PurolatorOne PL14615 Bypass Valve and Cold Flow Tests

[twX]

It can't really happen until shortly after you see oil pressure starting to register.

It can happen if there's enough restriction between the oil pump and the pressure switch, and if the oil is sufficiently thick. About a quarter of the oil pump's output pressure is dropped between the pump and pressure switch on these engines, at least in high rpm/warm oil conditions, with the oil cooler and oil galleries being pretty restrictive.

I do kind of doubt that ~200 cST would be enough for very significant oil pump relief before the oil got to the pressure switch though. Even if the pump was in relief the whole time, oil filter restriction doesn't seem to completely explain the faster pressure rise. I am leaning more towards the ADBV having something to do with it.

 

[ZeeOSix]

It can happen if there's enough restriction between the oil pump and the pressure switch, and if the oil is sufficiently thick. About a quarter of the oil pump's output pressure is dropped between the pump and pressure switch on these engines, at least in high rpm/warm oil conditions, with the oil cooler and oil galleries being pretty restrictive.

Where's the oil pressure sensor located between the pump output and the filter? I doubt the flow path between the pump output is that long and restrictive. The main galleries are typically pretty big in every engine and that's where the oil pressure sensor is located. I'd think on that Subraus having the capability of putting out 60 L/min of oil flow that they would not have some undersized main oil gallery. The oil pump still can't hit pressure relief until basically the whole oiling system fills with enough oil to create enough pressure at the pump to make it hit pressure relief. By that time, the oil pressure sensor should be registering full oil pressure or real close to it.

I do kind of doubt that ~200 cST would be enough for very significant oil pump relief before the oil got to the pressure switch though. Even if the pump was in relief the whole time, oil filter restriction doesn't seem to completely explain the faster pressure rise. I am leaning more towards the ADBV having something to do with it.

My theory is the main reason for the difference in oil pressure rise is because the oiling system drains down to different levels, and different oil filters may effect that depending on how well their ADBV works. From what you're describing about that engine, it sounds like part of the oiling system can drain down, even if the filter ADBV holds oil in the filter. But if one filter holds more oil in the filter vs the other, then that would impact the time it takes to see full oil pressure on a cold start.

 

[Fair enough]

Interesting to try some others like Microgard select. I guess I will put the Pentius xl on. Whip city had it looking very good also. Now, what to do with new oil filters that are probably never going to be used? Need to tighten up things on the excess buying.
For me it’s confusing because I see things like this. Not just Subaru.
https://www.baxterperformanceusa.co...epts-the-factory-recommended-oil-filters.html

 

[twX]

Where's the oil pressure sensor located between the pump output and the filter? I doubt the flow path between the pump output is that long and restrictive. The main galleries are typically pretty big in every engine and that's where the oil pressure sensor is located. I'd think on that Subraus having the capability of putting out 60 L/min of oil flow that they would not have some undersized main oil gallery.

The oiling path is shown in the figure I posted in post #11. The pressure switch is downstream of the oil cooler and oil filter, somewhere between (b) and (c). The oil passages are mostly 11-12 mm, but with some smaller reductions here and there. When pressure at the pump is just above the 102 psi relief pressure, an oil pressure gauge at the pressure switch location will typically read ~75 psi. I think the restrictive oil passages on these engines are a reason why the pump PRV needs to be set so high.

My theory is the main reason for the difference in oil pressure rise is because the oiling system drains down to different levels, and different oil filters may effect that depending on how well their ADBV works. From what you're describing about that engine, it sounds like part of the oiling system can drain down, even if the filter ADBV holds oil in the filter. But if one filter holds more oil in the filter vs the other, then that would impact the time it takes to see full oil pressure on a cold start.

I think that it's a lot more than just the filter that drains. In the first test of the Pentius filter, after it was installed dry, I could tell that both the upstream and downstream galleries were still full. The engine took around 5 revolutions for the light to go out, which was better than any of the tests where the engine was allowed to sit for hours.

With an oil pump output of 12 ml/rev, 5 revolutions is only 60 ml, which should be a lot lower than volume that might be required to fill the dry Pentius filter (which has a volume of around 300 ml, excluding the internals). I'm wondering if that might be explained by the filter maintaining an air pocket for a while.

This video with an oil filter with a clear canister shows an oil filter operating with an air pocket at lower flow rates. The vertical orientation of the filter on a Subaru might allow for a larger air pocket to be maintained since the oil wouldn't need to rise very high up the media to get to the outlet hole. The air pocket does shrink down with pressure after the engine starts, but the pressure in the filter should still be pretty low before the pressure switch sees 2 psi.

Would the taller Pentius filter with its lower restriction media be able to maintain a larger air pocket temporarily, resulting in more oil flow into the main gallery for a given volume pumped by the oil pump?

Maybe the oil light flicker with the Purolator was caused by the air pocket at the top of the filter suddenly shooting through the bypass valve or something.

Those oil passages in the timing cover in Fig. 11 will generally leak, but not everywhere, and probably not at the same place on the same engine. If they leak low down in the engine, I'd expect the oil level in the passages to drain to a lower level eventually. They could leak on the main gallery side, on the oil pump side, or both. I'm not sure the ADBV could do much of anything to prevent this.

 

[ZeeOSix]

I think that it's a lot more than just the filter that drains.

Those oil passages in the timing cover in Fig. 11 will generally leak, but not everywhere, and probably not at the same place on the same engine. If they leak low down in the engine, I'd expect the oil level in the passages to drain to a lower level eventually. They could leak on the main gallery side, on the oil pump side, or both. I'm not sure the ADBV could do much of anything to prevent this.

What I was getting at is depending on what filter is used seems to have an impact of how the whole oiling system can drain down (as well as the filter itself) while sitting after a shutdown. For instance, if the ADBV is working better on one filter vs the other, that could have an effect on how the rest of the oiling system wants to drain down. Even the way any oil may drain out through the center tube between different filters could have an impact.

 

[ZeeOSix]

This video with an oil filter with a clear canister shows an oil filter operating with an air pocket at lower flow rates. The vertical orientation of the filter on a Subaru might allow for a larger air pocket to be maintained since the oil wouldn't need to rise very high up the media to get to the outlet hole. The air pocket does shrink down with pressure after the engine starts, but the pressure in the filter should still be pretty low before the pressure switch sees 2 psi.

In that video, the air pocket was only there while cranking at low engine RPM. The flow rate at that low engine RPM didn't create enough flow through the filter for the air pocket to disappear - needs more dP from more flow to flush the air pocket through the media. Low dP from low flow just makes the oil flow through the bottom half in that horizontal orientation. In a vertical orientation like yours, the air pocket will probably remain while filling if cranked in a similar manner without starting, but as soon as the engine starts and RPM increases the air pocket should be flushed out.

As soon as the engine started and the flow rate increased, the air pocket went away very quickly. Even if there was an air pocket there for a short period of time, unless there is a ton of air being pushed out the filter (which there shouldn't because that air pocket is temporarily trapped), the oil pressure should rise quickly if mostly oil is leaving the filter. I've compared time to make the oil pressure light go out on a couple of my vehicles, comparing bone dry filters to pre-filled filters, and the time is around 3-4 seconds less for pre-filled filters. That includes my V6 Tacoma with a base down and vehicle mounted oil filter. Pre-filling as much as possible will cut down the time it takes to make the low oil pressure light go out.

Added: In this part of the video you can see how fast the filter fills without any remaining air bubbles when the engine is actually started without first extended cranking without ignition. And the idle RPM is pretty low because that engine is already warm.

 

[ZeeOSix]

Forgot to ask ... if you did the same exact test measurements 10 times with the same filter under the same conditions, how repeatable are the test results? It could be that the way the oiling system leaks down isn't even consistent each time without changing anything.

 

[twX]

Low dP from low flow just makes the oil flow through the bottom half in that horizontal orientation.

This is why media restriction should have an effect on the air volume in the filter.

In the test from that video, the oil galleries in the engine were likely completely full when the engine was started. The Subaru has some empty air space downstream of the filter, so the pressure in the filter should remain low for some time, even as the flow rate increases with engine speed.

We know that the pressure in the core of the filter can't be much more than 2 psi before the oil pressure light shuts off. If the filter had no media at all, the pressure in the entire filter would remain very low even at >1000 rpm while the oil pressure light is still on. A large air pocket should remain in the filter, and the downstream galleries should fill more quickly.

On the Purolator filter, the media dP will likely exceed the bypass pressure, so the entire filter will need to fill with oil. On the Pentius filter, the media dP should remain well below atmospheric pressure, so the air pocket shouldn't compress all that much. After the oil light shuts off, pressure in the filter will rise rapidly and the air pocket will disappear.

 

[twX]

Forgot to ask ... if you did the same exact test measurements 10 times with the same filter under the same conditions, how repeatable are the test results? It could be that the way the oiling system leaks down isn't even consistent each time without changing anything.

I only took a couple of videos with the Purolator filter to analyze in detail. However, I've watched the oil pressure light on most cold starts with that filter (100+ starts). Not once would the light shut off until some time after the cold idle speed was reached, and the oil light flicker afterwards fairly often.

With the Pentius, it's visually obvious that the light shuts off well before idle rpm is reached. Had the Purolator filter peformed as well as the Pentius, even on occasion, it's something I would have noticed.

I do have one interesting update though. So far with the Pentius filter, on one cold start out of 7, it performed just as poorly as the Purolator, at 20 revolutions (including cranking). The other 6 cold starts have all been within the range of 6-8 revolutions, better than the Purolator filter has ever performed.

I can't identify anything unusual about the starting conditions of that one cold start (24 hours sitting, 16 C ambient). I was parked on more of a downward slope than usual, but I'm not sure how that could affect anything.

Regardless, this one poor performance with the Pentius filter seems to imply that it's purely a drainage issue. The Pentius filter usually helps with this a lot for whatever reason, but in some conditions, maximum drainage still occurs eventually. I'm wondering if the oil's temperature/viscosity after engine shut down and during the sitting period is relevant. Thermal expansion of the oil gallery covers or the oil filter might play a role as well.

 

[ZeeOSix]

This is why media restriction should have an effect on the air volume in the filter.

In the video, any RPM above the low cranking RPM gave enough flow to flush out the air bubble. As said, that air bubble was a trapped small volume not going anywhere until the engine fired up. They cranked the engine long enough without starting to fill the oiling system and probably achieved oil pressure even with the air bubble still in the filter. Crank any engine long enough with the starter without starting the engine and you'll eventually get an oil pressure reading after the system is filled with oil and back pressure is achieved. If the filter was super gigantic, it might be possible to have a trapped air bubble in the filter until the flow and dP higher in order to force the air bubble through the media.

In the test from that video, the oil galleries in the engine were likely completely full when the engine was started.

Yes, if you're talking about the system filling from all the cranking described above. And in that case it probably already had some oil pressure before the engine started, even though there was still the air bubble in the filter. As soon as the engine fired and the RPM increased, the air bubble was flushed out. If they had a good pressure gauge and were watching, it probably wouldn't even be possible to see the oil pressure change when the air bubble got swept out of the filter. It would need to have a sensitive high resolution oil pressure gauge and relatively high speed data acquisition system to see a small air volume flush through the system. Doubt it could be seen on a low oil pressure light or mickey mouse pressure gauge unless the air bubble was a very large volume.

The Subaru has some empty air space downstream of the filter, so the pressure in the filter should remain low for some time, even as the flow rate increases with engine speed. We know that the pressure in the core of the filter can't be much more than 2 psi before the oil pressure light shuts off. If the filter had no media at all, the pressure in the entire filter would remain very low even at >1000 rpm while the oil pressure light is still on. A large air pocket should remain in the filter, and the downstream galleries should fill more quickly.

The pressure on the dirty side of the filter where an air bubble might be trapped is a function of the oil viscosity and flow rate through the media, regardless of what's happening down stream. We know that given the right situation, an oil filter could go into bypass if the pump is putting out lots of flow through the filter before the oiling system fills and creates enough back pressure to put the pump into pressure relief. So in that case, any air trapped in the dirty side of the filter should be flushed out due to higher flow and more dP across the media like seen in the video, even if there is still air in the system downstream of the filter.

On the Purolator filter, the media dP will likely exceed the bypass pressure, so the entire filter will need to fill with oil. On the Pentius filter, the media dP should remain well below atmospheric pressure, so the air pocket shouldn't compress all that much.

Only time the dP across the media of any oil filter could exceed the bypass valve setting in a cold startup situation with a "dry" filter and/or evacuated oil galleries is if the viscosity is thick and the flow is high enough due to the pump putting out lots of flow before it hits pressure relief. And if there is that much flow going through the filter, any air bubble will almost be instantly flushed through the filter and into the oiling system. A bone dry filter installed with an initial cold start with a high pump flow rate (after engine fires) is going to flush the filter of any air pretty quickly. If you just cranked the engine without it firing up, then there would probably be an air bubble in the filter. But any RPM above that should produce enough flow (even if well below the filter bypassing) to flush any trapped air in the filter.

After the oil light shuts off, pressure in the filter will rise rapidly and the air pocket will disappear.

What flushes out any trapped air in the filter isn't the oil pressure inside the filter, but rather the flow rate and dP across the filter. If you had a see through oil filter and the filter was bone dry and there was no oiling system on the downside of the filter (ie, it just exited to ATM), and a decent amount of flow was put through the filter, then all air would be quickly swept out of the filter. It's all based on the flow rate and resulting dP across the media, not the oil pressure inside the can.

 

[ZeeOSix]

I only took a couple of videos with the Purolator filter to analyze in detail. However, I've watched the oil pressure light on most cold starts with that filter (100+ starts). Not once would the light shut off until some time after the cold idle speed was reached, and the oil light flicker afterwards fairly often.

With the Pentius, it's visually obvious that the light shuts off well before idle rpm is reached. Had the Purolator filter peformed as well as the Pentius, even on occasion, it's something I would have noticed.

I do have one interesting update though. So far with the Pentius filter, on one cold start out of 7, it performed just as poorly as the Purolator, at 20 revolutions (including cranking). The other 6 cold starts have all been within the range of 6-8 revolutions, better than the Purolator filter has ever performed.

I can't identify anything unusual about the starting conditions of that one cold start (24 hours sitting, 16 C ambient). I was parked on more of a downward slope than usual, but I'm not sure how that could affect anything.

Regardless, this one poor performance with the Pentius filter seems to imply that it's purely a drainage issue. The Pentius filter usually helps with this a lot for whatever reason, but in some conditions, maximum drainage still occurs eventually. I'm wondering if the oil's temperature/viscosity after engine shut down and during the sitting period is relevant. Thermal expansion of the oil gallery covers or the oil filter might play a role as well.

It sounds like the oiling system can drain down inconstantly, and the oil filter used may have a factor in how the system drains down (as you pointed out with the Pentius vs Purolator in most cases), either because of the ADBV performance and/or how any oil may drain out of the filter through the center tube.

Re bold paragraph in you post: Even if it takes 20-25 engine revolutions to see oil pressure it's something I wouldn't worry about because there should be plenty of oil film on parts to keep parts lubricated for that short period.

On a side note - I usually check the oil level (a lot) while cold on my Tacoma, which has the filter vertically mounted with the base down. One time the oil level was higher than it typically was, and I concluded that the oil filter and some galleries had drained back down to the sump, resulting in the noticeably higher oil level. I can see the same thing if I check the oil level hot before and after punching a hole in the top of the filter (to let it drain to the sump) before doing the oil and filter change. So for some reason, the system drained down one, but I've never detected that again.