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Old 10-18-2009, 07:14 PM   #1
andys
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Default Why do I need a PCV valve or an oil seperator?

Why do I even need PCV plumbing and/or an air oil separator ***8216;catch can'?



What is inherently wrong with this simple modified PCV plumbing?


From the FAQ: Can't I just vent these lines to atmosphere? (Essentially my question)

You could indeed, but there are several reasons why you shouldn't.
1) You'll lose the benefit of having the inlet's vacuum help suck filthy air out of your crank case (thanks to Wylde Horses for this one)
2) It's bad for the environment
3) It'll make a mess of your engine compartment.
4) It'd let metered air out of the system


What I am thinking:

Re the FAQ:
1)This is absolutely true. You will lose the cleaning effect - but there were millions of cars produced up until the 60s that used the open system. This is also true with the Crawford ***8216;secure high boost' method. I'm pretty sure that if you car is not a winter commuter, you run it hard and you monitor and change you oil on a more regular basis then you won't have any problems. With the ***8216;vent to ground' system you also won't have the clogged catch can issues illustrated below.
2) Yes, it's bad for the environment. But so is burning the huge amounts of fuel required for high HP engines in the first place?
3) It won't make a mess of your engine compartment if you vent it down past everything. Trivial.
4) It won't let metered air out of the system if you don't take metered into the system as in the simple modified PCV plumbing pic.

Other stuff:
5) Yes, I know you'd have to eliminate any PCV related CELS that would arise. Not a big deal.
6) Yes, I know you run the risk of loosing oil - but I don't think this is an issue. The closed ***8216;drainable' catch cans don't return oil either.

Why don't I just run some kind of catch can?

I have a few pragmatic reasons:

1) I want to keep my custom high-flow intake plumbing extremely simple. It's a PITA to accommodate all the PCV send and return lines when fabricating a custom intake.
2) I don't want ANY potential for injecting oil contaminated mist into my detonation-sensitive engine (It killed my last one)
3) I don't want any extra hosing cluttering up the engine compartment and trapping pools of oil. My last engine had a hose become disconnected, and all kinds of oil dumped onto the down pipe filled my car with thick smoke. Not cool. Fire? Ask this guy: http://forums.nasioc.com/forums/show....php?t=1843715
4) I don't want to spend the time or money on complicated plumbing and the purchase or fabrication of parts that have zero benefit. Especially hundreds of dollars!

So, if you have any insight (stuff you can support, not just what you 'think') as to why the simple vent system is bad idea, and I haven't touched on them here, please let me know!



Background Information:

Catch Can FAQ:
http://forums.nasioc.com/forums/showthread.php?t=754710


Stock PCV plumbing - under vacuum and pulling out ***8216;volatiles' (aided by the vacuum lowering boiling points of water, fuel etc. etc. ). Pulls in 'fresh' AFM metered air into the crank case throught the heads and pulls it out through the port in the block. PCV valve provides regulated manifold vacuum 'suckage'.



Stock PCV plumbing - under boost and dealing with significantly increased blow-by via allowing the engine to ingest the oil mist and lowering fuel octane increasing chance of detonation. And so on. The two head and one block ports are now all exhaling crankcase volatiles and blow-by.



Oil return application with PCV vacuum based operation and off boost ***8216;oil cleaning'. (but not really - see post below)



Apparent Crawford Method - no on-vacuum PCV based ***8216;oil cleaning'. Immune to PCV valve failure. Prevents oil mist from normal vacuum operation causing detonation in highly-tuned engines. But why on earth is the output air routed back to the inlet? A) it's not metered air (it's 100% blow-by), it's useless and arguably a tuning interference and B) there is a ***8216;chance' of this air being full of oil. (and please don't tell me it's for environmental reasons on a 350hp+ Subaru***8230;***8230;_




Note:
Downsides to manifold based vacuum PCV fresh air ***8216;oil cleaning':
Under high boost if you PCV valve fails and lets boost into your engine crankcase you are toast. Seals go pop and you are also going to push huge oil into the intake. So you may want to implement the Crawford anti-PCV valve style plumbing - but then this has its own problems of not allowing engine cleaning PCV flow in off boost operation. (There's a reason why the stock system is as it is. It's the best solution from a long-term reliability and maintainence perspective)


Yellow goop in a 'Crawford(?)' oil seperator presumably due to no vacuum based fresh air flow PCV oil ***8216;volatiles' cleaning. Apparently from a winter commuter.

References:
http://en.wikipedia.org/wiki/PCV_valve
http://www.iwsti.com/forums/2-5-lite...ns-thread.html
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Last edited by andys; 10-20-2009 at 03:08 AM.
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Old 10-18-2009, 11:57 PM   #2
NSFW
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Two relatively recent Ixiz customers have said that Ixiz is no longer recommending keeping the PCV valve - the 'Crawford' approach is now what Ixiz recommends as well. The instructions at the Ixiz site had not changed as of a few weeks ago, though.

There's one big issue with the formerly-recommended-by-Ixiz setup: when the manifold is in vacuum, it sucks air/oil/crap straight from the crankcase to the intake manifold, through the PCV valve. It defeats the a/o separator. Also note that to the extent that the manifold vacuum would be reversing the flow through the separator - sucking on the line that's supposed to blow from the crankcase to the separator, and thereby sucking (via the separator) on the line that's supposed to blow from the heads to the separator. I haven't spoken with Ixiz about this personally but I'm guessing these are the reasons why it's no longer recommended.

Quote:
But why on earth is the output air routed back to the inlet? A) it's not metered air (it's 100% blow-by), it's useless and arguably a tuning interference and B) there is a ***8216;chance' of this air being full of oil. (and please don't tell me it's for environmental reasons on a 350hp+ Subaru***8230;***8230;_
If the separator works, the oil content should be negligible.

I hate to break it to you, but my 350hp+ Subaru spends most of its time making the 20-50hp required to get me around town. It's also got a cat in the downpipe. I still enjoy that 350+whp every chance I get, but I trust the separator to work well enough that I don't see any need to be spewing blowby directly into the atmosphere on top of all that exhaust. Call me a treehugger if you wish.
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Old 10-19-2009, 01:27 AM   #3
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Quote:
Originally Posted by NSFW View Post
when the manifold is in vacuum, it sucks air/oil/crap straight from the crankcase to the intake manifold, through the PCV valve. It defeats the a/o separator. Also note that to the extent that the manifold vacuum would be reversing the flow through the separator - sucking on the line that's supposed to blow from the crankcase to the separator, and thereby sucking (via the separator) on the line that's supposed to blow from the heads to the separator. I haven't spoken with Ixiz about this personally but I'm guessing these are the reasons why it's no longer recommended.

If the separator works, the oil content should be negligible.

I hate to break it to you, but my 350hp+ Subaru spends most of its time making the 20-50hp required to get me around town. It's also got a cat in the downpipe. I still enjoy that 350+whp every chance I get, but I trust the separator to work well enough that I don't see any need to be spewing blowby directly into the atmosphere on top of all that exhaust. Call me a treehugger if you wish.
I see your points about the IXIZ technique. I didn't see that. Thanks.

I also see your point about your driving cycle. But then why would you want to give up the fresh air flow through of a vacuum based off-boost PCV circuit? This would seem more important than a self-draining catch can. Occasional boost and most time spent not creating boost-induced blowby seems like a recipe for contaminating oil. My point being that the Crawford self draining approach (and air out question) perhaps isn't for 'commuter applications' due to the inherent lack of fresh air oil cleaning. It's perhaps more of a high-performance 'track' solution where you are not oil life and 'emissions focused' by definition.

Anyway, I'm mostly interested to know if the simple direct vent method is harmful to the engine in anyway.

And FWIW my car has to pass a gas chromatograph emissions testing routine so it has to have a cat as well as pass all the OBII diagnostics. Although I haven't looked formally into it - I ssuspect there is negligible emissions coming out of the air-out hose on a net per km basis. Especially when compared to tail pipe emissions. Not to mention we hear of guys collecting 4oz of catch can oil over 3000 miles... where 3000 miles = 150 gallons of fuel consumed. And so on. A little environmental perspective is always good.

Last edited by andys; 10-19-2009 at 01:50 AM.
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Old 10-19-2009, 02:10 AM   #4
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If I can get vacuum-based off-boost PCV with a separator, I will. I'm pretty sure that's do-able if you just put the PCV valve on the line that runs from the separator to the turbo inlet, perhaps with a restrictor on the turbo inlet side to keep the manifold from drawing directly from the inlet.

Since I'm about to switch to a blow-through MAF setup, I'll need an extra post-MAF nipple installed (right before the throttle body) but I do want to try this out. Perhaps I'm only going to find out why nobody else does this... but the mayo/yogurt pictures worry me.

I'm not particularly interested in debating environmental impact (I mean, come on, I drive a car with 350+ whp!) but less is better.
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Old 10-19-2009, 03:20 AM   #5
andys
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I think this will draw a vacuum on the crank case - depending on the restrictor - but it doesn't pull through any fresh air. It's probably 'better' at sucking out volatiles but a well engineered solution always keeps in perspective 'how much better', what's the risk and is it worth it? Furthermore, I'd be worried about the effects of pulling negative pressure on the subie motor's oil system. Who knows what seals are designed to withstand what pressures etc. etc.

The fresh air flow through system - I think - is key for clean, non-corrosive crankcase environment and long life oil. E.g daily drivers.

The OEM solution is nice and the ideal way is obviously to use two catch cans on each of the return connections to the intake. However this may cause the catch can on the head side to goop up since it will run cold compared to the other.


As far as the goop build up goes. Well here's my theory:

If you have no fresh air PCV circuit then all the volatiles build up in the engine oil and crankcase. Water, water vapor, fuel, fuel vapor and whatever else is in there. When you get on the boost and the blow-by effectively purges out the high concentrations of vaporised water, fuel and oil mist into the 'cold' canister where is condenses/coalesces forming the yellow goop. If the catch can and other was heated this would likely not be an issue. If the AOS/catch can wasn't there it also wouldn't be an issue as the blow-by pressure can easily blow the goop out of the free-venting tubes.

example: http://www.wrxtuners.com/forums/f75/...-inside-27321/

So, I'm not sure how confident I'd be returning the AOS/catch can line into my intake knowing I've created a recipe for oil drain blockage (see pic above) and eventual direct flow from he high pressure crank to the low pressure intake. But I live in Canada...

Last edited by andys; 10-19-2009 at 05:49 PM.
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Old 10-19-2009, 04:31 AM   #6
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Default catch cans

It looks like you can get the best of all worlds by adding a check valve to the connection of the head vents to the turbo inlet. This forces all the boost blow-by out the crank case port (I can't immediately see why this would be bad), allows for one warm seperator (self draining or not) and maintains full cross-flow PCV cleaning under vacuum.





Both of these systems require fresh metered air to flow through the system so you can't vent the nasty stuff. Not because it's not environmental but rather because it's not possible. But once you've committed to a secure high boost system that eliminated fresh air cleaning I'm still curious about why one wouldn't simply skip all the catch can stuff and simply direct vent. I'm sure all of my motorcycles have done this. In fact what's wrong with the following:



where all the blow-by can escape... looks simple to me. My choice


full crankcase vacuum where the PCV and another check valve in the vent are used to pull full manifold vacuum inside the engine to aid in volatiles removal. But may ingest some oil. Even tho there is no air flow through if you pull a strong enough vacuum - like <.2atm - you can do a good job at pulling out volatiles.


and building on that you can put a seperator/vacuum buffer in line with a ~1psi vent and then you can operate with FULL manifold vacuum in the engine - even when on the boost. This is aided by the 'brake booster sytle' catch can/vacuum buffer. In this scheme you get all the PCV valve failure protection and you get rid of the air losses inside the engine. Nascar style.





BTW - One thing I don't understand is why Subaru uses vents on both heads or even more than one vent on each head. In principle everything should work with one. This leaves me with a suspicious feeling that I am missing something. Something like there is a significant air restriction between the two heads and the block...

Edit: I have a theory on this now. All the early turbo and NA engines pre-avcs use the same PCV system that fundamentally requires low resistance air flow through the oil return ports in the bottom of the heads. Add avcs and now this is a bit more difficult due to the increased oil congestion in the heads - so Subaru had to allow for low restriction air flow elsewhere else. This is why there are three new ports directly plumed into the three main oil sections of the subaru engine. No baffles not nuthin' - just three holes so air can move around.

Last edited by andys; 10-20-2009 at 02:55 AM.
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Old 10-19-2009, 01:27 PM   #7
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assuming you have heads with dual breathers (JDM 2.0L or USDM 2.5L or others), and you arent MAF based

use one port on each head and the second crank port as an equalization/balance line

vent each head and the other crank to atmostphere (can be all vented in one pace or seperately, just be sure you have enough flow). you can vent all to atmo using a catch can, or a seperator, or nothing, but if you use a can, or a seperator, be SURE that you make a new big ass port/filter that can flow the combo of all three ports - the "intake sized" port is not big enough if you dont have the suction effect

the 'goop' in the pics will happen with any catch can, or seperator, in cold climes, the soloution is simple, a lot of guys will run small coolant lines (the overflow) around the can. Another example of why 'those guys in xxx place run this so it must be ok' doesn't work in places like Edmonton where its -20 all the time

a seperator is better than a catch can because the can doesn't fill up, and you "loose" less oil

not sucking it back into the engine makes for better go

If you are MAF based then whatever you do better be airtight (under vac and press)

p.s. if the heads flow to the crank, without breathers, then I'd say you've got some bottom end issues :-)

and if you've got the single breather heads you have a choice, use them as balancers to the second crank port and still vent through the single crank port, or vent each directly (better) using same method as above.

At all times, beware, if you have a car with slicks and suspension, that high Gs will toss all the oil to one head so the breather can get plugged, hence the balance lines, so if you have a single breather head a baffled sump is even more important. This is why you see guys at track days with intakes full of oil, on cars which otherwise dont do it.
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Old 10-19-2009, 02:05 PM   #8
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Quote:
Originally Posted by patr View Post
if the heads flow to the crank, without breathers, then I'd say you've got some bottom end issues :-)
Thanks Pat,

But I don't fully understand the above. On my single vent heads and in the stock application air is drawn in through the head 'vents' and out the crank 'vent' by manifold vacuum and PCV valve operation - so there is a pathway for air flow from the head ports to the crank port through the bottom end. if I plug the head breathers completely the valve-guide etc. blow-by gasses should still make their way out of the head and out the crank port by the same flow path and I shouldn't need to worry about high-g oil venting out the head. Or am I missing something?

So, it looks as if my initial pic at the top is the way to go. Cool. I'd rather plug both heads tho and use one crank 'vent' ... if possible.

Last edited by andys; 10-19-2009 at 02:12 PM.
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Old 10-19-2009, 02:14 PM   #9
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I meant if there were no breathers connected.

If you want to run a single vent in an equalization setup then yes tee them to one of the crank ports, and breathe the second crank port.If you dont tie it to the intake and you are running MAFless you dont really need a valve. But its not as efficient as beathing each one, just for volume's sake. At your power levels it probably wont matter anyways.
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Old 10-19-2009, 02:26 PM   #10
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Quote:
Originally Posted by patr View Post
I meant if there were no breathers connected.
If you want to run a single vent in an equalization setup then yes tee them to one of the crank ports, and breathe the second crank port.If you dont tie it to the intake and you are running MAFless you dont really need a valve. But its not as efficient as beathing each one, just for volume's sake. At your power levels it probably wont matter anyways.
I'm still confused. Maybe I didn't ask the question right. Sorry. Let me try with pictures.


This pic shows the OEM air flow from the head 'breathers/vents' to the crank 'vent/breather'. There has to be an 'air' flow path from the heads to the crank through the bottom end or the fresh air flow through 'oil cleaning' wouldn't work.


So why can't I do this with both head vents completely blocked off?

I'm not sure what MAF or MAP has to do with this later scheme. In the prior system MAF metered air is a key component. But in the later system it appears independent of any MAF considerations. There is no diversion of metered air used for anything.

But I must be missing something or everyone would be doing this later schem - at least with single vent heads. ... and maybe I need to understand why the 2.0 JDM and 2.5STI have dual head vents.... I'll look into this.
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Old 10-19-2009, 02:32 PM   #11
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re-read my original post slowly. dont do anything else.
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Old 10-19-2009, 02:33 PM   #12
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The only reason to keep the cc or AOS plumbed into the intake is to create a slight vacuum in the crank case. The slight vacuum helps the rings seal and makes the engine work more efficiently. That's the only reason to keep it.
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Old 10-19-2009, 02:38 PM   #13
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Ok I have a theory:

1) With the OEM solution air is drawn in through the heads via a relative vacuum on the crank vent.

2) The negative pressure in the crank case come from a combination of PCV operation/manifold vacuum and a purposeful flow restriction between the crank-to-turbo inlet pipe.

3) If the flow restriction is omitted then the PCV valve will suck everything directly from the turbo inlet and not the crank... you don't want this.

4) But if you don't have this vacuum leak to the turbo inlet (e.g. it's plugged) you sucking far too much air directly through the crank. More air flow = more oil mist ingested. And so on.

5) So under boost, if my theory is correct - the majority of the blow-by air flow goes out the heads - not out the crank port due to the flow restriction before the turbo inlet.

This can probably be confirmed by finding larger plumbing from the heads into the turbo inlet and by finding more oil residue at the head-to-turbo inlet pipe rather than the crank-to-turboinlet pipe.

So this is what makes the head plumbing important.

It still makes me think I can block the heads off completely if I'm not implementing PCV-based fresh air flow though.

Just a theory.... probably wrong somewhere.

Last edited by andys; 10-20-2009 at 01:32 AM.
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Old 10-19-2009, 02:49 PM   #14
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I re-read your post. Slowly. And, you're right - I did miss this:

Quote:
Originally Posted by patr View Post
the "intake sized" port is not big enough if you dont have the suction effect
While this is 'instructional', it still doesn't answer my question. If the port is too small then the crank case presure will go up by a fraction of a PSI or something to push the flow through the small 'intake sized port'. Why is this a problem - other than the obvious issue of not wanting to pop oil seals?

If I plug both heads thus forcing all the blow-by gas out the crank vent/port will this work? And if it doesn't work what goes wrong - and why?

I suspect that due to the mechanical topology of all the bits and pieces once I start blowing huge flow out the crank port I'll also lose a lot of oil - since it's not designed to flow that much air in that direction. Even in the original NA applications.

So this makes me perhaps think I should plug the crank vent/port and just use the head vents as the blow-by exit.

Now I am seeing that if vent the heads and the crank to atomosphere I may still experience excessive flow out the crank vent compared to the OEM solution - resulting in excessive oil loss. It would appear that I need to either block the crank outlet or at least put in the same restriction that fed to the turbo inlet.





BTW I may have to make more power than the original Spec C..... I've got some 650 cc injectors on the way. And an intercooler. he he.

Last edited by andys; 10-19-2009 at 06:14 PM.
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Old 10-19-2009, 02:54 PM   #15
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Quote:
Originally Posted by Bad Noodle View Post
The only reason to keep the cc or AOS plumbed into the intake is to create a slight vacuum in the crank case. The slight vacuum helps the rings seal and makes the engine work more efficiently. That's the only reason to keep it.
What do you think the vacuum pressure is at the turbo inlet at full flow? I doubt it's anything significant wrt to crankcase vacuum and ring seating or whatever. I bet the intake vacuum it's like .95 atm whereas the vacuum used for ring seating is like 0.1 atm - or a real vacuum and not a slight negative pressure.

But I'm guessing. I've never measured it.
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Old 10-19-2009, 03:11 PM   #16
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Old 10-19-2009, 05:22 PM   #17
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Quote:
Originally Posted by Bad Noodle View Post
yeah - read it - too much bishin! But that's where the pics came from and why I referenced it. But you always get more out of it reading it a second time. Thanks.

So far my questions are still unanswered and it looks like Crawford gets strung out to dry with their AOS by '405'. At least from a technical perspective. My opinion only.

It looks like you only NEED an AOS when you use metered air to vent your crankcase because you need to re ingest this metered air free of oil. But the Crawford AOS system forgets about fresh air crankcase cleaning (short term 'whatever') but still argues the need for an AOS. However the 405 guy is argues that omitting the PCV fresh air cleaning is totally stupid for high power daily drivers when you can actually implement a solution that solves all problems. Which the Crawford system apparently doesn't.

I think most don't people appreciate the fact that the stock PCV system SLOWLY and CONTINUOUSLY evaporates engine contamination with fresh CLEAN air flowing THROUGH the oil during the off boost stage of operation. Capturing oil mist and blow-by in at high boost is one thing that seems obvious to people - hence the 'catch cans' and their suggested plumbing. But slowly removing oil contaminants by washing the oil with a flow of clean fresh air OFF-BOOST seems to be lost on a good section of people who are commenting on this - and this is what removes most of the harmful crap form the engine. And I wouldn't be surprised if you did an oil analysis with the Crawford AOS architecture and you found super-high concentrations of crap dissolved in the oil... the same stuff that's showing up on boost in the catch can for rapid coalescing and goop up.

So a question is: is it cool to run a daily driver with no fresh air crankcase cleaning flow? Crawford seems to say yes. My impression is that is wouldn't be ideal wrt engine life. That blow by crap gets dissolved in the oil and you probably want to get that crap evaporated out of the oil ASAP. The fresh air venting theory seems a pretty sound way to do this. In any case there are some unanswered questions regarding the overall theory of operation for the Crawford AOS wrt: cold goop build up, overall volatiles removal with fresh air flow(not just blow by overpressure) and the amount of oil cleaning 'vacuum' you develop near the turbo inlet.


BTW my application isn't a daily driver so I'm not concerned with clean air flow-through PCV. But I'd be concerned about running a daily driver that had no obvious way of continuously cleaning out volatiles dissolved in the oil - especially when the stock system works very well. Perhaps it's a non-issue? The point is that it's not an obvious non issue.


Another reason to just avoid unnecessary stuff - which is my intention


Misc take aways:

"There are oil separators in the valve covers to limit the oil vapors that enter the PCV hoses attached to the valve covers. On AVCS-equipped cars there is also a second set of hoses connected to the valve covers that are not specifically part of the PCV system but are there to improve the oil return from the cylinder heads back to the block. It should be noted that oil vapor or mist is created by oil thrown off and whipped up by the crankshaft and the PCV system needs to allow this oil mist to separate out from the blow-by gasses."

"This is when our AOS shines as there is plenty of vacuum in the turbo inlet while making boost." Whatever plenty means. And what difference does it make. The blow-by will push all the gas out regardless of turbo inlet 'negative pressure' or not. It's all about deltaP and it doesn't take much dP to move that blow-by gas out of the crank. To the turbo inlet or to atmosphere. Pretty much the same thing IMO.

"A closed PCV system has two separate parts.
Clean side
Dirty side

The clean side brings fresh metered air into the crankcase. The dirty side evacuates combustion by products out of the crankcase.

Your design (Crawford design) joins the two sides at the AOS. The issue with this is reversion and system flow. Most stock PCV systems barely have the required capacity to properly evacuate the crankcase and keep pressurization at bay. Joining the two sides reduces the number of paths and causes issues due to reversion on the clean side. Maintaining both sides as separate parts is very important to system efficiency. "

"Like most factory PCV systems, system flow is not sufficient to evacuate the crankcase. So, under high blowby conditions the dirty side meets it's flow cabability and the pressure will go somewhere. Mother nature takes the path of least resistance. That somewhere becomes clean side reversion which brings carry over oil out of the valve covers, into the intake tube."

"Keep in mind the clean side is designed to flow INTO the crankcase, but will reverse flow when the dirty side is over capacity. It's all about DeltaP....when the pressure inside the crankcase exceeds atmospheric it will equalize. The clean side is the path of least resistance, so it reverses flow to equalize pressure. "

"I had the PCV fail on my 08 STI and put a quart or 2 through the intake. The intercooler was full of oil. It took 3 months to fully get it all out. The PCV failure also caused detonation and ring, piston, and rod bearing failure. "

Last edited by andys; 10-20-2009 at 02:35 AM.
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Old 10-19-2009, 06:04 PM   #18
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to sum up, for a NON Daily Driver application with no clean air ventilation and NO oil separator. (I'm not really that interested in the AOS/catch can debate):



Pat gives this approach the thumbs up. Cool. But I worry it might encourage too much oil mist flow out the crank port without some kind of restriction. Any feedback out there on this?




I like this approach becasue it prevents oil out the head flow at high Gs. Would encourage MORE oil out the crank port if this were to be an issue. Any thoughts?




This approach forces all the blow-by out the heads and elimates oil out the crank port. Is this a better idea?

Yeah I know the obvious answer is to go with the top option (what pat said) and monitor oil consumption (what I'm sayin'). But I am curious about thoughts on the other two schemes.

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Old 10-20-2009, 12:23 AM   #19
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Thanks for pointing out the shortcomings in my plans, guys.

I still think there's got to be a way to get the best of both worlds - separator to keep the oil in the engine, and PCV to keep the engine "clean." The setup andys posted with the check valve on the head breathers seems promising.

However, with a blow-through MAF system where the only source of metered air is sometimes pressurized, the problem gets harder.
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Old 10-20-2009, 01:32 AM   #20
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deleted for now...

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Old 10-20-2009, 02:02 AM   #21
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Well, for a number of reasons it's looking to me like most of the 'escaping' oil naturally exits the heads - and perhaps shouldn't exit the crank.

So put an AOS between the head and turbo intake and let the oil flow back into the head - aided by the natural PCV vacuum pull when off boost.

Then put a small - if any - catch can between the crank vent and turbo inlet where there will be less oil - I think

Last edited by andys; 10-20-2009 at 02:14 AM.
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Old 10-20-2009, 07:38 AM   #22
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My arguement against the pcv is:



I pulled my manifold off 2 days ago to install perrin fuel rails and found that I have a nice coat of oil on the intake ports to the heads.

I'm running a baffled mFactory catch can with clear lines and you can see how much oil is going in and how much is coming out. So my guess is the oil residue in the heads is from the PCV pulling in oil vapor from the crank case otherwise I would have a lot more oil in my intake or the exit of the CC
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Old 10-20-2009, 09:01 AM   #23
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clean engine means not using the engine's vacuum to suck on any of the gases meaning yo need an external source of vacuum.

why would you want that oil going back into the engine? Is this a track car? do you get that much blow by? maybe you should address that issue first instead of trying to fix a symptom, fix the problem. Is it too hard to check your oil every once in a while?

if you really need to pull a vacuum using your engine, put a properly baffled catch can/AOS btwn the crack case vent and a check valve before going into the intake manifold. the PCV is nothing but a one way check valve, fyi. also, you would need to try and keep the catch can cool so that the oil and/or fuel vapors will have a better opportunity to condense. from there you have a choice of draining it back into the oil pan or not.



oh, btw, your arrows in the pic on post #10 are going the wrong way. they should all be getting going towards the air intake duct not away from it.
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Old 10-20-2009, 09:17 AM   #24
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I did some more digging around as to weather you should VTA or attach the clean end of a CC or AOS to the intake.

I found a lot of mixed opinions:

- crawford says to hook up to inlet, something about piston ring seal. In their post they said to google the effects of vta on piston ring seals. I did, but couldn't find anything.

- Ford guys said to hook up to inlet because having a slight vacuum will ease air pressure in back of the piston and thus help make power and efficiency.

- race cars vta and that's "proven" and how much can 0.25 psi really help? Realistically, I would say it's about that or how ever much resistance your air filter has.

- no AOS or CC is perfect and there will always be some contaminates in the intake.


I'm on the fence about this... I can't find any real evidence either way
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Old 10-20-2009, 11:34 AM   #25
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Quote:
Originally Posted by Bad Noodle View Post
My argument against the pcv is:
yeah but this is totally normal..... that's what you need to understand!

In a super-high performance race application you can eliminate this 100%, sure, but are you willing to pay the 'price' of eliminating oil cleaning too?
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