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  1. #1
    Matrix 4-Tec spannerspencer's Avatar
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    Oil fogging all over engine bay msx 150. anyone had high oil tank pressure? help

    guys, i need some help big time. ok so ive just fitted a big turbo to the ski, along with the new oil tank. but the new oil tank is giving me a head ache, when the engine runs, even on idle, the oil tank is being pressurised!! why?? here are some photos of the oil being fogged out and covering the engine





    this is the catch tank i made




    when i unscrew the top of the oil tank, and run the engine on idle, if i stick my finger in the smaller hole in the top of the tank, it pressurises in seconds! why? :



    i plan to pull the tank now, but can any one shed any light on what ive done wrong?

    cheers


  2. #2
    Matrix 4-Tec spannerspencer's Avatar
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    just done some tests, and oil is pumping out of the oil return (to tank) at mega high pressure!!!! within seconds of idle, it pumps huge quantitys of oil and spits everywhere!

    with plugs out oil tank isnt pressured.

    with plugs fitted but just cranking over it dosesnt pressurise

    only when engine is running! oil pump ressure too high?

  3. #3
    Kosh's Avatar
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    The oil return sounds about right, It is a high flow low pressure return from the scavenge pump, it will return more tha the main pump can use.
    How much oil is in the motor no more than 3.5 litres?

    You will have some pressure coming out the breather this is the only place the engine has an opening to atmosphere. Discluding the small drain hose from the catch tank.

    More pictures of the plumbing please.

  4. #4
    Matrix 4-Tec spannerspencer's Avatar
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    Quote Originally Posted by Kosh View Post
    The oil return sounds about right, It is a high flow low pressure return from the scavenge pump, it will return more tha the main pump can use.
    How much oil is in the motor no more than 3.5 litres?

    You will have some pressure coming out the breather this is the only place the engine has an opening to atmosphere. Discluding the small drain hose from the catch tank.

    More pictures of the plumbing please.
    ok Kosh, so more test confirm pressure at from the top of the tank, so will check oil outlet at the bottom etc.

    whilst removing the oil tank, ive found a split hose, so this is how ive lost most of the oil, but before it must of split, i stll had tank pressure. perhaps low oil = tank air pressure? is this plausable?

    heres photos of split (ok so my fault for using a silicone hose, but the small hose from cyclone to sump isnt re-enforced hose is it?



    here is new oil tank cross section



    here is how i plumbed it all in, as per weber...







  5. #5
    Watcon's Avatar
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    You need to do a crankcase leak-down test.. I suspect the cylinder / rings are bad and you are pressurizing the lower end.. A simple compression test wont show you everything. http://www.watcon.com/Catalog_Pages/...n_Test_Kit.htm

    Randy

  6. #6
    Matrix 4-Tec spannerspencer's Avatar
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    Quote Originally Posted by Watcon View Post
    You need to do a crankcase leak-down test.. I suspect the cylinder / rings are bad and you are pressurizing the lower end.. A simple compression test wont show you everything. http://www.watcon.com/Catalog_Pages/...n_Test_Kit.htm

    Randy
    thanks Randy, that leak down kit looks good. i sure hope my pistons arnt bad. i have a bad feeling about them now though.. if my rings/cylinders where bad, wouldnt it smoke whilst running?

  7. #7
    Kosh's Avatar
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    Spanner,

    Attached is a nice picture of the external oil circuit.
    Attached Files Attached Files
    Last edited by Kosh; 06-19-2011 at 11:06 PM. Reason: spelling mistake

  8. #8
    Matrix 4-Tec spannerspencer's Avatar
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    ok so ive changed that blue hose for a longer stronger one. and put it back together. im going to test it this weekend so keep you posted on results. im going to run a long hose from the top of the breather spout on the oil tank onto the handle bars so i can check the crank pressure whilst riding!

    Kosh, thanks for the doc with the CAD drawing, that was mint.

    going to see why the ski wont go over 7k also, it may have a leak. guna pop on OEM impeller for know

  9. #9

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    Is your catch can sealed or does it vent someplace? If it is sealed the system is likely to build pressure in the tank until it finds someplace to go (the split hose???). The low pressure pump is putting oil into the tank twice as fast as the high pressure pump is removing it (page 4.65 service manual). Pressure will also build in the crankcase and reduce the effectiveness of the piston rings sealing ability and further compound the problem. I think the system needs a vent in order to function properly. A air/oil separator vented overboard may be a better solution than a catch can.

  10. #10
    desperado's Avatar
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    Ok Spencer... here is the bottom line.

    The oil scavenge pump has more pumping capacity than whatever volume of oil is present in the engine case at any point in time. This means the pump is always pumping oil AND air. The fact the scavenge pump is pumping oil AND air back to the oil tank means a greater volume is fed to the tank than the total volume actually extracted by the oil suction pump. Makes sense so far...? Ok, follow me...

    If the vent system is not large enough, then pressure will build in the oil tank. That pressure comes from 3 sources:

    1-) oil
    2-) raw air
    3-) tinny air bubbles trapped into the oil which increase the overall volume of the overall fluid into the oil tank.

    Your system needs to have a 17mm vent (minimum) that goes directly into the atmosphere and is not restricted in any way. The only reason for the oem catch tank is to avoid venting oil into the open. Any oil present in the oem oil catch tank system should drain back freely by gravity into the crankcase. The old cyclone system used to have a check valve to prevent positive crankcase pressure from reverting oil flow. If your system works properly, you should never see any oil in your catch tank. If oil is present in your catch tank, then something is preventing it from going back into the oil pan and that must be addressed.

    Finally, the fact you are not venting into the turbo inlet means you are missing the suction effect created by the turbocharger to scavenge any extra air volume in your oil tank. It is ok to not vent into the turbo air inlet circuit.... but choosing not to do so will force you to use a larger vent hose because you are now working with a 1 atm (1 bar) ambient pressure.

    Hope this helps.

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