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Thread: Oil catch cans on 7ms

  1. #1
    Slacker Grease Monkey
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    Default Oil catch cans on 7ms

    Hi all,

    I know im going to get stressed at for this question.

    Is it worth putting a oil catch can on a 7mgte?
    What are the benifits of putting one on?

    Cheers Scott.
    1988 MA70 Turbo A

  2. #2
    doctor ed Conversion King ed's Avatar
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    Default Re: Oil catch cans on 7ms

    first up - tell us why you think you need one
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  3. #3
    Slacker Grease Monkey
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    Default Re: Oil catch cans on 7ms

    why because ive notice there is oil coming from the cam breathers and entering just before the turbo.
    1988 MA70 Turbo A

  4. #4
    doctor ed Conversion King ed's Avatar
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    Default Re: Oil catch cans on 7ms

    how much oil?
    is the crank/cam breather blocked?

    a catch can will be useful if youve got a lot of blowby and are churning oil out the covers, but is a symptomatic fix
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  5. #5
    Gary Motorsport Inc. Too Much Toyota takai's Avatar
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    Default Re: Oil catch cans on 7ms

    Quote Originally Posted by ed_jza80
    how much oil?
    is the crank/cam breather blocked?

    a catch can will be useful if youve got a lot of blowby and are churning oil out the covers, but is a symptomatic fix
    Gee could never tell you are a doctor.
    The other problem is that with a non-plumbed back catch can you lose -ve pressure in the oil galleries and therefore you can start haemorrhaging oil out of seals.
    -Chris | Garage takai - Breaking cars since 1998
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  6. #6
    doctor ed Conversion King ed's Avatar
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    Default Re: Oil catch cans on 7ms

    if youve got a 'really' good, large bore breather system though, you should be able to get pressures back to atmospheric - and that will save your seals
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  7. #7
    Gary Motorsport Inc. Too Much Toyota takai's Avatar
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    Default Re: Oil catch cans on 7ms

    Yeah, the 4AG has that even with just one cover venting atm (both will be), but the 7M sucks on that regard, just started leaking out the back of the head...
    -Chris | Garage takai - Breaking cars since 1998
    Sparky - AE86 IPRA Racer | RZN149 Hilux - Parts and Car Hauler
    I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

  8. #8
    Longs to be a Conversion King RObErT_RaTh's Avatar
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    Default Re: Oil catch cans on 7ms

    It's no wander you two are over 1000 rep 1047 and 1048

  9. #9
    Forum Member 1st year Apprentice
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    Default Re: Oil catch cans on 7ms

    seroiusly if you fit a catch can and dont plumb it back into the intake before the turbo, the oil seals will start leaking? i dont really see how this can happen...as the blow by gasses still make there way out into the catch can and to atmo via a filter....might be a slight positive pressure in the crankcase all of a couple of PSI?

    maybe somebody in the know can clear this up for me

  10. #10
    doctor ed Conversion King ed's Avatar
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    Default Re: Oil catch cans on 7ms

    seals will weep and leak with only a few PSI, yes

    youd be very suprised as to the breather line sizes required to effectively depressurise the block and heads
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  11. #11
    Forum Member 1st year Apprentice
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    Default Re: Oil catch cans on 7ms

    yeah i can imagine as the holes are only 2x 3/8 on the 7m,

    if that therory is correct then wouldnt having positive pressure in ur engine also be bad for oil circulation? eg turbo oil return...postive pressure pushing the oil back into the turbo

    i might have to rethink my catch can ideas now...

    what do you guys have on your cars?

  12. #12
    back into it Chief Engine Builder
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    Default Re: Oil catch cans on 7ms

    Quote Originally Posted by takai
    Gee could never tell you are a doctor.
    The other problem is that with a non-plumbed back catch can you lose -ve pressure in the oil galleries and therefore you can start haemorrhaging oil out of seals.
    Good plan, but wrong! the seals are made to work with no pressure from either side and some neg if there!
    Every race engine ive ever known, wether circuit, drag or dirt run no pressure in the system and drag guys use pumps to create meager neg pressure.
    I have never had a race motor that leaked from the seals unless positive pressured or put in wrong etc. Even a return catch can you will have pressure relief threw the top, unless you want the nasty blowby products to reduce the octane of your finely tuned weapon
    I have never agreed with return catch cans because of the condesation from the hot oil that is sucked back in.

  13. #13
    doctor ed Conversion King ed's Avatar
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    Default Re: Oil catch cans on 7ms

    doesnt the cams manual enforce a catch can return line? dont make me go and read it!
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  14. #14
    Gary Motorsport Inc. Too Much Toyota takai's Avatar
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    Default Re: Oil catch cans on 7ms

    Quote Originally Posted by kingmick
    Good plan, but wrong! the seals are made to work with no pressure from either side and some neg if there!
    Every race engine ive ever known, wether circuit, drag or dirt run no pressure in the system and drag guys use pumps to create meager neg pressure.
    I have never had a race motor that leaked from the seals unless positive pressured or put in wrong etc. Even a return catch can you will have pressure relief threw the top, unless you want the nasty blowby products to reduce the octane of your finely tuned weapon
    I have never agreed with return catch cans because of the condesation from the hot oil that is sucked back in.
    I was talking stock engines. The 7M really doesnt have enough venting for the blowby which the engine can produce in stock form. My 4A on the other hand has enough venting thorugh only one PCV let alone two. I do agree that all seals are meant to operate with either neutral pressure differential or slightly negative pressure, but on most older engines in road cars this isnt the case and you are more likely to get slight +ve pressure when you disconnect the PCV.

    Quote Originally Posted by ed_jza80
    doesnt the cams manual enforce a catch can return line? dont make me go and read it!
    No it doesnt. It enforces EITHER a standard PCV setup or a venting to atmosphere so long as the can is >2L for U2L cars and >3L for O2L cars.
    -Chris | Garage takai - Breaking cars since 1998
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  15. #15
    Junior Member Too Much Toyota RONA's Avatar
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    Default Re: Oil catch cans on 7ms

    Quote Originally Posted by ed_jza80
    doesnt the cams manual enforce a catch can return line? dont make me go and read it!
    If the car is road registered its exempt altogether from that ruling so even with an open breather you can still run. Or run a catch can any size you want.

    Edit: Takai clarified the ruling but road regoe'd cars are still exempt to those applications as well.
    If in doubt power out

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