Does the bypass relief valve pressure matter much?

[zray1]

“……. The only other thing you can do to help keep the filter from bypassing when the oil is cold and thick is to keep the engine revs down until the oil warms-up.

^^^^^^
This is how to make engines last. And the first thing I was taught working in Uncles Burls repair shop. It was true 60 years ago and still true today. Only a fool, and there are some of those, will red line a stone cold engine. 2-3,000 rpm, OK. 4-6,000 rpm on a cold engine is just plain foolishness.

Z

 

[oil pan 4]

Ooo added a bypass filter to another 459cc predator engine.
When I would add oil restrictor to a turbo I usually would use a 35 thousands most of the time. That would give me about 1qt per minute at 20psi at idle and about 3qt per minute at 60psi hot of course and 15w-40 oil. Perfect oil flow for a big holset turbocharger on a diesel that isn't worn out.
A 50 thousands restrictor would give about double the flow of a 35. Didn't use 50s very often. Use those on Detroit's that barely make any pressure at idle.
With 15w-40 which is also what I run in the predator 459cc I would expect a 50 to flow about 1gpm hot, less cold at 50psi. I'm getting about 6 to 8 psid cold across my big 7 to 9gpm 10micron hydraulic filter, when cold and getting about 5psi hot, hot in this case was only about 150f as it was only an idle test run.
I'm just getting a surprising amount of psid across a pretty good size 3.66 x 5 inch filter at a very mundane flow rate.
I'll put a normal engine oil filter on there when I change the oil on these engines, but that's probably going to be a while.

 

[oil pan 4]

Well I looked up all the stuff at the bottom of one of those filter tests that fantastic is always posting.
The main thing is flow rate at 24mm²/second, that's a little less than 1qt per minute, say it's 1L/min, according to iso 4548-1 that approximate L/m of flowing oil is hot oil, sae30 heated to about 74c and/or sae40 oil heated to about 86c so it's property hot oil.
So you'll see about 1 to 2psi per L of hot oil flow per minute on a standard 3 inch wide by 3.3 inch long oil filter used on some V8 engines.
Seems to be about 1psi per L/m if you use a paper rock catcher and about 2psi with a higher end paper filter. About 1psi per L/m if you use synthetic media or glass.
Well the problem with that is, if it is problem since plenty of engines have ran like this for about the last 60 years. An old small block Chevy, one of the few engines where anyone's ever bothered to flow test the oil pump moves it about 2.4 to 2.5gpm at idle (say it's 10 L/m), the pump will max out at 20 to 22gpm at 6,000 crank RPMs, but the engine will only ever allow about 10gpm or 40ish L/m to pass through the filter and go out to the moving parts.
A Typical 3x3.5 inch sbc oil filter is typically only going to be rated for 10 to 25 L/m. 10 L/m on the high end paper filter and 25 L/m on the rock catcher.
So the bypass in your engine, what ever it may be is likey very active unless you're running a 50% to 100% oversized rock catcher.

 

[ZeeOSix]

Well I looked up all the stuff at the bottom of one of those filter tests that fantastic is always posting.
The main thing is flow rate at 24mm²/second, that's a little less than 1qt per minute, say it's 1L/min, according to iso 4548-1 that approximate L/m of flowing oil is hot oil, sae30 heated to about 74c and/or sae40 oil heated to about 86c so it's property hot oil.

The 24mm²/second (which is the kinematic viscosity in cSt) isn't a flow rate, it's the oil viscosity used during the ISO test. The flow rate during the test is listed near the top of the Spec Sheet in l/min.

The dP (in kPa) is shown for that test flow rate with that oil viscosity, and the dP is pretty darn low with 24 cSt oil at 6.6 GPM for the typical Boss Spec Sheet.

An old small block Chevy, one of the few engines where anyone's ever bothered to flow test the oil pump moves it about 2.4 to 2.5gpm at idle (say it's 10 L/m), the pump will max out at 20 to 22gpm at 6,000 crank RPMs, but the engine will only ever allow about 10gpm or 40ish L/m to pass through the filter and go out to the moving parts.

I highly doubt any small block Chevy with an OEM oil pump is going to be putting out 20 to 22 GPM at 6,000 RPM. Here's the oil pump flow data vs RPM for a Chevy LSx engine. No where near 20-22 GPM at 6,000 RPM ... more like 6.5 GPM.

A Typical 3x3.5 inch sbc oil filter is typically only going to be rated for 10 to 25 L/m. 10 L/m on the high end paper filter and 25 L/m on the rock catcher.
So the bypass in your engine, what ever it may be is likey very active unless you're running a 50% to 100% oversized rock catcher.

Don't think so.

 

[OVERKILL]

An old small block Chevy, one of the few engines where anyone's ever bothered to flow test the oil pump moves it about 2.4 to 2.5gpm at idle (say it's 10 L/m), the pump will max out at 20 to 22gpm at 6,000 crank RPMs,

As @ZeeOSix noted, those numbers don't sound right.

The venerable SBC had a cam driven (half speed) gear pump with a 50psi relief pressure. The LSx engines Zee posted have a crank driven (full speed) pump that's much larger.

The 5.7L HEMI pump, which is also a crank driven gear pump is:
500rpm: 1.90gpm
2,000RPM: 5.08gpm

 

[oil pan 4]

The lowest gpm I can find is about 13gpm and if it is say 5gpm through the filter to the engine, last time I checked 5gpm is still way more than 11 L/m. Although a 25 L/m rock catcher is looking better and better.

 

[zray1]

As @ZeeOSix noted, those numbers don't sound right.

The venerable SBC had a cam driven (half speed) gear pump with a 50psi relief pressure. The LSx engines Zee posted have a crank driven (full speed) pump that's much larger.

The 5.7L HEMI pump, which is also a crank driven gear pump is:
500rpm: 1.90gpm
2,000RPM: 5.08gpm

Since the SBC is mentioned; fwiw, the Ford FE series 427 had a pressure relief valve set at 100 psi. The oil filters had no trouble with that.

PS: btw, it might be confusing to some, but this topic has posts discussing two completely different area of pressure relief and conflating the two could be happening.

The engines pressure relief valve relieves engine oil pressure above a set level, while the oil filters relief valve acts on a pressure differential. Completely different.

 

[oil pan 4]

Since the SBC is mentioned; fwiw, the Ford FE series 427 had a pressure relief valve set at 100 psi. The oil filters had no trouble with that.

PS: btw, it might be confusing to some, but this topic has posts discussing two completely different area of pressure relief and conflating the two could be happening.

The engines pressure relief valve relieves engine oil pressure above a set level, while the oil filters relief valve acts on a pressure differential. Completely different.

The oil pump relief will be anywhere from 50 to 100psi depending on the engine.
If the oil filter has a bypass is built into it, most of them by pass at 7 to 11psi across the filter with virtually all of the built in ones relieving at 16psi or less, that is if the filter even has a built in bypass. If the engine has a built in filter bypass they can be factory set for as little as 3psi.

 

[OVERKILL]

The lowest gpm I can find is about 13gpm and if it is say 5gpm through the filter to the engine, last time I checked 5gpm is still way more than 11 L/m. Although a 25 L/m rock catcher is looking better and better.

I'm finding 4.3gpm for the M55 @ 2,000RPM, which is less than the HEMI and LSx pumps, which makes sense, given the half-speed drive.

On filter volume, Fleetguard noted to me that at 30 microns (100% efficiency):
LF16002 (FL-820S) flows 5.28gpm
LF3487 (FL-1A size) flows 14.27gpm

Not sure how they calculate that for efficiency (the 30 microns)

The LF3487 is 73% efficient at 10 microns.

 

[OVERKILL]

The oil pump relief will be anywhere from 50 to 100psi depending on the engine.
If the oil filter has a bypass is built into it, most of them by pass at 7 to 11psi across the filter with virtually all of the built in ones relieving at 16psi or less, that is if the filter even has a built in bypass. If the engine has a built in filter bypass they can be factory set for as little as 3psi.

Yes, but as he noted, the filter relief is a differential pressure relief, which means it only opens when the pressure-drop across the media is high enough to activate it.

 

[oil pan 4]

Yes, but as he noted, the filter relief is a differential pressure relief, which means it only opens when the pressure-drop across the media is high enough to activate it.

As we can see there's ample pressure differential across the filter with a higher end 3x3.3 inch paper filter making up to 2psid per L/m of flow with hot oil.

 

[OVERKILL]

As we can see there's ample pressure differential across the filter with a higher end 3x3.3 inch paper filter making up to 2psid per L/m of flow with hot oil.

Which filter are you referring to specifically? Because the two I listed from Fleetguard clearly wouldn't be producing enough delta-P to engage the bypass.

 

[ZeeOSix]

As we can see there's ample pressure differential across the filter with a higher end 3x3.3 inch paper filter making up to 2psid per L/m of flow with hot oil.

Don't know if you've seen and read this whole thread linked below, but if you haven't you should. The link jumps to a post where I summarized the dP vs flow data of the 5 filters that Ascent tested. There is no way any of them produced anything close to 2 PSI dP per L/min of flow with hot oil - if they did, you would see 100 PSI of dP at 50 L/min. The highest dP seen in this group was the Royal Purple at ~16.5 PSI at 50 L/min (13.2 GPM). That's a huge oil flow volume that not many OEM oil pumps can produce. And the viscosity of the test oil was actually a bit thicker than a 30 grade at 100C.

At half flow rate (25 l/min = 6.6 GPM ... what most cars would be flowing in normal driving), the low to high delta is only 50 in-H2O between all of these filters, which is only 1.8 PSI. Difference between the 3 most free flowing filters is 30 in-Hg = 1.1 PSI @ 13.2 GPM flow rate.

https://bobistheoilguy.com/forums/t...vs-flow-bubble-point-and-burst.334882/page-13

 

[oil pan 4]

Which filter are you referring to specifically? Because the two I listed from Fleetguard clearly wouldn't be producing enough delta-P to engage the bypass.

Something like a PL14006 which I know isn't ideal.

 

[oil pan 4]

Don't know if you've seen and read this whole thread linked below, but if you haven't you should. The link jumps to a post where I summarized the dP vs flow data of the 5 filters that Ascent tested. There is no way any of them produced anything close to 2 PSI dP per L/min of flow with hot oil - if they did, you would see 100 PSI of dP at 50 L/min. And the viscosity of the test oil was actually a bit thicker than a 30 grade at 100C.

At half flow rate (25 l/min = 6.6 GPM ... what most cars would be flowing in normal driving), the low to high delta is only 50 in-H2O between all of these filters, which is only 1.8 PSI. Difference between the 3 most free flowing filters is 30 in-Hg = 1.1 PSI @ 13.2 GPM flow rate.

https://bobistheoilguy.com/forums/t...vs-flow-bubble-point-and-burst.334882/page-13

View attachment 188885

Ya that's what happens when you use a big old truck filter. Also add a few grams of engine dirt and retest.

 

[ZeeOSix]

Something like a PL14006 which I know isn't ideal.

This is a test that Purolator did on a new (unloaded) PureOne PL14006 with hot oil. The dP is only about 5.5 PSI at 13 GPM.

 

[ZeeOSix]

Ya that's what happens when you use a big old truck filter. Also add a few grams of engine dirt and retest.

We are talking about new filters so an apples-to-apples of dP vs Flow can be discussed. Not "muddied" with loaded filters. That dP vs Flow graph in both my previous posts is with a clean filter, NO loading. The test was to measure only the dP vs Flow with 100% clean test oil ... not with test oil loaded with dust.

 

[oil pan 4]

This is a test that Purolator did on a new (unloaded) PureOne PL14006 with hot oil. The dP is only about 5.5 PSI at 13 GPM.

View attachment 188889

Then there's just the problem of the 20 minutes or so of running/driving that it takes the oil to get up to 100c.
The 4548-1 test shows 74c for sae30 developing 1 to 2 psi per L/m of flow depending on if you have the rock catcher or higher end version.
74c seems like a good almost wamed up or optimistic short trip temperature.
In the winter I'm at least half way to work before the oil hits 74c in my truck. If I take the truck to lunch, 2 to 3 miles each way it never hits 74c.
So sub 100c flow seems fairly important.

 

[oil pan 4]

We are talking about new filters so an apples-to-apples of dP vs Flow can be discussed. Not "muddied" with loaded filters. That dP vs Flow graph in both my previous posts is with a clean filter, NO loading. The test was to measure only the dP vs Flow with 100% clean test oil ... not with test oil loaded with dust.

Just something think about.

 

[zray1]

Then there's just the problem of the 20 minutes or so of running/driving that it takes the oil to get up to 100c.
The 4548-1 test shows 74c for sae30 developing 1 to 2 psi per L/m of flow depending on if you have the rock catcher or higher end version.
74c seems like a good almost wamed up or optimistic short trip temperature.
In the winter I'm at least half way to work before the oil hits 74c in my truck. If I take the truck to lunch, 2 to 3 miles each way it never hits 74c.
So sub 100c flow seems fairly important.

As long as you are not running at full throttle at high rpm before the engine has reached its full operating (oil) temperature, I don’t think it’s going to be an issue. This is when a little faith in the engine design team might be warranted, jmho.

Z