AOS/CC discussion about air oil separators and catch cans...

Ask for help with doing something on your car here.

Re: AOS/CC discussion about air oil separators and catch can

Postby bigBADbenny » Sun Nov 22, 2020 1:14 pm

So for clarity's sake, I'm going to refer to the CCV in the middle of the block as the CCV/balance vent.

And the block port that feeds the PCV as the sump breather vent (SBV?).

Unless you or the Perrin guide has a better solution.
User avatar
bigBADbenny
 
Posts: 9488
Joined: Tue Oct 04, 2011 6:36 pm
Location: Collingwood, Melbourne
Car: MY07 GT-B 6MT OBP Wagon
Real name: Ben Richards
Profile URL: http://tinyurl.com/agvbzop

Re: AOS/CC discussion about air oil separators and catch can

Postby Yowie » Sun Nov 22, 2020 1:19 pm

Sounds good to me.

Too many acronyms can be confusing though (even though I have said "PCV" a lot like a total hypocrite). If you're doing a round of editing perhaps consider using the long-form of each expression at least once per post.

(Not being a smarty-pants here)
User avatar
Yowie
 
Posts: 194
Joined: Tue Jul 21, 2015 10:05 pm
Location: Brisbane
Car: SH Forester XT

Re: AOS/CC discussion about air oil separators and catch can

Postby bigBADbenny » Sun Nov 22, 2020 1:20 pm

Yowie wrote:
(1) So the valve cover breather baffles must be there to prevent oil surging out of them and into the inlet.


Almost certainly. There are also baffles inside the engine just before the crank vent for the same reason.


AOS on the rear of the block indeed for the sump breather vent.

Yowie wrote: The idea is to deal with blow-by gas but keep the oil in the engine as much as possible. Obviously these baffles and even my catch cans are not perfect funk filters or some oil wouldn't be present on the "clean side" hoses after my catch cans.

I wonder how many efficient catch cans in series it takes to remove all oil residue & water vapour? It's a shame Mythbusters are not going anymore.


The simple answer is Provent filtered catch cans, but at what expense to PCV system efficiency?


Yowie wrote:
(2) I guess all the different hose sizes and restrictors in the system help to create a pressure differential in the PCV system with the majo vacuums being drawn at the PCV return in the inlet and the actual PVC valve in the intake manifold.


I would think so. I'm still intrigued by the factory restrictions in the crank F-shaped splitter and what is best practice (factory/some/nil restrictions) for a warmed-over road car. There are too many variables for my experiments to yield any answers.



(3) Another thread on LGT mentions that the heads/CCV balance pipe runs alongside the turbo coolant hose supply pipe in order to help evaporate sump condensation...


Interesting. That makes sense. Sump water vapour is a really big deal on E85 but still a factor on petrol (especially for "cold start 2 min drive to train station" usage where it can't boil off).

This is why I am not a fan of "drain back to sump" catch can setups, even if heated by coolant water. A trickle of liquid water into the sump (eg on cold start) cannot be a good thing. Andrew Hawkins of the Motive videos reports no issues with drain-back catch cans on E85, so I'm probably wrong to be such a sceptic.


(4) To add to the complexity, there's also the loose-built engine factor.


Yep, more blow-by.

A lot of those drag & dyno competition cars just vent-to-atmosphere from the catch can on my understanding. Probably better for their application for a lot of reasons including octane preservation under maximum effort runs.

Yet pulling a crankcase vacuum yields HP gains?


(5) Would be interesting to use a PCV as a one-way valve on the cam cover breather return.


Preventing which direction of flow?

On a related note, I'm interested in using a OCV on the hose between the pre-turbo pipe and the PCV so the PCV cannot draw clean air from the pre-turbo pipe under manifold vacuum conditions. I can stop worry about the restrictor issue then.[/quote]

Preventing flow from the heads to the inlet!
User avatar
bigBADbenny
 
Posts: 9488
Joined: Tue Oct 04, 2011 6:36 pm
Location: Collingwood, Melbourne
Car: MY07 GT-B 6MT OBP Wagon
Real name: Ben Richards
Profile URL: http://tinyurl.com/agvbzop

Re: AOS/CC discussion about air oil separators and catch can

Postby bigBADbenny » Sun Nov 22, 2020 1:27 pm

I have to say my approach is one of analysing the stock PCV system to understand how it works, and then seeing what solutions (if any) are available to improve it.

The major setup was sorting the stock system so no more cracked PCV pipes and leaking injector seats and sensor o-rings: no more phantom knock during cruise, no more oil in inlet.

Whereas you and others have an AOS/CC setup that may add complexity and drag on the stock PCV system and which still doesnt work perfectly or as expected.

I'm trying to close that gap by starting with comprehension of all the varied factors involved.

As regards ultimate wet sump oil control, I'm keen on the ArcTangent Design solution, where the engine was tilted during testing to simulate oil surge in high G corners. Its expensive though! :(
User avatar
bigBADbenny
 
Posts: 9488
Joined: Tue Oct 04, 2011 6:36 pm
Location: Collingwood, Melbourne
Car: MY07 GT-B 6MT OBP Wagon
Real name: Ben Richards
Profile URL: http://tinyurl.com/agvbzop

Re: AOS/CC discussion about air oil separators and catch can

Postby Yowie » Sun Nov 22, 2020 1:48 pm

The simple answer is Provent filtered catch cans, but at what expense to PCV system efficiency?


Is there any info about the actual scrubbing efficiency of these Provents? I suspect the "nothing is 100%" rule will still apply.

As long as air can flow through the catch can I'm not too worried. Note the "small holes" restrictions the factory puts on the crank vent system.

The pic below shows the modified internals to my Mishimoto "long compact" catch can. Air still flows easily (per breath test). See also intercooler and radiator basic principles - lots of metal surface area ('restriction') but the whole assembly is big enough for sufficient flow.

Image

Whereas you and others have an AOS/CC setup that may add complexity and drag on the stock PCV system and which still doesnt work perfectly or as expected.


The only complexity added by my approach is a catch can inserted in each of the factory loops before the engine ingests the dirty air. See comments above on flow.

Re "doesn't work perfectly or as expected", my only complaint is that scrubbing the dirty air is not 100% effective because some funk still gets past each catch can.


Yowie - A lot of those drag & dyno competition cars just vent-to-atmosphere from the catch can on my understanding. Probably better for their application for a lot of reasons including octane preservation under maximum effort runs.

Ben - Yet pulling a crankcase vacuum yields HP gains?


The perfect drag or dyno competition car would probably have mechanical crank gas extraction (to dry sump or otherwise). I suspect many don't and just vent-to-atmosphere for the sake of simplicity and those "low pressure sump" killer wasps are left on the table. "Not knocking at extreme load" is probably the priority, hence no crank gas ingestion by the intake.


Would be interesting to use a PCV as a one-way valve on the cam cover breather return. (Preventing flow from the heads to the inlet)


Then the engine is relying entirely on the crank case vent to exit the dirty air. The balance pipes would need to work harder, perhaps now in one direction only (towards the crank).

Noting the sh!tload of water vapour that gets extracted from my valve covers (on E85) I would be concerned about whether that water can escape as efficiently without condensing within the engine on a longer gas journey to the crank vent.
User avatar
Yowie
 
Posts: 194
Joined: Tue Jul 21, 2015 10:05 pm
Location: Brisbane
Car: SH Forester XT

Re: AOS/CC discussion about air oil separators and catch can

Postby bigBADbenny » Sun Nov 22, 2020 2:29 pm

But you said you still had some oil in the inlet and intercooler?

I mean that adding hoses adds drag to the system, changing restrictors and pipes around affects the pressure differentials.

We’re not talking absolutes here anyway.

This thread is 100% heuristic in nature.

Its a difficult system to test, other than going worst case cold start e85 torture.
User avatar
bigBADbenny
 
Posts: 9488
Joined: Tue Oct 04, 2011 6:36 pm
Location: Collingwood, Melbourne
Car: MY07 GT-B 6MT OBP Wagon
Real name: Ben Richards
Profile URL: http://tinyurl.com/agvbzop

Re: AOS/CC discussion about air oil separators and catch can

Postby Yowie » Sun Nov 22, 2020 2:48 pm

(1) But you said you still had some oil in the inlet and intercooler?

(2) I mean that adding hoses adds drag to the system, changing restrictors and pipes around affects the pressure differentials.



(1) Correct. I put that down to non-100% scrubbing efficiency of the catch cans and the remarkably large volume of (in descending order) water vapour, aerated oil emulsion and liquid oil coming out of the engine vents on E85.

When I ran on petrol the catch can volumes were much less and different in content blend.

There would be much more cr@p in my intake tract without the catch cans, so what can I do except tolerate it or try to add filtering efficiency?


(2) I've kept the additional hoses as short as possible & avoided mid-hose low points etc. I'm not overly concerned. Some systems advertised seem to run metres of hose to places like battery tie-downs. Such long hoses wouldn't be my choice but the users may comment on the efficacy of the longer-hose setups.

At the end of the day we're not talking mission-critical airflow like past a valve into a chamber. It's just finding a way to get blowby gas out of the engine. Longish hoses of sufficient internal diameter (with no mid-hose low spots) should be fine.

Changing restrictions remains an item of curiosity for me, but most reputable sources seem to say that a higher performance engine means you need larger-than-factory exits for all the extra blow-by gas.

If anyone can post some quality notes on "the value of the deliberate restrictions at different points of the OEM system (and their relevance to a warmed-over factory motor in a street car)" I would be very interested to read it.

Removing my deliberate 6mm restriction from the crank-to-preturbo loop seems to not have changed anything measurable. I removed it to (in theory) allow better crank venting at full load, perhaps at the price of worse crank venting at high vacuum. A worthwhile trade if true.
User avatar
Yowie
 
Posts: 194
Joined: Tue Jul 21, 2015 10:05 pm
Location: Brisbane
Car: SH Forester XT

Re: AOS/CC discussion about air oil separators and catch can

Postby Kimmo » Mon Nov 23, 2020 4:58 pm

Yowie wrote:Sounds good to me.

Too many acronyms can be confusing though (even though I have said "PCV" a lot like a total hypocrite). If you're doing a round of editing perhaps consider using the long-form of each expression at least once per post.

(Not being a smarty-pants here)

Mad props. Would make this info far more valuable IMO.

PCV systems are totally down in the weeds, extremely nerdy stuff; even as a fairly nerdy nerd myself, my eyes have glazed over several times already from all the unfamiliar TLAs.
User avatar
Kimmo
 
Posts: 59
Joined: Sun Oct 25, 2020 8:26 am
Location: 3015
Car: 07 GT-B

Re: AOS/CC discussion about air oil separators and catch can

Postby bigBADbenny » Tue Nov 24, 2020 4:44 am

Why not pinpoint where you’re uncertain and we can enlighten you. :good:

I’m more interested in joining the PCV system dots at this point and have left the intro post till last, where a more thorough over view will be placed.

There’s other threads on the subject here as well.

Like this one which is very handy:
viewtopic.php?f=18&t=23097&start=60

The important point is that ensuring no PCV system/inlet/intake/crankcase boost vacuum leaks and a not stuck PCV valve is crucial for proper engine running, with correct oil control.

From there, if choosing aftermarket AOS/CC, to correctly route it, with minimal drag on the PCV system.
The latter part seems to be a major hurdle.

Eg my working, tested stock system has no oil in the inlet & tmic, some blow-by residue in the throttlebody hose, thus I have a good basis from which to experiment.

At this point I’m at the same conclusion I reached years ago (linked thread): 2 small cans on opposite sides of the engine for failsafeing oil surge in the heads, one can for the sump breather, pre PCV intake/inlet return.

Basically a poor mans substitute for the KillerB pre AOS anti surge valve.

To really keep blowby out, these would need to be filtered cans eg Provent.
Eg 2x small cans and one medium small.

Although filtered and thus potentially more restrictive, the load is spead across 3 cans, reducing overall drag.
User avatar
bigBADbenny
 
Posts: 9488
Joined: Tue Oct 04, 2011 6:36 pm
Location: Collingwood, Melbourne
Car: MY07 GT-B 6MT OBP Wagon
Real name: Ben Richards
Profile URL: http://tinyurl.com/agvbzop

Previous

Return to How do I?

Who is online

Users browsing this forum: No registered users and 4 guests