8 cylinder front engine iconic vehicle
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By worf
#196355
Back to this thread. Sorry for the long absence.

hernanca wrote: Sat Jan 14, 2023 1:01 am 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.
Someone "stole" the metal filler neck. The metal neck was used until mid-'87.

I haven't seen your motor, but it is possible that GB swapped the metal neck for a GTS neck. There were (at least) two variations of the GTS neck. You can identify a GTS neck because it has two ports next to the fill cap. The left-side port is the familiar one for the Y-hose (on S4 at least) that goes to both the air guide and tank vent electric valve. The right-side port, unique to the GTS necks has several different "uses" depending upon which factory breathing system was used.

The advantage of the GTS neck is that you can use the right-side port for breathing. Since it's much higher up the neck it's in a better situation for windage than ports at the base.

The integrated baffle in the plastic necks may or may not be a restriction.

hernanca wrote: Sat Jan 14, 2023 1:01 am 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!
And it's in a bad place with respect to windage.

Note that the metal filler neck has no integrated baffle at all. That neck used a separate baffle plate with an integrated non-replaceable o-ring. It's been NLA for decades. However, liberal application of Drei-Bond will do the job just fine.

... if you can also get a used plate.

I'd recommend both a metal-neck's baffle plate and the "deep" baffle. The former is a 'bit' of an AOS and the latter prevents liquid oil from getting thrown at the former which otherwise hinders it's ability to 'begin' separating oil from the foam.

hernanca wrote: Sat Jan 14, 2023 1:01 am 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.
Those neck base ports are going to be filled with oil foam. With the metal neck, using only those ports, you'll not have a lot of breathing.

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.
hernanca wrote: Sat Jan 14, 2023 1:01 am 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?
Exactly correct and you get full credit.

First, let's deal with the last bit: Outside of corner cases, any effective means of air/oil separation is also a pressure restriction. Or, in other words, if you route big hoses to an AOS that can't handle the flow rate then the AOS hinders breathing.

Or, if you have several AOSs in series each one hinders flow rate. In that context AOS means anything the contributes to momentum change of the air/oil foam. It can be a 'grid' like in the ProVent or even a bend in a breather hose.

Back to the first: The oil drain should have gravity working in it's favor. The tube WILL be another breather. But, as long as breathing elsewhere is sufficient such that gravity driven oil flow overcomes any residual crankcase pressure then there won't be an oil back flow issue. Ideally, you wouldn't even need a check valve in the tube.

The proof of the pudding though, is a least 10s of seconds of engine operation at full load. That is a rather difficult test to do unless you're on a brake dyno.

Sterling's oil drain drains to the 16v factory location of the oil fill tube. The base of the tube is below the oil level when the engine's not running. When it is running the oil level is below the base. But, the location is far enough from the crank that windage isn't nearly as much an issue as it is above the crank and the oil filler neck port.

On 32v motors there may or may not be a "hole" at that location in the oil pan. Some of the "early" pans used on 32v motors just had a cover plate with a gasket over the port. Later S4 oil pans deleted the port entirely.

Sterling got himself an early oil pan.
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. 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.
This is a good description of construction for AOS systems. You have to "catch" the oil foam but also provide a means for the oil to flow with a vector different from that of escaping gas.

It's also a vivid description of how bad the windage situation is at the hole for the oil filler neck: the crank is literally throwing liquid oil and oil foam up into the neck.
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By worf
#196363
hernanca wrote: Sun Jan 22, 2023 3:25 pm Version 5-a-ii
Added AOS X-pipe intake to version 5.
This is the least complex.

hernanca wrote: Sun Jan 22, 2023 3:25 pm Version 7-a-ii
7 series introduces OFN base venting as part of OFN venting.
I have a suspicion that venting from the base will be less effective than 5-a-ii simply because those base ports will introduce a foam heavier with oil than from further up the neck.

hernanca wrote: Sun Jan 22, 2023 3:25 pm Version 8-a-iii (need to fix diagram 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).
Note that DR's SharkVent kits were constrained by his self-imposed requirement for a minimum of disassembly for installation. (In contrast to GB's kit that had NO constraints on required disassembly.)

hernanca wrote: Sun Jan 22, 2023 3:25 pm
  • Introduced fresh air vent to Left rear cam port
    (John Gill said he measured vacuum in his crankcase even though disconnected from the intake?).
It might be very interesting to start with this variation (minus the base venting) and actually measure/observe what's really going on.

This one is almost identical to the most effective system I'm assembled to date (mine only uses one ProVent though) so I KNOW it works well. But, once the breather system is "disconnected" from the air guide (a vacuum source in stock configuration) I am dubious that there will be any vacuum anywhere. It would be very interesting to determine the truth.
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By hernanca
#196417
worf wrote: Sun Jan 22, 2023 5:52 pm
hernanca wrote: Sun Jan 22, 2023 3:25 pm
  • Introduced fresh air vent to Left rear cam port
    (John Gill said he measured vacuum in his crankcase even though disconnected from the intake?).
It might be very interesting to start with this variation (minus the base venting) and actually measure/observe what's really going on.

This one is almost identical to the most effective system I'm assembled to date (mine only uses one ProVent though) so I KNOW it works well. But, once the breather system is "disconnected" from the air guide (a vacuum source in stock configuration) I am dubious that there will be any vacuum anywhere. It would be very interesting to determine the truth.
Sounds like this would be Version 5-a-iii, then, which we would want to monitor: (X-Pipe & Cam Intake Breather, no OFN Base breathing.)

Image

I will ponder. Letting go of the OFN base breathing is my quandary. I am a recent convert to the school of "open as many holes as possible" dont-cha know!
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By hernanca
#197744
So I thought about this some more. I am going to try to implement version 8-a-iiib (see below). I will make the OFN base breathing have clear hose so we can watch that area. If it seems problematic, I will cap it off.

The "b" re-introduces the cam breather I had in version 6. It may be unnecessary and overkill, but I like the idea of having the breather available to all 4 cam breather ports and also ensuring it "breaks" any attempt of the left side cam area trying to pull from the right side cam area.

A negative I see with 8-a-iiib is that all four cam vent ports have significant "pumping losses" (friction) associated with their vent path, as compared to the single vent in the left rear cam cover port (as in version 5-a-iii)

Image
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By worf
#197757
Check valves before the Provents?
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By hernanca
#197773
worf wrote: Mon Jan 30, 2023 1:15 am Check valves before the Provents?
Hmmm. Certainly the one from the cam cover breathers seems like it would not be needed, so that one can be eliminated. If that mythical non-intake-tract-related-vacuum does exist, then it seems prudent to keep the other one. (Edit: Though that presumes it would be a bad thing to have opposite flow around the Provents, even if momentary.)
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By worf
#197830
The equivalent of the stock system would be to plumb the Provent output back to the intake and thus ensure that the vacuum source is always ‘ahead’ of the ProVent.

There is no vacuum source in the latest breather system diagram. Nothing is plumbed back to the intake. There is no mechanism that would result in crank case vacuum.
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By hernanca
#201055
Final design. :deadhorse:
Next will be implementation attempts!

Some notes:
  • Check valves before ProVents removed.
  • Assumes no overall crankcase vacuum.
  • Tries to use elevation differences wherever possible by placing hoses further back in engine compartment and orienting hose connectors vertically.
  • Again, hose sizes are minimums required, will place larger when possible.
  • Will consider replacing X-pipe with Crumpler's box idea (think Mustang Mac Prochamber), to further help separate oil out based on how inlet hoses enter the box and how outlet hoses exit the box.
Image
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By hernanca
#212153
Bottom view of spare S3 intake roughly mocked up with 1 inch OD PVC pipes to find potential routing paths.... :smile:
Image
(Edit: updated picture - found one more (G))
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By hernanca
#212734
Question:

Any disadvantage to simply plugging the intake vacuum sources? I plan to keep the one on car's left side (U.S. Driver's side) because I believe it provides vacuum to something else. But the other two I was going to simply plug.

However, I started wondering whether the motor won't be happy that it can no longer pull air from these sources? Below is the stock S3 configuration (from 928 Specialists site).
Image


Should I instead route to the air box upstream of the filter and ensure the stock restrictive orifices are in those lines (yellow lines in following diagram)?
Image
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By worf
#212743
Lines from the air guide to the air box will be false air (i.e. high-idle, lean running, vacuum leak.)

As shown the the ‘stock’ diagram you can cap the two right sources at the air guide.
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By hernanca
#212792
OK, I will have them capped off. Certainly easier that way. It is also what the 928 Specialists SharkVent kit did.

I was assuming the motor is tuned to take into account these "controlled" (?) leaks somehow and I needed to keep/mimic them. However, thinking about it a bit more, my solution would not be replicating the RPM and throttle correlated pressures/vacuum, so who knows what it would have done!

Again, that whole bit about the stock CCV system tying in to the air guide/throttle body and how that tie-in affects or is accounted for in the AFR tuning is still a mystery to me. I'm glad I don't need to worry about it! (Coincidentally (or not)... I am past due on dusting off my tuning books and the SharkTuner and SharkPlotter material!)

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