Do I Need A Catch Can?

[KiwiRS4T]

1 hour ago, V28VX37 said:

Came up ok for a $90 setup.

Looks tidy

Surprisingly tight to run the 5/8" hose across the engine, especially with bonnet and fan clearance.
I have no idea how people run 1 or 2 litre catch cans with a stock-ish engine bay arrangement, not much space... 

They don't - they relocate the battery and/or get a custom unit made often incorporating the window washer reservoir

   

 

[V28VX37]

Went for a quick test drive, car runs well but there's something curious going on with the heater hose, there's like this fine white dust on the outer surface. It's kinda like talcum powder, similar to what you often see on the inside of brand new rubber hose. I did flush the inside of the hose with hot water before installing but I'm wondering if the powder used in manufacture to keep the layers separate is coming through the hose skin with (some) pressure and heat?

I'm guessing this won't impact performance but somewhat odd still. I've wiped the hoses clean and will keep an eye on them.

EDIT: Sounds like it's mold release, pretty standard with new rubber hoses, should be ok. 

[Dose Pipe Sutututu]

On 21/01/2017 at 0:13 PM, V28VX37 said:

I have no idea how people run 1 or 2 litre catch cans with a stock-ish engine bay arrangement, not much space...

My charcoal canister just fell out.. and now there's a catch can there lolol

Also, good job on mounting it down there.. nice bracket!

[V28VX37]

On 19/01/2017 at 8:05 AM, Kinkstaah said:

...

You *could* be massively dodgy and just run a hose from where you currently have it into something temporarily to see if it clears your oil up. But it's a strange place for oil to be accumulating in any case given it's not anywhere else in the system. Oil coming out of the compressor cover isn't usually what leads people to think they have a problem with blowby and want to catch it in a can.

I wiped the comp cover 100% clean last night and went for a longer drive today, there's a drop of oil in there again. It doesn't look like the simple catch can has made any difference so I'm with you now Greg, I'm not convinced it's the breather either.

Anyone got suggestions on what could be causing a leak at the comp cover? I've tightened all oil and coolant lines and the turbo core section seems dry as far as I can tell from above and below without pulling stuff out.

2 minutes ago, Dose Pipe Sutututu said:

My charcoal canister just fell out.. and now there's a catch can there lolol

Also, good job on mounting it down there.. nice bracket!

Cheers mate, aluminium flat bar is pretty friendly to work with  I was actually eyeing off that charcoal canister spot, would have been sweet. I'm sure that mine is 100% non-functional after some 150k on car.

[V28VX37]

You may have seen that I took the car to Sandown last month and blew the bottom end: https://www.sau.com.au/forums/topic/468826-blown-neo-bottom-end-next-steps/

Now, judging by the symptoms it's been a long time coming and really just a matter of time.

I was checking the catch can between sessions and there was barely anything until the second last session, after which it had perhaps 10mm oil in. However, after the last session (which eventually led to losing compression on 3 cylinders), I had heaps of crankcase pressure building and pushing oil and smoke out of the breather hose ends, the one running across the rocker covers. It also popped of the PCV hose on the intake cam cover. I pulled the catch can at this point and it was just over half fun.

The question is, whilst it most likely wasn't the root cause, do you think the catch can may have contributed to the demise of this engine?

[Husky33]

Nah mate the catch can would have had nothing to do with it. You obviously had a fair bit of crank pressure going on, how were the rings when you pulled it apart?

[V28VX37]

Nah mate the catch can would have had nothing to do with it. You obviously had a fair bit of crank pressure going on, how were the rings when you pulled it apart?

Cheers mate. Yet to be pulled apart, will keep youse posted.

[Husky33]

On 19/01/2017 at 8:49 AM, Dose Pipe Sutututu said:

A baffled catch can is the best option however if you're a tight skyline owner like myself a basic catch can with steel wool stuffed into it will also do the trick.

If you want, delete the PCV as well, block it plenum side and put a bung on the side of the cam cover. Then just run the breather hose from cam cover to catch can, then catch can to intake.

I wouldn't just block the pcv like that.

I don't mean to insult anyones intelligence, but there is a fair bit of misconception on the pcv valve. When the car is off boost, the intake manifold is under vacuum, which then sucks crank gasses through the pcv. The system needs fresh air though, which comes from the intake pipe. So off boost the air travel looks like this air->afm->intake tube->cam cover->crankcase->pcv->intake manifold.

When you are on boost, the pcv shuts, and the flow actually reverses. So you will get the crankcase gasses going back out the valve covers into the intake tube, to the turbo and into the manifold that way.

Now if you just block the pcv off, when you are off boost you won't be venting the gasses. You would need to add a vent to the valve cover or to the catchcan to vent the gasses off boost. If you don't, a lot of that fuel vapor will just sit around in the crankcase getting absorbed in your oil. The pcv is not that bad, as like I said it only vents to the intake manifold off boost. Yes you will get some oily vapors, but not that bad. And it's pretty efficient way of evacuating the crank vapors. On boost you will get a lot more crank pressure/vapor, which is where a catch can is much more important.

[KiwiRS4T]

11 hours ago, Husky33 said:

I wouldn't just block the pcv like that.

I don't mean to insult anyones intelligence, but there is a fair bit of misconception on the pcv valve. When the car is off boost, the intake manifold is under vacuum, which then sucks crank gasses through the pcv. The system needs fresh air though, which comes from the intake pipe. So off boost the air travel looks like this air->afm->intake tube->cam cover->crankcase->pcv->intake manifold.

When you are on boost, the pcv shuts, and the flow actually reverses. So you will get the crankcase gasses going back out the valve covers into the intake tube, to the turbo and into the manifold that way.

Now if you just block the pcv off, when you are off boost you won't be venting the gasses. You would need to add a vent to the valve cover or to the catchcan to vent the gasses off boost. If you don't, a lot of that fuel vapor will just sit around in the crankcase getting absorbed in your oil. The pcv is not that bad, as like I said it only vents to the intake manifold off boost. Yes you will get some oily vapors, but not that bad. And it's pretty efficient way of evacuating the crank vapors. On boost you will get a lot more crank pressure/vapor, which is where a catch can is much more important.

You are insulting people's intelligence. Johnny was suggesting blocking off the PCV IFF you have a catch can installed.

[Husky33]

1 hour ago, KiwiRS4T said:

You are insulting people's intelligence. Johnny was suggesting blocking off the PCV IFF you have a catch can installed.

My apologies.

However, just fitting a catch can doesn't mean you will vent crank case vapors off boost. Fitting a catch can between the right valve cover and the intake pipe has nothing to do with venting off boost. Will it vent a little bit, yes, but most of the vapor will stay in the crank case.

What I'm getting at is that it makes no sense to delete the pcv and still keep the vent from the cam cover to the intake pipe. Both are for emissions purposes, so why delete one and not the other? If you don't care about emissions, then put breathers on the valve covers and change your oil more regularly. Or even better, fit an evac or vacuum pump if it's a race car.

If you do care about emissions than the way to do it properly is to either fit two catch cans, once between the pcv and intake, and one between the valve cover and intake. Or one catch can that has lines that go to both location, with a couple check valves installed.

[KiwiRS4T]

1 hour ago, Husky33 said:

My apologies.

However, just fitting a catch can doesn't mean you will vent crank case vapors off boost. Fitting a catch can between the right valve cover and the intake pipe has nothing to do with venting off boost. Will it vent a little bit, yes, but most of the vapor will stay in the crank case.

What I'm getting at is that it makes no sense to delete the pcv and still keep the vent from the cam cover to the intake pipe. Both are for emissions purposes, so why delete one and not the other? If you don't care about emissions, then put breathers on the valve covers and change your oil more regularly. Or even better, fit an evac or vacuum pump if it's a race car.

I

The full monty approach taken by some people who regularly track their car involves two breathers from the sump (above oil level of course)  and one combined or two seperate hoses from the cam cover breathers going into a large baffled catch can - with an outlet going to the turbo intake.

It is true that there are a few not so well thought out set ups around...

[V28VX37]

On 21/01/2017 at 12:13 PM, V28VX37 said:

Came up ok for a $90 setup.

Surprisingly tight to run the 5/8" hose across the engine, especially with bonnet and fan clearance.
I have no idea how people run 1 or 2 litre catch cans with a stock-ish engine bay arrangement, not much space... 

Question: Is it possible to install a large 1 to 2L catch can without shifting everything around in the engine bay? I've seen some GT-R bays with a custom box where the battery is but that's obviously a battery relocation job.

One possibility could be the front left guard, at the OEM side mount IC location, but I have no idea how you would run the hoses there?

[GTSBoy]

3 minutes ago, V28VX37 said:

One possibility could be the front left guard, at the OEM side mount IC location, but I have no idea how you would run the hoses there?

Holesaw