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PCV oil catch tank's for direct injection engines , a brief introduction .

I'm Just Rob. Nov 11, 2018

  1. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    A short write up for those not sure on what the format is concerning oil catch tanks and how they are so beneficial to the direct injection engine.
    Also why they work so well in conjunction with pcv delete setup's, either part or full.

    So take a seat , get your cuppa and biscuit tin and have a read and make up your own mind on the subject.
    I'm an avid supporter of it so a tad biased but have a read and enhance your engines life.


    Catch can or no catch can , that is the big question.
    Are they really any good, do they really work and do i really need one, well the answer is most certainly yes.
    This write up may help to providing a better detailed explanation showing why a catch can is highly recommended in direct injection engine applications.

    First, let's go over what occurs in your engine without a catch can installed. All internal combustion engines that run off petrol are 4 stroke engines (not 2 stroke). This means that the piston has to go up and down a total of 4 times to complete a cycle. The piston first goes down with the intake valves open creating a vacuum. This draws in the cool dense air for combustion.
    At the same time, fuel is injected into the cylinder. The intake valves close and then the piston rises up towards the top of the cylinder. This compression creates an immense build-up of pressure in the cylinder. The only things containing this high pressure are the cylinder itself, the piston and the piston rings that seat against the walls of the cylinder.
    The intake and exhaust valves are obviously closed as well. The pressure is so high that a very small amount of the air escapes around the piston and piston rings into the crankcase. This is called blow-by. The amount of blow-by increases as the engine RPMs rise. Also, an engine with more cylinders will have more blow-by. Obviously not all of the air escapes or else combustion wouldn't take place.


    Inside the crankcase, you have the crank which is turning in the oil sump which is full of oil. This keeps it properly lubricated. PCV or positive crankcase ventilation is necessary to ensure there isn't a build up of pressure in the crankcase. This would cause the crankcase to possibly crack under the pressure and create a huge mess of oil . So the PCV system removes the pressure from the crankcase and reverts it back through the intake tract via crank case vents.

    This pressure isn't made up of 100% air. It will also contain a very small amount of oil and that oil will be contaminated by mositure etc and since there is so much in the oil pan at a high temperature. This air and oil mixture is then entered somewhere after the intake system, passes through the intercooler (if you car is turbo or supercharged) and then re-enters the combustion chamber (cylinder) through your intake valves to be re-burned.
    The oil will actually coat everything on its way back to the combustion chamber. It will develop in the intercooler, boost hoses, intake manifold and intake valves. Just on the other side of these valves is where the combustion is taking place where the temperatures are extremely high. This is what actually causes the oil to solidify on the valves. With the oil passing through the intercooler, it can actually coat the cooling fins which will hinder the intercooler's ability to cool the air therefore lowering the efficiency.

    The caking on intake valves is only a problem with direct injection engines. For all other engines that use port injection, the fuel is introduced before the combustion chamber which means it flows over the intake valves and enter the combustion chamber premixed with the air. This action of the fuel flowing over the intake valves actually cleans the valves from any oil that make already be on there. The oil never has the chance to cake on the valves in port injection engines.

    Having oil caked onto your intake valves can cause the following symptoms:

    Knocking
    Pre-ignition
    Loss in power
    Loss in fuel economy


    This is mainly due to the fact that the air that comes through your intake system and goes into the combustion chamber won't just be air. It will contain some oil particles which cause the combustion process to be slightly less efficient.

    You might ask why do car manufacturers revert this crankcase pressure back into the intake tract? Well, for starters there isn't anywhere safe to revert it to and you can't expel it into the atmosphere because it's not environmentally friendly and is considered to not be compliant.

    Another question that arises is why isn't a catch can included from the factory? Well it's pretty simple actually. Most people don't even change their oil (scary but true) so will they think to empty the catch can regularly? The answer is obviously and unfortunately, no.

    An oil catch can does just that. It catches or prevents the oil from re-entering the intake tract. A catch can is placed right after the PCV and before the intercooler.
    A PCV delete setup will remove the PCV valve completely or partially and oil catch can location can be customised to suit specific applications.
    This means that a more pure (sometimes 100% pure) air mixture will go through the intercooler and intake valves. A more pure air mixture entering the intake valves means no caking and none of the symptoms listed above.

    An oil catch can typically uses steel wool or a baffle system that removes the oil from the air-oil mixture. Higher quality cans use the baffle systems since it is less messy and better at separating the mixture. The oil falls to the bottom of the can where it is stored until the can is emptied.

    An oil catch can doesn't add any power or make any cool noises so it is often overlooked when modifying vehicles. However, a catch can will ensure you are always running the most power possible by having a cleaner intake tract free of oil.

    So there you go, something to think about the next time you jump in your car.

    Rob
     
    Last edited: Nov 11, 2018
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  3. Donfero

    Donfero Registered User

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    Rob, I assure you that more than half of the cars on this forum are running on the information and expertise you provide. Thank you.

    1 small question, how much oil should we expect in the catch can, and how often should we check?
     
  4. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    There is no set rule on quantity as every application may vary given driving style usage etc, with a smaller catch tank it would allways be best to drain it every couple of weeks really.
    The better your PCV delete and catch tank setup , the more contaminates will be found in the tank, so in this case more is a good thing as you can be sure its doing the job and keeping all that nasty stuff out of the engine.
    The benefits of having a drain valve on the tank becomes very obvious as it only takes a minute to drain the tank.
     
  5. Donfero

    Donfero Registered User

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    I have the setup exactly as per your instructions, I had a cheap catch can fitted and the amount of oil was practically nothing, a few days ago i fitted a new one but havent checked since.
     
  6. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    If i leave mine for 2 weeks there will allways be a fair bit inside , and its allways very nasty looking stuff but everyone will be different , if you dont push the engine hard then you will not create so much blow-by so less to get in the tank but its not a hard and fast rule .
     
  7. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    What is important to keep in mind is that a normally aspirated direct injection engine would only be catching oil from the crankcase pcv whereas turbo variants also have the VC outlet to address, this means there are now two sources of contamination to deal with.
    For example prior to my setup , over the course of 12months this is what had collected in the IC's , which doesn't include what would have been put back into the engine and burnt that way.

    sse4.JPG
    Now if you were to divide that oil up into weekly amounts , then add a some more from the crankcase pcv you'd end up with an approx amount of contaminated oil etc per /week in a catch tank based on a single tank with dual intakes.
    So weekly catch can volume may not be that much , its when you combine it all that you get a better understanding on things.

    Also one must remember that actual oil consumption may well increase slightly , this is allways going to be the case as you are removing oil from the engine indirectly via the PCV and VC , if your catching oil in a tank then that's oil that isn't going back to sump, not that you'd want that gloop going back anyway.
    Just something to be aware of , many owners suddenly expect oil consumption to stop, it wont its the nature of beast.
    So the more oil the catch tank collects the better, but in real terms, on a weekly basis the amount you see may seem a tad disappointing , but don't let that fool you.
    hope that helps.
     
  8. jarnold231

    jarnold231 Registered User

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    Is the PCV valve the same on a diesel engine?

    Sent from my ONEPLUS A6013 using Tapatalk
     
  9. trumz

    trumz Registered User

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    Whats your opinion on running a catch can in cold wheather? I live in Finland and must endure temps down to -20 or colder on occasion. I've heard of water freezing in the hoses causing potential damage. Any thoughts or experience?
     
  10. XPtuning

    XPtuning Registered User

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    I run a catch tank on my Exeo 1.8TSI and you need keep it empty in the winter period, there is indeed a chance of freezing of the oil+water solution when temperatures drop. When frozen, the engine cannot ventilate properly with the risk of blowing oil seals etc...

    At -20 degrees, I would not dare to use a oil catch tank.
     
  11. trumz

    trumz Registered User

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    Thanks for the feedback. I'll skip the catch can for now :)
     
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  13. Dan_Avant

    Dan_Avant Registered User

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    I’m with rob on this. I believe every enthusiast should fit some sort of catch tank.

    I emptied mine this morning after nearly 2 weeks of ‘spirited’ driving and this is what came out:

    C53F7F5C-F96A-4205-BAC7-5918D261A784.jpeg
     
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  14. Dan_Avant

    Dan_Avant Registered User

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    Ha ha. Don’t know why the image is sideways. It’s the correct way on my phone!
     
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  15. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    maybe this will help..


    sideways2.jpg
     
  16. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    Exactly , just consider how that will be impacting on the engines combustion etc if left to be returned via the inlet manifold , catch tanks may not seem to be required but they most certainly are .
    Why bother using top quality high octane fuel if all that is getting recycled into the combustion cycle, bonkers frankly.

    good job Dan.:icon thumright:
     
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  17. Dan_Avant

    Dan_Avant Registered User

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    Totally agree. And after seeing the amount of oil and sludge that was in my intercoolers recently I’m definitely going to look at a dual can set up or revise my existing one
     
  18. Donfero

    Donfero Registered User

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    Dan, do you have a design in mind for the dual can setup?

    Sent from my Nokia 7 plus using Tapatalk
     
  19. Dan_Avant

    Dan_Avant Registered User

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    @Donfero I do mate. There was a guy on here a year or so ago who had a dual can set up. I’ll see if I can find the pictures/thread for you.

    Pretty sure @Just Rob. had a dual set up too at one point
     
  20. Dan_Avant

    Dan_Avant Registered User

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    Can’t seem to find it. Hopefully rob has pics of his dual set up
     
  21. WOMBLERULZ

    WOMBLERULZ Registered User

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    just done catch tank mod. and now its smoking like a td ... must have piped it up wrong.. . help. photos to follow

    Sent from my SM-G965F using Tapatalk
     
  22. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    You should not have any issues with smoke or oil being burnt, if you have installed incorrectly then it may well cause problems, you don't want excessive vacuum in the system.
     
  23. WOMBLERULZ

    WOMBLERULZ Registered User

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    its blowing oil out off rocker cover gasket... engine now covered in oil

    Sent from my SM-G965F using Tapatalk
     
  24. WOMBLERULZ

    WOMBLERULZ Registered User

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    can you do me a diagram of engine and outlets and inlets etc.. as i think now breather sys now pressurized on boost should have leaft it alone

    Sent from my SM-G965F using Tapatalk
     
  25. Donfero

    Donfero Registered User

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    Robs guide is pretty straight forward, Take some pictures of what you have done maybe we can point you in the right direction.

    Sent from my Nokia 7 plus using Tapatalk
     
  26. WOMBLERULZ

    WOMBLERULZ Registered User

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    ive put return pipe on turbo boost not turbo inlet. what a numpty i am.... so bodge it and scarper tomorrow... then get silicon throttle inlet pipe.. then redirect catch can outlet to turbo inlet pipe lol what a numpty. i blame the extra painkillers atm . get a freshly burst disc in neck .. so numb hands

    Sent from my SM-G965F using Tapatalk
     
  27. XPtuning

    XPtuning Registered User

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    Fully agree, no TFSI without a catch can :)

    That the same kinda liquid my 034Motorsport catch can collect... sometimes it contains a bit of milky oil deposits but never dark brown/ black oil.
     
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  28. Sidrick

    Sidrick Registered User

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    Presuming Rob's not going to market his set-up, what's the best off the shelf option?
     
  29. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    I would if I had enough confirmed orders, they are not cheap to build up so only viable to build up a batch to order really.
     
  30. XPtuning

    XPtuning Registered User

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    034Motorsports makes ready to install kits....
     
  31. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    Only part delete kits ,and they still dont address the vapours from the primary oil separator into the secondary separator.
    they do a job yes so better than having no can at all, unless you intercept oil laden vapours leaving the primary separator before they reach the secondary , it s all still going into the vc and beyond, yes the part deletes with can work but not as well as they could.
    Why do half the job when the full job is so much better and not that much more involved.
     
  32. Sidrick

    Sidrick Registered User

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    How many orders would you need, guaranteed, to make it viable, Rob?
     
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  34. Donfero

    Donfero Registered User

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    A second catch can between the oil filter housing and the valve cover would solve this problem?

    Sent from my Nokia 7 plus using Tapatalk
     
  35. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    12 would be the min, as yet I haven't had even half that hence why I have not offered them yet.
    They aren't going to be cheap but they do work very well.
     
    Last edited: Feb 8, 2020
  36. Sidrick

    Sidrick Registered User

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    How much is not cheap?
     
  37. XPtuning

    XPtuning Registered User

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    My catch can collection from a couple of weeks Dutch weather driving...
    20200208_152442.jpg
     
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  38. Dan_Avant

    Dan_Avant Registered User

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    @XPtuning 034 catch can is what I’m running on mine at the moment mate
     
  39. XPtuning

    XPtuning Registered User

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    How do you empty your can?
    I have a small ~40cm hose attached to the bottom outlet, at the end of that hose I put an AN style end cap.
     
  40. I'm Just Rob.

    I'm Just Rob. Moderating or something, Staff Member Moderator Gold Supporter VCDS Map User

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    That's not a b7 2.0tfsi engine, 1.8tsi by some chance.
     
  41. XPtuning

    XPtuning Registered User

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    :thumbs up: It's a 1.8TSI CDHB in a Exeo ST(Audi A4 B7 platform/body)
     

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