CA18ET Breather questions

Hi folks.

I'm looking at using an oil catch tank on a CA18ET (for a few reasons - none of which are probably any good).

I found a thread about PCVs, EGRs and all sorts of other stuff, and I couldn't keep up with it (maybe I'm stoopid), and just ended up confused, lol.

Soo... I want this as simply as I can get it - I have no idea what a PCV is, whether or not I have one but I'd like to be rid of the maze of what appear to be breather pipes snaking around under my inlet manifold and make the engine bay neater and easier to work on.

The original plan was (without looking at the car) to run the breather pipes that go to the intake into a catch tank instead. In theory, this would simplify the pipework immeasurably AND stop oily nasty air from geting into the intake and hopefully stop the inlet getting gummed up with oily crap. Might even go better without oil vapour in the intake. And I heard a rumour that if the engine is worn it may even start to fill my intercooler with oily crap too...

However... now I'm confused about whether or not this is even possible to do without making the mixture lean right out - and it would be great to get a simpleton's guide to what the hell I'm doing here Cheesy

The car is track only and UK spec - emissions aren't an issue, nor is fuel milage.

Little help plz? Cheesy

if it were me in your situation, I'd run one line to the catchcan from the breather connection on the valve cover. Is the catchcan just a can with two connections, or does it have a filter on the top? If it has the filter on the top, you can just cap the other connection. If not, run the other hose to a filter.

Arro on 10:18:50 PM / 17-Sep-10if it were me in your situation, I'd run one line to the catchcan from the breather connection on the valve cover.

Arro on 10:18:50 PM / 17-Sep-10Is the catchcan just a can with two connections, or does it have a filter on the top? If it has the filter on the top, you can just cap the other connection. If not, run the other hose to a filter.

making a catchcan? yeah sounds like you have a solid plan in mind.

I wouldn't use any filters or vent any of this air to the atmosphere.  One thing to keep in mind though is that while I do have a ca18et, most of my knowledge on this subject is from my experience with Mitsubishi Galant vr4s and DSMs.  In stock form you will have both blow-by and boost pressurizing your crankcase.  Remember that the main goal is to relieve this pressure.  The secondary goal is to keep oil out of your intercooler if you have one.

You correctly said that the hose coming off of the valve cover goes into the intake pipe AFTER the airflow meter and is therefore unmetered.  This is correct, and I'm not sure how the ecu accounts for this, but you do want to leave this hose.  Obviously don't leave it open, I accidentally did let the hose disconnected and the car would barely idle.  When I put my thumb over that hole it smoothed out. 

But the real reason you want to keep that hose is because you need the vacuum from the turbo pulling air out of your crankcase.  You can put an inline catchcan in between the two to catch oil but keep the air flowing.  There are many different kinds of catchcans, some have filter elements to keep the oil in the bottom, and others have baffles.  I don't recommend the filter on the catchcan because then you won't have the vacuum you need to help ventilate the crankcase.  And if you don't have the ventilation you need, you will wear your rings worse, and start blowing out your dipstick, etc.

Another important thing to do: Install a check valve on your pcv hose between the intake manifold and crankcase, inline with the pcv valve.  At idle and when you're pulling vacuum your pcv valve will work as designed, but under boost they tend to let a lot of air into the crankcase.  They're not really designed to keep back air with any real pressure, so when you're intake manifold is pressurized, that air escapes into your crankcase, which is not what you want.  For a couple bucks you can get a one way valve designed for this.  You can also install a catchcan here, but remember to keep it all closed up with no filters breathing to the atmosphere - just like your other catchcan.

This guy seems to really know how to make a catch can: http://www.saikoumichi.com/

I wouldn't buy these because they're just super expensive check valves, but this is what I'm talking about and they explain it on their site: http://www.et-performance.com/turbo.html

This is a SERIOUS setup some guys local to me made and I really like the design: http://onelap.rochesterdsm.org/2010/03/crankcase-vent-tank/

This has been discussed on this site a handful of times over the years, and I myself have run just a filter on the top of the valve cover with no ill effect... normal idle, and it passed emissions fine so it obviously wasn't running rich. I've also owned two DSM's, and in no way does the DSM valve cover vent like the CA single cam cover. DSMs have a breather vent and a PCV both. On our DSM's, we would run catch cans with filters on the top, and one line to the PCV, the other to the breather. My own DSM had the PCV set up factory-correct, and a filter on the breather.

My Neon also has a check-valve off the front (PCV) and a baffled breather in the back of the valve cover, much like the DSM does.

But the CA20E and CA18ET have only one aperature. It's not a check valve nor would you want it to be. It's just a vent. It allows pressure back AND forth. Because of this, the given volume of air entering the turbocharger is neither added to or taken from, because the pressure zone doesn't vary enough in either push or pull (or for long enough) to make a measurable (or tunable) difference. But it does push and pull, because it is the ONLY vent, so you do NOT want a check valve on these valve covers.

In this way, the FJ engine is apparently the same. Nissan kept things simple. I can't speak for the VG30E or the CA18DET, but the KA24E and KA24DE are also just vents and nothing more. If I wanted to, I could plug the intake on my KA24DE and just run a little filter (or even a one-hosed catch can) off of the valve cover with absolutely no ill effect.

Again, this has been discussed in great detail on this site before, and I assure you that our valve covers are simply vented, you can indeed eliminate the hose to the intake, and just filter or catch at the valve cover vent.

Exactly why I added the disclaimer - Not out to misinform!  Thanks for the info, I have to look into this some more.  I think I've owned 7 or 8 DSMs and a handful of gvr4s by now so I've got it down to a science for that platform.  I have heard that in general you want the system closed, with no filters but I'm not clear on the reason yet.  I trust that it's not much of an issue for our cars.  I still have research to perform on the general subject.  I also have to learn more about my own car because I haven't had much time to work on it since I've owned it.  I feel like I definitely need to pull the engine to figure out what/where everything is and really feel comfortable under the hood.

1. Your car is beautiful and deserves your attention Tongue

2. The primary reason from the factory is emissions... oil vapors do not get vented to atmosphere, but instead are burned in the combustion chamber. Also, a closed system prevents dust from entering the valve cover, although a good filter on the breather or catch can, and regular oil and oil filter changes handle that fine. Your engine is more likely to die of a seized piston before it has problems with dust passing through a filter and into a valvecover.

Thanks lads Smiley

I'll get it all slammed together and update if and when it works Wink

Take pics of the catch can setup when it's done Thumbs Up!