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S2 industries Air/Oil Separator


nismovzr2003
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Whats the basis of these? Do they eliminate the need for a catch can? I assume two of the inputs are for crank case and cam breathers, these pass through the air/oil separator and the outlet goes back into the inlet?

Anyone used one or know how effective they are? Worth replacing catch can setup with one? Whats the go with the emission laws at the moment, are catch cans vented to atmosphere being ruled out? If so, would the air/oil separator be a feasible alternative?

Cheers

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 Andy_Mac said:
The plus side is they don't need emptying the way catch cans do, the downside is the oil fed back into the filler port isn't always as clean as you'd like it to be

what about having one of these that could mount into the top of a catch can? That way u eliminate any emissions being vented to atmosphere but still collect the contaminated oil?

Thoughts?

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Most separators aren't hugely cheaper than catch cans so would probably work out more in the end. What kind of fitting does the vent have?, not possible to modify it to attach some hose to it and feed it back to the intake?

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Not saying they don't work, but I wouldn't run one of these. Especially not on a higher km engine with a lot of blow by. Looking at the install setup and what's inside it, it's pretty much just adding another baffle to the PCV system.

Also highly restricting the OEM PCV airflow at the same time. The OEM PCV system has:

1x12mm left head breather line

1x12mm right head breather line (heads T'd together, into 12mm intake port)

1x20mm crankcase breather splitting to 12mm at PCV valve and 16mm at the intake

The GDB and later STI also has a second crankcase breather connected to the head breathers to equalize pressure between the block and heads.

The Grimmspeed and S2 Industries AOS combine all of these OEM breathers into one 12mm hose feeding to the intake. Also looking inside the AOS the connecting baffle ports are even smaller:

aoscondensation-2.jpg

aoscondensation-1.jpg

Air flow through the AOS:

aos_diagram_600.jpg

If I was going to fit one, I would only feed the head breathers separately through the AOS. Leaving the block breather OEM, or running through a separate catch can.

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 Rosssub said:
Not saying they don't work, but I wouldn't run one of these. Especially not on a higher km engine with a lot of blow by. Looking at the install setup and what's inside it, it's pretty much just adding another baffle to the PCV system.

Also highly restricting the OEM PCV airflow at the same time. The OEM PCV system has:

1x12mm left head breather line

1x12mm right head breather line (heads T'd together, into 12mm intake port)

1x20mm crankcase breather splitting to 12mm at PCV valve and 16mm at the intake

The GDB and later STI also has a second crankcase breather connected to the head breathers to equalize pressure between the block and heads.

The Grimmspeed and S2 Industries AOS combine all of these OEM breathers into one 12mm hose feeding to the intake. Also looking inside the AOS the connecting baffle ports are even smaller:

aoscondensation-2.jpg

aoscondensation-1.jpg

Air flow through the AOS:

aos_diagram_600.jpg

If I was going to fit one, I would only feed the head breathers separately through the AOS. Leaving the block breather OEM, or running through a separate catch can.

cheers for the awesome write up.

im currently running -10 lines from the cam breathers an crankcase into a custom catch can, am im going to have any issues with this setup?

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If your catch can is venting rather than connected to the intake, with no PCV valve operating during idle/manifold vacuum. Then technically it's not a positive crankcase ventilation system, instead just a ventilation system, or passive crankcase ventilation system.

When your driving along with the revs up the air intake (pre turbo) is sucking, so a constant vacuum or low pressure source that is connected directly to the crankcase. During idle and at low engine speeds there isn't enough vacuum in the intake pipe to keep the crankcase in vac, so the PCV valve opens. Giving the crankcase slightly restricted manifold vacuum during idle or low air intake speeds.

So with a venting catch can, your crankcase will always be in positive pressure, the higher your blow by and the higher the rpms the higher the crankcase pressure.

Positive pressure in the crankcase pushes against the pistons, lowering power and fuel economy. Also leads to premature oil leaks from gaskets and seals. While adding to oil consumption due to the pistons oil ring not sealing properly, eventually fouling plugs and leaving excess carbon build up in the combustion chambers. The high end of too much crankcase pressure can pop the dipstick out, or pump litres of oil out the dipstick hole (speaking from personal experience).

A constant vacuum source or working positive crankcase ventilation system. Stops added pressure on gaskets and seals. Helps seal the pistons oil ring by pulling it against the bore, lowering oil consumption. Adds power and fuel economy by giving the pistons nothing but vacuum to move into. Giving overall a more efficient, happier engine.

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All above true Ross..

But not all engines behave the same way it seems..

My engine is breathing thru a vented to atmosphere catch can and exhibits none of the above symptoms..Whats going on inside the crankcases at 7000 rpm.?.

Lots of air rushing around...

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How many kms? I was at 214,000 when I went 2 into 1 and pumped oil everywhere. Now at 11,500 I have no noticeable blowby.

I've currently got my PCV valve blocked off, with all OEM breathers back to intake. With the engine idling and the oil filler cap removed there is hot air escaping. But if I cover the oil filler hole with my hand there's a noticeable vacuum. I remember pulling the dipstick on the old motor at idle and having it float on the blowby pumping out of the hole.

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Could just put a T in the current crank breather line, then run a new hose from the T to the PCV valve.

Not sure, but thinking it could possibly cause AFR/MAF issues at idle or during manifold vacuum? With the PCV valve able to draw fresh unmetered air through the cans vent.

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Use existing pcv or is there an alternative? U've said to 'T' into the existing crank breather line between the engine an catch can, if its 'T' in will the pcv have any affect? Surely the vacuum and positive pressure will simply bypass the pcv as the line between the engine an catch can is still available?

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Probably easiest to use the original valve, but you can get after market inline PCV valves from most places.

On the OEM PCV setup the PCV valve is T'd into the crankcase-intake pipe line, so it would draw about the same as a stock PCV valve setup:

PCV_Diagram.png

Edited by Rosssub
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 Rosssub said:
Probably easiest to use the original valve, but you can get after market inline PCV valves from most places.

On the OEM PCV setup the PCV valve is T'd into the crankcase-intake pipe line, so it would draw about the same as a stock PCV valve setup:

PCV_Diagram.png

So the top 12mm line would go to the pcv and vent to atmosphere?

The bottom 10mm line that normally goes back into the air intake would got to the catch can?

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 Rosssub said:
Nah that's a pic of the OEM setup. You can just put a T into your crankcase-catch can hose, then a new hose from T to PCV valve.

Ok so to get it right in my head, when the vehicle is at idle there will be vacuum and therefore the pcv will allow air to be sucked in, when the engine is under load there will be positive pressure and the pcv will close and therefore the crankcase will have positive pressure?

If so, if i'm slimply 'T'ing the pcv into the current line between the crank breather and catch can, when the engine is under load the pcv will be closed and all pressure will pass directly to the catch can?

I'm trying to work out how positive pressure is maintained in the crank case if the pressure is simply bypassing the pcv and going straight to the catch can and venting out the air breather?

Sorry if im confusing the situation

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 GC8E2DD']Hrm, the PCV system is about generating vacuum in the crankcase right?

Spot on, positive crankcase ventilation = vacuum.

[quote name='nismovzr2003 said:

Ok so to get it right in my head, when the vehicle is at idle there will be vacuum and therefore the pcv will allow air to be sucked in, when the engine is under load there will be positive pressure and the pcv will close and therefore the crankcase will have positive pressure?

If so, if i'm slimply 'T'ing the pcv into the current line between the crank breather and catch can, when the engine is under load the pcv will be closed and all pressure will pass directly to the catch can?

I'm trying to work out how positive pressure is maintained in the crank case if the pressure is simply bypassing the pcv and going straight to the catch can and venting out the air breather?

Sorry if im confusing the situation

With a venting can the crankcase will always be in positive pressure. Reinstalling the PCV valve will cause it to get some vacuum when off boost.

Manifold Vacuum - PCV valve wide open, drawing from crankcase gasses.

Manifold boost - PCV valve closed, all crank gasses venting through catch can.

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 Rosssub said:
Spot on, positive crankcase ventilation = vacuum.

With a venting can the crankcase will always be in positive pressure. Reinstalling the PCV valve will cause it to get some vacuum when off boost.

Manifold Vacuum - PCV valve wide open, drawing from crankcase gasses.

Manifold boost - PCV valve closed, all crank gasses venting through catch can.

wouldnt the crank case get vacuum without the pcv anyway? Wouldnt it just suck back thru the catch can as the line between the crank breather and catch can is not restricted?

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