8 cylinder front engine iconic vehicle
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By hernanca
#191213
Note: I am aware of the other thread ("Oil Breather Can theory.") but it was centered around 16V CCV systems. Rather than dilute that thread with additional 32V discussion, I started this new one instead.

First off: My S3 side plenums have only accumulated about a tablespoon of oil in them over the last 3000-or-so miles, and we have not gotten to check under the throttle yet. I have also not had any oil usage issues.

Worth noting: this motor already has a Greg Brown oil pan spacer and windage trays (from a 2007 GB bottom end build under the PO). It also has (I believe both) S4 intake & S4 exhaust valves.

However, this is an S3 (32V) 6.5L stroker motor that has not been SharkTuned yet and I plan to remedy that as soon as possible.

In anticipation of this upcoming Shark/Dyno Tuning, and also as part of "while I'm in there" on a TB/WP/other-things job, I started thinking about Crank Case Ventilation (CCV). I am adding various related bits while the cam covers are off which will enable easy CCV configuration options later, if needed.

Unfortunately (for everyone involved), Greg Brown would not sell me, or the shop where I am having the work done, his basic cam cover oil control kit that he has sold to others in the past. I explained over messaging that the shop doing the work for me is extremely reputable and professional and would not copy his work, but he never replied. I probably should have called Greg and tried to talk to him, or had others try to talk to him for me, but frankly, I don't have time to try to sweet talk someone into doing something they say they don't want to do. So I just had to accept Greg's decision and move on.

I bought potdog's solution instead and will have that installed under the cam covers. I will be getting rid of the black tube under the passenger side cam cover. Potdog's cam cover baffles will be installed under all four cam cover ports, and I will also have installed a total of four opened up elbows (two on each cam cover).

Initially, all the hose plumbing will be put back together per the stock S3 configuration, essentially*, with the driver's (left) side cam elbows blocked off. See pics below from the 928 Specialists site - the 85-86.5 32V CCV system is very similar to 87-88 32V except the 85-86.5 32V does not have that patented "Y" fitting at the throttle housing.

US 85-86.5 32v (S3) stock CCV system:
Image

87-88 stock CCV system:
Image

* The exceptions to the stock S3 CCV configuration being I also plan to add some clear hoses or otherwise be able to check for oil vapor movement during tuning runs, and I want to easily fit vacuum/pressure gauges as follows:

A. at least one at each cam cover
B. one at the oil filler neck, and
C. one (or two) at angled exhaust taps (my vacuum sources).

The shop has not gotten to the oil filler neck yet, but I also plan on adding additional baffling under there. This motor build was completed in December 2007, so I don't know what additional under-the-oil-filler-neck baffling would have been available and installed at that time.

I plan on letting the vacuum readings and oil vapor observations from the tuning runs help me determine whether I need something better than stock for the final CCV plumbing configurations, and also help me figure out what that final configuration should look like. For now, based on reading most of the Gazillion 928 CCV threads on the topic, including learning about Herman K's, Alan's, Tuomo's, Fred's, Tony's (Las Vegas), Lizard's, and other's configurations, I came up with the following possible configuration for my 6.5L S3 (32V) motor:

Image

The black symbols depicting a triangle with a bar represent check valves to prevent flow in undesired directions. The one orange symbol depicting the same would be a more sophisticated valve that is designed to prevent undesired flow and also ensure (if needed) that I don't get too much vacuum. Sizing this latter valve will be based on motor vacuum and pressure readings during tuning runs.

The only difference between this version 4 and the prior version 3 is that version 3 did not connect the oil filler neck area (two ports) to the cam cover plumbing.

The goals I had in mind with the above CCV plumbing layout were:

1. zero oil vapor in the intake
2. improve CCV
3. introduce clean air to flush out the system when possible
4. have some minor vacuum when possible
5. balance crankcase pressures if possible.

I would have liked a closed system solution using a vacuum pump, but I am concerned about the longevity of such a system when applied to my S3 motor. Specifically, I might not have enough oil going through my CCV to keep a vacuum pump happy. With how costly those systems can be, I am not prepared to risk trying one.

Feedback/opinions (Nomex suit ON!) are welcome on what I have come up with so far!
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By smiffypr
#191242
I think you are doing the right thing by having air flow into the cam covers. Sucking air out there is causing air flow up the places where oil is trying to drain down and that is bound to cause more oil to be picked up in the air flow. But, as you are doing that, you don't need any baffles under the cam covers.
My experience with a "louvre" baffle under the oil filler neck was that it added more oil to the breathings for track use, I think the baffle gets covered in oil and oil that drips off is just picked up by the air flow.
I think your connection to the base of the oil filler neck is a waste of time, it will never do anything.
Make sure your one way valves in the drains are good as you will have more vacuum inside your provents than in the sump.
Personally I don't like provents, they work okay with a slight oil mist, but clog up with more oil, then, in a positive pressure situation, blow all the oil out the pressure relief valve. If I were you I would do some testing with provent under suction (using a wet and dry vacuum) and introduce some water spray to the intake, and see what happens when the "filter" gets saturated. You would be much better off with a cyclonic oil separator.
I would recommend using transparent hose on the inlet and outlet of the provents as you will quickly see if the hose gets oil stained, and hence find out if they are doing their job.
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By hernanca
#191249
Thank you for the feedback, smiffypr!
smiffypr wrote: Thu Dec 29, 2022 6:42 am I think you are doing the right thing by having air flow into the cam covers. Sucking air out there is causing air flow up the places where oil is trying to drain down and that is bound to cause more oil to be picked up in the air flow. But, as you are doing that, you don't need any baffles under the cam covers.
I wondered about that. However, at this point, I want to leave my options open, so if it won't hinder flow going into the cam covers I want to add them in case a later a solution flowing out of the cam covers is developed. Though at this time I do tend to favor only flowing into the cam covers.
smiffypr wrote: Thu Dec 29, 2022 6:42 am My experience with a "louvre" baffle under the oil filler neck was that it added more oil to the breathings for track use, I think the baffle gets covered in oil and oil that drips off is just picked up by the air flow.
That makes sense. I suspect the current set up simply has the 928 International deflector. From your experience, it sounds like just leaving that deflector would be best. To be clear, the louvered style baffling I am considering would be along the lines of what Tony, GB, and Hans have come up with and would NOT include any scrubbies/filler because I believe scrubbies/filler would hold even more oil in the manner you are pointing out.

I will re-read some of the CCV threads because I thought at least one indicated significant reduction in oil loss due to only adding a louvered style baffle (without scrubbies/fillers). I will look to see if any other changes were made at the same time that could explain their results. I also realize mine is not a GTS motor, and the results I read about may have applied to a GTS motor which may not be the best reference since the GTS motors seem to have a magnified set of oiling and CCV issues.
smiffypr wrote: Thu Dec 29, 2022 6:42 am
I think your connection to the base of the oil filler neck is a waste of time, it will never do anything.
I went through several scenarios in my head and it seemed there MIGHT be some brief scenarios where it could flow oil vapors or at least remain open and thus help balance crankcase pulses (along the lines of what PTUOMOV points out). Without real vacuum and pressure numbers from those different scenarios, however, I could not say for sure. Version 3 did not have that, and it may be that the numbers I collect will show it unecessary:
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smiffypr wrote: Thu Dec 29, 2022 6:42 am Make sure your one way valves in the drains are good as you will have more vacuum inside your provents than in the sump.
I did not think of this! Excellent point!
smiffypr wrote: Thu Dec 29, 2022 6:42 am Personally I don't like provents, they work okay with a slight oil mist, but clog up with more oil, then, in a positive pressure situation, blow all the oil out the pressure relief valve. If I were you I would do some testing with provent under suction (using a wet and dry vacuum) and introduce some water spray to the intake, and see what happens when the "filter" gets saturated. You would be much better off with a cyclonic oil separator.
I will look into cyclonic oil separators (recommendations would be welcome!). I understand the ProVent has an alternate mesh-like element which can be special ordered. It traps less oil, but also clogs less.
smiffypr wrote: Thu Dec 29, 2022 6:42 am I would recommend using transparent hose on the inlet and outlet of the provents as you will quickly see if the hose gets oil stained, and hence find out if they are doing their job.
Agree - I will add that to the list of places to add transparent hose!
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By worf
#191290
Carlos, I’ll try to process all of this soon.

In the meantime: The stock oil filler neck can’t vent enough crankcase pressure. Your diagram - V3 as I understand it - breaths the crank case *less* than stock.
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By hernanca
#191299
worf wrote: Thu Dec 29, 2022 9:33 am Carlos, I’ll try to process all of this soon.
:thumbup:

worf wrote: Thu Dec 29, 2022 9:33 am In the meantime: The stock oil filler neck can’t vent enough crankcase pressure. Your diagram - V3 as I understand it - breaths the crank case *less* than stock.
Well, that won't work then! I was thinking I need 3x the breathing since it is a 6.5L motor and the stock setup seems insufficient for the 5L.

It is not obvious in the diagrams and I forgot to include the detail, but I was thinking of adding additional ports to the filler neck and/or a Louie style oil filler cap, to route to the AOS's (ProVents in the diagrams). However, what you are saying sounds in line with what Crumpler experienced with his "nuclear option" (holed oil cap). May not be apples to apples since he has forced induction, but I was surprised he vented oil out the top of the cap with that setup.

I also haven't specified the hose sizes, but know they need to be as large as possible/practical. (Edit: and without any of the stock restrictors.)
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By maddog2020
#191342
there are other air/oil separators out there

I'm using this one.

https://www.mishimoto.com/universal-hig ... n-kit.html

On initial break in it was dry as a bone with using Hans's oil filler blanking plate and his oil shield underneath it, and a custom oil filler tube on the front of the engine. that drains to the front of the pan.
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By worf
#191359
Starting from scratch…

The best breathing system for an N.A. 5-liter 928(*) is a ~1.25” hole in the crank case.

Everything after that is one or both of EPA requirements and plumbing to keep windage from coating the engine compartment in oil and to keep oil in the sump.

(*) Should be good for almost any 5-liter motor.
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By hernanca
#191374
maddog2020 wrote: Thu Dec 29, 2022 4:04 pm there are other air/oil separators out there

I'm using this one.

https://www.mishimoto.com/universal-hig ... n-kit.html

On initial break in it was dry as a bone with using Hans's oil filler blanking plate and his oil shield underneath it, and a custom oil filler tube on the front of the engine. that drains to the front of the pan.
maddog, your motor is a stroked beast, correct!? Have you tested this AOS at high revs and found it sufficient? The specs that come up from that link make me think two of these might be needed as well? Admittedly, I am only speaking from gut feeling based on what I have read and rough calculations (see below)!

Image
worf wrote: Thu Dec 29, 2022 5:39 pm Starting from scratch…

The best breathing system for an N.A. 5-liter 928(*) is a ~1.25” hole in the crank case.

Everything after that is one or both of EPA requirements and plumbing to keep windage from coating the engine compartment in oil and to keep oil in the sump.

(*) Should be good for almost any 5-liter motor.
Thank you, D! I needed such a reference!

So, using my handy-dandy rough* pipe size equivalents lookup chart, and the fact that 6.5L is 1.3x a 5L:
1.3x that 1.25" ID pipe (using areas) gives a 1.43" ID pipe, which is about equivalent to two 1" ID pipes!

Image
(*rough for exhaust pipes because exhaust pipes are referred to using OD and this table does not account for pipe thickness and how that becomes more of a factor the smaller you go! For our purposes, however, we are talking ID, so it is perfect!)

Now, for me, the question remains, does the oil filler neck (and anything under it) ever get a narrower (interior cross section or equiv.) than the required 1.6 sq inch area I need for the stroker!?

Also, smiffy's comment (snapshot, below) is concerning me. I don't have actual vacuum/pressure numbers yet, but is it possible that oil drainage from a vacuumed AOS becomes a problem?
Image
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By worf
#191387
Two 1” breather hoses is what I would have suggested.
hernanca wrote: Thu Dec 29, 2022 9:29 pm … but is it possible that oil drainage from a vacuumed AOS becomes a problem?
In your diagram, what is the source of vacuum pressure in the crank case?

In a stock set-up what is the source of intermittent crank case vacuum?

In the “ideal” hole-in-the-case setup what, if anything, results in crank case vacuum?

Now, from the other side of the context, why is a AOS, intended to filter all crank cases gases from a line (or lines) with less than 1.25” area being overwhelmed by oil?

Lets go extreme: If you plum a single 1/2” line from a 5 or 6.5 liter N.A. as the only breather what happens at its outlet?

Note that I’m trying to lead towards understanding: the veritable fishing instead of fish since there are many possible solutions depending upon the requirements imposed externally (e.g. emissions compliance, engine bay space, fabrication wherewithal, etc.)
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By hernanca
#191394
worf wrote: Thu Dec 29, 2022 11:10 pm Two 1” breather hoses is what I would have suggested.
hernanca wrote: Thu Dec 29, 2022 9:29 pm … but is it possible that oil drainage from a vacuumed AOS becomes a problem?
A. In your diagram, what is the source of vacuum pressure in the crank case?

B. In a stock set-up what is the source of intermittent crank case vacuum?

C. In the “ideal” hole-in-the-case setup what, if anything, results in crank case vacuum?

D. Now, from the other side of the context, why is a AOS, intended to filter all crank cases gases from a line (or lines) with less than 1.25” area being overwhelmed by oil?

E. Lets go extreme: If you plum a single 1/2” line from a 5 or 6.5 liter N.A. as the only breather what happens at its outlet?

Note that I’m trying to lead towards understanding: the veritable fishing instead of fish since there are many possible solutions depending upon the requirements imposed externally (e.g. emissions compliance, engine bay space, fabrication wherewithal, etc.)
I'm taking the shortcut to respond this late at night - I labeled your questions, Sensei. Answers (I think) I know:

A. In my diagrams, the exhaust is the source of any crankcase vacuum, pulling through the ProVent AOS and the Oil Filler Neck (OFN). Vacuum should be stronger at higher RPMs. The source of pressure in the crankcase is any blow-by, which should also be greater at higher RPMs.

B. In the stock system, intermittent vacuum is provided by the throttle housing at idle and part throttle. It would be strongest at idle but a restrictor limits it (I think).

C. I would say nothing would create vacuum in that setup. Hmmm.

D. I am not sure, but if I am tracking, I would venture the guess of "because it is too small for the task"?

E. Also not sure (I had to take Physics I & 2, 2x in college, OK!), but I would venture to guess that a single 1/2 inch line as the only breather would act a whole lot like that hot 2 Litre full bottle of Root Beer when I shook it a little while opening it in the kitchen - a freakin geyser!?

Hmmm.
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By maddog2020
#191437
The challenge is to not make CCV too complicated. Simple things to keep in mind.
1. Small vents will have more velocity and carry more oil.
2. Cylinder head drains are too small so pulling any combination of air/oil from the heads is somewhat counter productive.
3. There is no magic bullet.

I haven't made full throttle runs. but the provent created a batman style smoke screen when I used it from DR's kit years ago.
It wasn't until I added the large air vent to the mix from the oil filler neck.

My initial run in on the current setup with the ITB's was to just vent to atmosphere and only use the Hans oil block off plate with a 1" hose going into the AOS, using Hans's air oil separator below the block off plates. & no venting from the heads. this is my plan going forward.
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By hernanca
#191469
worf wrote: Thu Dec 29, 2022 11:10 pm Two 1” breather hoses is what I would have suggested.
Forgot to mention I was glad to hear this! :thumbup:
maddog2020 wrote: Fri Dec 30, 2022 10:56 am The challenge is to not make CCV too complicated.
Simple things to keep in mind.
1. Small vents will have more velocity and carry more oil.
2. Cylinder head drains are too small so pulling any combination of air/oil from the heads is somewhat counter productive.
3. There is no magic bullet.
Thank you maddog. For my purposes, I agree on keeping it simple and the importance of the listed items!
maddog2020 wrote: Fri Dec 30, 2022 10:56 am My initial run in on the current setup with the ITB's was to just vent to atmosphere and only use the Hans oil block off plate with a 1" hose going into the AOS, using Hans's air oil separator below the block off plates. & no venting from the heads. this is my plan going forward.
Thank you for those data points! I recall that @hans14914 (hoping he will chime in :smile: ) designed his bits for his supercharged application, but I don't know his final CCV set up. So far in my paper scratches, however, I still believe I may need double 1" venting hoses for my (modest) application.

Of course, the other big variable is "how much blow-by"? I read somewhere there was usually some range of small percentages of [something (engine size? HP?)] which gave us the likely blow-by min and max numbers. It may be that a super "tight" engine can get away with a CCV system that would normally be less than ideal for that size/HP motor and its intended usage. If worf's 1.25" for 5L is based on a worst case / max blow-by value, I am good with designing for that worse case scenario even if my motor does not need it, because I know I would be kicking myself if I found myself in the opposite situation!!

On to a more simplified Version 5, assuming I got most of worf's answers right....

Edit: Anyone know the ID of the cam cover elbows, assuming any restrictions are routed out?
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By hans14914
#191524
I am taking a bit of vacation right now. I will likely have a chance to sit down and reply later Sunday or Monday.

I made to alternate versions to the original filler neck. One with a single -10ORB port (for use with a GZ Motorsports Sportsman pump), and then a single 1" hose nipple. It would be possible for me to make another filler with two ports, but I can tell you running the lines around the water bridge will not be fun.

I can order some XRP -16 Extreme Pro Plus to see how well that routes through. the 3" bend radius may be a problem for the driver side around the bridge. It would easily fit through the passenger opening. The -16 HS79-CSM hose would be a better alternative. It is slightly smaller in OD and has a 2" bend radius, but its pricey stuff.

Back later in the weekend to discuss theory, but a vacuum pump is a pretty easily solution in the original smog pump area and will evacuate plenty with a single -10 hose. It may even be cheaper than multiple separators and all that plumbing.

Happy New Years!
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By worf
#191610
I have a motor to finish out in the shop. But, I've apparently come down with a stomach-bug/flu/plague of some sort. Best I do something without warranty exposure like pontificate on crankcase breathing.

Everything below is based upon my imperfect understanding of the subject.

Thus, you have been warned LOL.

Square one.

Internal combustion engine crank cases get pressurized due to slight escape of high-pressure combustion gases past piston rings no matter how well the rings seal. Without a means to relieve the crank case pressure seals will be pushed out onto the pavement.

The simplest form of crank case breather "system" is a big hole somewhere in the crank case. Let's imagine that it's in the engine valley. So, we have a big hole through which you can look down and see the crank. Assuming we've sized the hole appropriately our crank case will stay at a low-enough pressure to retain seals.

When the engine is running, the inside of the crank case is basically a blender. With our hole in the top it's like making frozen margaritas with a hole in the blender's cover. Our imaginary engine will vent a bit of the contents into the engine valley. We'd see this as "oily suds" migrating out of the hole. This is the effect of windage: the crank's blender effect resulting in the foam and the foam essentially "trapping" the crank case pressure in little bubbles. The foam needs to expand somewhere until the bubbles burst and our hole in the crank case is the only way. The foam will eventually drip over the edge of the valley if doesn't separate into a pool of oil in the valley and gases escaped to atmosphere.

We don't really want to leave a trail of oil foam dripping out of the engine valley. Nor do we want a pool of oil in the valley. We can "solve" this by simply attaching a pipe, of the same or larger diameter as the hole, pointing straight up. Depending upon the specifics of our engine that pipe would need to be several feet high if we don't want any liquid oil dripping out of the top opening. That pipe is a very stupid-simple air-oil separator. It more-or-less uses gravity to break the bubbles in the oil foam.

Now, of course, we've got at least a couple of problems with this system. The pipe is ugly, it probably gets in the way of all the intake bits that we need to feed the engine, we can't close the hood, and last, but not least, it's not going to pass a visual check by any state inspection(*) authority that still cares.

At this point *every single thing* we do to make our breather system better causes complications.

(*)That latter issue requires a short history lesson:

In the dawn of the combustion age, a crank case breather system was indeed just a hole (or five) somewhere in the engine. But, crank case gases are noxious. At some point prior to the 70s (I've never bothered to figure out exactly when) various regulations were enacted to deal with crank case combustion gases. Where we find ourselves in the 928 context and indeed will all cars made after the 70s is that crank case gases must be reburned in the engine to clean them up before atmospheric release.

maddog2020 wrote: Fri Dec 30, 2022 10:56 am The challenge is to not make CCV too complicated.
This in a nutshell. Everything we find on our engines that isn't like the above "stupid simply" system just adds complication and new failure modes.

maddog2020 wrote: Fri Dec 30, 2022 10:56 am 1. Small vents will have more velocity and carry more oil.
worf wrote: Thu Dec 29, 2022 11:10 pm E. Lets go extreme: If you plum a single 1/2” line from a 5 or 6.5 liter N.A. as the only breather what happens at its outlet?
hernanca wrote: Fri Dec 30, 2022 12:01 am E. Also not sure (I had to take Physics I & 2, 2x in college, OK!), but I would venture to guess that a single 1/2 inch line as the only breather would act a whole lot like that hot 2 Litre full bottle of Root Beer when I shook it a little while opening it in the kitchen - a freakin geyser!?
Right.

The crank case (CC) pressure builds, we've given it an outlet, and it wants to go to the lower-pressure side of that hole. The speed at which the foam is ejected through the pressure relief can be (more-or-less(*)) calculated using incompressible fluid flow math. If the hole is 1/2" rather than 1" then the speed through the 1/2" hole is more-than-double that of the 1" hole (area rule, I'm just getting the math on the dart board.)

The difference between our big block hole and a tiny block hole is the energy imparted to the foam by its escape. And it is that energy that gets in our way.

But, in our way, how? Why do we care?

Well, probably because
- we don't want to loose a quart of oil to oil foam every few minutes
- we don't want to leave a trail of oil foam on the road

We want to kill the foam, separate the oil and combustion gases, release the combustion gases - somewhere not in the crank case - and return the oil to the engine.

How do we do that?

Well, let's go back to soapy foam. How do we turn soapy foam back into "liquidy soap?"

We smack it. Repeatedly.

What we are actually doing is imparting momentum change. We're imparting momentum to the bubbles. We're distorting them so that they burst and the soap goes one way and the air in the bubbles goes another way. If our soapy foam is "slow" and composed of big bubbles we don't need a lot of momentum change to break the big bubbles. But, if our soapy foam is composed of lots of tiny bubbles then we need much more momentum change to break the bubbles.

In an extreme situation, what comes out of a far-too-small breather hose might actually look like pure liquid oil but it is in fact a super fine oil foam with super-tiny bubbles.

So, we want big holes so that our foam is lazy and composed of big bubbles that don't require a lot of effort to bust.

(*) Incompressible fluid flow math is easy. It was developed centuries ago to move water around. Water is pretty incompressible. At the time it probably wasn't even called "incompressible fluid flow math" it was just called "fluid flow math." Air is pretty compressible though. The simple math doesn't work well once you get velocity, friction and big pressure differentials. My "pet" theory is that, until very recently when almost-free CPU cycles could be thrown at computational fluid dynamics to model breather systems with compressible fluid flow math, car companies were using the simple math and thus why so many breather systems just don't work very well.

In the "stupid simple" CC vent system with the pipe sticking out of the top of the block, the foam has to fight gravity. That fight results in momentum change. Also the friction of the foam along the pipe walls changes momentum. Thus, we get separation of the foam. Oil drips back down the tube and combustion gases escape, provided that the diameter of our pipe and hole allows enough area for the foam to move up at low velocity and the oil to drip back down. If we make the pipe too small, foam velocity - therefore energy - will be high. We'll need more pipe length to allow separation via gravity. And we'll impart upward momentum to the liquid oil trying to drain back down the tube.

maddog2020 wrote: Fri Dec 30, 2022 10:56 am 3. There is no magic bullet.
And then this. There are tons of things working against us here. Auto manufacturers have been working on this for 5 decades now and, in my mind at least, haven't gotten it completely solved even today. I "get" to drain a 1/4 quart of oil out of the left-side charge pipe of my 991 Turbo yearly because the AOS system isn't good enough.

What makes the manufacturers' jobs harder is, of course, the requirement to make the CC breather system a closed system.

worf wrote: Thu Dec 29, 2022 11:10 pm A. In your diagram, what is the source of vacuum pressure in the crank case?
hernanca wrote: Thu Dec 29, 2022 9:29 pm A. In my diagrams, the exhaust is the source of any crankcase vacuum, pulling through the ProVent AOS and the Oil Filler Neck (OFN). Vacuum should be stronger at higher RPMs. The source of pressure in the crankcase is any blow-by, which should also be greater at higher RPMs.
Looking at your V3 system it was not apparent that you intended the outlet-side of the AOS to be vacuumed. I assumed that the lines to the exhaust were simply to vent the CC gas in a way that might fool inspectors.

I'll come back to this.

worf wrote: Thu Dec 29, 2022 11:10 pm B. In a stock set-up what is the source of intermittent crank case vacuum?
hernanca wrote: Thu Dec 29, 2022 9:29 pm B. In the stock system, intermittent vacuum is provided by the throttle housing at idle and part throttle. It would be strongest at idle but a restrictor limits it (I think).
You are at least partially correct. My knowledge of pre-'87 plumbing fails me at this point. What I now write will only be completely accurate for S4+.

The breather lines from the cam cover and oil filler neck are plumbed upstream of the throttle plate. This is not a super-high vacuum area. Obviously behind the plate - engine side - is very-high vacuum. Obviously the "filter side" of the throttle plate where the breathers are plumbed is somewhat less than atmospheric but not a lot. (I have verified this by measuring vacuum to the vacuum system lines that, on the S4 air guide, are in front of, behind, and at the plate.) At idle there's minimal vacuum effect in front of the throttle plate. There's some. Just not a lot.

However, the piece that connects the hoses to the air guide is rather curious. It has a very specific profile, orientation, and a conical section such that when properly installed is "flush" with the curved surface of the air guide.

It's a venturi.

As air velocity in the air guide increases, suction on the breather hoses increases due to venturi effect. Venturi effect is another form of momentum transfer. As the air passes over the hole in the breather-hose-connecting piece it transfers some "toward the throttle plate" momentum to the gases at the mouth of the connecting piece and gets them moving towards the throttle plate. Those gases moving away from the hose result in differential pressure with the gases further in the hose and gets them moving towards the hole.

Back to:

hernanca wrote: Thu Dec 29, 2022 9:29 pm A. In my diagrams, the exhaust is the source of any crankcase vacuum, pulling through the ProVent AOS and the Oil Filler Neck (OFN). Vacuum should be stronger at higher RPMs. The source of pressure in the crankcase is any blow-by, which should also be greater at higher RPMs.
You are proposing to use venturi effect from the exhaust gas to vacuum the engine.

It may be that what you propose will work. I've never thought about it. One issue with it is the length of the lines and "pumping friction." It takes force to suck the CC gases out of those lines. You have friction force that is proportional to the length of the line opposing the sucking force. It's not clear to me that the exhaust gas energy would provide sufficient venturi effect to overcome pumping friction. Maybe.

On the other hand, why do you need this?

Our "stupid simple" CC ventilation system doesn't need vacuum. The factory set up uses venturi effect to help move CC gases to the intake because regulations require that CC gases be re-burned in the intake.

Look at it another way: In our "stupid simple" CC ventilation system, what happens when we apply a vacuum to the top of our tube? Our oil foam will just flow out faster and be harder to separate.

worf wrote: Thu Dec 29, 2022 11:10 pm C. In the “ideal” hole-in-the-case setup what, if anything, results in crank case vacuum?
hernanca wrote: Thu Dec 29, 2022 9:29 pm C. I would say nothing would create vacuum in that setup. Hmmm.
This was a bit of a trick question. I wanted you to consider the purpose of vacuum in the stock system.

The answer is that there really isn't that much vacuum in the stock system. What vacuum there is, is simply to assist in getting the CC gases back into the intake to re-burn them for regulatory purposes. I believe that the effect is minimal. And vacuum isn't a necessary component of the breathing system. It can help. But, you can still have an effective breathing system without vacuum.

worf wrote: Thu Dec 29, 2022 11:10 pm D. Now, from the other side of the context, why is a AOS, intended to filter all crank cases gases from a line (or lines) with less than 1.25” area being overwhelmed by oil?
hernanca wrote: Thu Dec 29, 2022 9:29 pm D. I am not sure, but if I am tracking, I would venture the guess of "because it is too small for the task"?
Yeah. But, that answer would not get you full credit on the exam because "you didn't show your work."

The answer is above. The too small line to the AOS results in too much foam energy and/or the AOS simply isn't "big" enough and can't remove the energy from the foam fast enough.

At this point, we've looked at "theory" except for windage. Or in other words, can we impart less energy to the foam before it gets to the 'hole' in the crank case? Specifically, can we make less foam?

Of course the answer is yes. There are plenty of starting points:

- keep liquid oil away from the crank: pan spacers, windage trays, crank scrapers.
- vacuum pump: don't keep any oil in the sump for the crank to whip up into a foam.

At this point the reality of constraints of the 928 engine press in upon us.

Where in the block can we "poke" a 1.5" hole? There aren't too many places. The oil fill area already has a big hole. But, we've got all sorts of stuff on top and around it that limit how much breather hose we can attach to it unless we do some serious redesign.

Also the oil fill area is very, very not good from a windage perspective since it's exactly like a hole in the cover of our blender. Heck it's more like not having a cover on our blender at all which is why we have so many variations of stuff to put on top of it.

We can make those variations more effective by better controlling oil in the sump via one or more of the methods above before the foam gets to it though.

Other than the hole in the block for the neck, we don't have a lot of options. Where are we going to poke a hole in the side of the block? And if we do we're going to have a LOT of foam. Well, there are the heads and they're almost the same thing as the crank case from a breathing perspective.

maddog2020 wrote: Fri Dec 30, 2022 10:56 am 2. Cylinder head drains are too small so pulling any combination of air/oil from the heads is somewhat counter productive.
I'm going to disagree slightly here: Cylinder head has several issues, so pulling any combination of air/oil from the heads is less effective that pulling it from the crank case.

The exhaust cams are immersed in oil at high RPM and whip up their own air oil foam. This problem is, IMO, a combination of too small drain holes, too much oil flow, and crank case pressure preventing oil return because the holes in the filler neck are just too small.

If the pressure in the heads were less the oil drains would be a little less too-small.

Last, the factory "plastic can" under the right-side cam cover at the rear is just a suction device that forces oil into the intake.

But, let's go back to total crank case and cam cover breathing. The stock 32v systems vent only through the the passenger side cam cover. (The late variations of the breather system added one hose to the driver side but didn't increase CC breathing volume.)

I think a lot of the "effect" of breathing from the heads is simply that of a "too small hose" imparting energy to the foam on its way out coupled with a bad windage situation from the exhaust cams.

... where am "I at" with 928 CC ventilation.

I've gone through, probably, a dozen variations of breather systems on 5.0 liter NA, 5.0 liter supercharged, and 6.5 liter motors over the years across many dozen 928s. Some of those variations where constrained by engine bay room, parts availability, my wherewithal to make parts when parts became unavailable, and expense/desire on the client side.

To date, the most effective system I've built and observed was on an N.A. 5.0 GT motor. It included windage trays for 1/5, 2/6, 3/7, an oil filler baffle, four cam cover breather elbows each with restrictions drilled-out, baffle plates underneath them, and a ProVent. The oil filler and three of the four cam cover elbows are vented to the ProVent. The fourth elbow is (effectively, but not actually) vented to atmosphere. This breather system seems to leave the ProVent almost dry. It's not clear to me that the owner drives foot-to-the-floor a lot. But he does report that the ProVent remains pretty dry. (And he's savvy about these things, I trust his observations.)

That above system is an evolution of another 5.0 GT motor. The predecessor motor was identical except for venting the fourth elbow into the ProVent. That motor did "wet" the ProVent noticeably more than the one that vents the fourth elbow to atmosphere.

Last, before I state my personal conclusion, I'll relate the story of the Zyclomat Rot car which was the subject of a number of pictures in the Random Picture thread circa 2020. This 928 came to me barely running and puking oil. It had had a "Victor" supercharger added to it. At some point someone had screwed up windage (long story) and attempted to cure the problem thus created by venting the entire 5.0 supercharged motor with a single 1/2" line from the top of the stock (GTS-style) oil filler neck.

Based upon the exposition above, I assume you all can guess, very accurately, how that turned out.

What I did to that Supercharged 5.0 was vent with five 1/2" lines to atmosphere: oil filler and four cam cover elbows - elbows drilled, with NO baffle plates under, but no OE "suction cups" either. I'll not describe the actual plumbing since it doesn't change the epilogue.

(Note, that this setup is intended to be an interim solution. Next time I see it, we intend to make it a closed system.)

After many miles of supercharged operation the owner - who quite enjoys foot-to-the-floor operation - reports having never seen liquid oil from the breather hoses. When I was "re-shark-tuning" it I did a LOT of WOT and high-load operation and also never saw liquid oil from the breather hoses.

There are two explanations for the "success" of Zyclomat Rot car:
- vastly increased breather volume
- many linear feet of breather hose: the pumping friction acts as an air/oil separator.

EDIT: The Zyclomat 928 has a pan spacer and oil neck baffle.

One item left to determine is how much oil is settling in the hoses: One thing for me to ping the owner about in the Spring.

So, my personal conclusion for 32v 928 crankcase ventilation:
- Remove the stupid "suction" cup under the passenger cover.
- Total breather volume needs to be the equivalent of three 1/2" lines for a 5.0 N.A. motor. This is about double the stock volume.
- The more places from which you can vent the better.
- From wherever you vent, you need to control windage.
- The oil filler neck port has limited utility because of windage. I believe that the various available baffles work, but they also work more effectively if the actual breathing occurs as far towards the top of the neck as possible. That extra "fight" against gravity and the need to "turn" imparts useful momentum change. (Thus, my preference for GTS necks that have NO ports at the base, but a single port - that can be drilled out - that's roughly 1/2" diameter right behind the cap.)
Last edited by worf on Sun Jan 01, 2023 12:22 pm, edited 1 time in total.
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User avatar
By Crumpler
#191843
I would consider the above treatise an excellent resource. More so, from one subjected to going to potty frequently.
:beerchug:
User avatar
By worf
#191851
Edit added to the above:

The Zyclomat 928 has a pan spacer and oil neck baffle.
User avatar
By hernanca
#191929
Well, Happy New Year, everyone!

Hans, thank you for referencing that tubing and those connection types. It was Greek when I first read it, but I looked them up and learned something. That one tubing MUST be pricey since at least one site said "call for pricing".... No need to fabricate anything (yet) - I am more interested in the rest of the crankcase breathing setup you have on your supercharged 928 and whether you are satisfied with it. What is appealing to me about the vacuum pump solution is that it is a relatively closed system and just moves the oil vapor from one place to another.

I hope you had the right amount of time off.

D., Holy Shyte man! You made things very clear for me with that simple zokusha/bosozoku pipe pointing straight up to vent the motor. Worf pipe? I have read your treatise at least four times and want to read it a few more times and then respond with any remaining questions/thoughts.

Excellent point I had not considered on the friction losses in getting from the AOS/ProVent to the potential vacuum source at the exhaust. As well as verifying your point about vacuum not being a requirement, though I am still pondering that one a bit. I get what you are saying, I am just not done reconciling it with my initial thoughts.

I hope you are feeling better, even if it means we miss out on additional discourses.

Following are versions 5-a and 5-b.

Version 5-a adheres to keeping things simple and as equivalent to the simple "worf pipe" as possible. I am assuming those cam cover elbows accommodate 1/2 inch tubing. It turns out that 4 of such cam cover elbows with 1/2 inch ID tubing equate to about a single 1 inch ID tube, so I showed the plumbing accumulate capacity that way.

Version 5-b assumes favorable pressure/vacuum readings at the exhaust port AND at the ProVent/AOS side of the required length of hose. Favorable meaning they match up closely with the crankcase pressure readings across the RPM range. Not too much and not too little vacuum. This seems unlikely, even if I try to manipulate the tubing sizes, but I would prefer to vent to the exhaust rather than to filtered breathers.

Crumpler, some great draft diagrams have originated from the ceramic throne room!

Image
Image
User avatar
By hernanca
#191932
P.S. I think both versions 5-a and 5-b need a one-way (check-valved) fresh air intake source on the cam cover plumbing?

(Edit: added fresh air intake source and created version 6-a based on version 5-a. See below with reasoning.)

P.P.S. Added a few more rows to the pipe ID equivalents spreadsheet:
Image

Version 6-a: (added intake to cam covers)
Image
Reasoning is: If there is ever a condition where either cam cover has less pressure than the push required through the AOS/ProVent, then the intake can step in to relieve the pressure differential and clean the system to boot.

Concerns/thoughts: what are the pressure measurements of the crankcase under varying conditions vs. the engine compartment pressure (if any) where I have been assuming all these breathers (2 outlet and 1 inlet) would reside? It MAY be beneficial to place the outlet breathers outside of the engine compartment in a potentially less (but not too much less) pressurized area, and place the "fresh air" intake in a relatively higher pressured area (e.g. in front of the radiator or feeding from the stock intake box).

Again, pressure measurements under varying conditions are required to determine the best set up!
Last edited by hernanca on Mon Jan 02, 2023 11:38 am, edited 1 time in total.
User avatar
By worf
#191947
hernanca wrote: Mon Jan 02, 2023 1:59 am P.S. I think both versions 5-a and 5-b need a one-way (check-valved) fresh air intake source on the cam cover plumbing?
Why?
User avatar
By hernanca
#191948
See my simultaneous edits, above (addition of version 6-a and reasoning).

My primary motivation, however, is to disrupt the left (drivers) cam cover from pulling from the right (passenger's) cam cover and thus hinder oil drainage in that right side's oil drains. Your question tells me (again!) that with sufficient breathing, this will not be a concern.
User avatar
By Benno
#192002
Fascinating conversation and I'll be following along as this evolves. I appreciate the dumbing down and detailed explanations from you all to help me learn.

Here is a really excellent research publication that compares the efficacy of various AOS systems including the Provent, Provent copies and cyclonic separation. The measured test metrics like flow efficiency and partial separation give you an idea of some concepts to keep in mind in the above discussion: Air Oil Separator functional comparison research document: https://www.researchgate.net/publicatio ... Separators

Here is some feedback on the vacuum pump system. You need to size your AOS to match the flow capacity of the pump. The P Provent 200 has a max airflow of 200Lpm. The GZ pump has significantly higher flow rates. You would need several in parallel to meet the airflow needs. My GTS had the GZ pump and Provent 200 and I would get oil spray overflowing from the Provent all the time.
GZ airflow.jpg
Some people have suggested using several cyclonic separators set up in series. I'd be interested to see how elegant that can be done.

I have since removed the pump and I am looking for a different solution.
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Last edited by Benno on Mon Jan 02, 2023 8:01 pm, edited 1 time in total.
User avatar
By smiffypr
#192011
My cyclonic separator is home made. I designed it by experimenting with transparent containers using a wet and dry vacuum cleaner to provide air flow and a spray gun to add water mist. What I concluded was that any kind of mesh of baffles need to allow oil to drain into the collection area, and not drip off into a high speed gas stream. What I ended up with uses a tangential input to get a cyclonic effect. Then to prevent oil being picked back up, the area of the outlet is huge so that the air flow speed at that point is low. Also, there needs to be a good distance between any air flow and where the oil drains to.
Image
Overall diameter is about 100 mm, the inner sleeve about 85 mm.
Overall height is about 300 mm, the inner sleeve is about 130 mm high.
Side tangential inlet and top outlet are about 25 mm diameters, drain
tube about 6 mm.
I don't have the drain connected to the sump because when driving on the road it collects condensation.
It works brilliantly on a 4.7 S on the track, I can see that because the outlet hose is unstained by oil.
User avatar
By hernanca
#192018
smiffypr wrote: Mon Jan 02, 2023 5:49 pm Overall diameter is about 100 mm, the inner sleeve about 85 mm.
Overall height is about 300 mm, the inner sleeve is about 130 mm high.
Side tangential inlet and top outlet are about 25 mm diameters, drain tube about 6 mm.
To me, that does look very good! The ProVent also has a tangential input, but the outlet is below it, probably to allow for the relief valve at its top? I like your design better. 2009 photo is courtesy Leon Speed on TOS:

Image

Is the 85mm inner sleeve on yours a mesh like material or solid?

Since it is not draining back to the sump, roughly how much oil is being collected after a track session or during normal driving (if you use it that way)?
User avatar
By smiffypr
#192038
It's all sheet metal, I found that mesh just holds oil temporarily. I did experiment with a mesh extension to the smaller diameter part. I collect less than 200ml per 20 minute track session. I drain it and put it back in. On the road it just collects water. The outlet goes back into the throttle body, and the unstained transparent hose shows that not much oil is going through there. Prior to making this, I was burning this amount of oil. With other attempts at separators I would typically collect some oil but also produce a lot of smoke at some times.
User avatar
By hernanca
#192056
Cool - thank you for those details. To me, its like a condensed sub-section of the super-simple (worf) pipe described above!

Note what worf said about the sides of the vent tubing also serving to separate the oil. If you can somehow extend the initial part of the engine venting hose in a rising inclination, it may help further reduce the little oil you are collecting - just a thought!
smiffypr wrote: Mon Jan 02, 2023 7:18 pm The outlet goes back into the throttle body, and the unstained transparent hose shows that not much oil is going through there.
You said 4.7, so no MAF to worry about? When You plumb your AOS outlet back into the throttle body, can I assume it is before the throttle itself? If so, then I would say you have an advantage. The challenge of making a closed system with an MAF equipped car is having a place to introduce the high rpm pressure back into the intake. As I understand it, before the MAF will contaminate the MAF hot wire when oil is present in the vapor.
User avatar
By smiffypr
#192058
The breathings are going in after (downstream) of the air flow plate and as it is all combustion by-pass it will be pretty much oxygen free, so no different to going back in between the MAF and the throttle. But really, that is not what I thought you were worried about, you could vent it to the outside or the exhaust. My experiments and experience apply to what's coming out of the block, it doesn't really natter where it goes once the oil is taken out.
User avatar
By hernanca
#192067
At this point I am worried about everything!

You are right, however, that it is not my primary concern (where to vent it), but if I could I would make it a closed system.

I will admit I don't know enough about how much might actually get vented and how that would impact the intake depending on where it is introduced, even if clean of oil.
User avatar
By worf
#192123
hernanca wrote: Mon Jan 02, 2023 11:44 am See my simultaneous edits, above (addition of version 6-a and reasoning).
Ok. My bad. I was just looking at the diagrams.

First let's look at this:

hernanca wrote: Mon Jan 02, 2023 11:44 am P.S. I think both versions 5-a and 5-b need a one-way (check-valved) fresh air intake source on the cam cover plumbing?
The inlet of your "fresh air system" will always be at one atmosphere by definition.

At what point will the other side of the check valve ever be less than atmospheric? Or, in other words, when, ever, will the "fresh air system" introduce air to the intake?

The answer depends upon plumbing. In your diagrams only 5-b has a chance of ever evacuating the crank case if the exhaust venturi vacuum theory holds true. In all those other diagrams there is no means of reducing crank case pressure below atmospheric. In addition as soon 5-b enables air into the crank case via its "fresh air system" you're just moving outside air through your crank case. To what end?

The stock system that re-burns CC gases creates a slight pressure differential via venturi effect. But, it's a closed system.

hernanca wrote: Mon Jan 02, 2023 11:44 am My primary motivation, however, is to disrupt the left (drivers) cam cover from pulling from the right (passenger's) cam cover and thus hinder oil drainage in that right side's oil drains.
There are a number of assumptions here:

- There is a pressure differential between the heads
- Breathing the right head into the left head is bad thing
- Even if both are true that the result is worse than not breathing the left head at all.

Remember from the first tome:

worf wrote: Fri Dec 30, 2022 10:49 pm At this point *every single thing* we do to make our breather system better causes complications.
Let's deal with the assumptions.

There is, theoretically, a pressure differential between the heads. The magnitude of the difference would, one expects, be proportional to power generation. The crank is a very inefficient "pump" that slings oil into the right head and kinda-sorta "vacuums" it a bit out of the left head. IIRC Tumo may have theorized on the magnitude of the difference. However, IIRC, no one has ever measured this in operation. If someone did and I read about it, then I suspect that the difference was not enough for me to worry about and thus remember.

In any case, so what?

If the right head breaths a bit into the left head, why does it matter? If any thing it'll reduce the energy of the gases going to the ProVent (or whatever is the final "catcher" for the system.) If it carries some liquid oil into the left head so much the better since the left head will always drain better than the right head because of crank rotation.

In the stock system with no vents in the left side, ALL the breathing happens through ONE hose on the right side and the filler neck (and the filler neck in the stock pre-'94 system is valved, contains a lot of oil from the stock neck, and can't breath much anyway.) Note, that the '92-'93 system vented across the heads. '92 to '95 the breather from the base of the neck to the air guide was deleted (because it just carried oil.)

Just adding more "holes" to the left side that actually can breather (even a bit) is an improvement over stock.

hernanca wrote: Mon Jan 02, 2023 11:44 am Your question tells me (again!) that with sufficient breathing, this will not be a concern.
Yup.

hernanca wrote: Mon Jan 02, 2023 1:36 am What is appealing to me about the vacuum pump solution is that it is a relatively closed system and just moves the oil vapor from one place to another.
An active pump system doesn't have to be closed. It could vent gas to atmosphere after separation.

Making the breather system truly closed requires serious thought about how to route the separated CC gas back into the intake system downstream of the Mass-Air Sensor with the "big hoses" needed to avoid back pressure.

hernanca wrote: Mon Jan 02, 2023 1:36 am Version 5-a adheres to keeping things simple
This system is more-or-less what I'm aiming you at(*).

There is one evolution of it that I would want you to ponder.

Your diagram assumes that breathing through the cam covers is equal to breathing through the filler neck. Or, it assumes that each AOS is big enough for worst case flow through one or the other.

I would not rely on this. What if the cam covers vent 1/3 of the total and the neck vents 2/3 of the total? Will the neck AOS be overwhelmed while the cover AOS is not very busy?

Assuming that one giant AOS can't be packaged in the engine bay, then I would add an "X-pipe" between the two breather subsystems to equalize the duty cycle of the two AOSs.

Also, don't be afraid to plumb two 1/2-inch hoses into a one-inch hose that eventually combines both one-inch hoses into a one-inch hose to the AOS. Fewer SKUs. :)

Last, remember that it is the ID of the "connection technology" between hoses that matters, not the hose ID.

hernanca wrote: Mon Jan 02, 2023 1:36 am Version 5-b assumes
... that the trouble to find and route the components is worth it. Of this I am skeptical. But, if you wish to pursue it then I'd suggest doing 5-a first and gather some data. Devise a repeatable test methodology and a way to measure flow or pressure (or something.) Conduct the test, record the data. Then do the same for 5-b and see what's what.

It will require Dyno time to get really good data since you need data across a variety of load/RPM tracks.

hernanca wrote: Mon Jan 02, 2023 1:36 am but I would prefer to vent to the exhaust rather than to filtered breathers.
That's a worthy goal even if the exhaust venting doesn't add to the breather system's efficiency.

I do wonder though what "check valve" would survive in that environment. I've never, until now, thought about it. I supposed it would be a variation on a turbo waste gate.

(*) There is one Elephant in the room that has been ignored so far:

Separated oil from the AOS(s) will only drain back into the sump when the crank case pressure is low. That's a potential problem with ALL of the vent systems that drain oil from an AOS directly to the sump. Of course a check valve is required to prevent the crank case from breathing through the drain hose INTO the AOS when load is high.

These systems only work for "short bursts." On a track, or a high-speed road race, the AOSs would fill with oil. Even for "street work" it would be best to enable the crank case to be drawn below atmospheric to help "suck" the oil out of the AOS. This is enabled in my breather systems (except for the Zyclomat S4) because they are closed systems: the AOS vents gas back into the intake and thus at low loads the CC is under some slight vacuum.

The Elephant is slain with a vacuum pump-based system.
Last edited by worf on Tue Jan 03, 2023 4:25 am, edited 2 times in total.
User avatar
By worf
#192124
Benno wrote: Mon Jan 02, 2023 4:04 pm Here is a really excellent research publication that compares the efficacy of various AOS systems including the Provent,
Thanks for that!
Benno wrote: Mon Jan 02, 2023 4:04 pm Some people have suggested using several cyclonic separators set up in series. I'd be interested to see how elegant that can be done.
Parallel separators would be far better. If you treat the gas flow as incomprehensible then series separators work. However, they will only work if the flow rate is low enough to remain in the realm of that simple math. The reality is that the foam is highly compressible and each stage of separator - assuming they are identical - will simply reduce flow. Put enough separators in series and there'll be no CC breathing at all.
Last edited by worf on Tue Jan 03, 2023 4:23 am, edited 1 time in total.
User avatar
By worf
#192125
smiffypr wrote: Mon Jan 02, 2023 8:21 pm The breathings are going in after (downstream) of the air flow plate and as it is all combustion by-pass it will be pretty much oxygen free, so no different to going back in between the MAF and the throttle.
Nope. Or, only 'yes' with qualifications. The air flow plate and the MAS, or in particular the control system design assumes that plate deflection because of mass flow or measured mass flow is of normal atmospheric composition. Once you introduce exhaust gases ahead of the the plate or MAS you have lowered the oxygen content. Neither the plate nor the MAS are "oxygen sensors." Deflection is deflection and mass-flow is mass-flow regardless of if the flow is 21% oxygen or 18% oxygen.

For the LH 2.3 systems, you can "tune" for that. But the stock system would otherwise always tend to run rich if indeed the mixture is outside of the trim range of the lambda control loop. At full throttle it would run leaner than expected. But, on the other hand 2.3 system run pig rich at WOT anyway. So, maybe it all washes out. But, one would want to instrument closed-loop operation to determine if the lambda loop is maxing trim.

On the gripping hand, with E10 fuel that we have in the states mixture is mildly fucked for the stock system anyway and all our 928s are running a bit lean unless lambda corrected.
Last edited by worf on Tue Jan 03, 2023 12:08 pm, edited 1 time in total.
User avatar
By smiffypr
#192142
(If you were running E90, you would have to adjust the mixture, I guess you are using E10.)
What I am saying is that on a K or LH jetronic system, the air comes in through the air filter, then it is measured, then the breathings are added and then enters the engine, so there is no difference between the two air flow measuring types, neither is measuring the breathings. If you suck the breathings out to fast and introduce a significant amount of air, you will weaken the mixture whether it is K or LH.
User avatar
By worf
#192222
smiffypr wrote: Tue Jan 03, 2023 8:55 am (If you were running E90, you would have to adjust the mixture, I guess you are using E10.)
You are right. That’s what happens late at night. I was thinking “90% gasoline.” I’ve edited the post to correct.
smiffypr wrote: Tue Jan 03, 2023 8:55 am What I am saying is that on a K or LH jetronic system, the air comes in through the air filter, then it is measured, then the breathings are added and then enters the engine, so there is no difference between the two air flow measuring types, neither is measuring the breathings. If you suck the breathings out to fast and introduce a significant amount of air, you will weaken the mixture whether it is K or LH.
And once again I must apologize for a too-late-at-night reading of your post. When I read it, I thought you were suggesting that it doesn’t matter on an LH system which side of the MAS the exhaust gases are reintroduced. That was clearly - re-reading this morning - not what you wrote.
User avatar
By hernanca
#192339
worf,

I have read and re-read your most excellent Tome to the point of diminishing returns (of insights) for me. Following are my comments and any questions I still have:

(Note: Printing* your Tome generates a good six 8.5x11 pages! (*My preferred media))


worf wrote: Fri Dec 30, 2022 10:49 pm [...]
Square one.
[...]
The simplest form of crank case breather "system" is a big hole somewhere in the crank case.
[···]
We don't really want to leave a trail of oil foam dripping out of the engine valley. Nor do we want a pool of oil in the valley. We can "solve" this by simply attaching a pipe, of the same or larger diameter as the hole, pointing straight up. Depending upon the specifics of our engine that pipe would need to be several feet high if we don't want any liquid oil dripping out of the top opening. That pipe is a very stupid-simple air-oil separator. It more-or-less uses gravity to break the bubbles in the oil foam.
[···]
At this point *every single thing* we do to make our breather system better causes complications.

(*)That latter issue requires a short history lesson:
[...]

From this first section (Square One up to and including the History Lesson), I hear several "requirements" for my CCV system:

1. Keep Motor Seals off Pavement (not too much pressure)
2. Keep the Blob (froth) Contained
3. Minimize Windage Effects
4. Burst Bubbles
5. Make it Pretty (subjective - Google "Bosozoku exhaust" :-) )
6. Pass Inspection (not currently required, but acknowledge the point)

The best part (included above), for me, was explaining the stupid-simple air-oil separator vent hole with pipe. That was an "Aha" moment for me!

I did try to come up with some alternatives where, maybe, just maybe, we could compress that pipe and therefore be able to still close the hood on it. It would be an interesting set of comparison experiments to perform, IMO!

Image

Later, the following was also enlightening, given we have lots of tubing, and that at least one 928'er seemed to benefit from extending and re-routing their right (passenger) rear cam cover tubing (along with adding/modifying baffling on that same came cover outlet) in their smog compliant system:
worf wrote: Fri Dec 30, 2022 10:49 pm In the "stupid simple" CC vent system with the pipe sticking out of the top of the block, the foam has to fight gravity. That fight results in momentum change. Also the friction of the foam along the pipe walls changes momentum. Thus, we get separation of the foam.


As smiffy can attest, I am a bit fuzzy on what happens when introducing the CC vapors into the intake:

worf wrote: Thu Dec 29, 2022 11:10 pm
worf wrote: Thu Dec 29, 2022 11:10 pm B. In a stock set-up what is the source of intermittent crank case vacuum?
hernanca wrote: Thu Dec 29, 2022 9:29 pm B. In the stock system, intermittent vacuum is provided by the throttle housing at idle and part throttle. It would be strongest at idle but a restrictor limits it (I think).
You are at least partially correct. My knowledge of pre-'87 plumbing fails me at this point. What I now write will only be completely accurate for S4+.
However, by knowing the 87+ CCV systems, you may know more about the 85-86.5 CCV system than you realize. The purpose of this Porsche patent is stated as for improving the 85-86.5 CCV system by using that special "Y" venturi, for packaging and economics reasons:

https://patents.justia.com/patent/4753214





worf wrote: Thu Dec 29, 2022 11:10 pm Back to:

hernanca wrote: Thu Dec 29, 2022 9:29 pm A. In my diagrams, the exhaust is the source of any crankcase vacuum, pulling through the ProVent AOS and the Oil Filler Neck (OFN). Vacuum should be stronger at higher RPMs. The source of pressure in the crankcase is any blow-by, which should also be greater at higher RPMs.
You are proposing to use venturi effect from the exhaust gas to vacuum the engine.

It may be that what you propose will work. I've never thought about it. One issue with it is the length of the lines and "pumping friction." It takes force to suck the CC gases out of those lines. You have friction force that is proportional to the length of the line opposing the sucking force. It's not clear to me that the exhaust gas energy would provide sufficient venturi effect to overcome pumping friction. Maybe.

On the other hand, why do you need this?

Our "stupid simple" CC ventilation system doesn't need vacuum. The factory set up uses venturi effect to help move CC gases to the intake because regulations require that CC gases be re-burned in the intake.

Look at it another way: In our "stupid simple" CC ventilation system, what happens when we apply a vacuum to the top of our tube? Our oil foam will just flow out faster and be harder to separate.

worf wrote: Thu Dec 29, 2022 11:10 pm C. In the “ideal” hole-in-the-case setup what, if anything, results in crank case vacuum?
hernanca wrote: Thu Dec 29, 2022 9:29 pm C. I would say nothing would create vacuum in that setup. Hmmm.
This was a bit of a trick question. I wanted you to consider the purpose of vacuum in the stock system.

The answer is that there really isn't that much vacuum in the stock system. What vacuum there is, is simply to assist in getting the CC gases back into the intake to re-burn them for regulatory purposes. I believe that the effect is minimal. And vacuum isn't a necessary component of the breathing system. It can help. But, you can still have an effective breathing system without vacuum.

Crankcase vacuum - I read somewhere on the InterWebz that crankcase vacuum was a good thing, and so I wanted to introduce it, especially if I could easily. I now see the folly of my ways. It will only lead to complexity and is not necessary. I have given up on chasing this illusion for my motor.

I have not, however, thrown out the idea of still somehow utilizing the exhaust system as an escape route for the separated vapors. I still want to get measurements on what kind of vacuum (if any) there exists both at the exhaust pipes I tap into and at the AOS end of the tube connected to it, but it is no longer a requirement for me to use the exhaust as a source of vacuum for the crankcase.


worf wrote: Thu Dec 29, 2022 11:10 pm [...]
Yeah. But, that answer would not get you full credit on the exam because "you didn't show your work."
I will take that partial credit!



worf wrote: Thu Dec 29, 2022 11:10 pm At this point, we've looked at "theory" except for windage. Or in other words, can we impart less energy to the foam before it gets to the 'hole' in the crank case? Specifically, can we make less foam?

Of course the answer is yes. There are plenty of starting points:

- keep liquid oil away from the crank: pan spacers, windage trays, crank scrapers.
- vacuum pump: don't keep any oil in the sump for the crank to whip up into a foam.
pan spacer - check
windage trays - check (see picture from previous owner)
crank scrapers - unknown

vacuum pump - Not interested - I want to keep my CCV relatively simpler and less costly.

Image

As a relevant aside, while looking at some of the other Gazillion CCV threads, I found that Louie Ott's Cam Cover Window video was available on YouTube:

https://youtu.be/SmjQn3IBsP8

worf wrote: Thu Dec 29, 2022 11:10 pm So, my personal conclusion for 32v 928 crankcase ventilation:
- Remove the stupid "suction" cup under the passenger cover.
- Total breather volume needs to be the equivalent of three 1/2" lines for a 5.0 N.A. motor. This is about double the stock volume.
- The more places from which you can vent the better.
- From wherever you vent, you need to control windage.
- The oil filler neck port has limited utility because of windage. I believe that the various available baffles work, but they also work more effectively if the actual breathing occurs as far towards the top of the neck as possible. That extra "fight" against gravity and the need to "turn" imparts useful momentum change. (Thus, my preference for GTS necks that have NO ports at the base, but a single port - that can be drilled out - that's roughly 1/2" diameter right behind the cap.)
Question: As long as we adhere to the above, are there any drawbacks (besides cost of tubing and difficulty in routing) if the breathing system is greater than what the motor needs. That is, anything wrong with a larger stupid-simple hole and pipe? From your later posts, I am thinking the answer is this would be OK (except for the costs and difficulties of routing larger hoses
User avatar
By hernanca
#192354
This is going to be a potentially rough work week (coordinating migration to cloud for point of use systems of two hospital campuses), so I am just going to reply now since it could be a week or two before I can have this much time again, otherwise.
worf wrote: Tue Jan 03, 2023 4:03 am

First let's look at this:

hernanca wrote: Mon Jan 02, 2023 11:44 am P.S. I think both versions 5-a and 5-b need a one-way (check-valved) fresh air intake source on the cam cover plumbing?
The inlet of your "fresh air system" will always be at one atmosphere by definition.

At what point will the other side of the check valve ever be less than atmospheric? Or, in other words, when, ever, will the "fresh air system" introduce air to the intake?

The answer depends upon plumbing. In your diagrams only 5-b has a chance of ever evacuating the crank case if the exhaust venturi vacuum theory holds true. In all those other diagrams there is no means of reducing crank case pressure below atmospheric.
For 6-a (Edit/corrected: said 5-a, but 6-a adds the fresh air intake to 5-a), I thought there might be the possibility of instances where the crankcase might vent faster than the cam covers, leading to less than atmospheric in the cam covers. However your point about any breathers being at 1 atmosphere helps me see that as unlikely. The other thought was regarding the left (driver's) side cam cover as you discuss further below.

worf wrote: Tue Jan 03, 2023 4:03 am In addition as soon 5-b enables air into the crank case via its "fresh air system" you're just moving outside air through your crank case. To what end?
Well, Sensei, again, on them thar InterWebz, they were sayin' it was good to "flush" out the system. I guess maybe so it would be more habitable for Gremlins or somethin'. I dunno. More folly? The worf pipe (stupid-simple air-oil separator) appears to frown upon it.


worf wrote: Tue Jan 03, 2023 4:03 am
hernanca wrote: Mon Jan 02, 2023 11:44 am My primary motivation, however, is to disrupt the left (drivers) cam cover from pulling from the right (passenger's) cam cover and thus hinder oil drainage in that right side's oil drains.
There are a number of assumptions here:

- There is a pressure differential between the heads
- Breathing the right head into the left head is bad thing
- Even if both are true that the result is worse than not breathing the left head at all.

Remember from the first tome:

worf wrote: Fri Dec 30, 2022 10:49 pm At this point *every single thing* we do to make our breather system better causes complications.
Let's deal with the assumptions.

There is, theoretically, a pressure differential between the heads. The magnitude of the difference would, one expects, be proportional to power generation. The crank is a very inefficient "pump" that slings oil into the right head and kinda-sorta "vacuums" it a bit out of the left head. IIRC Tumo may have theorized on the magnitude of the difference. However, IIRC, no one has ever measured this in operation. If someone did and I read about it, then I suspect that the difference was not enough for me to worry about and thus remember.

In any case, so what?

If the right head breaths a bit into the left head, why does it matter? If any thing it'll reduce the energy of the gases going to the ProVent (or whatever is the final "catcher" for the system.) If it carries some liquid oil into the left head so much the better since the left head will always drain better than the right head because of crank rotation.

In the stock system with no vents in the left side, ALL the breathing happens through ONE hose on the right side and the filler neck (and the filler neck in the stock pre-'94 system is valved, contains a lot of oil from the stock neck, and can't breath much anyway.) Note, that the '92-'93 system vented across the heads. '92 to '95 the breather from the base of the neck to the air guide was deleted (because it just carried oil.)

Just adding more "holes" to the left side that actually can breather (even a bit) is an improvement over stock.

hernanca wrote: Mon Jan 02, 2023 11:44 am Your question tells me (again!) that with sufficient breathing, this will not be a concern.
Yup.
Understood! If I get a chance to, I would like to measure the pressure difference between the cam covers. It would also be good to include clear tubing to see how much oil travels across.



worf wrote: Tue Jan 03, 2023 4:03 am
hernanca wrote: Mon Jan 02, 2023 1:36 am What is appealing to me about the vacuum pump solution is that it is a relatively closed system and just moves the oil vapor from one place to another.
An active pump system doesn't have to be closed. It could vent gas to atmosphere after separation.
When I say "vacuum pump solution", I am specifically referring to what some 928ers have come up with where they suck CC vapors out of the oil filler neck and pump it into the cam covers, IIRC. I thought those were closed systems. I have not paid too much attention to them because the combination of cost and complexity tells me to avoid it. I would be (not morbidly!) curious on Benno's experience with his.






worf wrote: Tue Jan 03, 2023 4:03 am There is one evolution of it that I would want you to ponder.

Your diagram assumes that breathing through the cam covers is equal to breathing through the filler neck. Or, it assumes that each AOS is big enough for worst case flow through one or the other.

I would not rely on this. What if the cam covers vent 1/3 of the total and the neck vents 2/3 of the total? Will the neck AOS be overwhelmed while the cover AOS is not very busy?

Assuming that one giant AOS can't be packaged in the engine bay, then I would add an "X-pipe" between the two breather subsystems to equalize the duty cycle of the two AOSs.
Yes, I was assuming they were equal, but the last question on Tome 1 was because I was pondering increasing the crankcase breathing to as large as possible, even though I would have cam cover breathing. I also like this X-pipe idea.






worf wrote: Tue Jan 03, 2023 4:03 am Also, don't be afraid to plumb two 1/2-inch hoses into a one-inch hose that eventually combines both one-inch hoses into a one-inch hose to the AOS. Fewer SKUs. :)
I had thought of bringing the larger hoses as close to the cam cover outlets as possible, but I hadn't thought of eliminating a size altogether. Probably too much HVAC Drafting embedded in me from early years. To your point, if the space existed, oversized hoses could be fitted with reducers at both ends - the hoses could serve as a space to immediately slow down the egress.







worf wrote: Tue Jan 03, 2023 4:03 am Last, remember that it is the ID of the "connection technology" between hoses that matters, not the hose ID.
Excellent tip - thank you. I figured since the cam cover elbows have a certain limiting ID (even when opening up the factory restricted ones), then we were doomed to that. However, just like with the oversize hosing idea above, we do not need to resign ourselves to such constraints.






worf wrote: Tue Jan 03, 2023 4:03 am
hernanca wrote: Mon Jan 02, 2023 1:36 am Version 5-b assumes
... that the trouble to find and route the components is worth it. Of this I am skeptical. But, if you wish to pursue it then I'd suggest doing 5-a first and gather some data. Devise a repeatable test methodology and a way to measure flow or pressure (or something.) Conduct the test, record the data. Then do the same for 5-b and see what's what.

It will require Dyno time to get really good data since you need data across a variety of load/RPM tracks.
Understood. Since the exhaust will be replaced anyway, I was going to poke some venturi in it and take pressure measurements during dyno runs as well.



worf wrote: Tue Jan 03, 2023 4:03 am
hernanca wrote: Mon Jan 02, 2023 1:36 am but I would prefer to vent to the exhaust rather than to filtered breathers.
That's a worthy goal even if the exhaust venting doesn't add to the breather system's efficiency.

I do wonder though what "check valve" would survive in that environment. I've never, until now, thought about it. I supposed it would be a variation on a turbo waste gate.
Hans could spec something better, I'm sure, but several variations of these (Edit: referring to just the check valves included in this kit) seem common:


Image


worf wrote: Tue Jan 03, 2023 4:03 am
(*) There is one Elephant in the room that has been ignored so far:

Separated oil from the AOS(s) will only drain back into the sump when the crank case pressure is low. That's a potential problem with ALL of the vent systems that drain oil from an AOS directly to the sump. Of course a check valve is required to prevent the crank case from breathing through the drain hose INTO the AOS when load is high.

These systems only work for "short bursts." On a track, or a high-speed road race, the AOSs would fill with oil. Even for "street work" it would be best to enable the crank case to be drawn below atmospheric to help "suck" the oil out of the AOS. This is enabled in my breather systems (except for the Zyclomat S4) because they are closed systems: the AOS vents gas back into the intake and thus at low loads the CC is under some slight vacuum.

The Elephant is slain with a vacuum pump-based system.
Hmmm, I didn't know about this elephant and didn't want to introduce a vacuum pump. If I was tracking earlier, wouldn't the vacuum pump impart unwanted momentum to the froth/Blob coming out of the holes?

(Edit: adding this question) Isn't this handled by draining below the oil level? I have heard (InterWebz, again...) that draining below the oil level (e.g., the oil pan oil drain adapter piece in DR's 928 Specialists kit had a tube that extended down - see pic below) would make the check valve unnecessary as the oil "lake" buffered the drain tube from the positive crankcase vapor pressure. Would this oil lake also create a buffer which would allow draining even for a pressurized crankcase. I would still want the check valve, in case that oil lake succumbs to sufficient G-force which would cause the extension to uncover and expose the drain tube to the CC vapor pressure.

Image



The elephant I do know about is the S3 Organ Pipe Intake sitting on top of everything!
Last edited by hernanca on Wed Jan 04, 2023 1:48 pm, edited 2 times in total.
User avatar
By hernanca
#192439
worf wrote: Tue Jan 03, 2023 4:03 am Making the breather system truly closed requires serious thought about how to route the separated CC gas back into the intake system downstream of the Mass-Air Sensor with the "big hoses" needed to avoid back pressure.
My reply to this got lost in the shuffle:

I am glad you said this because it validates my understanding of where the challenge is in a truly closed system.

However, I have questions about how this interacts with all the effort that goes into packing the heads as full as possible (VE) with just the right combustible mix before burning it. Wouldnt introducing these "cleaned up" crankcase vapors dilute the mixture and rob us of horsepower? Or is it:
a) considered negligible?
b) considered the price to pay for an overall higher horsepower result (like a supercharger draw)?
c) the price to pay to be environmentally responsible?
d) considered the cost to make everything work in order to meet environmental requirements, i.e., the oil draining elephant previously being ignored?
e) some combination of the above?

I don't see b) however.

(Edit: added options d) and e), plus general tidying up.)
User avatar
By worf
#193667
maddog2020 wrote: Tue Jan 10, 2023 10:58 am pics of my simple AOS setup
Monster oil drain tube. :thumbup:
User avatar
By maddog2020
#193690
With the ITB's the factory oil filler neck had to go, so I decided to make something similar to what Louie Ott made for his stroker beast. However I wanted it to look a little more like it belonged. I have 2 Provent 200 for sale if anyone is looking for some.
User avatar
By hernanca
#193759
The worst is over of a hellish (but at the end, successful) work week. Thank goodness.

worf wrote: Tue Jan 10, 2023 11:17 am Monster oil drain tube. :thumbup:

Motor is looking sweet, maddog! How was that alternate oil filler made? I read where someone said it was easy to create an alternate filler setup using that port, but no details were given. Is that a customized adaptation of something otherwise readily available?

maddog2020 wrote: Tue Jan 10, 2023 12:35 pm I have 2 Provent 200 for sale if anyone is looking for some.

Hmmm, why, yes, I am interested. Pics please.

Working on X-piped AOS vent lines version....
User avatar
By maddog2020
#193767
oil filler tube was my own making. lower 1/3 is a factory tube. then I added a 45 degree pre bent 1" tube as a middle section, with a machinist collet welded on with an aftermarket VW bug billet fill we with another 45 degree bend and billet cap. The machinist collet was me being cheap as I didn't want to spend $150 on the weld on bung that I could find. I have a funky strut bar to clear the ITB's so I needed to make this filler port accessible, so I added a few 45 degree sections to give me the flexibility I needed.

I'll dig out the provents to take a pic.
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User avatar
By worf
#194526
@hernanca I'll try to get back to this this weekend.

Of particular note though is the last "issue" of the oil drain. What I wrote previously was intended as a test of sorts. There's a fundamental flaw in what I wrote that appears if you go back to the 'super-stupid-simple' CC breather. add a big-enough AOS to it and give the resulting system some thought.
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User avatar
By hernanca
#194530
(Monday, Jan 16 Note: edited the below for clarity.)

Sounds good, sir. I will be working up another version (or three) over the weekend soon!

Some progress updates:

Went by the shop today and was able to look under the throttle plate: throttle plate had an oily film, but underneath there was no pooling of oil. Just barely a film of oil. So this motor seems pretty darn tight and credit must be given to Doc Brown.

I was also able to look under the oil filler neck (OFN). Unless the 86.5 came with a plastic OFN, the PO must have swapped in this plastic one that is there now. This plastic OFN simply had an integrated baffle and a built in restrictor on one of the base ports.

There was absolutely NO additional baffling under the OFN - NOT EVEN a 928 International oil filler neck baffle (Edit: aka oil deflector - see image below of initial prototype when first created for Joe Fan's race car, according to a thread on TOS). I expected to at least see that. So I am glad we peeked under there!

Image

I ordered an 85-86 metal OFN from 928 International and it had arrived at the shop, so I measured the heck out of it while there today (Edit: measurements added below). You were absolutely correct in indicating the top of the neck could not breath the equivalent of two 1" ID hoses! I measured the tightest area of the metal neck and it came out to 1.36 sq inches in area!

85-86 alloy OFN Measurements:
    Wall thickness = 3.5mm (average)
      Narrowest Dimensions (at middle neck turn, oil cap side) = 30.5mm×40mm
      The above is what comes out to the 1.36 sq. inch flow cross section mentioned.

      Additionally, the two base ports (no built in restrictor) = 11.5mm ID each.
      Calculating the area from these indicates the two ports combined equal the area of a 5/8 inch ID hose. (0.32 sq. inch flow cross section). I would like to take advantage of these ports as well, even though they are at the base of the OFN.

      More to follow.
      Last edited by hernanca on Tue Jan 17, 2023 9:47 pm, edited 6 times in total.
      User avatar
      By Crumpler
      #194581
      Very informative thread you guys.
      Obviously, I get to cheat a little bit with the track car, but my various iterations would support Worf’s principle strongly.
      After several unsuccessful iterations, my current set up seems to be working.
      Throwing cosmetics aside.
      Fabricated trap integrated with oil filler cap. Two large lines run to catch can which vents to atmosphere. Line from bottom of catch can back to pan.
      In addition, GB baffle under oil filler neck. The stock breather line on the neck still there but drilled out and also runs to catch can.
      Image
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      User avatar
      By hernanca
      #194910
      Crumpler wrote: Sat Jan 14, 2023 10:01 am Fabricated trap integrated with oil filler cap.
      Thank you, Crumpler.

      Any hints on how that trap is integrated with the oil filler neck? I can't imagine how that would be done, but I like the idea!
      User avatar
      By hernanca
      #195050
      Still have not gotten a chance to finish the "x-piped" dual Provent intakes version(s), but I wanted to address this:
      worf wrote: Fri Jan 13, 2023 10:31 pm Of particular note though is the last "issue" of the oil drain. What I wrote previously was intended as a test of sorts. There's a fundamental flaw in what I wrote that appears if you go back to the 'super-stupid-simple' CC breather. add a big-enough AOS to it and give the resulting system some thought.
      At first, I was like:

      Image

      But as I thought back again to the super-stupid-simple CC breather, I realized what you were probably getting at: with enough CC venting, there should be no CC pressure build up to speak of and so there should be nothing preventing the AOS's from draining into the oil pan, even if the drain tube is above the oil level. I realize you specifically said "big enough AOS", so I don't know if I will get full credit for this answer?
      User avatar
      By Crumpler
      #195115
      hernanca wrote: Sun Jan 15, 2023 10:25 pm
      Crumpler wrote: Sat Jan 14, 2023 10:01 am Fabricated trap integrated with oil filler cap.
      Thank you, Crumpler.

      Any hints on how that trap is integrated with the oil filler neck? I can't imagine how that would be done, but I like the idea!
      Essentially a billet cap with top removed welded to a rectangular box with the communication surface to cap cut out. There are several ridges welded to roof of the box, kind of like an egg carton effect.
      The oil seems to blow straight up against the roof and gravity drip back down through neck. Vapor continues lateral through lines into second catch can.
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      User avatar
      By hernanca
      #195133
      Crumpler wrote: Mon Jan 16, 2023 9:32 pm Essentially a billet cap with top removed welded to a rectangular box with the communication surface to cap cut out.
      Ah, so the cross bar has to be removed for it to screw in place via the cap threads - that's what I could not figure out!

      Crumpler wrote: Mon Jan 16, 2023 9:32 pm There are several ridges welded to roof of the box, kind of like an egg carton effect.
      The oil seems to blow straight up against the roof and gravity drip back down through neck. Vapor continues lateral through lines into second catch can.
      Those ridges and drip effect is clever! I will assume your cam covers are not vented and worf will tell us that if they were, then the oil would not be under so much pressure coming out.

      I like it because I want to tap into the two OFN base ports, in the name of increased breathing, and am concerned that such a low spot on the OFN will be oily. I keep coming up with having a y-pipe off those two base ports and running a single 5/8" or (increasingly) larger tubing, going up to meet with the OFN AFTER the narrow neck area I had measured prior. Having a box to go up to sounds even better.
      User avatar
      By hernanca
      #196328
      Finally!

      (Versioning key:
      -a=breather venting
      -b=exhaust venting
      -ii = X-pipe
      -iii=X-pipe & Cam Cover intake)

      Version 5-a-ii
      Added AOS X-pipe intake to version 5.

      Version 7-a-ii
      7 series introduces OFN base venting as part of OFN venting.

      Version 8-a-iii (Edit: fixed diag. title)
      8-series - can't leave well enough alone:
      • OFN base venting is part of Cam venting (inspired by DR's 928 Specialists S3 SharkVent).
      • Introduced fresh air vent to Left rear cam port
        (John Gill said he measured vacuum in his crankcase even though disconnected from the intake?).
      • Drew piping somewhat to scale based on OFN.
      Notes:
      1. Pipe sizes are minimums required - plan to use larger when possible.
      2. Ideally, AOS's will be placed in a cooler area, outside of engine compartment.

      Image
      Image
      Image
      Last edited by hernanca on Sun Jan 29, 2023 10:22 pm, edited 1 time in total.
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