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Well I just refuse to believe that there's going to be any relevant drop of oil pressure from before/after the filter.
 

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Well I just refuse to believe that there's going to be any relevant drop of oil pressure from before/after the filter.
I 100% agree been working on BMWs for 25+ years and if the oil pressure light is off then it is making correct pressure and there’s no reason for oil starvation. build a hundred plus engines including NASCAR cup engines and you have a great idea how the oil flows and your situation I wouldn’t give a second thought. I would put the new filter in correctly and fill with oil and be done. That little bit of oil in the filter housing is totally normal every bmw I have changed oil on always has a little old oil in there.
One of the worst oil filter snafu I have encountered was on a e32 740i about 20 years ago and it hadn’t been changed in over 40,000 miles. The guy would drain the oil and not change the filter. He couldn’t get it lose. When I got ahold of it I had to vacuum what was left of the filter out with the shop vac. Just put a new one in it and new oil and it had the correct pressure because I took the sensor out and installed a gauge to see what it actually was and it was in spec no lifter noises.


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I 100% agree been working on BMWs for 25+ years and if the oil pressure light is off then it is making correct pressure and there’s no reason for oil starvation. build a hundred plus engines including NASCAR cup engines and you have a great idea how the oil flows and your situation I wouldn’t give a second thought. I would put the new filter in correctly and fill with oil and be done. That little bit of oil in the filter housing is totally normal every bmw I have changed oil on always has a little old oil in there.
One of the worst oil filter snafu I have encountered was on a e32 740i about 20 years ago and it hadn’t been changed in over 40,000 miles. The guy would drain the oil and not change the filter. He couldn’t get it lose. When I got ahold of it I had to vacuum what was left of the filter out with the shop vac. Just put a new one in it and new oil and it had the correct pressure because I took the sensor out and installed a gauge to see what it actually was and it was in spec no lifter noises.
I think you missed the point that the OP and I was discussing.
 

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Discussion Starter · #67 · (Edited)
No normal engineer would design the system such that to waste the valuable pressurized oil going down the drain via the 4mm hole. so by logical reasoning, the assumption cannot hold even with measured data.
Like the "normal engineer" who designed the M54's CCV system? I never claimed it would be a good idea to design this way. I'm just throwing out a possibility that you could still achieve sufficient pressure and mass flow rate to the gallery, in response to your view that the stem hole goes all the way to the top and therefore the drain to sump must be the center/bottom portion of the OFH. We can debate the stem hole tangent, but isn't it irrelevant to your original question with the below picture? If you think the drain is bottom/center, why is there leftover oil at that location after unscrewing the cap??

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Re: pre-filter pressure convo with MrMCar:

This is not helpful. If you think I'm wrong then just simply state the fact with your measured data.
The oil pressure switch or sensor is located in the filtered oil path, not the pump's output dirty oil which is much higher than 50 psi.
I would think at least 10 psi warm oil , and higher with cold oil.
Did you measure unfiltered pressure, and if so at cross section are you measuring? Maybe I'm wrong but it comes across that you are presenting a hypothesis without data, and then telling someone else who has a different hypothesis that only they must supply the evidence?

In the OFH's flow pathway, the cross sectional area seems to be constantly varying. For dynamic internal flow, when cross sectional area decreases, fluid velocity increases and the static component of pressure (the component our sensors/switches measure) decreases...and vice versa. Higher measurement point also = less pressure. To state that pre-filter pressure is higher than post-filter pressure for a constantly varying pipe is like apples to oranges, unless you know you are comparing a pre-filter flow point that is equal in vertical position and cross sectional area to the oil pressure switch's location.

IF you were measuring two comparable points, yes, you'd probably have some loss in static pressure due to friction. I think there have been bench tests that use horizontal piping of constant diameter to demonstrate that with filters. But for complex plumbing like our OFH, you'd have to know velocity, height, areas, etc to establish total mechanical flow energy (potential energy via static pressure + kinetic energy via dynamic pressure) and how much is lost to friction/heating. If your point is that the oil loses mechanical energy passing through a filter, yes that's true, but it's different than static pressure alone.

Side note, according to Bentley manual table "Oil Pressure", it varies at the switch location from 7 psi (once warm) at idle to 59 psi at higher RPMs. PSI vs RPM was taken by another user here:
 

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We can debate the stem hole tangent, but isn't it irrelevant to your original question with the below picture? If you think the drain is bottom/center, why is there leftover oil at that location after unscrewing the cap??
It is hard to see the detail of the bottom hole in that pic -- quite deep in the small tube.

So there are 2 O-rings on the center rod, inserted in the tube, to create 3 separate chambers.
The top one is the filtered oil chamber.
Middle one: you proposed this connected to drain tube 11
Bottom one: TBD

What I'm saying is that your theory doesn't make sense of why it needs the bottom chamber. Why it doesn't have just one O-ring to create only 2 chambers?

On the pressures on two sides of the filter, Obviously it takes more pressure to push the oil through the filter, and Fd must be higher than Fc, unless there is zero or very little oil flow in the gallerias. What is the oil flow rate through the filter? I can't tell by looking at the crank and rod bearings, but I had seen oil spraying a lot out of the cam bearings and cam lobes lubrication. To supply this flow rate, the pump must be pushing oil hard through the filter. Look at the filter with the reinforce center hole wall to avoid being collapsed (some brands also used metal sheet with holes to support the filter). If there is small pressure delta between the dirty and the filtered sides, then there is no need for filter center hole metal mesh.
 

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Also, look at the number of the oil drain holes and their size in the head to drain the oil after came out of the cam bearings. The crank and rod bearings are much bigger and faster than the cams, so could be 3 or 4x flow rate of the head.
 

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Discussion Starter · #70 · (Edited)
It is hard to see the detail of the bottom hole in that pic -- quite deep in the small tube.

So there are 2 O-rings on the center rod, inserted in the tube, to create 3 separate chambers.
The top one is the filtered oil chamber.
Middle one: you proposed this connected to drain tube 11
Bottom one: TBD

What I'm saying is that your theory doesn't make sense of why it needs the bottom chamber. Why it doesn't have just one O-ring to create only 2 chambers?
If you haven't, try right-click -> open image in new tab for full size version. You can see the flash from camera reaches all the way to what appears to be a pool of oil and creates a reflection; it's more oil than just amber coating on the surface of metal (BTW oil in the pic is fresh / has less than 100 miles on it).

Bottom one: from the beginning of this conversation I have proposed the bottom portion of the cross section is simply part of the unfiltered oil chamber. See diagrams in my earlier posts and below.

If I understand the design function of OFH cap system related to fullness:
-cap installed: filtered and unfiltered oil remain in the OFH in their respective locations, so that the engine doesn't start with a dry OFH.
-cap removed: filtered oil and unfiltered oil drain back to the pan, e.g. for oil filter changes, or for removing OFH and not making a huge mess.

Below is an explanation of how I think it works and why you need two seals. This isn't so much my own "personal" theory as much as reading the patent last week, looking on a few other threads to get other people's views, and observing what happens when I take the cap off....

Yes, you'd definitely need two o-rings to drain both those chambers. The top o-ring prevents filtered oil from draining while the cap is on. Cap off and filtered oil drains per the orange arrow. The bottom o-ring separates unfiltered oil from the drain while the cap is on. Unfiltered oil drains per the red arrow when the seal is broken. If you wanted to design another OFH and put the drain on the bottom and unfiltered oil connected to the middle, I think you could do that / mechanically it'd work fine. However, on this particular OFH, the fact that there is leftover oil in the bottom center hole (per the above picture) suggests that the center is not the drain.

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Yes, you'd definitely need two o-rings to drain both those chambers. The top o-ring prevents filtered oil from draining while the cap is on. Cap off and filtered oil drains per the orange arrow. The bottom o-ring separates unfiltered oil from the drain while the cap is on. Unfiltered oil drains per the red arrow when the seal is broken. If you wanted to design another OFH and put the drain on the bottom and unfiltered oil connected to the middle, I think you could do that / mechanically it'd work fine. However, on this particular OFH, the fact that there is leftover oil in the bottom center hole (per the above picture) suggests that the center is not the drain.
I buy this, but it doesn't makes sense with the center rod hole connected to the drain tube 11. I need to blow into the rod hole :)
 

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Like the "normal engineer" who designed the M54's CCV system? I never claimed it would be a good idea to design this way. I'm just throwing out a possibility that you could still achieve sufficient pressure and mass flow rate to the gallery, in response to your view that the stem hole goes all the way to the top and therefore the drain to sump must be the center/bottom portion of the OFH. We can debate the stem hole tangent, but isn't it irrelevant to your original question with the below picture? If you think the drain is bottom/center, why is there leftover oil at that location after unscrewing the cap??

View attachment 944199

Re: pre-filter pressure convo with MrMCar:







Did you measure unfiltered pressure, and if so at cross section are you measuring? Maybe I'm wrong but it comes across that you are presenting a hypothesis without data, and then telling someone else who has a different hypothesis that only they must supply the evidence?

In the OFH's flow pathway, the cross sectional area seems to be constantly varying. For dynamic internal flow, when cross sectional area decreases, fluid velocity increases and the static component of pressure (the component our sensors/switches measure) decreases...and vice versa. Higher measurement point also = less pressure. To state that pre-filter pressure is higher than post-filter pressure for a constantly varying pipe is like apples to oranges, unless you know you are comparing a pre-filter flow point that is equal in vertical position and cross sectional area to the oil pressure switch's location.

IF you were measuring two comparable points, yes, you'd probably have some loss in static pressure due to friction. I think there have been bench tests that use horizontal piping of constant diameter to demonstrate that with filters. But for complex plumbing like our OFH, you'd have to know velocity, height, areas, etc to establish total mechanical flow energy (potential energy via static pressure + kinetic energy via dynamic pressure) and how much is lost to friction/heating. If your point is that the oil loses mechanical energy passing through a filter, yes that's true, but it's different than static pressure alone.

Side note, according to Bentley manual table "Oil Pressure", it varies at the switch location from 7 psi (once warm) at idle to 59 psi at higher RPMs. PSI vs RPM was taken by another user here:
If you think the drain is bottom/center, why is there leftover oil at that location after unscrewing the cap?

I just nip away at this one point:
The design of a center post was not a new one come the M52/54 engine. It's genesis (in the BMW world) started with the late version of the M30B36 engine. Now that the filter was mounted upside down, drain-back and constantly having to prime the filter housing on every engine start after sitting for 10 minutes or more would make short life for the engine, owing to the 1 to 2 second delay of getting the oil where it needed to be.

On the aforementioned engine, a metal cap is used with a long bolt and sealing ring at the bottom. If you remove the bolt/O Ring and filter. Then let it drainback. Reinstall the bolt ONLY (not removing the O Ring) and fill the OFH, oil will remain in the housing. It's the O ring or Rings that hold the canister full.

Insofar as some oil left; That is owing to the tilt of the canister and the non flat non horizontal shape of the floor of the housing itself.

I like that you are looking and studying this!
 

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Now that the filter was mounted upside down, drain-back and constantly having to prime the filter housing on every engine start after sitting for 10 minutes or more would make short life for the engine, owing to the 1 to 2 second delay of getting the oil where it needed to be.
On the aforementioned engine, a metal cap is used with a long bolt and sealing ring at the bottom.
This seems to imply that the bolt bottom O-ring is to prevent the oil in the filter drain back. I think this O-ring is for different reason.
First, let's define the drain back issue. I'm not clear if you said the M30B36 engine has the drain back issue, or it has the fix to the issue. What engine has the drain back issue? To avoid the simple drain back issue, all it needs is to have a check valve in the path from pump to filter housing (the E46 has the brown plastic valve next to the well known OFHG). The oil in the filter housing has 2 paths to drain back: the filtered oil can leak out the crank/rod bearings, and the "dirty" oil can drain back through the pump if it has no check valve. Which path are you referring to on the drain back?
 

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In my post I stated the "first".
If a filter or filter canister is higher than the sump and upside down, it will drain back to the sump unless it is stopped.

This applies to almost all BMWs now.
BTW same filter and similar canister on the 06-07 Ford GT. I service 2 of them.
 

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On the aforementioned engine, a metal cap is used with a long bolt and sealing ring at the bottom. If you remove the bolt/O Ring and filter. Then let it drainback. Reinstall the bolt ONLY (not removing the O Ring) and fill the OFH, oil will remain in the housing. It's the O ring or Rings that hold the canister full.
The O-ring is for empty the oil (cleaned and dirty) out of the "can" when replacing the filter. It was not designed to avoid the drain back during normal shut off the engine, as the check valve after the pump should take care the drain back issue.
 

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Try something. Replace your oil filter, leave the 2 small O Rings off. Then start your car after 2 days.

You may or not hear your lifters. However you will hear your bearings waiting for the filter housing to prime.
 

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Try something. Replace your oil filter, leave the 2 small O Rings off. Then start your car after 2 days.
I know that without the O-ring on the rod the oil will drain, because when they designed the new upside down filter can, they added the drain hole to empty the oil can (the old filter can was removed off the engine to empty the oil, or remove the bolt to drain the oil), and so they also added the O-ring to block out the drain hole in normal usage.
So, you either have the added drain hole and the O-ring, or no drain hole and no O-ring. The point is that turning the old design filter can upside down in the later design did not cause the drain back issue, but if they added the drain hole (for convenience of empty the oil) then of course they also needed the O-ring.
 

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I did, and the rod bottom hole goes through the whole length to the top end to the unfiltered oil. So the section between the 2 o-rings is connected to pressurized dirty oil, and this cannot be connected to drain tube 11.
This proves that the section D between the O-rings is not connected to the drain tube 11 as shown in the patent drawing.
My logic on this:
Section D connoted to dirty oil—the same oil surrounding the outside of the filter. The outside filter oil cannot drain down due to the check valve in the pump path, so it connected to section D via a hidden tube.
The bottom section below D is the drain. When the cap removed, oil in D is drained.
Why the cap rod has hole? Without this vent hole, you cannot pull the cap up to remove, as the dirty filled the entire section outside the filter and pulling up the cap creates suction which could open the check valve causing oil to drain past the check valve which is no good.
 
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