How critical is the bypass setting?

[XS650]

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Originally posted by Schultz:
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.

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You need to divide by 0.155 instead of multiply.

A good way to do conversions is multiply by one and carry the units through the conversion. It eliminates a lot of mistakes. For instance,

1cm^2/0.155in^2 = 1 You can multiply by that or it's inverse to convert between cm^2 and inch^2 and it is obvious which you should use because you need to have the units you are converting from cancel. If they don't, you are doing it upside down.

1ml/(cm^2 x min) x (1cm^2)/(.155 in^2) x
(0.0338 fl-oz)/ml

Note that 1cm^2/0.155 in^2 and 0.0338 fl-oz/ml both equal 1 because the upper and lower quantities in each individual example are indentical.

Multiply that out and you get:

1ml/(cm^2 x min) = 0.0338 fl-oz)/((0.155in^2 x min) = 0.218 fl-oz/(in^2 x min)

It is a lot clearer is you write it out on paper with the values directly over eachother rather than using / marks for dividing.

I think the spreadsheet would also be better if you made the column that shows total flow rate read in gallons/minute. That would be easier for most of us to relate to.

Nit piks aside, great test and spread sheet. Thank you for your work.

[ November 01, 2004, 08:02 PM: Message edited by: XS650 ]

 

[XS650]

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Originally posted by 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.)

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Whew! Put you shoes back on Jethro

The 13mm holder was for the bubble test, the 25mm holder for the flow test.

 

[427Z06]

quote:

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Originally posted by XS650:

quote:

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Originally posted by 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.)

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Whew! Put you shoes back on Jethro

The 13mm holder was for the bubble test, the 25mm holder for the flow test.

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OK...assuming a 25mm diameter round piece of filter paper, opposed to the 1 inch square patch I originally calculated, just divide my value by .761 and that gives 238 fl-oz/min or about 41.9 to 1 difference. Which jives with what you originally got. No?

 

[Gary Allan]

Gosh this is intense from the cheap seats. "The suspence is killing me ....I hope it lasts" (Gene Wilder in "Willie Wonka and the Chocolate Factory" when Augusta Kluge got stuck in the uptake tube)

 

[XS650]

quote:

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Originally posted by 427Z06:
]OK...assuming a 25mm diameter round piece of filter paper, opposed to the 1 inch square patch I originally calculated, just divide my value by .761 and that gives 238 fl-oz/min or about 41.9 to 1 difference. Which jives with what you originally got. No?

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Yup,close enough. It's 41.62314256 if you want to carry it out to a bunch of insignificant figures.

 

[427Z06]

OK...now let's tackle the non-laminar flow calculations of oil moving through the filter and engine.

 

[jsharp]

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Originally posted by Gary Allan:

quote:

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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...

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We agree!!

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

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I think we agreed all along.

I'd still like to know who thinks the bypass setting is critical and their reasons given the factors cited in our discussion...

 

[XS650]

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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.

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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.

 

[Schultz]

OK I see the mistake. I'll have to get a hold of greese and repost the corrections.

Thanks for the catch. It always seems too low of oil flow, but I just couldn't find why. Like you said doing it on paper the way we learned in science class the error pops out, but on the spreadsheet it seemed right.

Tim

 

[Filter guy]

Well i'm on the road so sorry for not answering some points in this forum before.

Gary has taken care of some of the answer but i'll chime in with a few other observations.

1) Engine Companies determine the by-pass valve settings. So any engine under warranty, make sure you use a filter with the correct by-pass setting. Which is why I earlier warned of not monkeying with the valve settings and I wasn't clear with my reasons.

By saying "correct" by-pass setting, I mean the one correctly cataloged by the filter manufacturer if there is a different rating from brand A to brand B.

If you use the correct valve setting as cataloged by the filter company, then that filter company will honor the warranty if their filter failed.

If you use the OEM brand filter and choose to use one with a different by-pass setting that is within their product offering, my educated guess is they won't honor the warranty on the filter or engine ( if there is some sort of engine damage as a result). As some may be aware, OEM's are voiding warranty on any "modifications" that consumers make with their vehicles when still under warranty. I think the OEM would determine that you chose to "modify" your engine by chosing the wrong element part number.

2) On out of warranty engines, you can always do what you want..

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If you choose to change to a different filter for whatever reason and the by-pass valve setting is different opt for the lower one.

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FYI..Ford is starting to switch from the 8-11 psi valve to a 18-20 psi one. VW is going the other way..from the 35psi one to 27psi.

So in the future, there won't be as much problem with switching between the two when used on out of warranty vehicles.

 

[Grease is the word]

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OK I see the mistake. I'll have to get a hold of greese and repost the corrections.

Thanks for the catch. It always seems too low of oil flow, but I just couldn't find why. Like you said doing it on paper the way we learned in science class the error pops out, but on the spreadsheet it seemed right.

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The Grease filter study updated spreadsheet is now posted. Thanks for everyone's help. Flow at 70F at 10psi is now rated in gallons! The .xls file is now noted as Version 3.1.

www.OilFilterStudy.com