Pros and cons of removing the pcv system

[SIR GTIR]

hey guys i've been tossing the idea of removing the pcv system to the throttle bodys and piping it into my catch can

can anyone give me a good reason to keep it as is i've replaced the hoses and know have the high idle again clamping the hose out of the pcv dropped the idle again so i'm thinking about binning the stock system

 

[velly4]

I was told by my engine builder to remove mine as the oil mist in the intake can cause detonation. Was a good enough reason for me to get rid of it.

 

[CruiseGTi-R]

The pcv does what it says - it ventilates the crankcase. Under normal driving the vacuum of the plenum sucks air through the pcv and draws out all the oily/fuely air thats in your crankcase. Its a good thing, protects your oil from getting contaminated. If you don't want the crap going back into the plenum then just put a little filter (one of those clear plastic fuel filter works well) or a catch tank, in the line between pcv valve and plenum.

If you block the pcv off the other hose will also allow crankcase pressure to vent under boost, but that other hose doesn't have a vacuum leading to it which actively draws the air out when you're not on boost. Only the pcv side does this, which is why its there.

Solve your high idle in other ways?

 

[gtirx2]

This thread is for a different car but still works around the same idea.It gos on forever and if you follow the links you should find out all the pros and cons of different breather setups.
http://www.toyotagtturbo.com/forums/showthread.php?t=29532
I have recentally changed my breather setup as before my pcv valve was blocked, but i now run a - 10 jic = 16mm line from the pcv outlet on the rocker cover to catch tank and another 16mm line from the other end of the rocker cover to catch tank with a large breather on the top of the can.
This is another controversial subject as there are so many different ways to do it.

 

[pulsarboby]

the pcv valves are known for sticking open which will give you high idle problems!
if you clamp the pipe on and off you should be able to hear the ballvalve clicking back and forth.....if you cant then the valve is more than likely carboned up thus constantly venting.

i personally think its a good idea to keep it as it allows far better breathing of the engine (not good to blank it completely as your then pushing all crankcase pressure towards breather at other end of rockercover) this is bad as it will fill your induction pipe and lines with oil, as crankcase pressure will build even on a good engine.

imo the best setup is to remove the ball valve itself, blank the pipe to throttle bodies then as you said either run a catchcan or just vent the pipe to atmosphere via one of those little breather filters which you can pick up off ebay etc

 

[SIR GTIR]

Hmmm Ok this is pretty much exactly what i wanted to know thanks every one

i've got a catch can and the far rocker cover vent is feeding in to that and then back into the intake so it will see a vacuum still Awesome =)

the pcv works clamping the hose you hear it operate =)

Thanks everyone for your reply's

 

[CruiseGTi-R]

I have recentally changed my breather setup as before my pcv valve was blocked, but i now run a - 10 jic = 16mm line from the pcv outlet on the rocker cover to catch tank and another 16mm line from the other end of the rocker cover to catch tank with a large breather on the top of the can.

You know that doing it that way means you have no vacuum on your lines during normal driving to suck air/oil out of your crankcase. Which is why the pcv originally connected to the intake.

Seems a lot of people do it the way you've described though.

 

[PobodY]

What about a catch can between the PCV and the vacuum source? - Essentially it would just be working as a trap to catch the oil etc and stop it going into the throttle bodies in much the same way you'd put an oil/moisture trap on a compressed air line... in fact that might be a good part to try.

I'm just brainstorming, so don't mind if people tear that idea to shreds.

 

[Fusion Ed]

Remove and vent both ends. The reason why it goes back into the engine is for emission/environment reasons. The vapor mist in a crank case is partially burnt hydrocarbons etc, they are taken in by the PCV off boost and into the turbo inlet (when still oem) on boost.

The air is always metered when stock. When the intake pipe is modded people usually leave this to atmosphere, this means air enters this passes the crankcase and then via pcv valve into the engine.

Thus you get unmetered air entering the engine causing potential idle issues.

 

[skiddusmarkus]

So as well as venting the one on the right hand side of the cam cover(mine goes into a forge breather), I should also removed the gubbins by the pcv and vent that also?Is that sufficient?

Do I then just blank off the pipe that was attached to the pcv?

 

[CruiseGTi-R]

You shouldn't block off the pcv, I don't know why people do this.

The pcv uses vacuum to suck all the crap out of your crankcase - its a good thing.

Just put a little filter in the line that goes from pcv to the plenum - you don't need a massive catch can here.

Then you get the best of both worlds - pcv sucking out the crap, but not the crap going back into your plenum.

As Ed says, if the other two ends (the hose from right hand side of cam cover and hose from crankcase/oil seperator) is vented to atmousphere (by them going into a vented catch tank) it means that at normal/idle speeds, the engine vacuum could pull air all the way through the catch tank, through the engine, through the pcv, into your intake and therefore be taken in as unmetered air.

If you have your catch can setup like that and you want to check whether its the cause of your high idle, just disconnect the hose from the right hand side of the cam cover when idling, and put your thumb over the end. If theres a decent vacuum, that is unmetered air getting back into your plenum.

I think the best way to solve it is not to have that catch can vented, it should be a sealed catch can, with a line going back to the intake pipe, so that any air the catch can is sucking in is from a source that is AFTER the MAF.

What I've ended up decribing is probably just the OE set-up, but with an in-line filter on the pcv hose and an in-line catch can on the other hose to trap the oil, but with it connected back to the intake post-MAF theres no unmetered air and all the benefits of the pcv valve system.

My catch can from right side of cam cover is vented and it idles ok.

 

[ashills]

if you are running a fair amount of boost you will be getting blow by etc and returning that all straight back into the inlet manifold and intake pipe is far from great on a stock car leave it as it is but when you strip the engines down and see the inlet manifolds and turbo inlets covered in a mass of oily grease you then think about routing to a catch tank
best bet is to take both of them to a catch tank then the breather pipe from the catch tank through a pcv valve and to the inlet manifold

 

[skiddusmarkus]

Can't you just put a one way valve before the vent to atmosphere on your catch can?That way it can only blow out and not suck in unmetered air.