breather catch can setups
Thread Starter
Le Mans Master
Joined: Oct 2010
Posts: 7,373
Likes: 1,128
From: cold & windy
breather catch can setups
for the catch can/PCV gurus out there...
i'm just curious as to how & why the airflow through a catch can is reversed when running a breather instead of a standard closed system.
simply applying my dumb redneck logic to the situation, the closed system makes sense in that oil vapors enter through the top, pass through the filter/condenser, and drip to the bottom allowing dry air to pass out the side at the top of the reservoir.
now if you put a breather on top of the can, you're running the airflow backwards - the oily air is entering through the side & passing up through the filter/condenser, then venting out the top. does this still allow the vapors to actually condense & drip to the bottom against the flow of air? it seems like the vapors would be pushed out the breather & collect on that filter element before having time to cool off. it seems like this would only really be effective if you had 2 catch cans rigged up in series: the first plumbed like a closed system & the second with a breather.
can somebody please explain this? thanks
i'm just curious as to how & why the airflow through a catch can is reversed when running a breather instead of a standard closed system.
simply applying my dumb redneck logic to the situation, the closed system makes sense in that oil vapors enter through the top, pass through the filter/condenser, and drip to the bottom allowing dry air to pass out the side at the top of the reservoir.
now if you put a breather on top of the can, you're running the airflow backwards - the oily air is entering through the side & passing up through the filter/condenser, then venting out the top. does this still allow the vapors to actually condense & drip to the bottom against the flow of air? it seems like the vapors would be pushed out the breather & collect on that filter element before having time to cool off. it seems like this would only really be effective if you had 2 catch cans rigged up in series: the first plumbed like a closed system & the second with a breather.
can somebody please explain this? thanks
Safety Car
Joined: May 2007
Posts: 4,812
Likes: 46
From: Taylorsville North Carolina
Actually I am switching my catch can set up to that right now. Instead of routing the supposedly clean air back into the intake, I am going to run it out to a breather and into the open air. The jury is still out on whether or not it will smell too bad. Some say no, some say yes. Even the best catch cans do not get 100% of the oil so why even risk it. Just going to plug port on intake and see how it goes.
Team Owner
Joined: Jan 2007
Posts: 29,063
Likes: 1,839
From: cookeville tennessee
Actually I am switching my catch can set up to that right now. Instead of routing the supposedly clean air back into the intake, I am going to run it out to a breather and into the open air. The jury is still out on whether or not it will smell too bad. Some say no, some say yes. Even the best catch cans do not get 100% of the oil so why even risk it. Just going to plug port on intake and see how it goes.
Robert
Thread Starter
Le Mans Master
Joined: Oct 2010
Posts: 7,373
Likes: 1,128
From: cold & windy
that's how i was advised by CCA to run at the track - reverse the plumbing on the can, put the breather on top, and plug the port. then for the street, undo that & run it closed
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Actually I am switching my catch can set up to that right now. Instead of routing the supposedly clean air back into the intake, I am going to run it out to a breather and into the open air. The jury is still out on whether or not it will smell too bad. Some say no, some say yes. Even the best catch cans do not get 100% of the oil so why even risk it. Just going to plug port on intake and see how it goes.
Racer
Joined: Jun 2012
Posts: 492
Likes: 1
I personally think the best way to do it is a hybrid of both. What I did was cap off the "inlet" line running from the passenger cover to the tb. I then tapped the driver cover in the back where the plug is and ran that to a catch can. I also ran the valley cover line to the same catch can (LS6). I than ran a line from the catch can to the intake manifold with stock PCV valve. Finally I added a breather filter to the oil fill. What this does is allow the breather to act as an inlet so the stock system can still draw fresh air and get rid of any moisture in the crank case, but also allow it to vent through the breather if needed during WOT. It the breather ends up misting too much like some report then I'll run a line from the oil fill to a vented catch can so I works the exact same but would catch any mist.
Safety Car
Joined: May 2007
Posts: 4,812
Likes: 46
From: Taylorsville North Carolina
I ran the p/s valve cover capped along with breather oil cap for a couple years. Problem is the oil port on the valve cover is not shielded like the valve cover port is. During track days, the rocker arms would throw oil right thru my ECS oil cap breather onto motor. So now I have a breather on the valve cover port (which is shielded underneath) and a stock oil cap. For just dd, the oil cap breather worked fine.
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Safety Car
Joined: May 2007
Posts: 4,812
Likes: 46
From: Taylorsville North Carolina
Problem with that setup is there is no vacuum working on the engine's crankcase, so you really don't get good evacuation which means there could be trapped condensation, etc inside the engine. I can see running an open breather on the track to help prevent oil ingestion through the intake manifold, but on the street it wouldn't ensure all the bad vapors are evacuated from the engine.
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
I personally think the best way to do it is a hybrid of both. What I did was cap off the "inlet" line running from the passenger cover to the tb. I then tapped the driver cover in the back where the plug is and ran that to a catch can. I also ran the valley cover line to the same catch can (LS6). I than ran a line from the catch can to the intake manifold with stock PCV valve. Finally I added a breather filter to the oil fill. What this does is allow the breather to act as an inlet so the stock system can still draw fresh air and get rid of any moisture in the crank case, but also allow it to vent through the breather if needed during WOT. It the breather ends up misting too much like some report then I'll run a line from the oil fill to a vented catch can so I works the exact same but would catch any mist.
Not sure if that's a big issue or not ... the ECU might be able to adjust for that. Haven't heard too many guys say their engine runs bad with an open breather setup so maybe the leaning out is minimal.
Last edited by ZeeOSix; Feb 6, 2013 at 07:55 PM.
Safety Car
Joined: Jul 2005
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From: Jackson Tn
St. Jude Donor '06-'07-'08-'09
Safety Car
Joined: May 2007
Posts: 4,812
Likes: 46
From: Taylorsville North Carolina
Just a quick update - I have changed my set up to block off port going back into intake and am running hose from valley cover to catch can to breather cap. So far no noticeable smell and 0% oil back into motor. If it works out for long term, I may just drop the catch can and run the breather directly out of valley cover port like Spinmonster's set up. You can go to C6 Tech section and there is a good thread on this set up along with oil analysis results etc.. HTH.