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PCV v7, an attempt to understand the Saab PCV system and fix it properly

741 Views 23 Replies 7 Participants Last post by  teo.petleshkov
This a continuing of my thread bombing of Assessing correct Crankcase Ventilation function using OEM saab PCV valve specifications, and avoiding problems caused by defective or non-oem valves

I went down the rabbit hole and did a bunch of PCV and evap research (my 02 has an 06 biopower ecu, so it should have the new evap routing...anyways).

I was sketching up the "proper" way to do this PCV system and was quite pleased with myself. Then I went back to PCV6 to analyze the flow paths (since its not on this site) and realized that saab did nearly the same thing. See pictures below for PCV6. The issue with every dang version of the PCV system on the PCV cars has been oil usage... because saab sucks directly from the valve cover to the intake. If you wonder why people in the PCV6 threads from 2006 say oil consumption is still occurring; this is why. They finally fixed this on the 04 cars, but couldn't be bothered to implement the same idea on the PCV6 kit for everyone else.

Bumper Microphone Bicycle part Automotive exterior Audio equipment


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So /rant. Onto the fix. Its quite simple looking at the above left picture; plug the small port at the valve cover and splice the hose leading to the check and intake in on the green line. Now the intake will suck in filtered air. In schematic format:
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The only catch for this is that rerouting the check valve to the green line will end up sucking clean air straight from the oil filler into the catch can via the oil drain which is no better. No fresh air for the crank case. (it would actually potentially destroy the engine if the catch can inlet was ever blocked, see third post). I believe the 04+ catch cans route fresh air through the catch can, to the valve cover, down to the hole in the block, out into the second catch can cavity and finally into the intake manifold. A few solutions to "single catch can" below.
  1. Check valve the oil return to the pan (seems risky, it would probably never open due to pressure deltas)
  2. Plug the oil pan, valve the drain on the catch can and drain manually at an interval (ehhh...)
  3. Use a second catch can for the vacuum side of the PCV system which still requires manual draining (Ehh...) (unless its design properly and also drains to the pan?)

So what does #3 look like:
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But wait, there's more! with two catch cans, everything gets much simpler (valve wise). not sure which route is better exactly.

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So there are a few things to address here before making a final decision:
  1. Understand what the pcv6 and 04+ catch cans look like.
  2. Retrofit the 04+ catch can (im assuming it is designed correctly internally to filter intake vacuum air) or fab a new catch can.
  3. The "single catch can" design can be used with the additional requirement that the drain be plugged and it be drained manually (every oil change?)
  4. The PCV system can be converted to something like "dual catch can v2" and the second can will have to be drained occasionally.

    And a couples notes:

  • "Catch can v2" will be most effective as a PCV system.
  • I need to look at how more modern turbo motors do PCV. I would guess it is down to correct catch can design?
  • some kind of restriction or flow metering is required for the intake vacuum path. Most pcv valves seem to be a 2in1 that use a spring and ball to regulate and check for boost. See typical internal diagram:
Rectangle Line Font Parallel Drawing
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Discussion Starter · #2 · (Edited)
just realized that "dual catch can v2" also has the vacuum through drain issue if the factory catch can is used. air goes in the catch can, out the drain and up the oil filler then into the intake. no clean air. If you swap the factory can to the intake side, it has no issue and wont foul the intake depending on can design.

v1 is better in that if the factory can is used for the boost side, there is definitely not an issue.

Edit: air actually not an issue. catch can drain is below oil level, should be essentially sealed, but the oil suction become a problem... see post below. v1 wouldn't have an issue.
 

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Discussion Starter · #3 · (Edited)
Last post gave me an idea. Pretty sure this following scheme fixes everything as long as the PCV6 catch can filters any air coming through the oil drain catch can drain is rerouted; see below.



Halfway through this post I figured out why Saab added the hole in the 04+ blocks for the catch can... if the inlet to the catch can ever gets blocked, the engine will suck all of the oil out of the pan into the intake through the drain tube (or should I say straw) that goes to the bottom of the pan. I need to think my way out of that one...essentially the catch can drain has to be above oil level.
 

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Discussion Starter · #4 ·
As I said in the previous post, the drain has to be above oil level. And the oil filler tube is very conveniently right there:
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So that's it, plumb per "single catch can v2" and re route the catch can drain to the oil fill tube. Not much else to say; I'll test this when I can.
 

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I run MY cars Blowby directly from the Valve cover nipple through a hose exiting down behind the Steering rack to atmosphere .

I turned off the evap system in the ecu.
Saves a LOT of goo being dumped into the Turbo inlet .. the Inter cooler and then into the Intake manifold.
Entirely eliminating engine Sludge formation source.
Yesss Not Eeko friendly at all..
But as Dump trucks in my region spew Solid Columns of Soot with each and every gear change.
My small contribution is totally irrelevant. .
G'luck.
 

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The issue with every dang version of the PCV system on the PCV cars has been oil usage... BECAUSE SAAB SUCKS DIRECTLY FROM THE VALVE COVER TO THE INTAKE
my 1997 2.3 non-turbo had a nice big hose running straight from the valve cover grommet to the throttle body. Even approaching 400,000 km, it used maybe 100mL of oil per 1000 km.

My 2003 PCV6 2.3 uses a litre of oil every 2500-3000 km or so. Same valve cover design--in fact, a 2.3 non-turbo valve cover (I like the black paint and "2.3".

So you have to explain why the non-turbo 2.3 didn't use oil, even though it on average was revving higher due to shorter gearing, sometimes multiple hours of 3000 RPM on the highway, and it totally drew straight from the valve cover without any catch can or drain back.. The 2.3t never does that kind of RPM.

(As one of the local Saab shops said, it's probably the turbo, not the PCV system, that causes the oil loss.).

I run MY cars Blowby directly from the Valve cover nipple through a hose exiting down behind the Steering rack to atmosphere .

I turned off the evap system in the ecu.
Saves a LOT of goo being dumped into the Turbo inlet .. the Inter cooler and then into the Intake manifold.
Entirely eliminating engine Sludge formation source.
Yesss Not Eeko friendly at all..
But as Dump trucks in my region spew Solid Columns of Soot with each and every gear change.
My small contribution is totally irrelevant. .
G'luck.
I guess you have no sense of smell. Because that's gotta smell awful. Crankcase vapours are foul. And the vapour recovery is the reason cars today (well, since around 1970!) don't smell like a gas station spill.

Plus the PCV system is "Positive Crankcase Ventilation" and it resulted in less sluge because the nasty vapours were all actively drawn out. You have gone back to a less efficient road-draft system.

Irrelevant doesn't even start to describe it.
 

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Discussion Starter · #8 ·
So you have to explain why the non-turbo 2.3 didn't use oil, even though it on average was revving higher due to shorter gearing, sometimes multiple hours of 3000 RPM on the highway. The 2.3t never does that.
I was thinking about this concept a bit as well. It's really as simple as non-turbo motors will have much less blowby so most NA motors don't have a catch can, just a baffle in the valve cover.

The connection directly to the intake from the valve cover will be an issue in two instances:
-worn motor
-high boost application.





I've also realized that my last idea still has an issue. The routing dictates that all vapors leaving the engine go through the oil filler which makes the valve cover baffles useless. Switching the air circuit around just brings back the poor fresh air circulation. Need to think on that more.
 

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The 2.3 NA was a B234, maybe the piston rings were stronger on the --4 engines. On the other hand, the compression was higher in the B234i than any B2x4 or B2x5 turbo motor.

I guess what I am fundamentally saying is that I don't see the vapour pickup point being in the valve cover to be an issue. Well, unless the two vent tubes clog up in the baffle clog up!

Anyway, there aren't all that many places you can put a PCV pickup point. The valve cover and the bottom end are all I can think of--and the bottom end/oil pan is going to be messier and more full of oil flung around than the valve cover.
 

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Discussion Starter · #10 ·
Yes, I wasn't intentionally trying not to pull from the valve cover. I was thinking about the fresh air flow path when I drew that. When I move the catch can drain point above the oil level for the suction issue and use the single catch can routing dwg to have fresh air go in the oil filler, the issue is that the easiest route for the intake to pull in air is from oil filler through the catch can tube.

Cams fling around oil as well. The catch can may be sufficient to catch everything when sucking from the oil filler.

I wouldn't be concerned about the suction issue if the two non boost check valves weren't there. They have a much higher failure rate than just tubing. They also add restriction in general that entices the vacuum to suck up oil.
 

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Discussion Starter · #11 ·
I looked at this again and a few requirements really force the direction of the system:
  1. gasses must be exhausted through the single port in the valve cover
  2. fresh air must enter from the oil filler and must come from the cobra due to the MAF
  3. Possible oil suction through drain
The solutions, in order of complexity (and increase in performance) are:
  1. Add small external catch can for the intake manifold PCV route (PCV6 + intake catch can dwg)
  2. Manually drain OEM catch can or replace with external (no by products drain to sump, should significantly increase oil life) (single catch can dwg)
  3. Using speed density instead of a MAF would get rid of the cobra ->filler neck feed (open to atmo with check valve)
  4. Adding a second baffle and pcv port to the front side of the VC would allow for just the single boost check valve, as you can "sweep" the VC with fresh air. This one is attached.

So that's it (for real this time I think). I'm going to start with #1 and look at possibly doing #2. I also want to stick a vac/pressure gauge on it to see what the crankcase is at under boost and idle.
 

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Discussion Starter · #12 ·
I run MY cars Blowby directly from the Valve cover nipple through a hose exiting down behind the Steering rack to atmosphere .

I turned off the evap system in the ecu.
Saves a LOT of goo being dumped into the Turbo inlet .. the Inter cooler and then into the Intake manifold.
Entirely eliminating engine Sludge formation source.
Yesss Not Eeko friendly at all..
But as Dump trucks in my region spew Solid Columns of Soot with each and every gear change.
My small contribution is totally irrelevant. .
G'luck.
FYI the vacuum provided by the various circuits of the PCV system is important to keeping the oil clean. Yes, the crankcase will still continually relieve itself, but not as efficiently at a positive crankcase pressure. And there is no fresh air.
 

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Discussion Starter · #13 ·
Bought this little (1.5x4") pneumatic air filter to monitor how much oil is going through the line towards the intake manifold. This is the metal bowl version and the drain is 1/8 npt so its easily replaced. SMC catalog has lots of other similar metal bowl PNs that would work.
Font Gas Cylinder Engineering Metal


I cant believe Jegs has the audacity to sell a crappy version of this for $85. The main issue is that they use a poly carb bowl which is neither heat nor chemical resistant... might as well just by an off the shelf filter for $13 at that point (SMC part is $23 new).
 

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So you have to explain why the non-turbo 2.3 didn't use oil, even though it on average was revving higher due to shorter gearing, sometimes multiple hours of 3000 RPM on the highway, and it totally drew straight from the valve cover without any catch can or drain back.. The 2.3t never does that kind of RPM.
I haven't ever had oil consumption issues on a B2x5 motor. The Viggen is definitely the worst, and it uses 1.5qt between 5000 mile changes.

I don't see how the PCV system can be a source of oil consumption. The separator on the back of block separates oil from gas and drains the oil back to the sump. Whatever gets burned off should be very slight. Most likely, any oil consumption issues are the result of ther low-tension piston rings... that's common amongst most engines from that era... VW, Mercedes, and BMW all suffered oil consumption increases during this period for the same reason.
 

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Discussion Starter · #17 ·
The only non filtered source is the small hose and check from the valve cover to the intake manifold. with poor rings, it will cause quite a bit of loss. I have forged overbore pistons and aftermarket rings, but I am running a tune and might upgrade to a larger turbo in the future (more blowby with higher performance). So yeah I did go down a huge rabbit hole for a small issue.

I am still curious and want to look at some other data points (crankcase pressure under boost, idle). I also want to look at what I think would bring the largest benefit to the engine system; drain the can separately, especially when running E85. If I could drain this once per oil change or have the drain in a good spot, I wouldn't mind.
 

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Discussion Starter · #18 ·
Received the check valves today. 5/16 A449 or A1235 check valves look like they will work well for the evap system.

The HAX36-DF0 3/8 checks are not as useful though. They flow less than the 5/16 valves, which isnt surprising considering the actual valve portion is smaller and the flow data says they all share the same core. These would probably work ok on the vacuum side of the PCV system, but definitely not to replace the large checks on pcv6.

The only remotely high flow valve ive seen is unfortunately made from acyrlic, so that will not work.
 

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Discussion Starter · #19 ·
Here's the filter (with cat tax). tapped the bottom to 1/8 npt and sealed with aircraft gasket maker (basically pipe goop). I already have a bunch of npt barb adapters for when I go to install this.
Cat Fluid Carnivore Felidae Small to medium-sized cats
 
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