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Oil Catch Can


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  • Donating Members
  • Member For: 12y 6m 22d
  • Gender: Male
  • Location: Perth, SOR

For those who don't want to weld AN fittings to the rocker cover VPW now sell proflow push on bungs (BA-FG) with AN thread on the end.

attachicon.gifImageUploadedByTapatalk1429788206.485825.jpg

They are a 8AN fitting size for those that want to know.

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  • 2 weeks later...
  • Donating Members
  • Member For: 17y 6m 7d
  • Gender: Male
  • Location: Darwin

That's a bit small isn't it.

I've been reading up on cans (here and other forums) for a while now and the more I read the more confused I get.

There seem to be arguments that it won't work if vented to atmo as it requires vacuum to suck out the gases. Others are saying this is not true.

Others say if you don't plumb it back there are idle issues.

Can someone have a crack at explaining how the oem system works. Which direction does the air flow through the two ports on the rocker cover.

I assumed that fresh air comes in through the front one, but it's dumping oil in my crossover pipe so it obviously heads the other way sometimes (is that blowby). Wouldn't a valve correct this or inline filter?

What's the purpose of the valve on the rear one, some people appear to remove it and just plumb straight to the can.

A dumbed down explanation will help me decide on my setup.

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  • ʎǝʞuoɯ ɹoıuǝs
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  • Member For: 16y 1m 13d
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the passenger side front one is a breather, it is connected to the pre turbo, air intake plumbing and serves as a breather. there might be a slight venturi effect sucking air from the crankcase into the airstream at the crossover, maybe.

the drivers side rear one is the PCV, under vacuum conditions it draws the crankcase gasses out and into the intake manifold. Under boost conditions the valve closes shut and the breather lets some oil out.

I have an inline filter on the breather, which only gets a tiny bit of oil in it. I have a catch can between the PCV valve and the intake manifold which gets more oil.

Edited by SuckSqueezeBangBlow
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  • ʎǝʞuoɯ ɹoıuǝs
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it should be clearer, and say:

"the drivers side rear one is the PCV, under vacuum conditions it draws the crankcase gasses out and into the intake manifold. Under boost conditions the valve closes shut and the other breather lets some oilly gasses out."

Edited by SuckSqueezeBangBlow
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  • Member For: 17y 6m 7d
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  • Location: Darwin

Thanks

So what's the purpose of the pcv and does the catch can still serve that purpose. Should the line from the intake manifold to the catch can have a check valve/pcv in it to stop boost leaking

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  • ʎǝʞuoɯ ɹoıuǝs
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so the oily gasses in the crankcase (from blow by) are reintroduced into the inlet manifold via the PCV.

I put a check valve in (really an inline PCV valve) on the line between the catch can and inlet manifold so the catch can doesn't see boost.

the catch can just catches some of the oil in the gas.

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  • Member For: 21y 9m 30d
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Alot of the setups here are not really the way to do it (like running both hoses to one can). You have two sides to a PCV system. One side works at idle and cruise and sucks from the rocker cover into the intake when in vacuum.

The other side vents the engine under load and vents it into the intake whist the other side connected to the intake has a one way valve in it to stop any pressure going into the engine.

To do this properly you need an oil/air seperator for each side.

It is an emissions device but if done properly you can make your car run as intended but even cleaner by having something that catches oil correctly.

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