Venting Crankcase Gasses
01-04-2009, 11:46 AM
#1
Venting Crankcase Gasses
I've had a dual catch can setup on my car for a while now, using the Husky air compressor filters, both for the driver's side and passenger side.
After staying updated on the catch can threads (I know, there's a ton) I have noticed what some of the high performance guys (e.g. Sharif, JETPILOT) of this forum are doing with their vacuum systems, and it seems like a closed-loop system is not the best design for optimal prevention of oil vapor from entering the intake system.
With that said, I'm just looking for information on how it's "okay" to let both the passenger side and driver's side crank case vapors vent to the atmosphere. I see it's being done with the FI crowd, and am wondering not only if it is okay to get rid of the closed-loop vac system on both the driver's and passenger's side, but why it's a good thing to do that. Excuse my inquisitiveness, I should have been a Mechanical Engineer.
If I do...
PASS side: PCV --> Catch Can --> Breather filter (and plug the port going into the manifold)
DRIVE side: Plug intake tube, Vent valve cover
...is this still allowing for the necessary gases to escape from the crank case? Isn't the "sucking in" of air from the intake tube and the manifold what causes the positive suction necessary to remove the over abundance of gases from the crank case? Or will these harmful gases just be able to "push" themselves out by themselves on both the driver's and passenger's side (w/ out the assistance of intake suction??).
Sorry for the long-windedness...I know there are probably a good amount of you who are boosting who have had to consider a solution to this problem before. Thanks in advance for your input!
After staying updated on the catch can threads (I know, there's a ton) I have noticed what some of the high performance guys (e.g. Sharif, JETPILOT) of this forum are doing with their vacuum systems, and it seems like a closed-loop system is not the best design for optimal prevention of oil vapor from entering the intake system.
With that said, I'm just looking for information on how it's "okay" to let both the passenger side and driver's side crank case vapors vent to the atmosphere. I see it's being done with the FI crowd, and am wondering not only if it is okay to get rid of the closed-loop vac system on both the driver's and passenger's side, but why it's a good thing to do that. Excuse my inquisitiveness, I should have been a Mechanical Engineer.
If I do...
PASS side: PCV --> Catch Can --> Breather filter (and plug the port going into the manifold)
DRIVE side: Plug intake tube, Vent valve cover
...is this still allowing for the necessary gases to escape from the crank case? Isn't the "sucking in" of air from the intake tube and the manifold what causes the positive suction necessary to remove the over abundance of gases from the crank case? Or will these harmful gases just be able to "push" themselves out by themselves on both the driver's and passenger's side (w/ out the assistance of intake suction??).
Sorry for the long-windedness...I know there are probably a good amount of you who are boosting who have had to consider a solution to this problem before. Thanks in advance for your input!
01-04-2009, 07:02 PM
#5
Jonny, explain to me why I want more airflow through the crankcase with my N/A setup. Is it because with FI motors, the boost pressure "replaces" the suction of the PCV system...enough to push the crank case gases out of a breather filter? So the FI guys essentially have double the crank case pressure to combat, and that is why they can cap off the pick up points of the system and vent? I'm just curious.
01-04-2009, 09:25 PM
#6
The PCV system is for emissions only. It is there to burn crankcase vapors that otherwise would be vented to the atmosphere. Before PCV systems cars ran fine venting crankcase vapors to the atmosphere. Without a source of vacuum from the plenum crankase pressure would still vent by itself since high pressure inside the crankcase seaks low pressure which is atmosphere.
01-04-2009, 09:36 PM
#7
The PCV system is for emissions only. It is there to burn crankcase vapors that otherwise would be vented to the atmosphere. Before PCV systems cars ran fine venting crankcase vapors to the atmosphere. Without a source of vacuum from the plenum crankase pressure would still vent by itself since high pressure inside the crankcase seaks low pressure which is atmosphere.
So with me being N/A and all, I'd be okay doing what you did on the PCV side? (the catch can + breather)
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01-04-2009, 10:01 PM
#9
There's no problem. The car runs very well. I just have had my manifold apart a few times now, and have noticed small amounts of oil each time. I read up on it, and have obviously found that oil in your intake is a bad thing. I guess the info I have found is best summed up under "Negative Effects..." on this website http://www.eliteengineeringusa.com/Catch_Can.html
After reading that, who wouldn't be concerned?
The DIY can I have now is just so small. It makes me think it's not doing as much as it could be. Instead of spending $100 on a properly baffled can, I thought I could use my smaller one, and attach a breather to the exit port instead of routing back to the manifold, to avoid recirculation of oil. That's it in a nutshell.
After reading that, who wouldn't be concerned?
The DIY can I have now is just so small. It makes me think it's not doing as much as it could be. Instead of spending $100 on a properly baffled can, I thought I could use my smaller one, and attach a breather to the exit port instead of routing back to the manifold, to avoid recirculation of oil. That's it in a nutshell.
Last edited by blackfairlady; 01-04-2009 at 10:03 PM.
01-05-2009, 05:23 AM
#10
the best systems use a vacuum pump to help actively scavenge. so it wouldnt make any sense (to me at least) to remove the vacuum source from a NA car.
If FI guys remove the vacuum source (the plenum) bc the PCV valve can be cracked the wrong direction and allow boost into the crankcase. Get rid of that, and the only way to pressurize the CC is from ring blowby. Thats where the assumption that larger, freeer flowing breathers will equalize the CC with the atmosphere readily.
If FI guys remove the vacuum source (the plenum) bc the PCV valve can be cracked the wrong direction and allow boost into the crankcase. Get rid of that, and the only way to pressurize the CC is from ring blowby. Thats where the assumption that larger, freeer flowing breathers will equalize the CC with the atmosphere readily.
01-05-2009, 06:28 AM
#11
the best systems use a vacuum pump to help actively scavenge. so it wouldnt make any sense (to me at least) to remove the vacuum source from a NA car.
If FI guys remove the vacuum source (the plenum) bc the PCV valve can be cracked the wrong direction and allow boost into the crankcase. Get rid of that, and the only way to pressurize the CC is from ring blowby. Thats where the assumption that larger, freeer flowing breathers will equalize the CC with the atmosphere readily.
If FI guys remove the vacuum source (the plenum) bc the PCV valve can be cracked the wrong direction and allow boost into the crankcase. Get rid of that, and the only way to pressurize the CC is from ring blowby. Thats where the assumption that larger, freeer flowing breathers will equalize the CC with the atmosphere readily.
I'm just under the impression that my small catch can - if you're familiar with the DIY air compressor catch can, only holds a couple ounces, and is unbaffled - will suck air in, deposit some oil, but seems like it will still allow some of the oil vapor to travel into the intake manifold. The inlet and outlet points are close, and the depth is shallow. I could just replace it with a "proper" catch can, but I'm just curious if some deposit of oil in the manifold is actually harmful, or not.
01-05-2009, 04:30 PM
#12
I guess it's really a different ball game once you add a turbo or SC.
I'm just under the impression that my small catch can - if you're familiar with the DIY air compressor catch can, only holds a couple ounces, and is unbaffled - will suck air in, deposit some oil, but seems like it will still allow some of the oil vapor to travel into the intake manifold. The inlet and outlet points are close, and the depth is shallow. I could just replace it with a "proper" catch can, but I'm just curious if some deposit of oil in the manifold is actually harmful, or not.
I'm just under the impression that my small catch can - if you're familiar with the DIY air compressor catch can, only holds a couple ounces, and is unbaffled - will suck air in, deposit some oil, but seems like it will still allow some of the oil vapor to travel into the intake manifold. The inlet and outlet points are close, and the depth is shallow. I could just replace it with a "proper" catch can, but I'm just curious if some deposit of oil in the manifold is actually harmful, or not.
01-05-2009, 07:18 PM
#13
I poked around different forums looking for the catch can that seems to have the best overall function, and I came up with:
http://www.saikoumichi.com/
Internal diagram (this is what made me like the saikoumichi): http://i112.photobucket.com/albums/n.../catchcan2.jpg
OR
http://www.eliteengineeringusa.com/Catch_Can.html
I'm just looking for a nice, baffled CC. It seems like the saikoumichi has taken the most steps to interrupt air flow, and encourage condensation / collection of oil at the bottom of the can.
What do you think? Any other brand recommendations? I'm looking for function, not necessarily looks (*cough* ARC...). It seems like the subie forums have ones they like, the evo guys have ones they like, and i've already seen the popular ones from the Z crowd. I'm sure there's no real answer as to which one is the best. I guess if I get a quality one with some engineering put into it, I should be in good shape.
Last edited by blackfairlady; 01-05-2009 at 07:21 PM.
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