Thoughts on catch cans.

[jfo]

Some people don't mind this stuff going into their engine, but I do. To each their own.

You also live in California.

[FlyPenFly]

Some people don't mind this stuff going into their engine, but I do. To each their own.

Drain some oil. Blend it with water and fuel. There’s way nastier stuff in oil than what you see there.

[old guy]

Let me start off by stating that I am not arguing for or against catch cans. My intent is to answer the OP's question "Thoughts on Catch Cans". The purpose of running a catch can is to remove the oil vapours entering the intake stream. This helps to reduce carbon build up on the intake ports and valves. A catch can also removes the condensation that forms in the engine. The condensation, when handled properly, is harmless.

This picture clearly illustrates the "catch 22" of running a catch can. As you can see it has removed some oil. But the majority of what you see is a water/oil mix. Unfortunately the majority of the water concentration is a result of running the catch can. Normally the water vapour is harmless.

2.0T Standard Block Breathing System
The main function is to provide a continuous purge of the block vapour and water condensation that is generated in the block. It does this by providing a continuous metered supply of fresh air that is actively being pulled through the block and into the intake manifold to be burned off in the engine. This process is active as long as the intake manifold is under vacuum. Once the intake manifold goes into a boost condition the purge is no longer active and the resulting block pressure gets relieved by shunting it into the pre-turbo intake stream. Unless you are tracking your car your intake manifold is under vacuum the vast majority of the time your engine is being operated.

2.0T With Catch Can
All of the 2.0T catch can installations that I have seen eliminate the intake manifold connection and run all of the oil vapours and condensation through the catch can and into the pre-turbo intake stream. This filters out the oil vapours and condensation. it also completely eliminates the continuous block purge and replaces it with a simple pressure blow off mechanism. Consequently this creates a situation where the block oil vapours and water condensation are no longer being actively purged with fresh metered air and will build up in high concentrations in the block until they are "pushed" through the catch can. These high concentrations are what you see being collected in the catch can.

Cliff Notes Version
Running a catch can will reduce the amount of oil vapour and water condensation entering the intake stream. But in the process it will also create a much higher concentration of these same vapours in the block that it has been designed to filter out. Failure to maintain the catch can system properly can have some rather nasty results.

[steviesteves]

To anyone who’s thinking of running a catch can I would say don’t. Or at least don’t buy one from CTS Turbo. I got mine installed professionally and within days my motor blew. Yes everything was connected correctly. Then a month later I was 10k down the drain for a new swap and toes and rentals. I would never run a catch can again in my life especially not from CTS. Had a 14 b8.5 a4


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[misiak]

To anyone who’s thinking of running a catch can I would say don’t. Or at least don’t buy one from CTS Turbo. I got mine installed professionally and within days my motor blew. Yes everything was connected correctly. Then a month later I was 10k down the drain for a new swap and toes and rentals. I would never run a catch can again in my life especially not from CTS. Had a 14 b8.5 a4


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How did you verify that your "motor blew" due to the catch can? From a design/functionality stand point what is the difference between the CTS one and any other catch can setup with a baffle??

[JustMtnB44]

The catch can mod was created by aftermarket companies who want to sell you their product because racecar.

Yes, race cars might use catch cans, but there are specific reasons for that, and they don't necessarily apply to daily driven cars.

Two questions to ask yourself before considering a catch can:
Do you trust aftermarket parts companies more than Audi and literally every other automotive company engineers?
Do you want to add another maintenance task (emptying the can) to your engine, knowing that if not done at the right time it can cause engine damage or failure?

I agree with everything old guy said above. In case that wasn't clear enough, here's a good video on how the whole system works: https://www.youtube.com/watch?v=PWz6vCnJ4CA

[JeriQo]

something you really dont need to worry about.
this just adds another level of anxiety lol. just drive your car in peace and follow the service intervals.
just pour some seafoam on call it good.

[dennej1985]

While intriguing, I have never gone to a catch can setup in about 15 years of owning 3 different turbo Audi’s. I live in Wyoming, I park my car outside, downside far outweighs the upside IMO. Properly service your car, use your revs.


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[mtroxel]

use your revs.

Damn straight. You can't have any fun shifting at 2500 RPM!!

[mtroxel]

If you live in a cold climate like I do, catch cans are a really bad idea. When they freeze up, really bad things can happen. Just see this post:

https://www.audizine.com/forum/showt...1#post13491387

[Jet08]

Not a fan of catch cans, more looks than function and even function is stretching it on a daily driven street car.

[sfl_A4]

Still debating if I should get a cc for my 2013 A4T MT6. Direct injected engines are prone to fouling valves with PCV contaminants and turbo blowby that accumulates in the intake and cakes the valves. Port injected engines spray fuel on the back of the valves and wash away the deposits, but on direct injected engines that isn't happening. Toyota is now making dual injection engines specifically for this reason, so they have an injector over the valves to help wash off carbon deposits, as well as an injector in the combustion chamber. I hope the Toyota design that catches on, or some other innovation like it comes along.

In the meantime, I was wondering if water injection in the intake runners or in the plenum would have a similar cleaning effect? Any thoughts on this? I know folks run water injection on turbos to minimize pre-ignition, and some of pictures I've seen appear to keep valves and piston tops shiny.

[elscotto80]

Still debating if I should get a cc for my 2013 A4T MT6. Direct injected engines are prone to fouling valves with PCV contaminants and turbo blowby that accumulates in the intake and cakes the valves. Port injected engines spray fuel on the back of the valves and wash away the deposits, but on direct injected engines that isn't happening. Toyota is now making dual injection engines specifically for this reason, so they have an injector over the valves to help wash off carbon deposits, as well as an injector in the combustion chamber. I hope the Toyota design that catches on, or some other innovation like it comes along.

In the meantime, I was wondering if water injection in the intake runners or in the plenum would have a similar cleaning effect? Any thoughts on this? I know folks run water injection on turbos to minimize pre-ignition, and some of pictures I've seen appear to keep valves and piston tops shiny.

If you are interested in a CC setup, mine is for sale. Shoot me a PM.

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[doublespeeded]

Nothing is going to stop carbon build up on direct injected cars, catch can can slow the process but its only a baidaid measure for this kind of stuff. It's an inherent flaw in the design overall.

yea I guess that's why VW/AUDI went Dual Multi/direct injection on the current Gen IIIs.

kinda ironic that Audi/vw group apparently were the first to release direct injection into full production...and yet, experience the worst carbon build up even when compared to other GDI engines.

[BMWManiac]

Once my motor is properly warmed up, and every time I drive, I find a way to rev the motor out. I don't know if this is an old wives tale, but I was always taught that this helps the engine burn off excessive carbon deposits on the valves....

I'm another "won't run a catch can ever again" club

[doublespeeded]

Nothing is going to stop carbon build up on direct injected cars, catch can can slow the process but its only a baidaid measure for this kind of stuff. It's an inherent flaw in the design overall.

Let me start off by stating that I am not arguing for or against catch cans. My intent is to answer the OP's question "Thoughts on Catch Cans". The purpose of running a catch can is to remove the oil vapours entering the intake stream. This helps to reduce carbon build up on the intake ports and valves. A catch can also removes the condensation that forms in the engine. The condensation, when handled properly, is harmless.

question is...since a catchcan is a 'Catch' 22 (by the way, I like your intended pun! :) for the Audi Engine ... there's cons and pros...

Does it justify to be better than running a new/reivs

This picture clearly illustrates the "catch 22" of running a catch can. As you can see it has removed some oil. But the majority of what you see is a water/oil mix. Unfortunately the majority of the water concentration is a result of running the catch can. Normally the water vapour is harmless.

2.0T Standard Block Breathing System
The main function is to provide a continuous purge of the block vapour and water condensation that is generated in the block. It does this by providing a continuous metered supply of fresh air that is actively being pulled through the block and into the intake manifold to be burned off in the engine. This process is active as long as the intake manifold is under vacuum. Once the intake manifold goes into a boost condition the purge is no longer active and the resulting block pressure gets relieved by shunting it into the pre-turbo intake stream. Unless you are tracking your car your intake manifold is under vacuum the vast majority of the time your engine is being operated.

2.0T With Catch Can
All of the 2.0T catch can installations that I have seen eliminate the intake manifold connection and run all of the oil vapours and condensation through the catch can and into the pre-turbo intake stream. This filters out the oil vapours and condensation. it also completely eliminates the continuous block purge and replaces it with a simple pressure blow off mechanism. Consequently this creates a situation where the block oil vapours and water condensation are no longer being actively purged with fresh metered air and will build up in high concentrations in the block until they are "pushed" through the catch can. These high concentrations are what you see being collected in the catch can.

Cliff Notes Version
Running a catch can will reduce the amount of oil vapour and water condensation entering the intake stream. But in the process it will also create a much higher concentration of these same vapours in the block that it has been designed to filter out. Failure to maintain the catch can system properly can have some rather nasty results.

Question is...since a catchcan is a 'Catch' 22 for the Audi Engine (by the way, I like your intended pun!) ... You've listed cons and pros..
Then does it justify to be any better than running a revised and/or new PCV valve?

[old guy]

I've tried to steer away from giving my opinion and instead just present the facts so anyone contemplating a catch can understands the issues involved. With that being said, here's my opinion and recommendations:

Carbon build up is coming from two separate sources. Some of it is blow by from the block. The current PCV block breathing system removes some of this but obviously not all of it. The second and probably worse contributor is the internal EGR design used by the 2.0T. This system allows for a lot of valve overlap. This overlap of exhaust gasses allows some of the exhaust portion of exhaust gas to remain in the cylinder and the residual gas is then mixed with the incoming fresh air charge. The amount of residual gas is controlled by phasing the camshaft. The downside is that the intake valves get exposed to the hot exhaust mix and create carbon build up.

If you install a catch can kit that eliminates the fresh air purge you will be creating a situation where you are generating more gunk to begin with than the standard block breathing system. So when you empty the catch can you can feel good about all the "gunk" that you prevented from entering the intake stream. Unfortunately you created most of the gunk just so you can then remove it!

There is a partial solution. Install a catch can between the PCV block breathing system and the intake manifold. Leave everything else in place. By doing this you will keep the block fresh air purge in place. Most of the time that you are driving your car the intake manifold is under vacuum. Even under mild acceleration it is under vacuum. So whenever you are under vacuum you will scrubbing the engine vapours with your catch can.

Once you go to a boost condition the PCV blocks the boost pressure and the block blow by pressure gets relieved through the turbo inlet pipe as designed. This blow by will no longer be getting scrubbed through a catch can. Fortunately the amount of time under boost is a very small percentage of the total engine operating time.

There is another really big advantage of this type of set up. If you forget to empty the catch can and it freezes up solid you will not pressurize your block and cause all sorts of damage. the PCV/block breather system will simply process the blow by into the turbo inlet pipe as it is designed to do.

With all that being said, I plan on replacing the PCV/block breather with an OEM unit every 50K miles as a preventive measure. No catch can.

[Jet08]

Thank you Fletch I think you have articulated it very well, I think this would suggest than an "Italian Tune Up" will exacerbate the build up not prevent it.

[mtroxel]

I think this would suggest than an "Italian Tune Up" will exacerbate the build up not prevent it.

The main benefit of the Italian tune-up is that it's fun!

[jfo]

The main benefit of the Italian tune-up is that it's fun!

I'm also of the opinion that high revs simply mean the equivalent of increased mileage on the engine, higher levels of fuel consumption with more by-products and more blow-by which= more carbon deposits. Is the idea that high revs will increase temps and somehow burn off carbon deposits? It would seem that short increases in temps would just bake it on faster.
I drive like a granny and after about 60K miles had minimal buildup when I changed out my injectors. I enjoy spirited driving in the mountains but don't get excited by frequent hard acceleration. My car has only seen red line maybe twice!

[Jet08]

No argument the Italian Tune Up is fun I was merely clarifying it's effectiveness in preventing carbon build up. On another note, I do go WOT once per day only for all of the reasons that jfo mentioned - except the fun part which he skimmed over :)

[doublespeeded]

There is a partial solution. Install a catch can between the PCV block breathing system and the intake manifold. Leave everything else in place. By doing this you will keep the block fresh air purge in place. Most of the time that you are driving your car the intake manifold is under vacuum. Even under mild acceleration it is under vacuum. So whenever you are under vacuum you will scrubbing the engine vapours with your catch can.

Great write up champion.

That's what I was actually thinking also, running both catch can, with the PCV. However, I haven't seen any products available or on the market that has one designed this way. Unless I guess you go 'Custom'.. but that would mean that someone would have to design a PCV system that's compatible with their proposed Catch can design.

That picture of that creamy beige colored residue seen from the hoses in Nano's picture... I recall seeing that drained out into the oil sump prior to installing the catchcan in my vehicle.

Since then, it is no longer present in the sump, and that colour doesn't seem to come out of the catch can like whats seen in that pic either. (wonder why)

unless now that Im changing oil frequently every 5000km (3106 Miles) has something to do with it?

[lettuce]

Posted this in another thread but then I saw this one and thought it was worth reposting here so people will actually have a chance to read it.

Our stock PCVs are not the most reliable parts and have had some design flaws as evidenced by the many part revisions over the years, but they're reliable enough for the function they have and cheap enough to repair or replace when they do break. And when they do break it's because they are fairly complicated and over-engineered, but they're over-engineered because they have to be to route and divert crankcase pressure in the way that our motors require. If any of the one-piece PCV replacement blocks you can buy would do what our motors need them to do, Audi would have saved themselves a ton of hassle, R&D time, and money and just done that themselves.

Besides that, the other reason people run catch cans is to reduce carbon build up, but that also just isn't going to happen because it's not doing anything to solve the root of the issue. I have done a lot of research on the subject as I was plagued by this as well, and the difference a little oil vapor in our intake tracks makes is negligible. Read up on direct injection and how it affects carbon buildup. It's not unique to our motors so there is a lot of research done and literature on the subject from lots of different angles.

DI has 3 inherent design flaws which cause this:

1) increased combustion chamber temperature caused by leaner A/F mixtures which is used to increase power and efficiency, which is one of the main benefits of using a DI system since you can't be as precise with a port injection system. Unfortunately this leads to increased heat being soaked up by your intake valves, which exacerbates the coking.
2) valve overlap used to further increase engine efficiency and cool down exhaust valves by flowing cool intake air over them, which exposes the intake valves to exhaust gases, which is the substance that's actually coking up your intake valves.
3) the lack of clean, unburnt fuel constantly washing over your intake valves to clean them.

All of these 3 things work in perfect symphony to lead to our carbon buildup issues. You can somewhat mitigate #3 with methanol injection, but that won't eliminate it, only lessen it. You can run richer AF mixtures to lower combustion chamber temps, but that will lead to a loss of power and increase in fuel consumption and eliminate most of the benefits of the DI system itself. Lastly, our cars already implement VVT which adjusts valve overlap with RPM to keep this in as good of a place as it can be from a power and efficiency standpoint.

TL;DR: Just keep your stock PCV, repair/replace it when it breaks, and do a carbon cleaning every once in a while. And get some meth if you can.