Oil Catch Can Plumbing

[abu]

Hey

I have been reading about how to hook up 100% plumb back oil catch cans to RB motors, RB20 to be specific

The catch can I will be using has 2 outlets and and with the diagram below, which I found while searching through the forums, isn't very clear to me

The hose on the left of the picture, from the intake manifold to the side of the rocker is a slightly different design on the RB20 as it goes to the top of the rocker cover and also joins onto that middle hose which runs in between the two rocker covers

With only two outlets how do I connect the catch can as shown below?

I have searched and read most of the information available, I just want a picture basically that shows 100% plumb back setup on an RB20 so I know I am hooking it up correctly and how it should look

Thanks

[W0rp3D]

if you read the thread you got that pic from it explains the difference from from rb25 (pictured) and rb20.

[abu]

You didn't read my question

I am not overly concerned about the difference between RB20 and RB25, overall they are practically the same. I just want to know how to hook up the hoses correctly

My catch can has 2 outlets and the picture above shows 3 hoses running to 1 side of the catch can, and 1 hose to the other

Picture also shows 2 of the hoses to the left side of the catch can flowing pressure to the can and the other hose from the can back into the intake

I don't understand how to connect the hoses to my catch can..

[femno]

Ha. No catch cans have 4 inlets/outlets.

And since when were you meant to have manifold vacuum direct to the catch can? Are you really supposed to? Wouldnt it draw through the turbo intake and create a leak?

If it was me i would just put it in between the hose on the right (turbo side) that way the oily vapour wouldnt go through your turbo and cooler, which is what its meant to do....

[BHDave]

Who did that diagram? They need to lay off the dooby.....

Ignore the lines on the left hand side. The pcv only opens under vacuum anyway and in all honesty a healthy engine isn't creating a hell of a lot of oil fumes when it's driving around in vacuum. If you did want to remove it then you'd just block those rather than run hoses.

The lines shown on the right side are correct. All you need to do is pick up the breather pipe where it comes off the passenger side cam cover and run it to the can, then run from the can back into the intake pipe.

[Beer Baron]

probably best to just follow the instructions that come with the can (assuming you got a GTST/RB20 specific one). I've always just bought the model specific cans purely for the right brackets, and bungs and hoses etc. but basically you want an outlet from the covers going to your can and then an outlet from the can going to your intake (between MAF and turbo). or bung up that pipe and just vent the can atmo (not the best though).

[abu]

Ha. No catch cans have 4 inlets/outlets.

And since when were you meant to have manifold vacuum direct to the catch can? Are you really supposed to? Wouldnt it draw through the turbo intake and create a leak?

If it was me i would just put it in between the hose on the right (turbo side) that way the oily vapour wouldnt go through your turbo and cooler, which is what its meant to do....

mm will have to check when it arrives, from the pictures I saw it only had the two outlets at the top

Its just a cheap shit catch can but will do what its supposed too

I have no idea how it all works really, pretty vague with the details. I have read so much on it and it has just confused me more probably due to the fact people just post useless shit which doesn't make any sense

Who did that diagram? They need to lay off the dooby.....

Ignore the lines on the left hand side. The pcv only opens under vacuum anyway and in all honesty a healthy engine isn't creating a hell of a lot of oil fumes when it's driving around in vacuum. If you did want to remove it then you'd just block those rather than run hoses.

The lines shown on the right side are correct. All you need to do is pick up the breather pipe where it comes off the passenger side cam cover and run it to the can, then run from the can back into the intake pipe.

Sydneykid did the digram in an older thread

Yep thats what I was thinking as I have been looking through a lot of pictures and noticed that most are setup that way and others slightly different

Will do it that way

probably best to just follow the instructions that come with the can (assuming you got a GTST/RB20 specific one). I've always just bought the model specific cans purely for the right brackets, and bungs and hoses etc. but basically you want an outlet from the covers going to your can and then an outlet from the can going to your intake (between MAF and turbo). or bung up that pipe and just vent the can atmo (not the best though).

Unfortunately its not vehicle specific so won't have any luck there

Yep would rather have it 100% plumbed back

Thanks for the info people, anyone want to draw me a pretty little picture with the correct plumbing setup please?

[Sydneykid]

Who did that diagram?

That would be me.

Ignore the lines on the left hand side. The pcv only opens under vacuum anyway and in all honesty a healthy engine isn't creating a hell of a lot of oil fumes when it's driving around in vacuum. If you did want to remove it then you'd just block those rather than run hoses.

Who says the engine is 100% heathly? The idea of a catch can is for it to work no matter what condition the engine is in. If the engine is 100% healthy, then it doesn't need a catch can because there is no blow by of any significance.

When any engine is cold they all breath, and you don't want that in your inlet, all through the pipework and the intercooler. Much better to run it straight into the combustion process via the inlet manifold. Hence the need for the hoses that facilitate that direction of flow.

The lines shown on the right side are correct. All you need to do is pick up the breather pipe where it comes off the passenger side cam cover and run it to the can, then run from the can back into the intake pipe.

All the hoses are in fact correct. For the above reasons, plus running one hose from the cam covers to the catch can is generaly not enough and you get too much airspeed through the one hose. So it carries oil along with it, which is not a good idea. All you want the catch can to do is filter oily air, not catch hot oil pumped out along too small a hose.

So to answer the question the thread starter asked................you bought the wrong catch can. Since you already have it, you can still use it. Just join up the hoses with 2 "Y" pieces as follows;

1. As close to the catch can as possible, join the 2 hoses from the cam covers.

2. As close to the catch can as possible, join the hose to the inlet pipe and the hose to the inlet manifold.

Don't forget to put the PCV valve somewhere in the hose to the inlet manifold. If you don't you will get boost leaking out of the inlet manifold into the catch can and the rest of the circuit. Very messy.

Cheers

Gary

[Roy]

It is an RB20, my catch can was a waste of money. On the street i plumb it back to the turbo inlet, on the track to a bottle with sock sealing it. It has never breated any oil, was an interesting experiment though, think i need more boost

I removed the PCV all together

[Sydneykid]

It is an RB20, my catch can was a waste of money. On the street i plumb it back to the turbo inlet, on the track to a bottle with sock sealing it. It has never breated any oil, was an interesting experiment though, think i need more boost

I removed the PCV all together

Which RB20 was that?

Cheers

Gary

[Roy]

I never had a catch can on my original RB20. Though i did remove the cooler pipes and IC on two occassions to see how much grime/oil film had built up on them. So including the original IC install, the subsequent removals were a waste of time as they were always clean .

The current RB20, which was a replacement from a slipped timing belt after a cam gear install has always had a catch can, so thats 4 years. I think it has more to do with the location of the RB20 breather hoses in the rocker covers then anything else. This motor has never done below 14psi and 215rwkws, has spent a lot of time at 18-19psi and 230-260rwkws odd. Has done something like 25,000-30,000kms as well.

[BHDave]

That would be me.

Who says the engine is 100% heathly? The idea of a catch can is for it to work no matter what condition the engine is in. If the engine is 100% healthy, then it doesn't need a catch can because there is no blow by of any significance.

When any engine is cold they all breath, and you don't want that in your inlet, all through the pipework and the intercooler. Much better to run it straight into the combustion process via the inlet manifold. Hence the need for the hoses that facilitate that direction of flow.

All the hoses are in fact correct. For the above reasons, plus running one hose from the cam covers to the catch can is generaly not enough and you get too much airspeed through the one hose. So it carries oil along with it, which is not a good idea. All you want the catch can to do is filter oily air, not catch hot oil pumped out along too small a hose.

So to answer the question the thread starter asked................you bought the wrong catch can. Since you already have it, you can still use it. Just join up the hoses with 2 "Y" pieces as follows;

1. As close to the catch can as possible, join the 2 hoses from the cam covers.

2. As close to the catch can as possible, join the hose to the inlet pipe and the hose to the inlet manifold.

Don't forget to put the PCV valve somewhere in the hose to the inlet manifold. If you don't you will get boost leaking out of the inlet manifold into the catch can and the rest of the circuit. Very messy.

Cheers

Gary

I'll bite,

3 serious concerns with your response

1) I said healthy, not 100% healthy. My stock bottom end track only rb25det is far from 100% healthy (as i am sure roy's rb20det is) yet it doesn't even stain the catch can.

2) the pcv and piping will suck any oil vapour straight into the inlet manifold when the engine is cold, why would you want the added complication of running it through the catch can when potentially it is half full of oil, with the associated additional vapour? The pcv is doing exactly what it is supposed to do and exactly what you are recommending, why mess with it? If we were talking a dedicated track car with no emissions concerns then i'd block it, as i suggested earlier, and additionally vent the can with no return to the intake. Perfect solution for a track hack. Immediate defect on a street car.

3) Surely the job of the catch can is to catch oil? I would suggest if a 3/4 inch hose is insufficient for crank case breathing then there is a more serious issue with your bottom end. How much is your engine breathing if you are considering air speed out of the breathers? Again, as we are talking about retaining a pcv valve then we are talking street car, or at least a registered car, so i would suggest that spewing hot oil out of the breathers would be considered an engine issue when 99% of street registered r32gtsts will never achieve the cornering loads necessary to do it on a healthy engine.

I won't make an issue of the picture making no mention of retaining a pcv valve as i will assume that the original block of text that went with it included that point.

[Kwyjibo]

Hi SydneyKid,

Sorry this is offtopic but could you please have a look at the r32 gtst suspension group buy thread. I really need an answer or at least an estimate on when my stuff will arrive and your PM's are full and have been for awhile. Its been well over 10 days now and I haven't even received a consignment number.

[Sydneykid]

Hi SydneyKid,

Sorry this is offtopic but could you please have a look at the r32 gtst suspension group buy thread. I really need an answer or at least an estimate on when my stuff will arrive and your PM's are full and have been for awhile. Its been well over 10 days now and I haven't even received a consignment number.

My PM inbox had penty of space 4 times over the weekend and it filled up 4 times. It hasn't been full for 1 whole day let alone 10 days, you just haven't been lucky enough to get in before the other 40+ guys each day. Every PM gets answered in the order in which they are received, as they always have.

Cheers

Gary

[Sydneykid]

I'll bite,

3 serious concerns with your response

1) I said healthy, not 100% healthy. My stock bottom end track only rb25det is far from 100% healthy (as i am sure roy's rb20det is) yet it doesn't even stain the catch can.

2) the pcv and piping will suck any oil vapour straight into the inlet manifold when the engine is cold, why would you want the added complication of running it through the catch can when potentially it is half full of oil, with the associated additional vapour? The pcv is doing exactly what it is supposed to do and exactly what you are recommending, why mess with it? If we were talking a dedicated track car with no emissions concerns then i'd block it, as i suggested earlier, and additionally vent the can with no return to the intake. Perfect solution for a track hack. Immediate defect on a street car.

3) Surely the job of the catch can is to catch oil? I would suggest if a 3/4 inch hose is insufficient for crank case breathing then there is a more serious issue with your bottom end. How much is your engine breathing if you are considering air speed out of the breathers? Again, as we are talking about retaining a pcv valve then we are talking street car, or at least a registered car, so i would suggest that spewing hot oil out of the breathers would be considered an engine issue when 99% of street registered r32gtsts will never achieve the cornering loads necessary to do it on a healthy engine.

I won't make an issue of the picture making no mention of retaining a pcv valve as i will assume that the original block of text that went with it included that point.

Let me try and convince you;

1. Maybe you're just lucky and of course Roy has an RB20 . I don't know the condition of the poster's engine, so I always assume the worst. In this case I have to assume that he wouldn't have bought a catch can if he didn't think the engine needed one. And/or he was intending doing some track work that necessitated a catch can.

2. Scavenging the catch can directly into the combustion process under vacuum (no boost) is never ever a bad thing. Even if you only save the inlet tract from 1 drop of oil being sprayed through it, once per day. I am not saying it is necessary, that it absolutely has to be done. What I am saying is it's not a bad idea, has no downsides, so why not do it and take advantage of the upsides.

3. The job of a catch can is to firstly separate the oil from the engine's oily air discharge. Then allow the air to escape (to atmosphere and/or into the combustion process) and trap the oil. One of the things that works well in that process is to take the velocity out of the airflow. That's why I always suggest 2 hoses. Once again I am not saying it is 100% necessary, just that it's not a bad idea, has no downsides, so why not do it and take advantage of the upsides. The problem with most off the shelf catch cans is that they are too small, they aren't large enough to take the velocity out of the airflow. Runing 2 hoses effectively increases the size of the catch can.

I have had 9 x RB's since 1999 and every one of them breathed, some more than others of course. I have used probably 20 x GTR standard intercoolers and every one of them had a volume of oil film inside preventing them from working efficiently. So I rely on my own personal experiences, that's why I posted up the various options for catch can plumbing.

Cheers

Gary

[Roy]

1) I said healthy, not 100% healthy. My stock bottom end track only rb25det is far from 100% healthy (as i am sure roy's rb20det is) yet it doesn't even stain the catch can.

LOL, shoosh. Ignorance is bliss. If the rings/pistons dont flood the catch can then the engine is 100% ok. Dont mind the knock it has on deceleration or the knock value it gets when starting If it doesnt breathe under boost then she is good for next years Bathurst 12hr.

[madevo3]

i have got a catch can as well and it has only got two oulets as well and mine is a big brand catch can as well

Edited June 11, 2008 by madevo3

[Kwyjibo]

My PM inbox had penty of space 4 times over the weekend and it filled up 4 times. It hasn't been full for 1 whole day let alone 10 days, you just haven't been lucky enough to get in before the other 40+ guys each day. Every PM gets answered in the order in which they are received, as they always have.

Cheers

Gary

Sorry to reply to this offtopic again. Looking at my sent items I have had a PM manage to get through to you on the 3rd, the 5th and the 10th of June but still no reply. I know your busy and I don't want to sound pushy but I'd just like to know when they will arrive or grab a consignment numb er so I can organise someone to be home.

[Kwyjibo]

Sorry to reply to this offtopic again. Looking at my sent items I have had a PM manage to get through to you on the 3rd, the 5th and the 10th of June but still no reply. I know your busy and I don't want to sound pushy but I'd just like to know when they will arrive or grab a consignment numb er so I can organise someone to be home.

Sorted.

[DaveB]

Hey all just wondering, if I make a connection on the plenum side of the PCV valve won't I get boost pressure? I thought one of the functions of the PCV valve (in a boosted engine, at least) was to prevent boost pressure from entering the crankcase, yet to allow the crankcase to vent to the inlet under vacuum (thus, a one-way check valve... just more critical in boosted applications?)

Just wondering 'cause I don't want my catch can to go BOOM!