Quote: Originally Posted by OBT100 The whole point of a catch can is to CATCH the oil and oil vapour, and STOP it from entering the engine inlet tract.Oil and oil vapour is low octane and induces pinging(detonation) That is why you direct both the rocker cover fittings in to the can with the can having a filter on it, to VENT it to atmosphere, not into the engine. That is why people do away with the PCV system OK!!!!!!!!!!!!!!!! Just read this post I see why your saying its wrong, but the rear rocker cover fitting drains back to the sump, and the reason I have a catch can is to catch oil that gets forced out under boost and would usually get thrown into the inlet manifold then into the engine, im not worried about oil vapour as it is no major drama, its not a race car, and it does the job. It is also illegal, not to mention dangerous to vent vapours into the atmosphere, and if you are going to all the trouble to tap both fittings into a Y piece, why not just have each going to the catch can and have a filter on top of the can to vent it?

your rear rocker cover breather drains back to your sump?? didn't know that was even possible... you got any pics?? from what i've read here, there isn't any oil going into the plenum under boost, so that kinda defeats the purpose of having the can hooked up like that. just going by what i've learnt here, so sorry if i'm wrong. the reason i don't just have both hoses going to the can and a filter on top is because it's a sealed catch can. still considering getting another one with a filter though..

If there is no oil going into the plenum under boost then there is no point in having a catch can at all. Mine is sealed also but you can knock a hole in it and stick a filter on the top. And yeah from factory there is a metal line that drains the rear rocker breather into the sump and I have an AVO intercooler kit designed for a VL so it keeps all the lines etc. as they were from factory. Im not having a go at you, just saying OBT100 reckons my setup is wrong, which it isn't.

by into the plenum, i mean through the PCV valve in the plenum which is closed under boost. the rear breather actually runs to the inlet pipe joining onto the turbo, not the sump. have another look where yours goes. so, under boost, the oil goes through the rear breather hose, into the turbo, through the cooler (as i've found tonight), and then into the engine. so there is a point to having a catch can... your setup (and my current setup) isn't wrong, but its a little pointless. have a read of this. very helpful... http://www.skylinesaustralia.com/for...howtopic=68174 (http://www.skylinesaustralia.com/forums/index.php?showtopic=68174)

Which is the same link i posted on page 2........ It's obviously not an RB30 but the principle is identical.

yeah monsta, that link didn't work for me, so i found it and put up a new link to it. very helpful article. i now have mine hooked up correctly and have cleaned the oil from my cooler and piping for the last time. fun job... :P

there is so much wrong info in this thread its not funny! Quote: Originally Posted by vltrb-0 u dont block the pcv u just leave it there yeah , so that it just sucks air the whole time your foots off the throttle. The engine would run rough as guts like this - if it ran at all, due to the unmetered air entering the engine, which isnt allowing fuel for this air as it hasnt passed through the air flow meter. Quote: Originally Posted by vltrb-0 lol if u plumb it back through the turbo there is no point of having a ctach can that and as soon as that hot oil hits the heat soaked blade your gonna get a smoke show and cause that poor unsuspecting driver to stack his car cause he cant see lol having the system vent back into the inlet isnt a problem, if you do this and you still have oil in your inlet your oil/air seperator obviously isnt working and you wasted every cent you spent on the system. Quote: Originally Posted by Antho Quote: Originally Posted by OBT100 The whole point of a catch can is to CATCH the oil and oil vapour, and STOP it from entering the engine inlet tract.Oil and oil vapour is low octane and induces pinging(detonation) That is why you direct both the rocker cover fittings in to the can with the can having a filter on it, to VENT it to atmosphere, not into the engine. That is why people do away with the PCV system OK!!!!!!!!!!!!!!!! Just read this post I see why your saying its wrong, but the rear rocker cover fitting drains back to the sump, and the reason I have a catch can is to catch oil that gets forced out under boost and would usually get thrown into the inlet manifold then into the engine, im not worried about oil vapour as it is no major drama, its not a race car, and it does the job. It is also illegal, not to mention dangerous to vent vapours into the atmosphere, and if you are going to all the trouble to tap both fittings into a Y piece, why not just have each going to the catch can and have a filter on top of the can to vent it? No the rear rocker cover vent is the PCV systems fresh air vent, it draws air from after the filter into the engine so it can "breathe". PCV systems.The crankcase sees positive and negative pressure, the amount of positive pressure it see's depends on the amount of wear on the engine. more wear=more blowby=more positive pressure. At off throttle times when the PCV is open, it draws all the fumes from the engine into the inlet and burns them, these fumes, depending on how good the standard baffling in the rocker cover is, will cary oil vapour into the inlet via the pcv system. On an RB30ET this means that the fumes are being drawn from the front rocker cover breather, through the PCV and into the inlet to be burned. At the same time, any vacuum in the crankcase caused by this process is offset by fresh filtered air being drawn in from in front of the turbo. Now on throttle, the pcv closes. This means any positive pressure is now going out the rear rocker cover fitting and the oily fumes are being drawn into the intake in front of the turbo, which is where our problem lies. So, with an oil/air seperator:- if you only feed the front fitting into the oil/air seperator,then to the pcv, you are only filtering the crankcase fumes at idle. If you only feed the rear fitting into it then to pcv you would only be filtering the fumes on acceleration - which is what we want. If you feed both hoses into the seperator then to the pcv, thats fine, but you also need to be able to draw air into the system while off throttle so the fresh air vent from in front of the turbo needs to be plumbed into the seperator too. In a system like this the can should be baffled and packed with a filtering material, like stainless steel wool. the fresh air feed and the line to the pcv should be well away from th elines coming in from your rocker cover. For a catch can:- run both hoses to the can with your filter on top. plug up the pcv valve and the fresh air vent and youre off. to have a catch can with a filter isnt wrong, its just illegal. If you like getting hassled by the cops, epa etc, go for it. to have an oil/air seperator hooked up so it breathes back into your pcv valve isnt wrong either, its just the legal way of doing it. If your oil/air seperator is working properly you wont have the oil going into your inlet as it wil be "cleaned" air going in there. Check that SAU thread out, its correct in its info, with a couple of pics/diagrams to help you work it out. Cheers Scott.

Quote: Originally Posted by vltrb-0 lol i dont even run a filter the hose i got jsut sits in the engine bay over the plenum no oil anywhere So when the crankcase is in vacuum your system is drawing all the grit, dust water etc in through the open hose with no filter on it into your engine, i dont think that will do your bearings etc much good mate.

Can someone actualy SHOW where the piping goes? Is the setup in the 2nd picture correct? Or is it is supposed to connect with a 3rd pipe? Thanks Bare without what i think is right What i think is right but i need confirmation Some original photos have not been recovered yet.

i have a new one now, set up the same as the one (pic earlier in the thread) but with a filter on the top for breathing.

Hey guys why is it wen i take off the rear breather pipe it runs like a dog, wen i block it with my finger for a lil while the car runs normally again... Not to mention there is a heap of suction wen i unblock it... My car is partly converted and has the turbo injectors put in, the turbo fuel reg and 910 fuel pump... Jim

ok but that doesnt answer my question! Is the way i have the lines running from the enginge to the catch can correct?

if you've got a breather on the can, just block the pcv valve in the plenum and run both rocker cover hoses to the can.

any1 know the problem with my VL

Quote: Originally Posted by DJ Mitzi any1 know the problem with my VL Dude there's nothing wrong with your VL, they will all do that. It's because when you unblock the hose, you have unmetered air going into your crankcase, then into your plenum via your pcv valve, so you're basically creating a vacuum leak.

oh ok. now i have the front hose goin to the PCV valve normally and the rear one is not connected as the cooler piping doesnt hav a hole for this do i just block it off or do i have to get a catch can?

on a standard vlt the rear one goes to the metal intake pipe just before the turbo..

Ive got the two hoses from my rocker cover going into my catch can. They are joined by a t piece, just before. The catch can has a filter on top. There is a plug at the bottom to let me plumb it back into the engine if i want but i dont. All i have to do is empty it once a month.

this is confusing me heaps too .. im guessing the way to do it is: 2 breathers on the rocker cover to the catch can (with a breather) inlets, and the hole in the plenum is blocked up? ppl are probably gettin angry by now, but is this cooool?? sorry !!

yes, that will work fine darkjedi