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Why you NEED a catch-can

183K views 653 replies 149 participants last post by  Red Raspberry 
#1 · (Edited)
There does seem to be a lot of confusion on pretty much any forum in regards to catch cans and what they do.

First I'll start off with what a catch can is;
-A container that catches fumes and vapors from the valve assembly or crank case prior to being introduced back into the intake system for emmissions purposes.

Now this is a bit different than a breather or breather style catch can;
Breather - a filter that replaces a valve case or crank case tube that usually recirculates the fumes to the intake for emmissions purposes, with the filter, fumes and vapors are now vented to atmosphere.

Breather style catch can - A container that catches fumes and vapors from the valve assembly or crank case and vents through a filter to atmosphere rather than back into the intake system for emmissions purposes.

Now that we know what our options are, why should we and what is our best option?

Why should we install a catch can?
The reason to install a catch can is simple, to catch those fumes and vapors to prevent them from re-entering the intake system. These fumes and vapors could be anything from oil, to fuel, to condensation (yes.. WATER!).
These fumes reduce performance, longevity and can actually reduce the octane level in your cylinder during combustion that steals fuel economy and could cause harmful detonation. Grime and sludge also build up on the valves and cylinder head further making a mess of your engine.

Which option then is best for you?
Well it honestly depends on your engine and to what degree you plan on adding protection to your vehicle, also local and state/provincial laws regarding emmissions control.

A simple catch can is usually the safest route to go because it covers all your bases. It also allows you to keep vacuum on the system which helps to collect the vapors.

Just a breather filter on isn't always the best or legal method as those vapors will go straight to atmosphere. Usually the filter gets all plugged up and could leak caught vapors down the side of your engine or get sprayed under hard acceleration. This method also doesn't allow you to use your engines vacuum to help remove those pesky fumes.

A breather filter catch can helps keep your engine bay clean by trapping the fumes but also allows the valve assembly or crank case to breathe however it likes to. Again, though, it doesn't allow you to use the engines vacuum to aid the process.

Anything I should know for installing one?

Make sure though that a catch can NEVER sees boost from a turbo vehicle (such as our 2.0T's), boost going into a catch can can just end up pushing all that sludge in one gunky mess right into your intake and cause massive issues.

PCV valves are another consideration, they are probably the #1 contributer to gunk and condensation, they should have a catch can installed on them, again though, make sure on turbo applications that the can isn't routed to see boost.

NEVER install a catch can on an external EGR system, it could cause a fire or damage your engine.

Ok, it's installed... now what?
Well just like your air filter or tires, it needs to be checked and serviced regularly. Check it every oil change (5000km's or 3000miles) or every time you open your hood. For the first 5000km's try and check it every 1000km's, that way you'll be able to tell how much collected is normal. It's perfectly normal for your car to burn through a litre of oil per service interval, expect around 60 to 100ml (2-3oz) to end up in the can.
But you'll have more than just oil in there, there will be fuel that escaped while the valves were open, condensation from valve cover and crank case during hot shut downs. How much of the 'other' stuff will depend on anything from how rich your car is running, altitude, how hard you drive and even environmental things such as whether it's been raining a lot lately.

Once you know what's normal, start looking out for things that are not normal. If your catch can came with a magnetic plug make sure it's always clean, you should never have metal shavings in your catch can.. if you do.. it's a sign you've got some serious issues and your car should NOT be driven until it's been inspected.

Coolant is another thing that should NEVER been in a catch can, it means you've got a seal or gasket that's broken and leaking coolant into your engine. Again, if it's there... don't drive your car.. you'll just make things worse.

To check for coolant the easiest method is to use a glass container to collect your catch can contents.. then freeze it in your freezer. Water will be at the bottom with lots of heavy sludge, then oil, then coolant, then fuel. The best way to check is the freeze method as it causes everything to seperate and become easily identifiable.

Any pictures for me to reference against?
What's a good outline without pictures?

First picture,
Here is a freshly caught catch can sample after slightly over 5000km's.



See how its slightly seperated at this point but we still can't say for sure how much is oil and how much is condensation or anything else.. but there is a lot of sludge in the bottom... ew.

Second picture,
After being stuck in the freezer over night the oil is clearly visable in contrast to the sludge and water. There is a very thin layer of fuel on the top.



Empyting your catch can:

I'm just adding this for a complete guide, but your catch can contents are considered oil and need to be disposed of correctly in accordance with all federal, state/province and local bylaws and regulations. Even though there may be water or fuel in it it should be accepted by any place that disposes of oil after oil changes, the environment levy was paid when the oil went into your engine so no additional expenses should be expected. Not to sound like a hippy but think of our environment and be responsible.

How to Install
 
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#131 ·
You don't want a lot of suction on the valve cover side.

I really don't know what the internal design is of the one can setups. But with the normal PCV system one side is open to intake vacuum, quite high, the other side is the make up air to replace what is being pulled out by the intake suction.

Throw the turbo in there that pressurizes the intake. The coupe uses a check valve to prevent the crankcase from building up pressure, at that time the valve cover side is seeing a slight vacuum from the pull of the intake air going through the charge pipe. It is nothing like the vacuum of the intake though.

My fear with a one can system would be over pressurization of the crankcase, leading to blown seals, and not removing the combustion byproducts (blowby) from the oil.
 
#133 ·
Huh. I've had mine on for like 3k or 4k km and I don't have any of those issues. My car makes a sucking noise at WOT but that's the AEM CAI. No CEL or anything, and my dipstick is still firmly planted in her.
 
#134 ·
The filtered Passenger side AGP can works by allowing the system to draw fresh air in, when running around in manifold vacuum, and to allow crankcase pressure to escape, under boost pressure.

The problem with this setup is that the fresh, filtered air goes back through a filthy catch can.
 
#138 ·
Sorry for some confusion on this.

Diagrams and video was pulled to prevent others from installing those ways until I'm done investigating the potential issue. Dual Catch cans with a check valve is and always has been the safest method possible to install a CC setup on ANY car hence it's still up however the potential issue could occur even in this setup.

This condition would only be present in climates that dipped below -18c and has NOTHING to do with catch can contents freezing, it relates to an engine component that could even cause an issue without a CC installed.

Hyundai Canada has been made aware of this issue and it is being investigated actively.

Hyundai Canada has also informed me that breather style catch cans are not recommended and could cause undesirable opperation outside of the emmisions control aspect.

I'll update when I have more information or a conclusion to the situation. Thanks.
 
#140 ·
exactly because as you stated before the crank case need to have a suction on it in order to be effective.
 
#141 ·
At this point, no.
Just for reference, -18c = ~0f

exactly because as you stated before the crank case need to have a suction on it in order to be effective.
Well at first that was just my interpretation of Hyundai's design and data, this time it's coming from HMCC's tech dept.
I was also told that "wrongful installation of vapor collectors will be investigated on any engine related warranty claims that are relevant", that being said they saw how my CC system was installed and said it was not related to my turbo seal failure.

Now that does not mean that all the recent turbo failures are Hyundai's specific issue and they will never warranty component failure if the ECU has been tampered with in regards to boost and fuel. They also will deny turbo related claims for devices including; boost controllers, turbo timers (don't know why), recalibration (wastegate mod), specific diverter valves (wouldn't give me a list), changed internals and choked oil lines.

Now this is Hyundai Canada, this does not affect US customers and they wouldn't comment on how Americans would be handled because they have no control or influence on it, but they did say "American DSM's and CTM's tend to be a lot less forgiving."

We are looking at a different component but it's now out of my hands and up to HMCC to come to their own conclusion, I'm just giving out info I've been given.
 
#142 ·
Typical "we wont warranty your car" cuz you built the engine....a.k.a. making it way better, put in a cc a.k.a. saving your engines lifespan and performance, getting a tune a.k.a making the car run the way it should have from the factory!, changing you tires a.k.a making your traction and safety better. anything they can think of to say..."oh no, he must be a racer! He put on a cold air intake so the engine can breath better, he put in a more efficient intercooler and radiator to make the engine safer, he put on a A/F gauge to make sure the car isn't messing up!..DENIED"

*end of rant*
 
#145 ·
I am so confused right now.

I have a greddy airinix SRI, and i have a 2012 genesis coupe in 6 speeds. There is a hole where i can just connect it back to the intake pipe, without running a catch can. I was just thinking about to get the hose and connect them back together

In that case, will that ruin my engine life span? Currently, i have a breather filter on it as a temp fix cuz i couldn't find the right size hose.

Or if it is better just to clean my breather filter regularly?
 
#146 ·
Just get a hose and run it back to the intake for now, if HMCC says no to breathers for operation more than likely HMA will too.

Catch cans ADD to engine life, remember, in normal operating conditions (not modded) your engine is good for at least 10 years if properly maintained. Catch cans will help extend that time and help keep the HP nominal over that time (HP decreases usually with age, TopGear proven).
 
#150 ·
I would empty your catch can on the service desk and tell the service department you are saving Hyundai money.

I don't see how a turbo oil seal would be broken by a catch can. I can see an over boosted turbo breaking an oil seal though.
 
#149 ·
The problem with catch cans in the winter is if the inside is baffled in such a way that freezing liquid clogs it up. The cheap ebay cans will not do this as the two ports are on top and the whole thing would have to be full to clog it due to freezing.

It really depends on what type of can you have.
 
#151 ·
Neither I, my service dept. or the DSM felt the catch can would result in a blown turbo seal. Since my car has a stock tune (verified by Hyundai's CTM) they are just replacing the turbo.

The CTM only stated to not run a breather as the crank case was designed to be under vacuum while in boost at higher rpm's. His reasoning has nothing to do with environmental issues.

As for removing it for winter..
As red said, I think it would depend on your can. I'm not going to.
 
#152 ·
Hey you never answered my question..the line on the back of the engine that comes from what looks like a 4way check valve on the right side of the engine, and goes behind the engine to the intake port...Im pretty sure that is just a simple breather port and it should be ok to just put a Breather filter on it...but inform me if im wrong.
 
#154 ·
That is part of your braking system, it's so you can recharge your brake booster when your car is under boost. Under normal driving conditions you won't notice not having it connected but it would be VERY unsafe to not have that connected pre-turbo during track driving or any situation that requires heavy brake use.

There is a one way check valve between that metal pipe and the intake pipe that needs to be in place to prevent boost leaks.

Do NOT put a breather on either of them, it's safer to put both to intake if you don't have a cc for the ccv and there is no need to cc the brake booster.
 
#155 ·
thank you! i guess i WILL take the breather off and put it back to the intake.....i put my IM side VMS oil catch can on today also i put a fuel filter right after the can and a PVC check valve right after that before it gets to the IM like you said, makes sense to me, ill post pics tomorrow. ty
 
#156 ·
ok, so breathing the crankcase is going to be bad for the engine; does that put the AGP crankcase side CC out of the loop, or is it possible to just pull off the breather filter and run a hose to the intake? will the IM side CC fit over on the crankcase side?

Snoopy, what is your opinion on Mishimoto vs AGP vs S-Max? i haven't seen the baffle system in the mishimoto, in your opinion which is the best route to go? Also how do you think these would be mounted at an angle? unless i get the AGP i would be looking at putting driverside CC by the fuse box, and putting the passenger side behind the headlight (windshield wiper fluid container has been removed). I have moved my passenger side fuse box because i have a top mount and it started to melt and i don't really feel putting the CC on that bracket by the turbo would be the best spot for it. If you want i can shoot you some pictures of my engine bay so you can see what im working with.
 
#157 ·
One thing that most don't seem to realize is the contents from the two sides is different. The PCV valve side is not an oil liquid as it comes out of the PCV valve but a gas. It is combustion gases, water and petroleum byproducts. This condenses into a liquid and is thinner than what comes out the other side. Internal to the valve cover should be some sort of oil separator. I don't know for sure but there has been one every other motor I've set up a CC system on. I call the can on this side a condensation can.

The turbo side is an oil mist that comes off the top of the valve train. It is mostly oil and will only come out when under boost as when the intake is vacuum this side has air going into the valve cover to make up the gases being drawn off through the PCV valve.

That's why I keep them separate and use individual cans. No need for check valves. And a fuel filter is not going to do anything. If used on the PCV side the blowby gases will just pass through. If any do condense in it there will be way too much to collect in the filter.
 
#158 ·
The PCV valve side is not an oil liquid as it comes out of the PCV valve but a gas.
Unrelated story...

I was emptying my catch can Wednesday into an ice cream container. This is when the neighbor kids came over and asked what I was doing. So I told them 'emptying some gunk from my car', and showed them.

Then the one kid asks 'is that how you make ice cream? that looks like melted ice cream'

Good thing I am not a bad neighbor...
 
#159 ·
I emptied my catch can into a
McDonald's sweet tea styrofoam cup. Forgetting that gas dissolves styrofoam. To anyone wondering how much gas is in the contents, it dissolved the styrofoam cup within seconds and leaked all over the ground. :)
 
#161 ·
@Sheijo
Mishimoto's cans are not baffled.
I don't know if you could pop the breather off the AGP and connect a host, most likely could with some hose reducers though.
PM some pics if you'd like help with placement.. that and I'd like to see your engine :)
 
#162 ·
too easy, ill snap some when i get off work and send them your way. did you see my youtube videos floating around?
 
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