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Thread: DIY: Oil catch Can installation

  1. #1
    GTRCer RR32GTRR's Avatar
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    DIY: Oil catch Can installation

    Let me first start off by saying the there ARE MANY DIFFERENT WAYS to install a catch can on a Rb20/25. I have a car in the project thread and I got 6 different PM's on if I can show how I installed mine. Well here it is.

    This is on a Rb25



    There are some people who say you should also put a mini filter(ie breather) on your catch can. I have not done this yet myself.


    This Is on a Rb20


    Any comments would be helpful. Also the next person who says, "SEARCH, this has been done before", Go straight to hell because the pics don't work and visual confirmation is key.
    (O - O) S K Y L I N E (O - O)


    1990 300zx- Rb25 swap in the future
    1991 R32 coupe- Rb25 and a money pit.
    2006 Porsche Cayman S- Im growing up.

  2. #2
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    doin it wrong,

    before we get into what type of catch can you SHOULD be using educate your self on crankcase pressure...
    ""copied directly from another post of mine"


    So here we go, i can never explain it to people unless I'm hands on with them.

    1st. - Oil pressure: the pump is pressurizing the oil system, and pressure is released through out, squirters, bearings, turbo lines etc...
    after the oil is pushed out these squirters it drains down holes in the block and back into the oil pan.
    2nd - crankcase pressure: Ok, so you know how a piston makes pressure on the way up?... well guess what it also makes pressure on the way down... pushing pressure into the crankcase, oil pan, oil drain holes (returning to the pan), valve covers etc...
    3rd - now keep in mind how fast the rotating assembly, the rods, and pistons move.
    If you "could" see them in motion @ 1000 RPM's it would look like a wheel spinning at speed, you know how it sometimes appears to spin backward. same concept
    example: 3000 RPM's would not be visible, it would be a total blur, no motion visible at all
    At higher RPM's the pressure in the crankcase grows very strong and will blow out any way it can ( usually the valve covers)
    -picture a tea pot pressurizing and blowing steam out the top.

    Now here is what your looking for,
    having the intake sucking out that pressure as its being made. So the pressure under each piston is greatly reduced and reducing strain on your motor.

    Is this explanation understandable?

    -at this point, having a good sealed catch can that can collect oil at the bottom and have clean crankcase pressure being sucked back out of the top.

  3. #3
    GTRCer RR32GTRR's Avatar
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    Quote Originally Posted by ChrisCheezer View Post
    doin it wrong,

    before we get into what type of catch can you SHOULD be using educate your self on crankcase pressure...
    ""copied directly from another post of mine"


    So here we go, i can never explain it to people unless I'm hands on with them.

    1st. - Oil pressure: the pump is pressurizing the oil system, and pressure is released through out, squirters, bearings, turbo lines etc...
    after the oil is pushed out these squirters it drains down holes in the block and back into the oil pan.
    2nd - crankcase pressure: Ok, so you know how a piston makes pressure on the way up?... well guess what it also makes pressure on the way down... pushing pressure into the crankcase, oil pan, oil drain holes (returning to the pan), valve covers etc...
    3rd - now keep in mind how fast the rotating assembly, the rods, and pistons move.
    If you "could" see them in motion @ 1000 RPM's it would look like a wheel spinning at speed, you know how it sometimes appears to spin backward. same concept
    example: 3000 RPM's would not be visible, it would be a total blur, no motion visible at all
    At higher RPM's the pressure in the crankcase grows very strong and will blow out any way it can ( usually the valve covers)
    -picture a tea pot pressurizing and blowing steam out the top.

    Now here is what your looking for,
    having the intake sucking out that pressure as its being made. So the pressure under each piston is greatly reduced and reducing strain on your motor.

    Is this explanation understandable?

    -at this point, having a good sealed catch can that can collect oil at the bottom and have clean crankcase pressure being sucked back out of the top.
    Like i said there is MORE THAN 1 WAY of doing this. But if you felt like contributing then you should put up a pic of how it is done.
    (O - O) S K Y L I N E (O - O)


    1990 300zx- Rb25 swap in the future
    1991 R32 coupe- Rb25 and a money pit.
    2006 Porsche Cayman S- Im growing up.

  4. #4
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    i agree with cheezer . if there is no intake sucking the vapours back then you might experience some blow by.

  5. #5
    GTRCer m_melen's Avatar
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    okays, let's get pics of the way that has a solution for the crankcase ventilation solution. maybe not eliminating that line to the valve cover? or maybe routing that line from the pcv into the catchcan somehow?
    I've been brushing my teeth with jack but it's resulted in terrible amounts of tooth decay.

  6. #6
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    Quote Originally Posted by m_melen View Post
    maybe routing that line from the pcv into the catchcan somehow?
    .......... what do you mean "maybe"! FAIL


    .... do you really need pictures?
    I shouldn't have to post pictures. i believe its explained perfectly well.

  7. #7
    GTRCer Skym's Avatar
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    The point of having a catch can is to separate oil from blowby gas. The reason why is oil affects octane of fuel that affects how much ignition timing you can run. More ignition timing + lower octane fuel = engine knocks.

    The way the factory PCV system works -

    PCV valve on intake manifold is open at idle and when engine is under vacuum. PCV valve closes as engine transistions to boost (around 0 on boost gauge), so blowby gas is vented (actually sucked by turbo, engine at higher rpm's, boost levels) the opposite way to PCV valve, into intake piping infront of turbo via exhaust camcover breather vacuum hose that goes to intake pipe infront of turbo. That's why camcovers are connected together via a vacuum hose, as both camcovers can be vented into intake manifold when engine is at idle or into intake piping infront of turbo when engine is under boost.

    Since oil + blowby gas exiting camcovers happens at higher rpm's, boost levels and PCV valve will be closed when engine is under boost, the catchcan has to intercept oil + blowby gas via vacuum hose from exhaust camcover to intake pipe infront of turbo.

    This oil, blowby gas exiting camcovers happens at higher rpm's, higher boost levels. What happens is boost or vacuum for NA engines at higher rpm's leaks past rings, (known as blowby gas) creating more blowby gas in sump and since oil moves to head, blowby gas gets shifted with oil via oilpump, oil gallery's, etc to inside of camcovers and out the cam cover breathers.

    This is the proper way to do it using 2x catchcans on a RB20DET -



    1st catchcan separates oil from blowby gas and drains oil to sump via a drain under 1st catchtank (green line in above photo). The 2nd catchcan catches left over oil (if any) and clean blowby gas (no oil) gets sucked back into intake pipe infront of turbo from 2nd catch tank.

    That person with dual catchtank setup on his RB20DET always had a problem with a single catchcan filling with oil and had to pit every 2x laps. The addition of 1st catch tank was the solution, where oil drains back to sump and engine doesn't lose oil. Loss of oil in sump could could have resulted in oil starvation, engine failure. Also he doesn't have to pit every 2x laps.

    Catchtank size is important due to blowby gas slowing down enough, so oil can be separated. Catch tank size is based off capacity of engine (amount of blowby gas), so catchtank varies in size from a RB20 to RB30 engine.

    You'll see a dual catch tank setup on Mines R34GTR. Now you understand why it has 2x catchtanks and why the catchtanks are a certain size. Mines go one step further by fitting baffle plates to cam covers to separate oil from blowby gas before it exits camcovers.

    Mines R34GTR -



    Mines have copied others that having been doing the 2x catchtank setup since the 80's on Group-A RB20DET racecars, Group-A R32 GTRS, etc, but modified it slightly -

    http://www.skylinesaustralia.com/forums/post-a226835-

    Also there are other added benefits, mentioned in this link -

    http://www.burtonpower.com/technical...er_system.aspx

    Also they mention draining oil to sump from catchtank in last paragraph, so it's maintenance free. So draining catchtank to sump is nothing new.
    RESPONSE MONSTER

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  8. #8
    GTRCer m_melen's Avatar
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    Quote Originally Posted by ChrisCheezer View Post
    .......... what do you mean "maybe"! FAIL


    .... do you really need pictures?
    I shouldn't have to post pictures. i believe its explained perfectly well.
    dude. i was being passive and helpful. obviously some people are still unclear on this DIY
    I've been brushing my teeth with jack but it's resulted in terrible amounts of tooth decay.

  9. #9
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    thanks skym, that verified alot when i go to install mine, thats how i thought it worked but the way chris explained it i had myself second guessing lol.

  10. #10
    GTRCer Skym's Avatar
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    It's one of two ways you can vent blowby gasses (via vacuum hose to infront of turbo or to atmosphere near back of engine via vacuum hose). Some vent it to atmosphere, but you need to retune engine to suit. So for most people the recirc setup would be better and has been proven to work on racetrack with higher boost levels with RB20DET engine.
    RESPONSE MONSTER

    The most epic signature ever "epic".

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