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Catch can or AOS


J CHILN

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Yeah this topic is quite confusing. So many mixed opinions. 

My Perrin AOS has its breather plumbed into the intake which confuses me as oil can go back into the intake and into the turbo. 

 

I get heaps of black soot out of exhaust every time i do cold start now. Not sure if cos of aos plumbing or just forged motor build. 

 

But yeah, would have thought you would not want oil vapours going back into the intake 

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any 'good' catch can will have a baffling in it (like scouring pad / steelo) to give the vapour something to adhere to / seperate the oil

 

if it doesn't, it is just a breather

 

or I've read / been told you can buy swarf from any engineering shop to do the trick

 

@pedro group buy some 'sets'?

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2 hours ago, Niran said:

Yeah this topic is quite confusing. So many mixed opinions. 

My Perrin AOS has its breather plumbed into the intake which confuses me as oil can go back into the intake and into the turbo. 

 

I get heaps of black soot out of exhaust every time i do cold start now. Not sure if cos of aos plumbing or just forged motor build. 

 

But yeah, would have thought you would not want oil vapours going back into the intake 

Blowby from your crankcase can include oil,water vapour and unburnt fuel.With a AOS you ideally want only the oil returned to your crankcase.The better AOS cans are well baffled,include a water trap and are heated.The baffles and heat in AOS helps burn off the water and fuel which is removed by your intake leaving the oil to return to the crankcase.

 

Edited by Dre
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13 minutes ago, Dre said:

Blowby from your crankcase can include oil,water vapour and unburnt fuel.With a AOS you ideally want only the oil returned to your crankcase.The better AOS cans are well baffled,include a water trap and are heated.The baffles and heat in AOS helps burn off the water and fuel which is removed by your intake leaving the oil to return to the crankcase.

 

This is what the Radium one says 

"The built-in heater keeps water from condensing in the AOS. And because water is more dense than oil, there is an integrated water trap found around the bottom perimeter of the can. This prevents water from descending into the oil pan if ever present. Furthermore, because the water is trapped against the heater, it will eventually boil and evaporate out of the system"

 

So seems to be a good option 

 

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What’s the oil capacity of your engine.Loosing 1 litre of oil out of a oem twin scroll sump could be fatal with hard driving.The car also has to be dead level to correctly check the oil.
Twin scroll fill capacity is pretty much the same as the single scroll but deeper, and hence is better with regards to oil starvation. I.e. Oil level is higher under static conditions.

Sent from my E5823 using Tapatalk

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17 hours ago, Joker said:

now there is also a rule for some tracks you must have a catch an of X Size for racing too

 

was it same or 1/2 your engine capacity?

 

Don’t they dislike VTA setups too?

Any idea on the wording and how an AOS that returns oil to the engine fits into that?

 

Surely it would have to be half. That would be super fun to try find 6+ litres of space on a Holden or what not with a LS3 or bigger...

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http://manual.motorsport.org.nz/index.php/knowledgebase/36-2-01a-schedule-a-1/#a1-5

 

Section 5.1 (5) has all the details for catch cans to comply to MSNZ Schedule A.

 

If you are on sticky tyres and concerned about a lot of oil filling your catch can when at track days, easiest solution is to block off the outside head breather (put a bolt in the hose or something). The engine can still breathe perfectly fine out it's other 2 ports. On Manfeild, Hampton, and Pukekohe block the LH port. at Taupo block the RH port. This will stop the oil that gets held up in the outside head from being blown into the can - it's still stuck in the head though, so still has to make it's way back to the sump, but at least it's still in the engine! Worked for me until I decided to make a better solution (that Pedro now owns).

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20 hours ago, Niran said:

Yeah this topic is quite confusing. So many mixed opinions. 

My Perrin AOS has its breather plumbed into the intake which confuses me as oil can go back into the intake and into the turbo. 

 

I get heaps of black soot out of exhaust every time i do cold start now. Not sure if cos of aos plumbing or just forged motor build. 

 

But yeah, would have thought you would not want oil vapours going back into the intake 

Black is generally unburnt fuel, could be a bit rich on cold start. Mine burns oil (bluey/white smoke) on first start up after sitting for a few weeks/months, with VTA catch can.

I doubt it's blowby but you could un-plumb it from the intake and test. and leave it un-plumbed, only thing you need it plumbed in is for cert I believe.

 

I need to run my vent to under the car rather than next to the cabin air inlet xD.

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22 hours ago, Niran said:

I get heaps of black soot out of exhaust every time i do cold start now. Not sure if cos of aos plumbing or just forged motor build. 

 

I don't want to hijack this thread but jesus, what the F*** :/

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17 minutes ago, boon said:

 

I don't want to hijack this thread but jesus, what the F*** :/

 

Mine spits a bit of black S*** when cold as well... I think it's just moisture loosening some of the black stuff that builds up in the exhaust... no big deal.

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If you want a decent but reasonable AOS look at what the diesel guys use.Made for high compression,intercooled engines.Im looking at this,ProVent 200.Can be run as AOS or VTA.Has some interesting additional features.

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fyi Pics of the DIY setup Tony made & the base for much of this discussion

 

Quote

3. Custom Breather/Oil control System. I designed this breather/catch can set-up to prevent the common issue of oil being blown out of the heads when driving on the track, Sustained high G corners cause oil to fill up the outside head, and then blow it out the breather. This system catches the oil in the tubular can, then once the car straightens up, the oil can then drain back down any of the other various ports back into the engine. There is a baffle plate in the can, and if any oil makes it past this, it gets caught in the secondary catch can/breather (off to the side). This set-up was custom made to suit my car, but shouldn't be too hard to modify to suit your own set-up. Mounts on centre of ver. 8 Spec C inlet manifold which has been flipped. It is made to work with AVCS heads that have the extra 2 balance ports on the rocker covers, but I have also used this set-up on early heads, and just added the extra ports myself. It seems to work really well, and I have only ever got condensation crap and a little oil residue in the secondary can. Comes as pictured with -8 & -10 fittings and hose (may need longer hoses depending on set-up), and also have the -12 hose that goes back to main crankcase breather as well (not in picture). $250

IMG_5065_zpsft9esnim.jpg 
  Krmlcsel.png

Fitted on my car:

IMG_3944_zpskwmx8rqz.jpg 
  0HTWXCul.png

 

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@Inked, the whole thing was custom made to suit my car. The above pictured one is V2 which I made when I changed inlet manifolds. I also had a different design tank to suit my old early inlet manifold, which was sold to another clubsub member from Wellington.

I can't take credit for the design, it was originally thought up by Al from Macbilt and used with success on one of the circuit cars he used to run. Since you are Wellington based, it would be worth going to see him about it as I am sure they could fab up something to suit.

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to be fair the hard part (if you're not an engineer) is to get the 3 inlet ports, one from each head, plus the Crank case, and dual outlet ports, one to drain & the other to feed the filtered air back into the intake

 

= 5!

 

that is that the basics right?

 

if i read right some heads have dual breathers/ ports that you can / could Tee into one hose & feed to your can / catch / AOS?

 

oil drain need to go to a non-pressurised port or Sump (so you cany use the usual spots for get Oil temp or pressure from on the head / block

 

and I know yep : I am over thinking this too

 

that's why I love this forum, almost everything Turbo Subaru JDM has been covered before / written down in here somewhere!

 

there's been some cool setups in NZPC's over the years relocating Battery to the boot & using that space

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  • And the best thing about this sort of system is the reduction in Carbon build up which the Subaru Upper Engine Cleaner is renowned to attack

 

with the exception of the Perrin I always thought it was odd the off the shelf products above (catch can AOS whatever you want to call them they are the same to me)

 

never seem to have those 5 ports, just the bare minimum

 

Quote

THIS IS NOT A CATCH CAN

The PERRIN Air Oil Separator is not a catch can. Catch cans capture water and oil vapor filling with a sticky mess requiring it to be emptied. The PERRIN AOS separates engine oil from water vapor and allows it to drain back into the engine. Oil entering from the crankcase vents spins counter clockwise through the entire body of the AOS, passing along four walls equaling roughly 50.25 sq/in of surface area. The multiple baffle walls in our compact design simulate the surface area of an AOS that is 13.5" tall!

As oil accumulates on all the walls, gravity pulls it to the bottom of the can where it drains back to the engine block while water vapor and air merge with the intake air and are re-burned in the engine. This means little maintenance or upkeep.

 

 

would that mean, if you fitted an AOS you'd still need a Catch can for racing / to meet Schedule A?

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Thanks for the links @Joker Think I am set on the Radium kit, it has the best reviews online and @Andy_Mac likes his so good to have feed back from a forum member. plus the added bonus of ML Racing being a sponsor are happy to do the best price I can find on it :D . not up to competitive track days as of yet so this should serve the purpose for playdays as well. 

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