Thread: Crank Case Ventilation fully explained. (Turbocharged edition.)

No, no, no, no, no. Go look up what semantics means. It has nothing to do with personal preference. It has to do with how you label something.

You think the idea is not acceptable. I think it is. It's my thread, so my recommendation stays. It is on a spectrum of acceptability and I've drawn the line somewhere. You draw it somewhere else, changing the labeling (semantics) but none of the actual arguments or facts. By nature, I had to draw the line somewhere, so I picked there.


You seem to be confusing the word "acceptable" or "fine" with "best" or "bestest".

It would appear you've not read the N/A version of this thread as you were instructed to. You will find all sorts of better options spelled out, including what you're describing and more. All of these are listed as better ideas than the valve cover breather, allowing each reader to decide where on the spectrum of bad-to-good performance they want to land.

As mentioned in these threads, emissions are not taken into account in the recommendations. We are ignoring emissions, and so the valve cover breather ends up being an acceptable solution. OEM's can't ignore emissions, so obviously it is not acceptable for them.

Did my threads make it seem otherwise? I feel you've missed the N/A portion of this discussion, I really think you have.

I think I can shed some light on this.
In compiling this thread, I wanted to separate the benefits/pitfalls into the smallest units possible. I didn't want one benefit to get mixed up with another benefit. Because of this, I was trying to describe if a certain modification did at least the minimum of preventing excessive pressurization of the crank case. There are some modifications that would even ruin that function. I can see that it is not 100% clear, so I will amend it to say something like "Maintains stock prevention of excessive crank case pressurization".


See below.

Just because it's there in parenthesis, doesn't mean it is a correct term. If you take a look at the SR20 Manifesto, or the other one I've done for the Z3 crowd you will see countless bad names for things, all in parenthesis, all with the correct names front and center.


That is the main restrictor I'm talking about, yes. Obviously there is another one hidden in the small PCV hose between the check valve and the intake manifold, but I guess we're not discussing that one. (I see you've posted a picture to it in post #160.)

I haven't seen enough stock turbo (JDM?) setups to know for sure if they all have them, but I don't see why they wouldn't. Without it, idle air is less controllable, and the crank case can't ever really hold a vacuum at all. If you don't have one, I'd wager to guess it was lost somewhere along the way. Did you buy your car and engine new? Did you have the fire suppressor in there for that matter?

The restrictor ALWAYS applies. I can't imagine running without one. What would be the point? You could never maintain a vacuum in the crank case without it at idle or any other time. See above on the same topic.

Please, please, please, please go read the N/A version of this thread linked a half dozen times in the first couple posts. It covers the later valve covers (FWD, but RWD is similar) and heavily advises their use especially over most catch can solutions.


I think I've had enough for tonight, and I KNOW everyone else has. You're welcome to make your own thread on the topic. No one will stop you.

perfectly acceptable reasoning. And when I said semantics, personal preference, I simply meant both at once. Not that they meant the same thing. And it seems we each have our own personal preference. Perfectly reasonable.


The only thing is this...


I see what you are saying, because that WOT hose would be like a breather when the engine was in vacuum. However,

This makes me think you never put your finger over the T-fitting on an S13 sr20det valvecover while the engine was running. Or you would have noticed something
The valvecover has some kind of restrictor inside it already. If you disconnect the WOT PCV hose you will detect the pulsing as each cylinder draws air and that vacuum signal is passed through the intake side PCV check valve. Each pulse has its own distinct feel, and it readily builds a strong vacuum in the crankcase.

And all the aftermarket intake plumbing, such as greddy and HKS, do not include any kind of restrictor. Either they overlooked it, or thought it wouldn't matter. I am not saying coorlation is causation here, but I am pointing out that fact, that restrictor is strictly an OEM piece.

And thanks for responding fully, you don't get that very often. I have a final exam tomorrow them I am going out of town. This was just a way to take a mind rest, and try to do some good.
Thanks again.

I am tired.

Sent from my SAMSUNG-SGH-I747 using Tapatalk

read with much interest, and a few thoughts and experiences to throw out:

one benefit of scavenging these gasses that has been unmentioned is the removal of the contaminants in the vapor. The blowby gasses are, apparently, not the cleanest. So clearing these contaminants out of the engine is a good idea. draining the captured oil in the separators and catch cans back into the engine has pros and cons.

pros to self-recycling: less maintenance, less loss of oil

cons: more maintenance, loss of oil and more contaminants in oil

having to drain a catch can is more work, and you have to monitor oil levels more frequently, but clearing out the bad stuff, for myself at least, is worth the extra work.


Running the crankcase breather into the valve cover and then out seems to me inferior to keeping the crankcase breather separate from the valve cover breather(s) as the contaminated blowby from the crankcase has to pass through the valve cover, potentially letting the valve cover's baffles separate this contaminated air. So the examples of running the crankcase into the valve cover and then from the new port on the valve cover to the intake would be good for evacuating air, but bad as it would encourage the contaminates from the crankcase to be removed into the oil in the head.



Observation 2:

the less pressure in the engine (crankcase pressure) the better. Getting into actual vacuum (up to about 15in/hg seems to be the accepted limit) is even betterer.

putting a vacuum on the engine promotes ring seal and increases power. It's been pretty well-established.

So venting to atmosphere is good to help give the pressurized gasses an exit, but you will never get vacuum.



Observation 3:

Vents on the ccv with a pcv connected will introduce unmetered air into the intake.

Your pcv, as you should know through the awesome illustrations in this thread, when not on boost, pulls air from the valve cover, into the intake and burning it.

IF you have a breather anywhere else on the ccv system, as long as you are not in boost (which shuts the pcv valve or pushes air INTO the motor through a missing/malfunctioning pcv valve), the motor will be pulling in unmetered air. The air will go in through our little filter (on your valve cover or on the crank case breather or on the catch can you've run one or both of those to), through the motor, through the pcv and into the engine.

Is it a big deal? maybe maybe not. But it could cause problems. In a completely closedccv system (where you run those vents back into the intake), you won't have that issue. You will also not have that issue while on boost.


Observation 4:

my car is a track-only car. I have it set up with the proper pcv system on one side. the other side has the crankcase going to the vc T (without a separator) and from the T to a vented catch can.
thoughts on this: I wish I had a [stock] separator. I just bought one to put on and there is not really enough room. but luckily, I don't get much oil in my catch can.

my car idles and runs great. HOWEVER, it is likely pulling unmetered air in through the catch can when not on boost. but because it is track-only and runs fine, I'm ok with this. it doesn't matter once I hit boost.

I want to improve the system. I tried a set up similar to one that was suggested later in this thread where the pcv is rerouted to the T on the vc and then everything goes to the intake.

I capped the vacuum source on the intake manifold and ran my pcv to a new T in the line between the valve cover and the catch can. I was shocked at the difference. It probably cost me 20+hp. I put it back to how I had it and it was fine. I figured that running my pcv into that loop would give me an extra outlet but somehow it hurt me.

I still don't know exactly why, but I theorize that it must have increased the crankcase pressure somehow. the way it was and once again is hooked up, my pcv route SHOULD have been completely closed under boost, leaving only the crankcase breather-vc T-catch can as my only ccv.

I want to test it next time by leaving the ccb-vcT-cc the same, and plugging the intake manifold vacuum port and running the pcv line to a breather and see if there is any negative effect. I expect it will not have an adverse effect. I would only expect to see a positive effect if my pcv valve (quite new) is leaking under boost and pressurizing the motor. simply venting it would prevent the pressurization that could be happening if that was the case.


Observation 5:

my next plan is to run a vacuum pump (electric as it's easier) after my catch can [so it would go: crank case-vcT-catch can/separator-vacuum pump-vent to atmosphere] and take the pcv side and plug the intake manifold port, remove small pcv valve, and run a hose from that location to a 1-way check valve to a vented catch can. The 1-way valve would allow air to flow out of vc and into cc, but if the vacuum pump starts to pull more than the pressure in the motor, the check valve will close, allowing the vacuum pump to hopefully put something of a vacuum on the motor.

This would, as I see it, remove the contaminated oily vapor, give more power, and eliminate any oil in the intake system anywhere.



This is a little long, but I wanted to cover a few things. I think Ben has done a great job of explaining a lot of what is happening, and these ccv systems are very easily jacked up.
based on my experience of losing an incredible amount of power, I wonder how many people have done the same thing unknowingly. I would have never looked at the system I came up with and thought it was bad but boy was it ever!

So the 3/4" hose that in this pic is shaped like an opposite "C", it is currently connected to the white tube in the bottom left up to the intake. This tube of course being connected to the charge pipe see's boost. Is this connected correctly, if not where should it be connected?


And after reading your threads (N/A and Turbo) I don't believe this is good, so currently the one line as you can see goes from the side of the block up to and joins at the "T" at the top of the valve cover, then down to the inlet side of the turbo.
https://www.facebook.com/photo.php?fbid=1451877981737004&set=a.1451877675070368.1073741842.100007444471645&type=3&theater

https://www.facebook.com/photo.php?fbid=1451878051736997&set=a.1451877675070368.1073741842.100007444471645&type=3&theater

So am I correct in feeling the steel braded lines are correct except I need to add a catch can? Or do they need to be rerouted elsewhere?

Thank you for your help anyone who does :-)

That looks like the hose that feeds the idle control. That is okay to see boost. In an ideal world maybe it wouldn't, but I think even the factory setup has the idle hose connected to the charge pipes (and I do on my car too). You should be fine here. Unless that hose doesn't go to idle? You can check by idling the car and then pinching that hose. The engine should struggle and/or die.


Sentence in bold is correct. Line placement sounds good. You've just lost an oil separator.

I thought so... thank you.

I ended up just adding a port and taking a tube from the intake down to the pip the air filter is clamped to (pre turbo)... No it is always vacuum like it would be factory. This is ok, no?

It was fine before and just needed the stock oil separator to be added back. Now I have no idea what you've done. Picture?

I will take one, I changed nothing major, have not added the can yet. All I did was extended the 3/4" hose the originally went from the intake manifold to the charge pipe just before the throttle body inlet (which originally woulda been vacuum always)...
Seen here...
https://www.facebook.com/photo.php?fbid=1455302428061226&l=75e11b1a20

And I replaced it with a longer tube, routing it cleanly from the intake manifold down to the pre turbo inlet (replaced the polished tube where the circle with the "X" is, replaced with a steel tube adding a welded 3/4" bung not shown in the pic)
As seen here...
https://www.facebook.com/photo.php?fbid=1455302451394557&l=10de2a4d8a

So now that tube sees vacuum only and always just like it would stock (originally).

Bad idea? Or just not needed overkill? lol