AOS install: advice required please.

[bigBADbenny]

Afaik the CCV pulses somewhat, but is mainly pressurised (blow-by) especially under boost.

The inlet pipe is always under vacuum, assuming your BOV is working.

The inlet mani has vacuum under idle, cruise and engine braking.
It's pressurised obviously under boost...

The heads are either under vacuum during idle etc or pressure during boost. Dependent somewhat on how well the valves are sealing...

The heads are either scavenged or or fed air from the inlet pipe under boost or vacuum respectively.

The head breathers and balance pipe are crucial in assisting oil to drain back to the sump after eg extended high g cornering. Ideally each head having its own AOS located on the opposite side of the engine bay.

The role of the PCV is to scavenge the CCV to the inlet mani when the inlet mani is in vacuum, under boost the PCV closes and the inlet pipe scavenges the CCV via the 3 way connector between the CCV, PCV and inlet pipe.

Therefore the most appropriate location to plumb in AOS's are after the CCV and another between the heads breather inlet pipe return

Dual AOS's with seperate drains with taps allow for easy dianosis of major engine issues eg if you're loosing oil via the CCV (rings), heads (valves, valve seals) or both.

Some say oil cap AOS's are not recommended for extreme track use or extended high g cornering. Ymmv...
Meaning they're good for 99.9% of people 99.9% of the time

However any AOS anywhere in the system is a good thing
The key being to keep oil out of the inlet pipe and inlet mani...

[tom_kauf]

I've also been trying to find the best way to install my Kap Industries twin chamber catch can (which I've had for months).

From all my research (significant but probably not as much as BBB), it isn't advisable to join the 2 breather systems.
I also won't be blocking off any of the stock system - I think that can also cause problems. Tapping into each system and installing the Catchcan in-line is my preferred method. Not just from research, but also from the experience of a local 2.5 GTB owner who had his catch can professionally installed with a section of the stock system blocked off, and he has had nothing but problems with it - smoke blowing on start up and no oil collected by it at all.

But finding exactly where to run the hoses to/from isn't easy.

[bigBADbenny]

I'll be posting install info as soon as I do mine, but briefly, find a bolt in the area under the snorkel, it looks like a standoff bracket will be req for clearance from the radiator shroud. The AOS is long and thin, so that's just one mounting location option.

Fit your drain hoses and taps and make an appropriate hole in your engine plastic under tray for draining. That's optional but find the most convenient solution as the cans will need draining eventually...

Take off tmic, either tap 2x angle connectors into the pcv/CCV inverted C shape return to inlet pipe, or do same between the CCV and 3way connector. Run the lines forward, under the inlet mani hopefully, to and from one side of the AOS.
If you have an aftermarket inlet pipe, chances are that the CCV/pcv return to inlet pipe has already been extended to forward of the bov and heads breather return pipes.

Find the head breather return pipe, forward of the bov return tube on the inlet pipe, and tap 2 angle connectors and run lines forward and back to the other side of the AOS.

If you can get away with straight connections, straight connectors or 45degree connectors, all the better for smooth airflow.
Gates nylon connectors or eg champion brass connectors are available from most repco or bursons etc...

IMHO it's preferable to get the CCV filtered before the 3way connector to keep blowby out of the inlet mani via the pcv under vacuum.

Hopefully there's enough room to do so

[Alkem1st]

Damn you people and your useful suggestions, you made me get a separate catch can for the crankcase vents. Happy now? haha.

Nah it made a lot of sense. My AOS purely handles the heads breathers now and reuses stock connectors where possible. Basically I've used my own tubing for the rocker cover connectors and a y-piece going in to the AOS and then reused the solid plastic pipe to go back to the intake (with a 16mm chair leg rubber on the driver-side end to block that hole).

As for the crankcase vents I added a very short section of pipe with elbow joint at the top of the stock t-piece and ran that under the intercooler to the new catch can. A line returns from there into the stock C section intake pipe using another elbow piece. The catch can itself is near the wiring harness connection on the passenger side, I had to move this off the bracket for space and currently it's not very securely focussed but I'm just sorting that out tomorrow (also better baffling as the catch can looks like an ebay special a grabbed from some gumtree dude. Not proper internal baffling.

Pretty happy with it, I can still fit the stock engine cover. FYI Ben, there isn't a great amount of space under the inlet manifold although it may be better with an aftermarket intake pipe. I struggled and under the intercooler / along the manifold worked best for me.

Stock PCV valve retained and with this config it still pulls crankcase vapours into the manifold under vacuum. The catch can is used under boost which I figure is the biggest concern for blow by gases. Also generally the intake and intercooler should be much less likely to get oil condensing in there...

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[tom_kauf]

Thanks Ben ,
I think I'll need very detailed instructions for this (w pics). I don't know why this seems more complicated than eg doing stuff on wiring, but maybe because I know very little about these breather systems and what goes where.

The mounting location of the KI Catch can was one thing I had no trouble with though. Mine was well clear of the radiator shroud, so I'm not sure what was different about yours. When I first got mine, Russ confirmed it uses the stock bolt that looks like it attaches an earth strap (on the RH side of the engine bay against the inside of the painted fender).

I never got around to deciding on what to use for drain taps. I wasn't so keen on bunnings PVC irrigation ones. What did you use?

Russ sent me this link from what looks like a Forester owner who installed his KI Catch Can. It helped a bit, but without a little diagram (or some sort of overview) I still couldn't work it all out.
http://smg.photobucket.com/user/OverBored/library/UUC-233?sort=3&page=1

Ah ok, cool - thanks for the info on the Gates nylon connectors or champion brass connectors. What would you choose?
I don't mind spending a bit extra and getting brass ones (which are probably more expensive). But unlike the 3Port BCS, where I went with metal barbed connectors, I don't see the big risk of them cracking and causing any damage (and these are bigger with much thicker plastic). Usually I wouldn't trust plastic as much, but the engine bay is full of stock nylon connectors.

[tom_kauf]

Thanks for the write-up Allan . Maybe I'm over-thinking this, but I think I'll still need more detailed info/pics. Or it's just coz the AOS is a bit different to the dual catch-can install (and we're installing in another location, but that's not much of a difference).

[Alkem1st]

Thanks for the write-up Allan . Maybe I'm over-thinking this, but I think I'll still need more detailed info/pics. Or it's just coz the AOS is a bit different to the dual catch-can install (and we're installing in another location, but that's not much of a difference).

No worries. The AOS is pretty similar but just drains back down into the oil filler. As you say though, the mounting locations would affect how you route the hoses.

I'll try and do some diagrams later with the pictures I took. It is a bit confusing to start with but after reading lots of threads it makes a lot more sense.

[bigBADbenny]

Tom: break it down into knowledge bites
It's defo confusing.
Yet very clear once you grasp the concept.

Can you look at an inlet and ID all the pipes?
Can you look at the nasioc diagram I linked to, and ID the CCV (not labeled).

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The pic from nasioc is very clear, remember some of the AOS lines have hugely exaggerated lengths to give the diagram clarity... Esp the 3way to pcv line.

Are you on a stock inlet?
Do you have a tmic?

I'd use the nylon connectors/reducers...

[Alkem1st]

I've attempted a horrible diagram below.

catchcan-can-aos-diagram.jpg (204.13 KiB) Viewed 9907 times

I've tried to separate the two areas into the rocker cover breathers on top that I'm using my SG motorsports AOS for currently (will likely switch to another catch can down the track) and the crankcase breather at the bottom.

Red is the vapours going into the AOS/Catch Can and blue is the line to the intake. For the crankcase my set up is slightly different as it's after the T-piece which means that under vacuum the PCV takes vapours directly into the manifold (green line). I'm fine with this as my main focus is under boost where the PCV is closed and most of the vapours are generated.

Hopefully this helps a bit. I found it easier to consider these parts separately. Some don't even bother with the rocker cover breathers in an attempt to simplify the install.

[kiwigene]

I've installed the GrimmSpeed AOS that takes both the PCV and the head breathers. Wasn't too difficult. If anyone in Sydney needs help with an install, just let me know.

[tom_kauf]

Thanks guys. Sorry for the slow reply. First I pulled my back working on the car, then the car was idling really bad - so I had to fix that before today (turned out that the BPV hose had come off the other end).

Cheers Alkem1st, I'll take your diagram and get in front of the car tomorrow to try to work it out. I just prefer not to block anything off, so I'll go with a slightly different setup.

Cheers Ben. Yeah, I think I can ID all the inlet pipes.
Cool, thanks - that diagram didn't come up when I was on my phone the other day. That's a good one!

Yes, stock inlet.
Yes, I have a TMIC (Mishimoto one, so I've removed the TMIC several times).

Mounting the Catch Can was simple (using the stock bolt):


Clearance is good in my case:


This is what almost every PCV Valve assembly looks like:


But my T-piece (circled on the right) doesn't have the metal valve. Am I correct in thinking my PCV is what I circled on the left?

[tom_kauf]

Oh and finally, have you bought drain Taps yet Ben? If so, what did you go with?

[Alkem1st]

Yeah the one you've circled on the left is the PCV. Keen to see how you go with your install

[bigBADbenny]

The vertical tube on the rhs leading to the 3way connector is the CCV.
If space allows, that's where I'll be plumbing the CCV breather lines...
If not, then the tube going from the 3way to the inlet tube

Iirc extra heater hose and taps can be sourced from Clark Rubber.

[tom_kauf]

Cool, thank you guys, I think I'm getting there .

1) So space permitting, this hose (circled in red) is what you'll remove and install the catch can in between?
2) That's also the one coloured in red in the diagram below, correct?

3) So would you discard that hose (#15), and run a new section of hose from the 3way to the IN of the catch can? And the OUT of the catch can to the intake hose I assume?

4) Btw, in the Kapp Industries Catch Can, we have one larger diameter and 3 of the same smaller diameter ports. Which is the larger one designed for (PCV or Head)?