AOS install: advice required please.

[bigBADbenny]

Just getting my act together to install my SG Motorsports AOS, kindly refurbed by cruisn.
So its a similar install to a GS AOS, but has only 2 ports for just inlet and return.
Its not the ultimate solution for tracking but as Coyote said, "its tons better than no AOS"...

I plan to use these install guides:
Tomioka AOS for Legacy http://forums.nasioc.com/forums/showpos ... ostcount=3
Grimmspeed AOS for Legacy: https://www.grimmspeed.com/install_guid ... wrxLGT.pdf‎
And http://legacygt.com/forums/showthread.p ... 32381.html

Here's the WSM diagram of the CRANKCASE EMISSION CONTROL SYSTEM

The aim is to improve crankcase breathing and to keep oil out of the inlet tract.
I was under the impression that the heads were the priority to be vented to the AOS, and that the crankcase breather was an option.
I was planning to join the head and crank breathers, run them to the AOS and then outlet the AOS to the inlet.
I'm no longer 100% certain after looking at the diagram above. Can anyone advise?


As regards the PCV's for the heads, I can see 7, 8 and 9 PCV pipes, but I'm not sure where 6 joins up or where it runs to the intake pipe.
Any advice?

Also, since I'm installing an AVO silicone inlet, is it possible to temporarily remove the inlet manifold for better access without A: losing coolant or B: disconnecting the fuel line/s?
I think the answer is yes based on reading this how to: http://legacygt.com/forums/showthread.p ... 04330.html kindly linked to by kiahatsiu at this thread:http://forum.liberty.asn.au/viewtopic.php?f=18&t=23092&start=0

[bigBADbenny]

I've been over this a few times but there does seem to be a few different approaches: e.g. http://forums.nasioc.com/forums/showthr ... 782&page=2



So I'll be reading up on this massive thread:
IWSTI Engine & Drivetrain > 2.5 Liter/Litre Factory Motor > The Official STi engine Venting, A/O Separators, and Catch Cans Thread!!
http://www.iwsti.com/forums/2-5-liter-l ... hread.html

[dat50]

This does appear to be a bit of quandary. How in the diagram above is the PCV duct meant have any impact on emissions when the crank case (and head) ducts are downstream from it (i.e. closer to the turbo). Technically the PCV system would have no chance of picking up any dirty air.

In this regard the best approach may be to join the head and crank breathers, run them to the AOS and then outlet the AOS to the PCV duct. Does you AOS also have "filtered" vent to atmosphere. If so, this should vent any pressure build up in the AOS whilst at WOT (and PCV closed).

[bigBADbenny]

This:http://www.iwsti.com/forums/2530939-post91.html
Post 91 and getting somewhere

[bigBADbenny]

So from what I'm reading in that thread, I'm good to vent both heads and crank case to the AOS since I have a high K lib that gets through the oil
I'm considering a catch can between the AOS and the inlet too...

[Alkem1st]

Digging up a really old post here. How did you go in the end Benny? I've got an SG AOS too that I want to hook up tomorrow. Think I've got it mostly sorted but any pics you've got might help!

[bigBADbenny]

I changed my inlet recently as the original one had perished, from age and all the blow-by oil that collected in there from the CCV/PCV.

It's easy enough to install, take off the tmic, locate the hose that runs from the PCV/CCV to the inlet and tee your send and return lines neatly to the AOS, taking care to set the send line without too many changes in elevation so as to reduce the chance of oil pooling in the lines.

You can tee the heads breather into the CCV/PCV send line, the GS AOS has a seperate inlet for this purpose.
Either way, iirc the heads breather return is capped off, as the inlet will use a single return...

I'm installing a Kap dual chamber AOS soonish, I'm just trying to nut out if I want to put the CCV loop prior to the PCV tee or or after it as described above. I guess the nut is me, generally speaking: any AOS setup is better than none

image.jpeg (76.97 KiB) Viewed 15139 times

^ Stock inlet, PCV/CCV return is the topmost pipe, basically an inverted C shape.
The heads breather is the next largest in diameter, it's the next one below the BOV return on the RHS of the inlet...

image.jpeg (159.14 KiB) Viewed 15139 times

Comparison of stock vs Perrin vs AVO inlets. Perrin keeps the stock CCV/PCV return location on top at the compressor end of the inlet, the AVO moves it to the side of the inlet, these are usually supplied with a nylon joiner and a length of heater hose to bridge the gap.

You can see the PCV valve in the pic, this being a great opportunity to remove, clean or replace it. Soaking it in UEC works well to remove the gunk.

If you really want to get picky with how your AOS is setup, take a look at this post from Nasioc.
http://forums.nasioc.com/forums/showpos ... tcount=120
I'm liking this approach as it puts the seperator immediately after the CCV.

[Alkem1st]

That's awesome. Thanks heaps for the info.

Yeah I'd like to eventually move to a better dual catch can set up but this came up for a good price and it helps for now. Will let you know how I go

[Alkem1st]

So I'm pretty much done, just need to chuck the intercooler back on and hook up the solenoids near the intake as well as the filter etc. I started off in a way that would've meant a lot of the hoses coming out alongside the intake, in the way of some of the solenoids and up over the alternator. In the end I mostly followed the grimspeed guide which is more along the back under the intercooler and needs less overall tubing.

20151121_172343edited.jpg (231.47 KiB) Viewed 15104 times

^ This is the plastic tubing that runs along the back of the manifold. The inlet remains plumbed into the intake but the hoses from the heads are removed, driver side blocked and passenger side becomes the "out" side of the AOS.

20151121_181844edited.jpg (125.86 KiB) Viewed 15104 times

^ New tubing used from the driver side rocker cover (I went a bit overboard with the oil-resistant, high-temp hoses from pirtek but at least they should last some time lol).

20151121_172501edited.jpg (137.11 KiB) Viewed 15104 times

^ Left the stock T-piece from the intake/crankcase/PCV->Manifold in place but the C-shaped pipe was removed and plugged on the intake as shown below.

20151121_182321edited.jpg (116.7 KiB) Viewed 15104 times

A bit hard to see but at the back standing up is a sealed bit of tube a little smaller than a thumb.

20151121_181848edited.jpg (131.83 KiB) Viewed 15104 times

^ The new tubing from the driver-side rocker cover runs along the back over the turbo inlet into a T-piece to combine the crankcase/PCV T-piece outlet (that used to run to the intake) and it then continues under the intercooler and manifold/throttlebody inlet.

20151121_185607edited.jpg (231.1 KiB) Viewed 15104 times

^ The final result has the combined rocker cover tubes and tee'd in crankcase/PCV outlet (all the blue hoses) with the normal heater hose return line into the hard plastic tubing running back to the intake.

Took a lot longer than I expected as I completely changed approach half-way through and then needed to duck out to get extra connectors/T-pieces but hopefully that set up will work out well. I may have to play a bit with the tubing near the throttlebody, as you mentioned I don't too much change in the elevation but it should be ok. Didn't really need the hose clamps but less to worry about that way haha.

[bigBADbenny]

A layer or two of heavy duty electrical shrink tube is a more gentle substitute for hose clamps.
I'm going to use that for my AOS install as well as redo about 20 clamps on the vacuum hoses on my m20b23 ljet E30

[Alkem1st]

A layer or two of heavy duty electrical shrink tube is a more gentle substitute for hose clamps.
I'm going to use that for my AOS install as well as redo about 20 clamps on the vacuum hoses on my m20b23 ljet E30

Nice! that sounds like a fun project.

[bigBADbenny]

Make sure you work out the correct orientation for the SG AOS unit.
Iirc the body indexes with the cap to allow the hoses to vent though to the oil filler.

So take off the AOS, remove the hoses, align the holes and mark the point on top of the unit.
Once reinstalled, if they don't line up where you need them to, either shim the seal to the oil filler or extend the hoses to suit.

Also keep the seal well lubed and don't overtighten the cap or it will get stuck on...

[Alkem1st]

Make sure you work out the correct orientation for the SG AOS unit.
Iirc the body indexes with the cap to allow the hoses to vent though to the oil filler.

So take off the AOS, remove the hoses, align the holes and mark the point on top of the unit.
Once reinstalled, if they don't line up where you need them to, either shim the seal to the oil filler or extend the hoses to suit.

Also keep the seal well lubed and don't overtighten the cap or it will get stuck on...

Good point Ben and thanks for that. It's not mentioned anywhere I've read but I definitely see what you mean about the alignment of the holes.

[bigBADbenny]

Cheers, that's advice from studying my SG AOS, blowing through the holes.
So aligning the parts and making an index mark from the cap to the body is a good idea.

[mynameisdaniel]

After reading/looking at the stock intake system I can't see how the full function of the standard breathing system can be maintained without at least two isolated catch cans. That's not to say an AOS isn't effective, but it seems case 2 below really needs to be done via a catch can if it's to be maintained.

The way I see it there's basically two airflow paths under either boost or vacuum:
1. Under boost the PCV is shut and the airflow path is out through the head breathers as well as crank breather (basically sucking out the dirty blow by air) thanks to the vacuum generated pre-turbo.

2. Under engine vacuum the PCV is open and the greater vacuum generated by the engine draws air out through the PCV via the crank case breather. Due to the vacuum difference at the throttle body and inlet pipe this allows fresh air to be drawn into the crank case via the head breathers.

I 'think' I can see what you've done and joining these two systems will be effective at filtering oil from going into your intake, but it's limiting the crank case ventilation and fresh air feed under vacuum. This doesn't seem to be an issue with EJs, but it's a huge problem with RBs - usually people go down the opposite path and enhance the crank case ventilation to stop them filling the head with oil and eating bearings