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Re: BOBISTHEOILGUY FILTER TESTS #315086 04/13/03 05:40 PM
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Spector Offline
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quote:
Originally posted by pedaltothemetal:
So I'm interested in how many miles a filter will become dirty enough so it becomes the restriction and not the engine. Leo

That is the $64,000 question. I just cut open a filter that went 10,041 miles over 8 months. I was surprised that the flow back valve still appeared to be in good shape and bypass still sturdy. The media, well, I scraped and scraped and to the naked eye nil debri but I will look at through mangifying glass this week. Quick observation, this filter could have gone much, much longer in service. The oil analysis results will be here in a week or so. The diff between this sample and previous is that this 10,000 mile change had no filter change at 6000 miles. previous two went 12,000 with a filter at 6000. Again. my premise is that in todays modern engines and great oils a filter is a useless appendage that is good for catastophic failures only with the assumption the engine has been maintained since day one etc.


This was an Amsoil SDF 29
Will see.

[ April 14, 2003, 09:41 AM: Message edited by: Spector ]

Re: BOBISTHEOILGUY FILTER TESTS #315087 04/13/03 06:45 PM
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satterfi Offline
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Don't forget we're using PD pumps here. They pretty much put out the same flow regardless of downstream resistance. The engine alway gets enough flow, clogged filter or not.


quote:
Originally posted by pedaltothemetal:
... and unless the filter is extremely clogged and goes to bypass mode, there will always be enough filtered oil for the engine. ...


Re: BOBISTHEOILGUY FILTER TESTS #315088 04/14/03 01:25 AM
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OneQuartLow Offline
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quote:
Originally posted by satterfi:
Don't forget we're using PD pumps here. They pretty much put out the same flow regardless of downstream resistance. The engine alway gets enough flow, clogged filter or not.

Even new positive displacement pumps have efficiency curves. Flow drops as backpressure increases. Add "acceptable" pump clearances and it's easier to understand why tests show flow isn't immune to restrictions.

To me this is less about the safe zones and more about the low margin. i.e. cold starts and lugging or short shifts. And can't say I'll miss the "I think's" in filter discussions. [Wink]

Re: BOBISTHEOILGUY FILTER TESTS #315089 04/14/03 02:33 AM
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fields Offline
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Unless I read wrong, he is putting a 40 lb pressure differential on the oil filter itself. I personally think this test has a flow rate that can not even be anywhere near the actual flow in an engine. These differences would then be extremely magnified in relation to real world numbers in our engines.

richard

[ April 14, 2003, 06:34 PM: Message edited by: fields ]

Re: BOBISTHEOILGUY FILTER TESTS #315090 04/14/03 03:22 AM
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OneQuartLow Offline
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Richard, you're right, the numbers aren't yet matching reality as far as the pressures you'd see in an engine. Think of them as the other end of the spectrum from Jason's airflow data. We're still toying with heaters and instruments.

Once a test rig can duplicate operating temps, pump RPM, and then engine restrictions, things will look more realistic. Until these things are complete, with good gauges, pressure drops are either tough to determine or swing wildly as viscosity/temp and simulated engine restrictions change. So close but yet so far... [Smile]

Re: BOBISTHEOILGUY FILTER TESTS #315091 04/14/03 05:21 AM
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Michael SR Offline
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quote:
Originally posted by satterfi:
Don't forget we're using PD pumps here. They pretty much put out the same flow regardless of downstream resistance. The engine alway gets enough flow, clogged filter or not.

true, the pump's flow is almost constant (for a given rpm). but the output from the pump is not, since most pumps have internal bypasses.

also, note that the bypass is usually right back to the pump's inlet, rather than back to the sump. this is both good and bad, depending on point of view.

-michael

Re: BOBISTHEOILGUY FILTER TESTS #315092 04/14/03 05:30 AM
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satterfi Offline
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quote:
Originally posted by OneQuartLow:
Even new positive displacement pumps have efficiency curves. Flow drops as backpressure increases. Add "acceptable" pump clearances and it's easier to understand why tests show flow isn't immune to restrictions.

I agree. For example the pump curve Im looking at shows that clearly (Waukesha size 18 rotary pump). At 400 rpm pumping 10cps fluid, this pump will put produce 11 gpm at 25psi or 10 gpm at 50psi.

That's why I said "They pretty much put out the same flow ".

Re: BOBISTHEOILGUY FILTER TESTS #315093 04/14/03 05:44 AM
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See? That's very different from the new Melling Mopar 318 gear pump I'm using. Flow appears to drop by >50% with net pressure somewhere near the 318 in my pickup at ~2Krpm engine speed. (though don't hold me to it until I can maintain temperatures with consistency)

My point is that it's pointless to generalize about pump performance or theory. Certainly with pumps made for different engines or completely different purposes.

Re: BOBISTHEOILGUY FILTER TESTS #315094 04/14/03 05:45 AM
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satterfi Offline
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quote:
Originally posted by Michael SR:
but the output from the pump is not, since most pumps have internal bypasses.

I don't know if most oil pumps have internal reliefs or not. I don't see how it matters if the relief valve is internal or external. They are set to control max system pressure, like 85psi. Maybe I don't understand your point.

Re: BOBISTHEOILGUY FILTER TESTS #315095 04/14/03 05:59 AM
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OneQuartLow Offline
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Michael, I'm also seeing interesting differences that make me suspect the varying specs for internal clearances. I've only tested two pumps so far (Melling Mopar 318 and Jeep 242) but while I'm not ready to name numbers I am confident there's significant loss from this factor, increasing at higher pressures (even with the relief valve disabled). No doubt this means ordering OEM pumps for comparison. Eventually. It'll never end. [Smile]

[ April 14, 2003, 10:00 PM: Message edited by: OneQuartLow ]

Re: BOBISTHEOILGUY FILTER TESTS #315096 04/14/03 08:11 AM
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Michael SR Offline
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quote:
Originally posted by satterfi:
I don't know if most oil pumps have internal reliefs or not. I don't see how it matters if the relief valve is internal or external. They are set to control max system pressure, like 85psi. Maybe I don't understand your point.

i was the one who didn't understand. i realized my mistake after re-reading your post.

however, given a clogged enough filter, the flow rate through the engine will indeed change. if the restriction is high enough to cause the pump to bypass, oil that would otherwise go through the engine is now just circulating through the pump.

an extreme, sure...

on the subject, it's amazing how much those pumps flow. i've seen 2 where the bypass stuck closed. one ballooned a 300psi burst rated racing filter enough to unseat the gasket. the other blew a regular oil filter like a tactical nuke went off inside. (it's amazing the oil pump driveshafts can live.)

also seen them with the bypass stuck wide open. in a ford 302 (the type of pump bob used, if i remember correctly), this caused idle pressure with hot oil to be ~2psi, and 2000rpm pressure about 20psi. actually, not bad, considering...

-michael

Re: BOBISTHEOILGUY FILTER TESTS #315097 04/14/03 08:16 AM
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Michael SR Offline
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quote:
Originally posted by OneQuartLow:
Michael, I'm also seeing interesting differences that make me suspect the varying specs for internal clearances. I've only tested two pumps so far (Melling Mopar 318 and Jeep 242) but while I'm not ready to name numbers I am confident there's significant loss from this factor, increasing at higher pressures (even with the relief valve disabled). No doubt this means ordering OEM pumps for comparison. Eventually. It'll never end. [Smile]

oh, sure, they're all different. i used to take the time to blueprint them. on a few i even "ported" them in addition to the blueprinting.

those types of mods raise oil pressure to the block. that means, i guess, that output flow goes up without the bypass regulator seeing a pressure change.

fwiw, OEM pumps seem the best overall, to me. certainly the stock aluminum-bodied ford 302 pumps beat any aftermarket jobs, and ditto the sbc pumps installed on LT1/4 engines. if you disassemble them, the clearances are all almost perfect.

-michael

Re: BOBISTHEOILGUY FILTER TESTS #315098 04/15/03 01:23 AM
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For what it's worth guys:

Shigley and Mischke, in "Mechanical Engineering Design,"
show that the oil flow required to maintain a 28 F differential between oil-in temp and oil-out temp of a bearing of 0.00175" clearance, is Q = 0.252 m^3/s for SAE 20 weight oil, at a shaft speed of 1800 RPM. This is for a bearing D = 1.5" and Length = 1.5." The lubricant temp is 130 F.

A Chevy main bearing in a 350 V8, by comparison, has an average clearance of 0.001925", a length of 1.21875", and a diameter of 2.448".

[ April 15, 2003, 05:44 PM: Message edited by: MolaKule ]

Re: BOBISTHEOILGUY FILTER TESTS #315099 04/15/03 06:13 AM
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MolaKule

.252m^3/s is 3995gpm

Re: BOBISTHEOILGUY FILTER TESTS #315100 04/15/03 04:54 PM
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Nice work Bob!

I have a couple of suggestions:

1) Heat the oil to 190F-200F - a 10w-30 is fine ...
2) Increase the supply side pressure to a more representative pressure of 60-80 psi. Many high performance engines like Acuras and VW's run much higher oil pressure than 40 psi, even after fully warmed up.
3) Test a 40wt or 50wt oil for comparison to look at flow rates and pressure drop.

TooSlick

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