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Discussion Starter · #1 ·
So I replaced the PCV valve with a new one, I understand some of the high RPM smoking could be the seals or rings. Car has high mileage. I want to invest in a catch can set up. I have seen different options and I would like feedback on this set up.

2 port in - 1 port out catch can
one line in from breather box (no PCV)
one line in from valve cover
one line out to intake manifold vac source

Any input on this set up? The catch can is sealed, so no vac leaks.

Thoughts?

Thanks!
 

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93 Civic HB SI
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Are you going to invest in an engine rebuild at some point as well?

If not, you might want to also route the catch can to drain oil back into the crankcase.

If you have high blowby, that catch can might fill up quicker than you might like. If it gets full of oil AND it's connected directly to the intake manifold, the chance is present for the engine to suck up a brief but large quantity of oil through the line leading to the intake.

Depending on how much blowby you have, if the catch can is full the crankcase pressure could force a bunch of oil into the intake, potentially causing a hydrolock situation. The oil will take the path of least resistance, and if it has a shot to escape to the intake, it will.

The whole point of a catch can though is to prevent oil vapor from being drawn into the engine in the first place, which is why they usually vent to atmosphere. If the stock oil separator/pcv valve is being overwhelmed by oil vapor through blowby, adding basically a "remote" oil separator might not fix anything at all. It will still draw in and burn a bunch of oil vapor even with another catch can added.

If exhaust smoke is what you are trying to cure, you can see whether or not it is blow by by disconnecting the PCV hose from the intake and capping the intake port with a rubber hose cap. Let the PCV hose vent to atmosphere and go for a drive. If the oil burning is still there or just as bad, adding a catch can won't fix the oil burning problem.
 

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Discussion Starter · #3 ·
Are you going to invest in an engine rebuild at some point as well?

If not, you might want to also route the catch can to drain oil back into the crankcase.

If you have high blowby, that catch can might fill up quicker than you might like. If it gets full of oil AND it's connected directly to the intake manifold, the chance is present for the engine to suck up a brief but large quantity of oil through the line leading to the intake.

Depending on how much blowby you have, if the catch can is full the crankcase pressure could force a bunch of oil into the intake, potentially causing a hydrolock situation. The oil will take the path of least resistance, and if it has a shot to escape to the intake, it will.

The whole point of a catch can though is to prevent oil vapor from being drawn into the engine in the first place, which is why they usually vent to atmosphere. If the stock oil separator/pcv valve is being overwhelmed by oil vapor through blowby, adding basically a "remote" oil separator might not fix anything at all. It will still draw in and burn a bunch of oil vapor even with another catch can added.

If exhaust smoke is what you are trying to cure, you can see whether or not it is blow by by disconnecting the PCV hose from the intake and capping the intake port with a rubber hose cap. Let the PCV hose vent to atmosphere and go for a drive. If the oil burning is still there or just as bad, adding a catch can won't fix the oil burning problem.
Makes solid sense. That was a concern. If it does have alot of accumulation and I am not on it, and its ingested into the intake - I risk damage that way. Good idea by disconnecting the PCV. Whats your recommendation on how to run the catch can set up if the problem is alleviated?

Thanks for your time!
 

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If the problem is alleviated by isolating the PCV system from the intake, and you have no intention of adding cylinder pressures via turbo or supercharger, you will have to do at least 2 mods to the valve cover to add appropriate air flow to get the breather/catch can setup successful.

If it does turn out to be blowby overwhelming the PCV oil separator system causing your oil burning, you will need to install bigger orifices for crankcase vapors to travel through. This will require you to have at least one fitting welded to the valve cover to ensure adequate flow, for reasons stated below.

Remove the oil separator/baffle plate from the inside of the valve cover. Drill the aluminum studs out, and remove the metal plate.

Use a tap set to cut threads into the stock valve cover breather port, and thread a block off plug into the end of it to block it off entirely.

Once the plate has been removed and the stock fitting plugged, you will need to have a fitting welded to the valve cover in an appropriate way to avoid contacting the valvetrain components.

This next bit is easiest from under the car or intake removed. Remove the stock oil/air separator from the back of the block. You will be left with a hole in the block that you need to fill with this guy:

https://www.ebay.com/itm/Honda-Acur...ting-to-10AN-Honda-D-Series-D16-/281883574030

This fitting allows a hose to be run from the crankcase to a catch can, where air can still move freely and oil can be allowed to "drain back" from the catch can.

You need to buy an appropriate catch can and fittings to run the setup. After adding the larger breather port where the stock black box oil separator used to be, it is critical an equal or larger size of fitting is added to the valve cover.

If you do NOT increase the size of the orifice in the valve cover, the path of least resistance for the air will become the larger added crankcase fitting. Without the valve cover fitting mod, your oil will be trying to drain back into the crankcase through the larger hose. Since it is the path of least resistance out of the crankcase, you will have higher crankcase gas volumes moving through this hose, potentially pushing the oil back up into the catch can. You want to allow for air and oil to move somewhat freely through this large hose, with air vent duties being somewhat equally shared between the valve cover port(s) and the crankcase port.

The rest is up to you. Once you have these fittings installed, purchase the appropriate fittings, hoses and catch can to achieve a design like I drew up in the attached picture. This will allow the crankcase to breathe freely and for any oil that accumulates in the catch can to have a path to drain back to the crankcase.
 

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I don't want to give too much away through pictures, as I am in the process of trying to get my build thread finished but here are some pictures showing what I did to create a somewhat maintenance free externally vented breather setup on my D16Y8. These pictures were taken during a lot of the "mock up" time, but it illustrates what I did:


I relocated the battery, so I had room for a catch can of this size. I had to build a tray and hold down assembly to support it:








The VC fittings after welding, using boiling hot water to test for any pinholes:






This is the fitting that replaces the "black box" oil/air separator:




Hose routing under the boost piping:



 

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Meat Popsicle
91 CRX Si
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What engine setup are you running? Is this the carbeurated SOHC ZC D15 that you mentioned in your other thread?

If it’s a mostly NA setup, there’s not much of a reason to run an aftermarket catch can.

If you’re running some sort of highly tuned NA or a forced induction setup, there are benefits to running a vented catch can. Otherwise, there’s really very little to be gained.
 

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Discussion Starter · #7 ·
What engine setup are you running? Is this the carbeurated SOHC ZC D15 that you mentioned in your other thread?

If it’s a mostly NA setup, there’s not much of a reason to run an aftermarket catch can.

If you’re running some sort of highly tuned NA or a forced induction setup, there are benefits to running a vented catch can. Otherwise, there’s really very little to be gained.

Ah, no sir. That was a project car I sold before I go to that point. This is a stock build D16Z6 in my 93 Si. The catch can would be to reduce the smoking on acceleration if its a blowby issue.
 

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Discussion Starter · #8 ·
If the problem is alleviated by isolating the PCV system from the intake, and you have no intention of adding cylinder pressures via turbo or supercharger, you will have to do at least 2 mods to the valve cover to add appropriate air flow to get the breather/catch can setup successful.

If it does turn out to be blowby overwhelming the PCV oil separator system causing your oil burning, you will need to install bigger orifices for crankcase vapors to travel through. This will require you to have at least one fitting welded to the valve cover to ensure adequate flow, for reasons stated below.

Remove the oil separator/baffle plate from the inside of the valve cover. Drill the aluminum studs out, and remove the metal plate.

Use a tap set to cut threads into the stock valve cover breather port, and thread a block off plug into the end of it to block it off entirely.

Once the plate has been removed and the stock fitting plugged, you will need to have a fitting welded to the valve cover in an appropriate way to avoid contacting the valvetrain components.

This next bit is easiest from under the car or intake removed. Remove the stock oil/air separator from the back of the block. You will be left with a hole in the block that you need to fill with this guy:

https://www.ebay.com/itm/Honda-Acur...ting-to-10AN-Honda-D-Series-D16-/281883574030

This fitting allows a hose to be run from the crankcase to a catch can, where air can still move freely and oil can be allowed to "drain back" from the catch can.

You need to buy an appropriate catch can and fittings to run the setup. After adding the larger breather port where the stock black box oil separator used to be, it is critical an equal or larger size of fitting is added to the valve cover.

If you do NOT increase the size of the orifice in the valve cover, the path of least resistance for the air will become the larger added crankcase fitting. Without the valve cover fitting mod, your oil will be trying to drain back into the crankcase through the larger hose. Since it is the path of least resistance out of the crankcase, you will have higher crankcase gas volumes moving through this hose, potentially pushing the oil back up into the catch can. You want to allow for air and oil to move somewhat freely through this large hose, with air vent duties being somewhat equally shared between the valve cover port(s) and the crankcase port.

The rest is up to you. Once you have these fittings installed, purchase the appropriate fittings, hoses and catch can to achieve a design like I drew up in the attached picture. This will allow the crankcase to breathe freely and for any oil that accumulates in the catch can to have a path to drain back to the crankcase.

A personal thanks for taking time out of your day to write that up. Very helpful. Your follow up post is even more so. If i go that route, I see the benefits. Other than a possible issue with the can filling up quickly, what detriment would be if I did as I originally posted but keep the PCV valve just run the hose from the pcv to one of the inlets to the can? Not vented, still sealed. I am thinking out loud. Wondering if I can make what I have work before I have to go through a whole redesign of my plans. Otherwise back to the drawing board as you have guided. Thanks!
 

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Meat Popsicle
91 CRX Si
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Ah, no sir. That was a project car I sold before I go to that point. This is a stock build D16Z6 in my 93 Si. The catch can would be to reduce the smoking on acceleration if its a blowby issue.
Hmm. I’m not so sure about that but perhaps.

Blowby means that the rings or the valve guides are leaking combustion gasses from the cylinders into the crankcase. Some leakage (a few percent) is normal. Leakage of those kinds of gasses doesn’t cause smoking if they’re recycled into the intake charge via the PCV system.

In an engine that’s functioning correctly, the purpose of a catch can is to catch some of the unburnt hydrocarbons and help prevent carbon buildup. You may catch some oil vapors in the catch can from the churning of the oil in the crank case but the quantity should be relatively low.

Remember, the black box on the back of the engine (where the PCV valve is installed) is basically an OEM catch can that drains back into the crank case.

Smoking comes from burning oil. So if it’s smoking, there’s probably oil making its way into the combustion chamber.

I would think the best way to reduce smoking would be to find out why oil is leaking into the cylinders.


For reference, I have between 1-3% cylinder leakage on my supercharged D16A6. I run a vented catch can that’s plumbed to the black box and the OEM port on the cylinder head. Although I can see vapors coming out of the catch can, I havent been able to drain any quantity of oil from it when I’ve tried.
 

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Other than a possible issue with the can filling up quickly, what detriment would be if I did as I originally posted but keep the PCV valve just run the hose from the pcv to one of the inlets to the can? Not vented, still sealed.
It won't really be detrimental, but it may be pointless to do so. Perform the test I suggested of venting the valve cover and the black box hoses to atmosphere first, and determining if the oil burning situation is still present. If so, the original complaint of oil burning will have nothing to do with the PCV system. Other sources of oil consumption are present (valve guides/seals, worn rings/cylinders, etc.)

If removing those hoses solves the oil burning problem, it still won't be worth it to install an additional closed loop catch can setup on the stock engine for anything other than looks.

(closed loop meaning still connected to the engine air intake system)

Like I said before and what Paterico also said, the PCV system was not designed to handle excessive amounts of oil or oil vapor.

PCV system uses the baffling in the black box oil separator and the valve cover to help allow oil/crankcase vapors to have a chance to drag against and collect on a solid surface to allow oil to adhere, accumulate and drain back into the engine.

In stock engine form, if there is a volume of oil moving through the PCV system in vapor form that exceeds what the black box and the valve cover baffling can handle, resulting in oil being inducted into the cylinder and burned, it's a pretty good indicator that 1) the black box is full of crud and coking deposits and needs to be replaced or 2) it's probably time for an engine rebuild.

Any amount of oil vapor that can make it past that system will likely also not be caught by an aftermarket closed loop externally mounted catch can. It will most likely begin to accumulate liquid oil over time, yet the crankcase vapors will still likely contain the same amount of oil vapor that caused your engine to show signs of oil burning in the first place.

Just an FYI, if you chose to go to an open-to-atmosphere catch can setup with heavy blow by in a daily driver, the smell of oil and crankcase gases under your hood making their way into your interior will really suck after a while. Ask me how I know this :)

The goal of an open-to-air catch can setup on a non-OEM forced induction engine is to allow more crankcase vapors to move out of the crankcase freely, lowering the overall crankcase pressure AND preventing any minute oil traces from making it into the cylinder, which can cause hot carbon deposits leading to sources of pre-ignition within the cylinder.
 

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Discussion Starter · #11 ·
It won't really be detrimental, but it may be pointless to do so. Perform the test I suggested of venting the valve cover and the black box hoses to atmosphere first, and determining if the oil burning situation is still present. If so, the original complaint of oil burning will have nothing to do with the PCV system. Other sources of oil consumption are present (valve guides/seals, worn rings/cylinders, etc.)


I did so. Only removed the PCV hose, not the valve cover hose. Either way the issue was still present

In stock engine form, if there is a volume of oil moving through the PCV system in vapor form that exceeds what the black box and the valve cover baffling can handle, resulting in oil being inducted into the cylinder and burned, it's a pretty good indicator that 1) the black box is full of crud and coking deposits and needs to be replaced or 2) it's probably time for an engine rebuild.

Leaning towards the later. When I said high mileage, the shell has 300K and I have no clue about the engine. It was stock, so I assume its the original unit. Though the valve cover was crudded up when it was off to do the timing belt service. I cleaned up best I could - but the black box thing intrigues me. Though I may be grasping at straws for a resolution which more than likely isnt a cheap and easy one.

Any amount of oil vapor that can make it past that system will likely also not be caught by an aftermarket closed loop externally mounted catch can. It will most likely begin to accumulate liquid oil over time, yet the crankcase vapors will still likely contain the same amount of oil vapor that caused your engine to show signs of oil burning in the first place.

Just an FYI, if you chose to go to an open-to-atmosphere catch can setup with heavy blow by in a daily driver, the smell of oil and crankcase gases under your hood making their way into your interior will really suck after a while. Ask me how I know this :)

Lol.

Thanks again for your time. Looks like I got my answer. Thanks again for everyones time!
 

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Meat Popsicle
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Just an FYI, if you chose to go to an open-to-atmosphere catch can setup with heavy blow by in a daily driver, the smell of oil and crankcase gases under your hood making their way into your interior will really suck after a while. Ask me how I know this :)
Agree. This happened to me while it was cold outside and I had the windows up and the heater on pretty high. I actually started to get dizzy at one point.
 

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Is there a solvent that will clean out the OEM catch can ?
I have degreased, petrol, carby cleaner, brake cleaner till the cows came home and went back out, still I have some surface gunk inside the catch can that cannot be reached .

Thanks
 

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BATSLOMAN GIVES NO FUCKS.
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atf?
 

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Is there a solvent that will clean out the OEM catch can ?
I have degreased, petrol, carby cleaner, brake cleaner till the cows came home and went back out, still I have some surface gunk inside the catch can that cannot be reached .

Thanks
Remove it and use a parts washer with heated solution. It may not come all the way clean, unless it is media blasted and repainted.
 
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