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  1. #1

    HKS supercharger bushings

    With the extreme loads that the 18 psi wheels create on the shaft and bearings, it seems there have been a few failures out there. Info i have received is that all 3 shafts have been experiencing problems, stock, Riva, and R&Ds...
    Since i am going to use one of these wheels, i have been a little nervous about it, so i have been researching everything out there, and i have to agree with this theory.
    The bushings are fed oil pressure from the engine, and the housings oil feed port to the bushings is only chamfered approximately 90 degrees of the full 360 degree circle it should be.
    This may be the problem as it doesnt allow the entire bushing and shaft to be fully pressurized the full 360 degrees and (float) on oil pressure the way it should, and therefore prematurely wears the bushing, which causes the initial failure of the shaft.
    The area that receives the highest load is the top side of the rear bushing, and that is the area that is not fully channeled for oil pressure to flow to.
    Oil pressure enters the lower side of the bushing and needs to flow a full 360 degrees aroud the bushing to properly oil it, and allow it to fully (float) on oil under these extreme speeds and loads.
    Slotting either the bushing, or the housing where the bushing sits will solve this oil starvation problem. Slotting the bushing is easier, and it really shouldnt make a difference which one you slot, either one will allow the bushing and shaft to be under oil pressure the full 360 degrees instead of only 90..
    I will be doing this to mine before any riding is done..
    Ross
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  2. #2
    JD 1's Avatar
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    Quote Originally Posted by rossnemo View Post
    With the extreme loads that the 18 psi wheels create on the shaft and bearings, it seems there have been a few failures out there. Info i have received is that all 3 shafts have been experiencing problems, stock, Riva, and R&Ds...
    Since i am going to use one of these wheels, i have been a little nervous about it, so i have been researching everything out there, and i have to agree with this theory.
    The bushings are fed oil pressure from the engine, and the housings oil feed port to the bushings is only chamfered approximately 90 degrees of the full 360 degree circle it should be.
    This may be the problem as it doesnt allow the entire bushing and shaft to be fully pressurized the full 360 degrees and (float) on oil pressure the way it should, and therefore prematurely wears the bushing, which causes the initial failure of the shaft.
    The area that receives the highest load is the top side of the rear bushing, and that is the area that is not fully channeled for oil pressure to flow to.
    Oil pressure enters the lower side of the bushing and needs to flow a full 360 degrees aroud the bushing to properly oil it, and allow it to fully (float) on oil under these extreme speeds and loads.
    Slotting either the bushing, or the housing where the bushing sits will solve this oil starvation problem. Slotting the bushing is easier, and it really shouldnt make a difference which one you slot, either one will allow the bushing and shaft to be under oil pressure the full 360 degrees instead of only 90..
    I will be doing this to mine before any riding is done..
    Ross
    +1, did that and now runing a E1 @ 9100rpm's with zero issue's.

  3. #3
    Moderator RX951's Avatar
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    Quote Originally Posted by rossnemo View Post
    With the extreme loads that the 18 psi wheels create on the shaft and bearings, it seems there have been a few failures out there. Info i have received is that all 3 shafts have been experiencing problems, stock, Riva, and R&Ds...
    Since i am going to use one of these wheels, i have been a little nervous about it, so i have been researching everything out there, and i have to agree with this theory.
    The bushings are fed oil pressure from the engine, and the housings oil feed port to the bushings is only chamfered approximately 90 degrees of the full 360 degree circle it should be.
    This may be the problem as it doesnt allow the entire bushing and shaft to be fully pressurized the full 360 degrees and (float) on oil pressure the way it should, and therefore prematurely wears the bushing, which causes the initial failure of the shaft.
    The area that receives the highest load is the top side of the rear bushing, and that is the area that is not fully channeled for oil pressure to flow to.
    Oil pressure enters the lower side of the bushing and needs to flow a full 360 degrees aroud the bushing to properly oil it, and allow it to fully (float) on oil under these extreme speeds and loads.
    Slotting either the bushing, or the housing where the bushing sits will solve this oil starvation problem. Slotting the bushing is easier, and it really shouldnt make a difference which one you slot, either one will allow the bushing and shaft to be under oil pressure the full 360 degrees instead of only 90..
    I will be doing this to mine before any riding is done..
    Ross
    awesome fix Rossman

  4. #4
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    that is a great find, in fact I was over at Art from Engine Tech's place last week and he was saying the EXACT same thing! Coincedence? Were you talking to him??? Anyways this is a great find for the Yami 4 strokers to run the best wheel available!

  5. #5
    speedskixp's Avatar
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    Quote Originally Posted by henn View Post
    that is a great find, in fact I was over at Art from Engine Tech's place last week and he was saying the EXACT same thing! Coincedence? Were you talking to him??? Anyways this is a great find for the Yami 4 strokers to run the best wheel available!
    Art posted it on the other site.

  6. #6
    SHOBiz's Avatar
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    Interestingly my bushings look fine. However, the snaprings have obvious wear on the sides. I don't see anyone selling those...

  7. #7
    Addicted Member 5001craig's Avatar
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    Isn't there an updated bushing from R & D for the SC? Think there's a few options from them.

  8. #8
    I decided to slot the charger housing for the oil feed channels instead of cutting the bushing. Maybe a little scared of weakening the bushing by slotting it, personal preference.
    This is very delicate work, needing good lighting, a magnifying glass, and a VERY steady hand. It can be done very nicely with standard dremel tools.
    The small round saw to make the cuts, and a stainless steel brush to clean them out after the cut is made.
    At these insane supercharger speeds i would stress to everyone to use at least, your favorite synthetic oil, to help keep the heat levels down on this small diameter shaft and bushing setup, especially running any hi boost wheel.
    Here is what i chose and will be using. I know everyone has their favorite oil and thats great, dont want to start a big (best oil) debate..
    Maybe im a little old school, but some good old STP will be mixed with the royal purple.
    Ross
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  9. #9
    Boilerman Bill BPnta's Avatar
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    Nice work. No way I'd trust myself with a dremmel in there!

    But either mod reduces the surface area of the oil film that the bearing rides on right? So over time it'd wear faster.

  10. #10
    Quote Originally Posted by BPnta View Post
    Nice work. No way I'd trust myself with a dremmel in there!

    But either mod reduces the surface area of the oil film that the bearing rides on right? So over time it'd wear faster.
    No, it should actually do the opposite and not wear at all. The shaft should fully (float) on oil pressure now..

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