how much of a difference does oil catch can design and brand make?

[ANVIL]

In the market for an oil catch can finally and just wondering about them. They range from $35-$250ish from what I've been seeing. What's they key factors that I should consider? Whats the difference with the ones with filters on top?

[feito]

The only thing I can tell you is that the cheap ones are basically useless unless you modify them. I bought a cheap one for this very reason. They are completely hollowed, no baffles at all, just a big chamber and that's it. But they are disassemblable, so you can take them apart and mod them. If you dont want to mess with it make sure you get one that has plenty of baffles and divided chambers inside, regardless of the brand. Look at the designs from different makers.

[jr_ss]

Like stated above, you want a baffled can. I have a custom can and added some of those coarse stainless steel scrubbing pads, this adds more surface area for oil vapor to cling too. Cans under a small amount of vacuum make more power on a dyno and supposedly help seal the rings better. I am not a fan of atmosphere cans because gases are forced or evacuatesd out by excess crank case pressure. SR engines are notorious for having large amounts of pressure because the crank case is not sealed from the head. There is a large channel in the front of the motor which cause a lot of gases to rise to the top of the motor via the timing chain cover.

[Kingtal0n]

3 phases we care about: liquid, solid, gas.
1. Solids. the least likely thing to be in your oil. The closest thing to solids in an engine (under normal operating circumstances) are bits of microscopic debris from the outside world (pollen, spores, etc..) or from normal wear and tear, and this is why engines incorporate an oil filtration system.

2. Gas. Also known as "vapours" or "vapor". Gasses are pushed into the crank case from the combustion chamber past the piston rings, all engines do this to some degree it is called "blow by". Gasses are then sucked out of the crank case by your Positive Crankcase Ventilation (PCV) and into the combustion chamber to be burnt. This is the OEM design for all internal combustion engines of all makes. No length of plumbing or catch can will stop or catch a gas phase molecule, unless you can get it to change phase to liquid or solid before it reaches the combustion chamber. This means "collecting" gas to liquid or gas to solid phase molecules somewhere. Please see letter A

3. Liquid. Engine oil is a great example, but there are also water molecules in the atmosphere which will collect inside an engine, especially while it is off and cold. Liquid, just like solids, should not be allowed into the PCV system. The OEM valvecover on the S14 sr20det incorporates a baffle to prevent this from happening. The S13 sr20det valvecover is not as well baffled, and incorporates a side-route back to the crank case in the event that oil is sucked up by the PCV headed towards to the compressor.


Summary: solids should not enter the pcv system to begin with unless there is a problem. Gasses that enter simply get sucked into the engine to be burnt up. Liquids should not enter the pcv system, but those that do, primarily engine oil, are usually re-routed back to the crankcase if this by OEM design. Notice the S14 has no re-routing for engine oil due to improved baffling, therefore, the optimal PCV design limits or prevents liquid engine oil from entering the PCV system.

A: Now we come to catch cans. What does it do. Why doesn't the factory engine use one. Why should we use one.

First, solid factual detail to get us started. Have you ever looked inside the rubber intake in front of an sr20det turbocharger? Have you ever run your finger inside the convolutions to find "gunk" and "sludge"? Where does that come from, what is it? Is it supposed to be there?

Is it supposed to be there?
Since 1980's all the way to 2000+ the oem Nissan design has never been "improved" to eliminate the sludge buildup in this location, although they have made many other significant improvements, this was not one of them. One may surmise then, the reason it is there to begin with, is because Nissan allows it to be there, and it is on all factory sr20det equipped vehicles.

What is it? Where does it come from?
This part requires a slight organic chemistry background information to detail. The "sludge" is likely not simply engine oil, although it may have started as engine oil, and there may be engine oil included with it. However, for the most part, the "sludge" we are referring to is random combinations of partially oxidized hydrocarbons in various conformations. To be more specific, partially burnt engine oil and gasoline are often mixed together in blow-by gasses, which then make their way through the PCV. Interactions between themselves "hydrophobic interactions" and with compatible surfaces (surfaces that will hold hydrophobic substances) cause them to group together, just like a cell membrane in a biological entity.


So... I need a catch can... right?
The first thing everybody overlooks is the PCV port at the back of the intake manifold on the sr20det. Notice that this port is actively scavenging blow-by gasses from the crank case during vacuum. These gasses are identical to the ones coming out of the other side of the valve cover... the one connected to the turbocharger. So installing any kind of catch can on the turbo side will not prevent "sludge" products from reaching the combustion chamber.


So... Whats the point of a catch can then!!!
There are a few good reasons to use a catch can anyways.
Reason 1: your engine is built to the hilt, and has an enormous piston-wall clearance because of that 500 shot of N2O you run at the track, so you need something to collect the gallons of oil that comes spilling out of the engine every time you make an 8 second pass.

Reason 2: You never clean your intake plumbing, so sludge buildup is a problem as it coats your compressor wheel. In this case, installing ANY volume of plumbing between the valvecover and compressor will cause less of that sludge to reach the compressor. It does NOT have to be a "catch can". Even if you just lengthen the tube by 12" you will significantly slow the progression of sludge as it works it's way towards the turbocharger. The factory rubber tube has convolutions that increase surface area. Just having a compressor wheel present guarantees that oil in some way or the other, even if it is just an insignificant amount, will still work it's way out eventually.


What drawbacks do we consider when using catch cans? Why not just add it for safety?
The problem associated with catch cans and additional plumbing volume is you are also weakening the pressure signal provided by the compressor. In other words, during boost, the only place on the sr20det to get a lower pressure than atmospheric is the compressor inlet. If we move the compressor farther and farther away (by the addition of the volume of a catch can) we are reducing the effectiveness of that low-pressure signal, and thereby reducing the PCV action of the turbo. THIS is my theory as to why the factory never installed a true catch can system on the sr20det, the signal for PCV during boost was already so weak to begin with, why make it worse just so you don't have to clean your intake rubber once every couple of years?

[omgRWDgoodness!]

↑ As informative and well-written as that article is, unfortunately it's above the reading comprehension & literacy level of about 90% of Zilvians.

iz jus da inturrnet who givs a fuk


Also, the factory catch cans seem to do the job just fine. If it ain't broke don't fix it.

[anti tyler]

Originally Posted by omgRWDgoodness!

↑ As informative and well-written as that article is, unfortunately it's above the reading comprehension & literacy level of about 90% of Zilvians.

iz jus da inturrnet who givs a fuk


Also, the factory catch cans seem to do the job just fine. If it ain't broke don't fix it.

I think he covered that. The fact that these cars don't come with factory catch cans...

Theres an awesome write up on taking an eBay rectangle shape catch can and making it into a great working baffled catch can. if I can find it again I'll link it in this post.

[Aki180sx]

Originally Posted by anti tyler

I think he covered that. The fact that these cars don't come with factory catch cans...

Theres an awesome write up on taking an eBay rectangle shape catch can and making it into a great working baffled catch can. if I can find it again I'll link it in this post.

Only cool people have factory catch cans.

[ANVIL]

I have an RB25 and no catch can. While all that info is great im probably still going to get one. How does a baffled one perform better? Just by having more area? And why not the kind with the filter? Seems those are more spendy generally

[jr_ss]

Originally Posted by ANVIL

I have an RB25 and no catch can. While all that info is great im probably still going to get one. How does a baffled one perform better? Just by having more area? And why not the kind with the filter? Seems those are more spendy generally

Baffles create obstacles for the air to bump into as it flows through the can. Without these obstacles, air simply flows through the can with very little interaction with the side walls. The more area inside the can, the better chances of keeping the oily vapor in the can rather than into your turbo or exhaust depending on how youve plumbed the suction lines.

[supersayianjim]

ah,THE MORE YOU KNOW!!!

[seagrasser]

Still struggling with running mine in an optimum way.

Right now I have the two valve covers combing to one, going to one side of the can, with vacuum pulling vapor through.

I am also using vented, just in case the valve covers get pressurized under boost.



What I am missing is the PCV valve on the passenger side valve cover. It goes directly into the intake.

[seagrasser]

Mine is baffled, vented, and has a valve at the bottom. Spent roughly $50 on it.

[ANVIL]

Thanks for the input guys, i think im going to go with this one:

http://rhys-millen-racing.myshopify....-oil-catch-can









seems legit, what do you guys think?

[Matej]

It seems pointless to connect a vented can to the intake, unless I am missing something about its design that prevents the intake just sucking in air directly from the filter. In fact, one should definitely not connect a vented can after the MAF, and even before the MAF I would rather not take chances of the MAF element getting gunk on it, in case blow-by or droplets still make their way through the can.

If you want a vented can, for example if you are running an open turbo without an intake, you only plumb it to the valve cover. For this application, it is not necessary for the can to be baffled, as it only acts as something to catch whatever the motor pukes out from ruining mother Earth.

I would assume that a non-vented can connected between the turbo and MAF (or between the throttle body and MAF on an NA motor) would be the most effective, because it would serve a dual purpose of not only trapping blow-by, but also creating negative pressure in the head directly proportional to the amount of load the motor is under, thus (in theory at least) helping fight undesirable conditions such as head lift.

Personally, I am not going to run a catch can because I know I would never empty it. I will just let my motor suck in its own filth.

[ANVIL]

Originally Posted by Matej

It seems pointless to connect a vented can to the intake, unless I am missing something about its design that prevents the intake just sucking in air directly from the filter. In fact, one should definitely not connect a vented can after the MAF, and even before the MAF I would rather not take chances of the MAF element getting gunk on it, in case blow-by or droplets still make their way through the can.

If you want a vented can, for example if you are running an open turbo without an intake, you only plumb it to the valve cover. For this application, it is not necessary for the can to be baffled, as it only acts as something to catch whatever the motor pukes out from ruining mother Earth.

I would assume that a non-vented can connected between the turbo and MAF (or between the throttle body and MAF on an NA motor) would be the most effective, because it would serve a dual purpose of not only trapping blow-by, but also creating negative pressure in the head directly proportional to the amount of load the motor is under, thus (in theory at least) helping fight undesirable conditions such as head lift.

Personally, I am not going to run a catch can because I know I would never empty it. I will just let my motor suck in its own filth.

but dont you think it wouldnt really suck enough to make a difference because the feed to the line is so small compared to the 3" its sucking after the maf

[S14DB]

Originally Posted by ANVIL

but dont you think it wouldnt really suck enough to make a difference because the feed to the line is so small compared to the 3" its sucking after the maf

I guess you have never had a vacuum leak.

[KAT-PWR]

Pcv and vc connected to catch can, catch can to intake.
Baffled can
Also for what it's worth I barely get more than a drop or two in the can. No preturbo sludge

[WheelWhore]

Going to be running a Peterson on my RB25. -10 Lines.

[ANVIL]

Originally Posted by S14DB

I guess you have never had a vacuum leak.

got me there. but TONS of people run the vented/filtered cans.

anyone else wanna chime in? what factors do you consider when vented vs not? what negative effect could a vented can have

[Kingtal0n]

Originally Posted by ANVIL

got me there. but TONS of people run the vented/filtered cans.

anyone else wanna chime in? what factors do you consider when vented vs not? what negative effect could a vented can have

1. everybody does it so it must be ok

2. Vented anything means no pcv. The term "PCV" infers some sort of vacuum / pressure signal, which is completely obliterated by any sort of venting.
So, You could say, the negative effect of venting is the removal of a functional PCV system.

[TheRealSy90]

I bought a Kazama catch can because it looks cool. Never had a problem not running a catch can at all for the last six years... I'm 99% sure the Kazama can is completely hollow inside lol. (pic for reference) If anybody has ever cut one open i'd like to know, if not i'm going to cut mine apart when it comes in and shove some stainless shit in there or whatever.

[seagrasser]

Here is a pretty informative thread from the DSM guys

http://www.dsmtuners.com/threads/the...system.366890/

[Tom N]

Running a vented catch can back into the intake is pointless and a bad idea. If you don't see why that's a problem please put down the tools and step away from the car.