ...so I think 4 psid is liberal given our viscs after warm up.

I'm open to counter arguement and opinion.

[ November 01, 2004, 08:08 AM: Message edited by: Gary Allan ]

 

[Gary Allan]

Ah-ha! Found it!!

ISO 4572:1981 Hydraulic fluid power -- Filters -- Multi-pass method for evaluating filtration performance

Technical committee: ISO/TC 131/SC 6

Withdrawal date: 1999-12-16

Replaced by:
ISO 16889:1999 Hydraulic fluid power filters -- Multi-pass method for evaluating filtration performance of a filter element


Naturally it doesn't detail the mulitpass procedure ...perhaps Filterguy can add this missing info

 

[jsharp]

quote:

---

Originally posted by Gary Allan:

quote:

---

But, if we increase the flow rate of the filter element by using a different media or larger filter element then it's possible we could have a filter with a lower bypass setting, yet have it actually filter more completely than one with a higher setting.

---

Do you mean velocity? The "rate" should be the same for any filter media as you sorta said here.

quote:

---

That would end up being effectively a larger pressure drop

---

quote:

---

Why do you think VW and some other European cars use 30 - 35 psi oil filter bypass pressure relief settings as opposed to 8 to 16 psi?? Special motors? Or perhaps they want to see more oil filtered with each cycle?

---

Well, I would kinda turn that around on you and ask "why don't US autos use 30-35 psi bypass settings? Special engines? or do they perhaps want very limited amounts of oil filtered with each cycle?

It would seem to me that VW obviously factors this into their oil volume/pressure and filter media component scheme ....and "we" do too. For all we know it's due to their extended drain program and the disapation of that higher bypass setting is part of the program ...as may oil shearing in a 7500 OCI with a common dino for a US man.


I think that we over 'guesstimate' the pressure drop over the media. Bob's filter study and Grease's filter study didn't use any heated fluid ..and I don't believe either of them used something that had a CST of 10-12 @ room temp ..nor did either test it, IIRC (I may be wrong in Grease's study). I think ATF would have a higher visc than 40 weight @ 200 F.


I have a Greshen hydraulic filter right in front of me. #K22001. This filter has NO bypass valve. I, btw, just went out and groped through my garage since I did have this filter sitting at my computer for about a year with it's mount ..often pondering putting it inline in my transmission. I cleaned my computer room ...and it got piled with all my other "fine junk" in the garage. It's 6:45 a.m. and rather cool.

I'll give you all the spec's list on the side just to show you have "good" the media is:

ISO 4572-1981 (I don't know what paper trail this would lead to)
TWA and TYP are assumed to mean time weighted average and typical where indicated.
TWA Beta10=2 TYP
TWA Beta20=20 TYP
TWA Beta22=75 TYP
Capacity 8 gms TYP

Delta P @ 10 gpm 150 SSU = 4 psid


So, if I read this correctly ..at a 10 gpm flow ....this filter will pass 10 weight oil @ 100 F with only a 4 psid. I'm assuming the lower scale ..if this is the upper scale ...then the fluid tested is probably a 70 SAE weight ..which I doubt.

What auto filter is this "tight" and will see any higher delta P ...at a 10 gpm flow rate? How many will ever see a 10 gpm flow rate? How many have a Beta10=2? None virtually ...so I think 4 psid is liberal given our viscs after warm up.

I'm open to counter arguement and opinion.

---

Gary - I should have used the term "reduce the filter restriction" instead of "increase the flow rate".

Read it that way and see it it makes more sense....

The point I was trying to make is this - That the bypass pressure is only critical if we substitute a filter that's virtually identical other than the bypass setting.

Once we start using oversize filters, less restrictive filters, etc., then it becomes less of an issue as long at we don't select a filter that is a greater restriction that what we're replacing...

 

[Gary Allan]

quote:

---

Once we start using oversize filters, less restrictive filters, etc., then it becomes less of an issue as long at we don't select a filter that is a greater restriction that what we're replacing...

---

We agree!!

(visions of Rodney King's infamous statement - insert quaking/shaking voice "Why can't we all just get along?")

 

[427Z06]

XS650, nice work! I always thought there was something outta whack with the numbers in Grease's filter study. Found one myself, a few months ago.

I'll just add that the most restrictive filter there is the Pure1 equivalent of the FL400S, which has about 60-100% more media than a lot of filters that are now being speced for many DOHC V6s and I4s with 8-11 psi bypass settings. Put 6K miles on a restrictive dinky filter and run the numbers and it's way to close for my comfort.

If anyone is interested in learning more about ISO 16889:1999 Multi-pass Test, short of purchasing papers try this:

http://www.practicingoilanalysis.com/article_detail.asp?articleid=564&relatedbookgroup=OilAnalysis

 

[Gary Allan]

Thank you very much, XS650.

 

[427Z06]

quote:

---

Originally posted by Filter guy:
427Z06..chill..

No disrepect was intended with my comment about visiting with filter engineers. That's who have guided me the last 20 odd years. Obviously you have a grasp on filtration as it relates to engines. My expertise is on the manufacture and construction of the filters themselves, design and testing, and the basics of engines as they relate to filters. I'm not an engine expert /engineer by any stretch.

If your down in Dallas, i'll buy you a bevvy of your choice.

---

Thanks for the offer. I apologize for being so harsh, but occasionally I get miffed when someone swaggers into the forum, claims to be an expert and then condescends to everyone here. There are a lot of knowledgeable people here both technically inclined professionally and/or by hobby. We present facts, experiences, opinions and debate so that we all may learn something.

Next time I get up to Dallas, I'll take you up on that cold one.

 

[Ugly3]

XS650 - You are my new hero.

I just knew that there had to be some misunderstanding, there was no way that full flow oil filters were in bypass all the time and have engines going 300,000 miles.

Now, get your butt to work on the apparent low wear rates on the back end of long runs of synthetic oils.

 

[jsharp]

quote:

---

Originally posted by Ugly3:
XS650 - You are my new hero.

I just knew that there had to be some misunderstanding, there was no way that full flow oil filters were in bypass all the time and have engines going 300,000 miles.

Now, get your butt to work on the apparent low wear rates on the back end of long runs of synthetic oils.

---

Exaclty.

Good job by the XS650 man...

 

[XS650]

Thanks guys, but all I did was find one error in Grease's otherwise outstanding work.

I am glad I was able to add some value to his valuable test work. Very few people go to the work Grease did and give it away on the web.

 

[Schultz]

quote:

---

posted November 01, 2004 12:52 PM
--------------------------------------------------------------------------------

quote:
--------------------------------------------------------------------------------
Originally posted by Gary Allan:

I think that we over 'guesstimate' the pressure drop over the media. Bob's filter study and Grease's filter study didn't use any heated fluid ..and I don't believe either of them used something that had a CST of 10-12 @ room temp ..nor did either test it, IIRC (I may be wrong in Grease's study). I think ATF would have a higher visc than 40 weight @ 200 F.


--------------------------------------------------------------------------------

Gary, I just took another look at Grease's filter flow study. It's one of the better bits of filter related test work on the web, but there is a big conversion error that understates filter flow by a factor of 41.6 when he converts to fl oz/in^2. Once you correct that, it shows that the filters he tested flowed between 1.3 and 7.8 gpm of 30 weight at 70F (21.1C). None of those filters is going to bypass at all at 100C on any normal car engine no matter how fast you rev it.

Assuming he used a straight 30 weight with a VI of 120, the most restrictive filter in the test would flow 6 gpm at a 10 psi pressure drop at 50C (122F) and over 20 gpm at 100C.

---

Greese and I teamed up on the testing. He did the filter disection, and I did the media testing. I put together the spreadsheet you mention with the cacluations. I looked over the formulas again and I'd like to get it right but I can't find the error. Help me out if you would.

In colum N with Fram TG the media flowed 35 grams of 30w oil. The next colum converts this to ml/cm2/min with a correction for density. The formula is =N11/2/4.9*1.125 (colum N divided by 2 for 1 minute, times 4.9 cm2 for a 25mm die cut, times 1.125 density correction). Then in colum P we conver to oz/in2/min. =O11*0.0338*0.155 (answer from colum O times .0338 to convert ml to fl-oz, then times .155 to convert cm2 to in2). In colum L the answer in colum P is multipled by total square in of EFA.

Tim

 

[427Z06]

Here's my crack at it:

34.5/.882 = 39.1 mL density correction (29 API Gravity)

39.1 mL/in^2-2min = 19.6 mL/in^2-min

19.6 x .033824 = .662 oz/in^2-min

.662 oz/in^2-min x 274 in^2 = 181 fl oz/min

181/128 = 1.42 gpm

(Didn't the spreadsheet say he used a 25 mm die to cut the filter paper so we don't have to convert from cm to inches?)

[ November 01, 2004, 06:21 PM: Message edited by: 427Z06 ]

 

[427Z06]

I was just thinking about the Beverly Hillbillies episode where Jethro had to remove his boots to do the extra fancy ciphering.

 

[427Z06]

Whoops. Just read the spreadsheet again.

You guys used a 13mm filter paper holder.

(Hey Baby, Take your shoes off again and come here, I gots more ciphering to do.)