AVO Catch Can Does Nothing? Alternatives?

[ChrisD]

I've had the AVO dual breather system / catch can installed on my GT86 ever since I got the AVO turbo installed over a year ago.
I've done plenty of track days and hard driving, and not once has the catch can ever had any oil in it.

However my intake manifold does have a fair bit of oil in it and we've also found oil pooling up in the cylinders (but haven't 100% confirmed if this is purely from oil from the inlet manifold yet, as the engine was rebuilt recently so need to rule out rings and valve stem seals etc).

AVO supply a T piece that comes from the PCV port on the engine and one end goes to the catch can and one goes to the top of the inlet manifold:



but we found that the hose coming off there going to the catch can was bone dry (and so was the catch can). But the line that goes back to the top of the inlet manifold was covered in oil inside. This is where it goes back into the inlet manifold:




So I have 3 questions:

1. How is the catch can ever meant to actually get any gas going to it in this current setup? What's stopping all of the gas/oil just going straight back into the inlet manifold, as its only a simple 2 way split as far as I can see and the inlet manifold is often going to have vacuum so surely that will just suck it all in and none will go down the other branch to the catch can.

2. At the moment we're planning to just cap off the port on the top/back of the inlet manifold and force all of the gas to go to the catch can - is there any issue with this? The catch can has a hose going back to the inlet piping (after the air filter and before the turbo), so presumably this will still end up recirculating pretty much just as well as it would by dumping it straight into the inlet manifold? In fact I'm not sure why it needs to do both normally - why does the AVO system keep the feed from PCV to inlet manifold when it also feeds from catch can into inlet piping). I did see someone say that the PCV venting system relies on the vacuum from the inlet manifold, but that contradicts several other articles stating that the whole point of the PCV system is release excess pressure in the crank case (in which case surely you don't need vacuum if you already have pressure blowing it out).

3. Would I be better off just replacing this whole setup with something a bit simpler like the mishimoto catch can that just sits inline directly between PCV valve and inlet manifold: http://www.mishimoto.co.uk/subaru-br...-can-2013.html
Any issues with using just that on a stage 4 turbo engine that's going to be running about 17 psi of boost?

[go_a_way1]

Originally Posted by ChrisD

I've had the AVO dual breather system / catch can installed on my GT86 ever since I got the AVO turbo installed over a year ago.
I've done plenty of track days and hard driving, and not once has the catch can ever had any oil in it.

However my intake manifold does have a fair bit of oil in it and we've also found oil pooling up in the cylinders (but haven't 100% confirmed if this is purely from oil from the inlet manifold yet, as the engine was rebuilt recently so need to rule out rings and valve stem seals etc).

AVO supply a T piece that comes from the PCV port on the engine and one end goes to the catch can and one goes to the top of the inlet manifold:



but we found that the hose coming off there going to the catch can was bone dry (and so was the catch can). But the line that goes back to the top of the inlet manifold was covered in oil inside. This is where it goes back into the inlet manifold:




So I have 3 questions:

1. How is the catch can ever meant to actually get any gas going to it in this current setup? What's stopping all of the gas/oil just going straight back into the inlet manifold, as its only a simple 2 way split as far as I can see and the inlet manifold is often going to have vacuum so surely that will just suck it all in and none will go down the other branch to the catch can.

2. At the moment we're planning to just cap off the port on the top/back of the inlet manifold and force all of the gas to go to the catch can - is there any issue with this? The catch can has a hose going back to the inlet piping (after the air filter and before the turbo), so presumably this will still end up recirculating pretty much just as well as it would by dumping it straight into the inlet manifold? In fact I'm not sure why it needs to do both normally - why does the AVO system keep the feed from PCV to inlet manifold when it also feeds from catch can into inlet piping). I did see someone say that the PCV venting system relies on the vacuum from the inlet manifold, but that contradicts several other articles stating that the whole point of the PCV system is release excess pressure in the crank case (in which case surely you don't need vacuum if you already have pressure blowing it out).

3. Would I be better off just replacing this whole setup with something a bit simpler like the mishimoto catch can that just sits inline directly between PCV valve and inlet manifold: http://www.mishimoto.co.uk/subaru-br...-can-2013.html
Any issues with using just that on a stage 4 turbo engine that's going to be running about 17 psi of boost?

for #1 I think its just a poor design
for #2 you want your crank case to be under a slight vacuum as far as I know.
for #3 buy the radium dual catch cans and call it a day

[ChrisD]

Originally Posted by go_a_way1

for #1 I think its just a poor design
for #2 you want your crank case to be under a slight vacuum as far as I know.
for #3 buy the radium dual catch cans and call it a day

That's pretty much exactly what I was thinking. The more I look into it and read various other threads on here, the more I think I should just replace this with the Radium dual cans

[Rifle]

I use a radium single catch can, PCV side, and it has saved my ass following my supercharger install. After I was dynoed, the car began to lean out for some odd reason, wasn't quite sure what it was at the time. Mid driving, the car went into limp mode. Got it all back home and took it apart, turns out the bolts that hold the driver side manifold rattled off and caused a leak pre-o2 sensors. This caused the car to read lean and dump more fuel into the block. Pulled the catch can, had a little oil but a lot of gas.. Drained the oil, emptied the catch can, redid everything. Never had an issue since.

[humfrz]

Originally Posted by Rifle

......................Pulled the catch can, had a little oil but a lot of gas.. .

....... ...... you discovered a whole new use for the "catch can" ..........


humfrz