Oil catch can

RYU said:

Thanks B! See what happens when you spend more time here than at the 'Delete' thread?

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chudson1549 said:

So Vegas you have your throttle body intake capped? You have 3.0 valve covers running the stck PCV location from the front bank to a "T" which one line goes to the vented catch can then the other line goes to the rear bank vent. The lower line off the catch can runs back to the oil pan.

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Vega$ NSX said:

Bwahaha, you know me too well. Les had a long talk with me the last time he was up here. It was kind of like an Off Topic intervention. :biggrin::tongue:

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Vega$ NSX said:

Good question. Actually, like the "how often do you empty your catch can" the answer varies. Depending on multiple conditions, the oil levels range from needing to top it off to don't change at all. Surprisingly, there is very little oil that is burned, especially after my latest tune. I haven't had to add any oil for the last several months.

I will say this, there is definitely a ton more emptying of the catch can required than topping off my oil. Which leads me to believe that what actually gets collected in the catch can isn't much oil and a lot more of something else. Water? I'm not sure. It's why I prefer to play it safe and not return it to the pan.

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Vega$ NSX said:

No, I only have one line going into my catch can. It "T's" off the bank vent to the stock PCV line. There is no lower line and I don't run the oil back into the pan. The anodized blue thing is a cap which I use to empty into a cup. I tend to prefer to "play it safe" over the "convenience" trade off.

I added some pictures back on my other post on catch cans on page 1 that should really clear up the different catch can set ups. :smile:

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stevenlee said:

Thanks for the compliment. It took me roughly 50 hours to design and build it. The fitment was very important to me. I like all of my mods to look and function like they are designed and built by Mother Honda.

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Vega$ NSX said:

Ok in fully discussing this with my engine guru buddies, here is what we were able to come up with.

Background: In a typical engine, there is often a oily vapor that comes from the engine block. This vapor is oil blow by from tolerances such as the piston and cylinder interface. Since a typical combustion process is high in pressure and there isn't a perfect seal between the piston and cylinder wall, some air (with oil vapors and other combustion vapors) will leak around piston seals and into the engine block. All of this oily vapor is routed to a tube, and for emission purposes put back into your intake manifold where it can be reintroduced into the engine cylinders and used/burned off.

N/A and Boosted: In a N/A engine the intake manifold is normally under negative pressure as the pistons down stroke to "vacuum" intake air in the cylinder. The engine block is under positive pressure and will push the oily vapor blow-by into the vacuum created in the intake manifold. HOWEVER, in a boosted engine the intake manifold is under positive pressure (not negative). Also the combustion process is intensified, so this results in two things:

1) More blow-by around the pistons, increasing the amount of oily vapor being pushed into the block.
2) The intake manifold is now under positive pressure. Therefore the intake manifold check valve (PCV) prevents the positive intake manifold pressure coming from the super/turbocharger from pushing air/pressure back into the engine block.

As a result of these two items an oil catch can essentially becomes highly recommended, if not mandatory.

Setups: There are multiple setups for setting up a catch can. The most common is to route the block exhaust and intake manifold to a catch can with a vent. The SOS catch can, stevenlee's, EAC's catch can are all set up this way. Under boost, since the manifold is under positive pressure and the block is under positive pressure, AND the catch can is open to ambient, the flow of air will always go to the direction of the catch can. This will allow the catch can to catch all vapors off of the engine block. While not on boost, the vacuum will suck a tiny bit of air through the catch can while the block pressure will push the vapor exhaust to the catch can. Note, since the engine block vapor is NOT being returned back into the intake manifold, this car no longer technically passes emissions since the oily vapors are now open to the ambient.

My set up is different. My catch can is "Tee'd" off of the line instead of being inline. (See picture)

To keep the PCV or to not keep the PCV? That is the question. This is pretty simple once you understand how the oil catch can works and what kind of set up you have. If you have a catch can that is inline then it really doesn't matter if you have a PCV or not. The PCV is basically there to keep intake manifold air from pushing back on the oily block exhaust. Since the intake manifold air is now routed to an oil catch can and not the block, then it really doesn't matter since it cannot push back on the block anymore. The only reasoning I could possibly think of for not removing the PCV is that under positive boost, it would leak some boosted air out the catch can. But the pressure loss would be so minimal that it really wouldn't matter one way or another.

Now in my catch can setup, I would have to keep my PCV in. Otherwise, the oily block exhaust would flow right past my catch can and into my intake manifold OR the boosted intake manifold would blow past my catch can in the other direction, blowing into the block and prevent the oil blow-by to be relieved. By keeping the check valve in place the positive intake manifold pressure will keep the check valve closed, essentially dead ending that path. Therefore the oily engine exhaust has nowhere to go but into the catch can.

Route catch can oil back to pan?: Some people will say that the oil vapor leaving the exhaust will have products of combustion, water vapor and other contaminates in it and it will all be caught by the catch can. Others will say that being open to the ambient it will expose oil in the catch can to water vapor and the ability to condense water out as it cools in the catch can. All of these statements are somewhat true and if you've ever seen what's in the catch can, it is a pretty nasty frothy mess of watered down oil with god-knows-what else is in it. So does that mean you should absolutely not return this back to the oil pan? Not necessarily. What is caught in the catch can is what the engine would see normally anyway. And in a N/A engine, this is already returned right back into the intake manifold. While it's true there might be some water vapor introduced through the catch can due to condensing, it's not any more amount than the engine would typically see under normal operation. So ultimately, if you don't want to deal with the hassle of having to constantly empty an oil catch can, then the general consensus among my group of people seem to think it is ok. There are a number of installation where this is done with no long term affects that I know of. Although, however, if you don't want to take any chances and any risks of introducing any water and other nasties back into your system, then take the safe route and do not route the oil back into the pan. It's a peace of mind vs. convenience trade-off decision that you'll need to make.

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nsxotic911 said:

What about the following setup in a supercharged scenario.
-Both valve covers vent to a breather kit/drain kit, BUT the top end where the breather cap would be is instead blocked off. In lieu, the bottom drain is ALWAYS left open.
-Supercharger inlet hole is blocked off permanently - no air in or out.

At first glance, this seems like it 'should' work... The opening at the bottom of the can would function as a suction and relieve incoming gasses/oil/gunk/whatever.. no?

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Vega$ NSX said:

Yes, I agree in theory, it "could" work. Basically all the oil catch can needs is an opening/port for air to freely flow in and to let out vapor and pressure. However, there are some fundamental issues/questions that come to mind in regards to your theoretical application.

1) If it is an open port, where does all of the oily vapor mix go? You are going to let it drip down your engine bay and on to the road? Keep in mind, sometimes there be a substantial amount of "gunk" that accumulates. I wouldn't want this on my garage floor or in proximity of my rear tires. Also, if you are leaving that port open, then why even use a catch can at all? You could just route tubing to the manifold and block and just route it down near the ground. But again, do you want oil dripping all over the road? If you put a pan or something underneath to catch it, then you are basically just using a catch can anyway.

2) When not on boost, the engine will naturally pull a vacuum and pull air through the tubing/catch can. While it's not a lot, do you really feel comfortable pulling in completely unfiltered air into the intake manifold. I understand it's not a lot of air, but it's completely unfiltered and I can't imagine this would be a good thing. Every time you are idling or not at boost, it's constantly sucking in unfiltered air into your intake manifold.

I guess I'm just trying to figure out your end game and what you are trying to accomplish. I'm not seeing much benefit to doing what you are suggesting (other than never having to empty a catch can, simplified installation) but I can think of a lot of potential concerns.

Not sure if that answers your question or not, but I hope it helps. :smile:

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nsxotic911 said:

Thanks Vegas! Your expertise is always appreciated. To answer some questions..

My end goal is to
a.) provide an egress point for the oily vapors so it doesn't get sucked into the supercharger. It doesn't have to be 'perfect' or 'most optimal' just better than sucking all the gas and pushing it into the engine by the supercharger is an improvement..
b.) allow my t-top to fit as 'comfortably as possible'
c.) Not have a bunch of gunk/oil vapors in the engine bay, made worse by a targa top.

Constraints: DALI coolant/oil catch can w/ STMPO T-brace bar. Each make it very tight, and impossible together. I don't want to remove the T brace, but am willing to compromise on the other.

SOLUTION? Based on what you're saying, it seems that the route which will achieve all of those goals is a line from the valve cover to underneath the car, and place a filter at the end of it. It might not make very good use of the oil catch can itself.. but I am willing to compromise on that as long as the approach above isn't counter-productive, or adds increased risk of engine or supercharger damage. What do you think?

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Vega$ NSX said:

Sure, no problem. Sorry I've been running around and never got a chance to call. I'm able to pull this off while being bored during calls and conference calls. :tongue:

Ok, I think I see what you are doing. I suppose you could put a line off of the valve cover and put a little metal mesh filter on it. However, you'd still need something for the engine block to blow into with pressure relief so you would still need some catch can of sorts. In which case, it would still make sense to route your valve/manifold line there.

Are you completely stuck on the Dali coolant/catch can? Have you considered just using a separate catch can that you can relocate in a T-Brace bar friendly location. There should be a spot you can put a catch can on the rear firewall under the T-brace (basically where the big white sticker is located on the firewall) that should allow you easy mounting and access to the catch can.

Is it just the mesh filter getting in the way or the entire Dali coolant/catch can combo that won't fit with the T-Brace? If it is just the filter, is there room to just elbow and hose away the filter in a better location?

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nsxotic911 said:

I'm not sure I understand this, " However, you'd still need something for the engine block to blow into with pressure relief so you would still need some catch can of sorts. In which case, it would still make sense to route your valve/manifold line there."

What engine block..? I thought the only egress points were the valve covers...

The Dali tank + STMPO brace is a complete PITA. For anyone thinking about getting the combo, DON'T DO IT. I was, until I gave up, squeezing a plastic hose (within a plastic hose..) over the two entry points until I got frustrated and went to the board.. They were very tight and there was a significant 'bend' to it. Not enough to completely block it, but way too tight overall. I also had to saw off the holes about half of the wholes, just to get that far.

I'd totally be ok with ditching the tank, however, $$ is an issue... Already have $250+ into a tank. It also makes an extra can redundant and takes up more space.

If skipping the tank won't in fact work (I'm not sure I completely understand the issue you are mentioning above) I may just need to get a separate catch can.. I guess.

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FastraxTurbo said:

Maybe I can shed more insight on PCV and catch cans.
During the combustion process, gases escape pass the pistons rings into the crankcase. You can also think of this as blow by. The amount of blow by is generally caused by many factors, such as loose piston to cylinder wall clearances, excessive ring end gaps, low tension rings, scored, rough cylinder walls, and/or uneven walls causing ring bounce.
The higher the cylinder pressure, the greater the amount of gasses that can get past the pistons. These gasses will contaminate and dirty the oil faster.
The PCVs function is to recirculate those gasses back into the cylinders to be reburnt. This process only occurs at high vacuum conditions, which means idle, cruising, and decel. It will not affect power. The benefit to a PCV is keeping the oil cleaner, and creating a vacuum in the crankcase which improves ring sealing.
Some cars incorporate an electric vacuum pump that actuates at WOT to help keep crankcase pressure low.
All the oil that is being pushed out of the valve cover is because of insufficient, or poorly designed baffles. They cannot block/separate all the oil being sprayed around from the valve train, so it gets pushed/sucked through the PCV hose into the intake manifold.
On my car (NA) I used a ARO-Flo pneumatic filter inbetween the valve cover and PCV valve. This trapped any oil from entering the manifold (and settling in the lower plenum.
Some cars may show a milky color of the oil accumulated. This is usually caused by condensation that forms on the inside of the valve covers during warm up. The condensation will eventually evaporate from the oil as long as the engine runs at normal operating temperature for a sufficient amount of time. Short drives and low oil temps will not allow the water and contaminants to burn off. I'd rather not put milky colored oil back into my engine. But if you're not in an area where condensation builds as easily and clean oil fills the catch can, I see no problem draing back into the motor.
If using a PCV valve with a turbo or supercharger, make sure it seals under positive pressure. If pressure is allowed past the the PCV valve, you will pressurize the crankcase. This will push more oil out of the breather, cause higher oil consumption, and possibly blow your crank or cam seals out. It will also cause or create more oil leaks.
If eliminating the PCV, make sure you block the manifold side, or you will have a vacuum leak. Under boost, again you will pressurize the crankcase. The PCV is a controlled vacuum leak.

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StmpoRaceProducts said:

and shame on you for logging in... you know better than that

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