Excess blow by from breather
Registered!!
iTrader: (8)
Joined: Mar 2003
Posts: 3,024
Likes: 1
From: Zulu Alpha Tango Foxtrot
Rep Power: 312 
Originally posted by JohnyBlaze
There's a ton of info on the Honda PCV system for both NA and FI on Honda-Tech.com. Some of the info contradicts others.
What seems to be fact is that, during vacuum/idle, the VC breather is *intake* for the PCV system and the PCV valve lets the crankcase pressure exit into the manifold. During boost/load, the PCV valve is closed and so crankcase pressure is forced up into the valve cover and OUT through the VC breather.
So my previous post was only half right. The other half is that under load/boost, the VC breather absolutely becomes an outlet rather than intake.
IMO, the best solution would be to put a catch can inline from PCV valve to intake manifold to catch crankcase blow-by oil vapor (which is increased with turbo conversion cars) and to route the VC breather to the air filter pipe, pre-turbo (same as what I said in my last post :-). BUT, I'm not sure how much oil vapor come out of the VC breather while the PCV valve is closed. If there's a lot, the oil will build up in the IC after being sucked in by the turbo. Could get ugly in the longer term. So it might make sense to put a second catch can inline from VC breather to air filter pipe.
You cannot use the same catch can because the one inline from PCV valve to intake manifold will see vacuum and pressure. You don't want that for the one inline from VC breather to air filter pipe.
Might not be the only correct solution, but is definitely one of them ;-)
There's a ton of info on the Honda PCV system for both NA and FI on Honda-Tech.com. Some of the info contradicts others.
What seems to be fact is that, during vacuum/idle, the VC breather is *intake* for the PCV system and the PCV valve lets the crankcase pressure exit into the manifold. During boost/load, the PCV valve is closed and so crankcase pressure is forced up into the valve cover and OUT through the VC breather.
So my previous post was only half right. The other half is that under load/boost, the VC breather absolutely becomes an outlet rather than intake.
IMO, the best solution would be to put a catch can inline from PCV valve to intake manifold to catch crankcase blow-by oil vapor (which is increased with turbo conversion cars) and to route the VC breather to the air filter pipe, pre-turbo (same as what I said in my last post :-). BUT, I'm not sure how much oil vapor come out of the VC breather while the PCV valve is closed. If there's a lot, the oil will build up in the IC after being sucked in by the turbo. Could get ugly in the longer term. So it might make sense to put a second catch can inline from VC breather to air filter pipe.
You cannot use the same catch can because the one inline from PCV valve to intake manifold will see vacuum and pressure. You don't want that for the one inline from VC breather to air filter pipe.
Might not be the only correct solution, but is definitely one of them ;-)
Thread
Thread Starter
Honda Civic Forum
Replies
Last Post
raymondxcho
Mechanical Problems/Vehicle Issues and Fix-it Forum
2
Sep 29, 2015 09:00 PM
MommaLiz
Mechanical Problems/Vehicle Issues and Fix-it Forum
3
Sep 7, 2015 10:42 PM
