Turbo - PCV / catch can / breather setup ?????

[CMF_Danvillan]

Sort of trying to figure out how this will be set up for a turbo setup.
I believe the PCV is a one way valve (correct me if I'm wrong) so shouldn't be effected by the boost but it wont be releasing crankcase pressure if plumbed to the intake manifold.

I was thinking the breather can either go to an oil catch can or pre-turbo , rebuilt motor shouldn't have too much blow-by.

Does going pre turbo suffice as a vacuum source?

So basically if someone has a clue I want to know the best setup to achieve the following:
1. Keep emissions legal
2. Allow the crank case pressure to breath while under boost.
3. stop oil entering the intake
4. Any other consideration I need to consider?

 

[CMF_frank2]

yes a 1 way valve dan, and when i block the rubber pipe and cable-tie a bag onto the p/c/v, it shows a small positive pressure (inflates the bag).
and when i fit the bag to the breather on the other end of the cam cover (the vent that goes to the airbox) it deflates.
i have a pipe attached to that vent, for 1/4 mile regs (pictured) and if that starts to spray oilmist, i know that the ringlands have let go (not for 12 months now, finger,s crossed)

 

[CMF_Danvillan]

Hey frank, still not 100% on the setup. So you say the PCV is blowing and the other breather hose is sucking? The dramas I have is that if the PCV is blowing and it's plumbed to the intake there will be two air flows pushing against each other while under boost, correct?

 

[CMF_frank2]

i,m saying that the crankcase pressure and fumes exit via the p/c/v dan, after being scrubbed by the oil separator under the cam cover lid.
so you could fit a (sealed) catchcan between the p/c/v and inlet mani i guess (pretty pointless imo)
or else a catchcan on the vent that i have the pipe fitted to ^
but that will be sucking off-boost, and mildly blowing on-boost
mine shows no residue at the pipe exit after many months, so i wont be bothering with any catchcan personally

 

[CMF_asdame]

I've once written a metaphor to describe the PCV circuit here:

http://micra.org.uk/threads/my-little-knitting-needles-sw7672-1-3-turbo.52965/page-30#post-622193

the PCV only allows crankcase gases to be sucked one-way into the inlet mani to be burnt during high vacuum closed throttle.

during +ve boost that PCV shuts

on the other hand, the PCV breather port at the rear right of the rocker cover is simply an open two-way port.

when the internal crankcase pressure is lower than where that port is plumbed into (free air or pre-turbo), such as during high vacuum, then fresh air flows INTO the breather port, through the crankcase, PCV and into the mani.

when the crankcase pressure is higher than outside that port, such as during boost when the PCV is closed and/or large amount of blowby has entered the crankcase, then all that oily watery pressurised gas flows OUT of the breather port. that oily mist will eventually condense on the cooler parts of whatever that port is plumbed into (nearby engine bay, breather filter, catch can or turbo compressor).

the catch can tries to CATCH most of the oily watery mist before it reaches and contaminates the cooler components down the line such as the turbo or inlet mani or MAF.

so basically a catch can is there to trap oil vapours and keep the inlet mani, turbo inlet and anything else down the flow path such as MAF, injectors etc cleaner for longer to operate more efficiently.

ideally on a turbo setup you'd have a catchcan near the PCV (to keep inlet mani clean) and near the breather port (to keep the turbo inlet and plumbing clean)

 

[CMF_Danvillan]

Thanks Asdame, I like the analogy you used to explain the PCV and breather hose relationship. Really helps to understand the process.

I probably wont need the oil/air separator as the motors newly rebuilt but I was thinking of possibly using a small oil/air separator from an air compressor (see picture). Using one between the PCV and intake manifold. One between the breather hose and pre-turbo.

I know they are small but should work, just have to keep an eye on it more often.

What do ya'll think?

 

[CMF_frank2]

sounds good dan
its a sealed unit, so wont affect the idle eh

 

[CMF_Danvillan]

Frank, I think this will be the least of my problems when it comes to idle problems, LOL.

1. Using the SR20 TB with no ICV.
2. Lumpy cams.

I suppose one less thing to stuff the idle is good though.

 

[CMF_frank2]

i doubt you will have any idling problems mate, here,s mine with an idle control valve delete and 4kg flywheel, you can see when i switch the headlights on then off, it still idles at 500rpm (and on lift too)