I need a bit of help chewing over my options for plumbing my inlet hose / breather system on my MY98 WRX. t'll help if you've modded your own breathers so I can get technical without losing my audience!

For some time now I've been running a modified breather system with standard OE turbo inlet pipe. Rocker cover breathers are totally standard, drawing fresh metered air in from the side of the inlet pipe as they should. Crankcase-to-PCV line is also totally standard as most of my driving is everyday commuting etc, so I feel happier knowing that when driving off boost, the manifold vacuum is drawing on the crankcase vent. The only difference is that I run the other crankcase vent through a remote catch tank on the bulkhead and then back to the standard location on the turbo inlet pipe. It's basically a 'green' system with a catch tank intercepting the 'on-boost' crankcase-to-inlet breather line. It's been working perfectly.

Now here comes the problem. My OE inlet pipe started coming away from the turbo so I've sleeved over the turbo joint with silicone hose and fixed that problem. However, while doing that I managed to snap off the small connector on top of the inlet pipe that the catch tank return pipe fits onto! So now I'm left with a hole in the inlet pipe that I cannot fix, so I've gaffer taped it over for the time being, so at least it won't draw in any unmetered air. The main problem I now have is what to do with the loose hose now?

As far as I can see, I have two options - either leave it open to atmosphere, or seal it up. I was all for leaving it open, but it seems to be drawing a very slight vacuum on idle and presumably it may vent out a little while on boost? I can live with that, but the thing is it's still going to be drawing metered air out of the inlet pipe, through the rocker covers and through the crankcase. It can't reverse into the inlet pipe at all because I have a second PCV valve in that line. So if I bung it closed that keeps the system sealed from the atmosphere, which I'm more comfortable with, but then obviously it can't vent out while on boost. As far as I can see, the main PCV valve will just be pulling a little more vapour through than usual when it operates in vacuum.

So, any advice? Anything I've really misunderstood here? What can I do in the future to fix this problem properly, apart from replace the inlet pipe? Is it safe to leave that main crankcase breather open to atmosphere and will it still draw through from the rocker covers? What will the ECU do about the missing metered air that isn't recirculated back again into the inlet?

HELP!

PS here's an idea that I'm mulling over - replace the OE inlet pipe with a Prodrive rally pipe (i.e. with no side breather outlets at all) and only the crankcase to PCV line connected, running through the existing sealed catch tank. I'd seal up the rocker cover breathers so end up with a fair vacuum in the crankcase when off boost, and who know what when on boost, probably positive pressure in there. What would be the effect of this?

 

I changed my rocker cover breathers to atmosphere, blocked crankcase to manifold and fitted a hose from crankcase to a catchtank.
The result was a lot of goo in a small collector I had below the vent to the rocker cover breather.
When I fitted a hose from catchtank to inlet again the collector below the rocker cover breather more or less stopped filling.
So. if you don't have a return to inlet vacuum you will probably get more flow crankcase->rocker cover.
1 suggestion is to disconnect rocker cover hose from inlet and connect a filter there, and connect your return from catchtank to the now free connector on the inlet.
Or buy a Samco or similar inlet pipe...
/Adam

 

Silent,

I have just redone my breathers on my MY98 WRX. It now has the PCV valve removed from the manifold as I needed the location for a temp sensor. I filled the larger hole from the crankcase breather and now have only the smaller one left which is now T'eed into the other 2 head breathers. Its going to a catch can on the inner wing and venting to atmos.

Could you use the above method in the following way.

Completely block off the breather from the broken lug and use the other one only.

You can get to the breather that feeds the PCV with the TMIC off the car.

Also, if you are still able to run closed loop with a lambda then the small amount of air should be compensated for by the ECU as the air isn't metered for by the MAF in the same way as open loop. Its only when its on open loop when there could be a problem.

Wayne.

 

Hmm some interesting thoughts there, cheers. I've just done a couple of hundred miles with the hole in the inlet pipe blocked up and the now open end which eventually leads back to the crankcase, blocked also, so that the only breather circulation is via the PCV when off boost.

It seems to be running OK. I wonder if I could leave it like this permanently, so that whenever it's on boost, the breather system closes, and when it's in vacuum it opens up and works in the normal fashion?

Can anyone think of any ill effects?

 

OT:
The PCV valve to the manifold,where is it located, if I fit my airtemsensor in the unused breatherinlet, isn't the PCv inside of that? Or is the PCV placed down where the hoses pass out from the crankcase?

 

The PCV is a small metal valve, basically cylindrical, only an inch or so long. One end is threaded to screw into the manifold directly underneath the throttle body; the other end is a plain tail to push fit a half inch pipe onto. As standard it is joined by a fairly short L shaped pipe to the crankcase breather outlet.

 

Ah, thanks
My 'L-shaped' hose have a steelball pushed halfway in to stop any air/oil :-)
Do you know what thread the bolt-part have, I'll try to avoid cutting it apart.

 

I'm trying to work that out right now, the thread that is.