Topic: Oil Catch Can vs Oil Breather Tank

[Carbon Sky]

I was pretty intent on getting the DDM OCC, but I was a little uncomfortable plumbing the return line back to the turbo.  I know the OCC should remove any oil from the crankcase before letting the vapour go back into the intake.  In previous cars, I disconnected the PCV line that would run from the crank to the intake, and I'd add a breather instead to let the PCV vent to atmosphere.  And figured I'd do the same here.  I thought, perhaps I'll just put a breather on the exit nipple on the OCC.

That's when I realized, such a device, or an OCC that vents to atmosphere appears to be called an oil breather tank.  And like I mentioned, instead of like an OCC that then reroutes the exit from the OCC back into the intake, a breather tank will merely just vent to atmosphere as I desire it to.

Here's a pic of one to give you an idea:



Basically the black AN looking fitting is where the line from the heads runs to the turbo, where oil has a tendency to come out.  You'd normally run this line to the OCC.  In my case, I'd run it to this black AN fitting.  There is baffling/(thick steel wool) inside, and then it vents to atmosphere through the filter on the top.

The best part, you can get breather tanks for about half of what a baffled OCC goes for.

Any input or experiences with breather tanks?

[miller11386]

A catch can setup is superior to a breather setup. The vacuum of a proper catch can setup causes the can to pull pressure out of the block and  have less oil blow by on the rings... less pressure in the block = Less resistance in the block = more power.

A breather is better than pressurizing the crankcase, so if you like doing things half way, go for a breather can. If you want the best setup, go for a properly vented catch can.

[Carbon Sky]

A catch can setup is superior to a breather setup. The vacuum of a proper catch can setup causes the can to pull pressure out of the block and  have less oil blow by on the rings... less pressure in the block = Less resistance in the block = more power.

A breather is better than pressurizing the crankcase, so if you like doing things half way, go for a breather can. If you want the best setup, go for a properly vented catch can.

"Pulling pressure"?  That doesn't make sense to me, it might "vent" faster, but not in a "superior" manner.  If there is pressure, why would you also need vacuum to vent it?  Unless you're trying to speed up the venting from nearly instantaneous (with vacuum helping) to perhaps a second or two (without vacuum helping).  I'm only trying to relieve pressure after all, and not create vacuum in the crankcase.  So if the crank case is vented to the environment, how could it build pressure for anything more than a very brief moment?

In fact, using your logic, wouldn't the catch can unnecessarily pull oil from the crank case?

Remember, the purpose is to remove excessive pressure, not to have maximum flow rate.

I hope TS chimes in . . . I think he was the one that put together that OCC thread about what lines to attach to your OCC and why.  Thanks for your input . . . please feel free to convince me I'm wrong.  Still trying to rationalize and figure it out to a more certain degree.

[JoshMcMadMac]

A breather allows for unmetered air...which is bad.

[Carbon Sky]

A breather allows for unmetered air...which is bad.

Unmetered air?  So you're saying the engine would draw air in through the breather tank, into the crankcase, and past seals?  Interesting . . . I haven't heard this argument yet.  Gonna do a little internet digging.

Wouldn't this be even more of an issue with NA cars?  And wouldn't you have really poor compression (leaky rings/seals) across cylinders for this to happen?  I'm just thinking if these combustion chambers are handling 20+ psi without issue in terms of sealing, would they be able to also then allow leakage for this small amount of vacuum relative to the extreme pressure of the boost?

[Critterman]

The system is designed as a closed system, so one would think there is a reason that it is closed.  Even if it only is an enviromental concern.

[Carbon Sky]

The system is designed as a closed system, so one would think there is a reason that it is closed.  Even if it only is an enviromental concern.

It's entirely for environmental concerns, and no other (I've looked into PCV systems before).  Don't assume otherwise unless you have some information please.

[Critterman]

Read my post CS  EVEN IF IT IS ONLY means just that!

[Carbon Sky]

Read my post CS  EVEN IF IT IS ONLY means just that!

I thought you were trying to make the sticking point that regardless of environmental concerns it should run as a closed system, and I disagree with that.

What I mean is that even if it is designed as a closed system doesn't mean it won't run equally well if not better open.  The closed system is adding unnecessary function, and if partially defeated can definitely provide benefits.  This is not the first car I've run where the PCV vented to atmosphere, all were "designed to run in a closed system" and all ran better as a result of venting to atmosphere in that no more oil of any kind, even vapor was being ingested anymore.  In fact I'd argue it would run even better because now that it's an open system the vapor can no longer affect and skew fuel trims randomly as the oil comes up to higher operating temperatures.

The way I see it, if I'm going to go through the trouble of insuring no oil will be ingested in any form (including vapor), I might as well make damn sure, by venting to atmosphere.  It's no more difficult or complex, and arguably simpler.  I've heard the argument similar to millers about lack of vacuum to help "pull" the vapor out of the crank case, but it doesn't seem to make sense to me for the reasons I mentioned.

[TomatoSoup]

I see notting, I know notting.




I wouldn't do the 'breather' method personally, if only for environmental reasons, as Critter said. 

I have also heard of the 'push-pull' vent mechanism in the factory setup... supposedly why the inlet/outlet points are at different places, as well as why the crappy airbox attachment is at an angle - to provide positive pressure from the intake air.  HOWEVER, I can claim no oracle status on the veracity of those statements... and the 'plastic tube' angle may purely be for mechanical reasons.

Bottom line - it comes back to environmental concerns.

[Sol Asylum]

If you live in an area that inspects cars in order for them to be leagal to drive then a breather will get you a fail simply for environmental reasons.  But CS it would seem you don't really care and are going to do whatever you want regardless of what others say so maybe the better question is why even ask if you have already made up your mind?

Miller how does less pressure in the crankcase reduce blow by?  Blow by is when the higher pressure gases in the combustion chamber push past the rings and into the crankcase.  Reducing the pressure on the back side of the piston increases the pressure differential which would lead one to think blow by could be increased.

If you are talking about oil that gets past the rings and enters the combustion chamber that's different and technically not the same as blow by.  That's failing oil control rings.

[Carbon Sky]

If you live in an area that inspects cars in order for them to be leagal to drive then a breather will get you a fail simply for environmental reasons.  But CS it would seem you don't really care and are going to do whatever you want regardless of what others say so maybe the better question is why even ask if you have already made up your mind?

Miller how does less pressure in the crankcase reduce blow by?  Blow by is when the higher pressure gases in the combustion chamber push past the rings and into the crankcase.  Reducing the pressure on the back side of the piston increases the pressure differential which would lead one to think blow by could be increased.

If you are talking about oil that gets past the rings and enters the combustion chamber that's different and technically not the same as blow by.  That's failing oil control rings.

More so, I'm not going to do it for emissions reasons alone.  If you really cared that much about this minute amount of hydrocarbons, you wouldn't be filling up your gas.  Those little drops of gasoline evaporating make up significantly more hydrocarbon pollution than the fuming from your PCV.  If there is a functional improvement, I'm all ears, but apparently because I have given this a lot of thought and have been able to address most of the concerns brought up so far, that's a problem?  Sorry, should I be totally ignorant, ask questions that have been asked ad nauseum and then relish in the opinions given without much fact behind them?

Anyways, I do a heck of a lot of other things far worse for than environment that we all would consider justified like heating  a home to 23* C instead o 21* C, which would pollute a lot more is the point I'm trying to make here.

Notice how the one person that has brought up a new possible problem I'm now researching and looking into as a viable reason to go with the OCC than the OBT?  Guess that one slipped by you.

[Sol Asylum]

The unmetered air post?  You got to be joking, what part of crankcase ventilation is metered if you plug the return line to the intake and vent overboard?   

If you don't understand the system you can't possibly understand what altering it does.

[Carbon Sky]

The unmetered air post?  You got to be joking, what part of crankcase ventilation is metered if you plug the return line to the intake and vent overboard?   

If you don't understand the system you can't possibly understand what altering it does.

Exactly, it's the only argument I haven't come across yet, and I want to look into it before I instantly dismiss it without any information which you seemed to accuse me of just now . . . interesting  . . .

[Carbon Sky]

When did I dismiss that the cross flow could be good?

So you dismiss the facts and entertain the BS and that somehow proves what?

Sounds like a troll to me.

I addressed millers and what you claim to  be the "facts".  If you know so much, why not rebut with information?  Why not address the questions I posted for miller?

Here I'll even repost them again for you, to help you out.

"Pulling pressure"?  That doesn't make sense to me, it might "vent" faster, but not in a "superior" manner.  If there is pressure, why would you also need vacuum to vent it?  Unless you're trying to speed up the venting from nearly instantaneous (with vacuum helping) to perhaps a second or two (without vacuum helping).  I'm only trying to relieve pressure after all, and not create vacuum in the crankcase.  So if the crank case is vented to the environment, how could it build pressure for anything more than a very brief moment?

In fact, using your logic, wouldn't the catch can unnecessarily pull oil from the crank case?

Remember, the purpose is to remove excessive pressure, not to have maximum flow rate.



So how about it?  What do you have to say now since you know so much?  Please grace us with your obvious expertise in this matter.

BTW, remember this classic?

http://www.skyroadster.com/forums/f5/synapse-synchronic-bov-sky-red-line-35166/

Miller got the same flack.  He asked the forum to prove him wrong.  I'm still welcoming constructive ideas even if SA has suddenly turned this into, a big argument that no longer has to do with why to go with the OCC with the OBT seems to work just as well besides the pollution aspect, which I have mentioned I do not care about.

[Sol Asylum]

The only one not reading post would seem to be you.  Miller's post doesn't make any sense to me and I said so, I'm not going to repost everything like you, go back and read what I wrote.

What more facts do I have to add?  PCV is an EPA thing, there is no metering system of air in the crankcase.  Miller doesn't seem to know what blow by is, or is using the wrong wording.

I don't hang out at skyforum because I don't have a sky, and the forum is a POS compared to this one so no I don't remember that and don't care to waste my time reading it.

So since the whole reason for the OCC is maintaining EPA compliance and you don't care about that, your own words, you just proved my point that you asked a question but don't care what the answer is. 

[Carbon Sky]

So since the whole reason for the OCC is maintaining EPA compliance and you don't care about that, your own words, you just proved my point that you asked a question but don't care what the answer is.

Who said that "the whole reason for OCC is maintaining EPA compliance"?  Many are stating that it is superior in function to venting the crankcase compared to an oil breather tank.  I tried to get people to show me reasons why the OCC would be superior. 

[Arabas]

Afaik occ was initially used for enviromental issues and for protection measure if a car really has an oil problem through the crankcase, for not allowing oil to drip on the road or hot parts of the engine. Of course directing the fumes and oil through a closed circuit to the intake mani was much more cost efficient for auto industries.
Older cars used the breather to let the fumes and oil get out without letting anything getting in by a small filter.
 The pros of an occ are two imho.
Enviromental - for what is worth
Ability to check how much oil has been collected and easily identifying any possible oil problem ( by monitoring the collected oil)

The one thing that should of course being taken into account when using a vent to atmo, is closing the turbo inlet where the hose used to attach.
We have two nipples out the crankcase.
On which one are you using that to? Both?

[Carbon Sky]

Afaik occ was initially used for enviromental issues and for protection measure if a car really has an oil problem through the crankcase, for not allowing oil to drip on the road or hot parts of the engine. Of course directing the fumes and oil through a closed circuit to the intake mani was much more cost efficient for auto industries.
Older cars used the breather to let the fumes and oil get out without letting anything getting in by a small filter.
 The pros of an occ are two imho.
Enviromental - for what is worth
Ability to check how much oil has been collected and easily identifying any possible oil problem ( by monitoring the collected oil)

The one thing that should of course being taken into account when using a vent to atmo, is closing the turbo inlet where the hose used to attach.
We have two nipples out the crankcase.
On which one are you using that to? Both?

Thanks for the input

Just like there are oil catch cans that are entirely empty on the inside, and there are proper ones with some kind of baffling or other media inside for oil vapor to condense onto, there are breather tanks that are entirely empty on the inside, and others with some kind of baffling.  The most common kind of condensing medium I've seen in these PCV and OCC and OBT seems to be something like this:

.

Basically as the hose enters to the AN fitting on the OCC or OBT, it condenses on this material, and collects in the tank.

Speaking of which you can get OBTs in volumes ranging from 1 pint to 1 quart most commonly(about 500mL to 1L).  And I'm sure they have smaller and larger ones.  They also have some that have a sight level, and some that don't, just like OCCs.  And petcocks on the bottom to drain them.  The main difference seems to be, an OCC plumbs the exit side back to the turbo to draw the vapor in to be consumed, while the OBT has a filter to vent to atmosphere.  Technically if you were to not connect the return line on any OCC and simply put a filter on it instead, it becomes an OBT.

If I decide to do this, the easiest way for me to set it up would be disconnect the "B" line in this pic.  From what I've seen, OCCs on the Kappa use a 3/8" hose that goes on the end of the 3/8" nipple that is at the "B" in the pic.  I would put a 3/8" internal diameter hose on this, and ring clamp it on, as I have seen in other OCC setups.

(Thanks to TS for the pics)



To address the end at the turbo, I think the easiest way for me to seal it off would be to remove it from the car, and use my MIG welder to fill the tip in.  It's such a small job it would take me significantly longer to set up the welder than it would to do the actual welding (probably 5 minutes ish), so it's not nearly as involved as say plasma cutting my homemade "backbone" for example.  And makes me feel like I'm getting some value for renting the tanks of various mixes of compressed gas (I really should use the stuff more often, but school is killer lately).  And I'd leave the other red line connected.  That way there would still be this "forced" effect from the intake area on the plastic piece that breaks easily, going into the engine, and then exiting the engine through the PCV, into the OBT, and then to atmosphere.

I dunno, just thinking about it still.   Not sure if DDM is throwing a 12 days of christmas sale.  And even if they do, I might just put a filter on the end of the return line, instead of connecting it back to the turbo.

[Gentleman Jack]

I don't care about the environment....  I don't care about messy engine bays.   Buy the OCC because it supports a good cause (I think Ivy is a good cause) and because I said so.

[GASNGO]

Next,
Should you block off the PCV valve that is built into the intake manifold so it stops sucking oil vapor etc. from the crankcase into the intake manifold and then possibly gumming up the intake valves?
Jerry 

[Gentleman Jack]

I think if you just put some cement in the PCV it will clear everything right up.

[Carbon Sky]

Next,
Should you block off the PCV valve that is built into the intake manifold so it stops sucking oil vapor etc. from the crankcase into the intake manifold and then possibly gumming up the intake valves?
Jerry 

If you block that off, it can't vent and it has to.  Nothing should be going inwards, only outwards anyways assuming the PCV one-way valve is working properly.

[miller11386]

Here are some videos explaining in detail what I was talking about. Negative pressure in the case is necessary and the SLIGHT vacuum that the air flowing in the intake provides give you the slight vac in the system to allow air to flow. Hence why its superior on the kappa platform. It allows the pcv system to still work and pull the moisture from the block and let the system do its job. If your system is not working properly, you can pressurize the crank case, which causes the resistance and the oil loss at its weakest point. May be rings, may be turbo seals, may be the head. All depends on the car.

Talking Pros and cons of Catch cans vs breathers:
Sector111 Educational Video: PCV System Part 2

Explaining how a PCV is designed to work. (on a lotus, but its the same idea in the kappa
http://www.youtube.com/watch?feature=player_embedded&v=vabonLBYx9s#

Sorry for the brief first response. Hopefully this clears up my first reply. I don't frequent these boards as much as I used to.

[Carbon Sky]

Here are some videos explaining in detail what I was talking about. Negative pressure in the case is necessary and the SLIGHT vacuum that the air flowing in the intake provides give you the slight vac in the system to allow air to flow. Hence why its superior on the kappa platform. It allows the pcv system to still work and pull the moisture from the block and let the system do its job. If your system is not working properly, you can pressurize the crank case, which causes the resistance and the oil loss at its weakest point. May be rings, may be turbo seals, may be the head. All depends on the car.

Talking Pros and cons of Catch cans vs breathers:
Sector111 Educational Video: PCV System Part 2

Explaining how a PCV is designed to work. (on a lotus, but its the same idea in the kappa
http://www.youtube.com/watch?feature=player_embedded&v=vabonLBYx9s#

Sorry for the brief first response. Hopefully this clears up my first reply. I don't frequent these boards as much as I used to.

Now that's a great response!  Thanks man.   Will definitely look into this. 

More reading for anyone else that might be interested.  I wonder how much vacuum we're supposed to have in the crankcase?  Anyone have an idea?  Apparently most street cars don't make enough vacuum in the crank case for the performance gain.  Even this guy in your videos says "SLIGHT" vacuum.  However, in race dry sump setups with multi stage pumps and what not, apparently when they get upwards of 20" of Hg!  Holy Shit!

So yes, apparently a little bit of vacuum is good.  I just need to find out how much now.

Thanks again miller!


http://nutterracingengines.com/racing_oil_pumps/crankcase_vacuum_facts.html


Another thing I've learned since delving into this matter is that there is a big difference between the venting the heads (where the OCCs are currently being used), and venting the crank case.  They are vastly different things, and there have been a number of ambiguities, and misconceptions confusing the two already in this thread and in the videos.

I did a little digging around at the PCV stuff on the intake manifold side of the engine bay and compared its function with what's going on with the heads on the turbo side of the car where OCCs and OBTs are being discussed.  The "blow by" or pressure/gas getting by ring and what not, causing pressure in the crankcase, gets relieved by the PCV, which makes sense considering it's the positive crankcase ventilation, as in letting positive pressure from the blow by out.  This is vastly different from the ventilation of the heads where the OCCs and OBTs can be used.  And it seems there's all kinds of confusion between the two so far.