lower pulley worth it?

Discussion in 'SRT Hellcat Performance' started by BAADCAT, May 14, 2016.

  1. BAADCAT

    BAADCAT Senior Hellcat Member

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    I have Metco 2.75 upper going on and I planned on just pinning the stock lower, but is it worth going ahead an swapping on the ATI OD? Seems you can make just about all the boost you want with different uppers. So is it worth swapping the lower?
     
  2. Bstudey01

    Bstudey01 Gold Member

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    I think if you start trying the really small uppers you would need to make as much boost as lets say the 2.75 upper/10% ati lower that you will start experiencing belt slip on that upper pulley. Also the ati has a damper that will help with torsional vibration.
     
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  3. TNCHARGER

    TNCHARGER SRT Hellcat Supporter Gold Supporting Member

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    The OEM upper pulley has a clutch built in that the aftermarket pulley doesnt have....I was advised if I was only going to replace one pulley it would be better to leave the upper on....and that is what I did..
     
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  4. Bstudey01

    Bstudey01 Gold Member

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    I
    I would probably agree with this.
     
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  5. Jettster

    Jettster Gold Member Hellcat Car Club

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    Can you put on the ATI lower as a stand alone mod? Seems like it would take you from 11.5 to 13 pounds of boost-or will the computer just open the bypass as it senses over boost?
     
  6. TNCHARGER

    TNCHARGER SRT Hellcat Supporter Gold Supporting Member

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    I believe a few have installed w/o a tune and it works...a/f is on the ragged edge though.....I would not install it on my car w/o a tune.
     
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  7. goingsolo2

    goingsolo2 Beast will be back bigger and better than ever! Hellcat Car Club Gold Supporting Member Hellcat Supporting Vendor

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    I run only the ATI lower, and I am getting 14.5 lbs. of boost. I made 791whp (A8)...plenty of power for me. I won't touch the upper pulley either because of the built-in clutch. I read and heard that it is there to prolong supercharger life, so I am not touching it. The lower is plenty!
     
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  8. TNCHARGER

    TNCHARGER SRT Hellcat Supporter Gold Supporting Member

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    I am running only the ATI lower and only get 13psi based on the EVIC gauge..hmm
     
  9. goingsolo2

    goingsolo2 Beast will be back bigger and better than ever! Hellcat Car Club Gold Supporting Member Hellcat Supporting Vendor

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    Not sure....it's what we saw on the dyno, and I saw 14 on the EVIC gauge last time I punched it.
     
  10. TNCHARGER

    TNCHARGER SRT Hellcat Supporter Gold Supporting Member

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    Could be difference in altitude and DA...
     
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  11. DB2

    DB2 Silver Member

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    I wondered about the clutch on the aftermarket pulleys......that answers that. I dont like that you have to grind off a bolt head for the lower ATI but i think when i mod its what i will do.

    I would like low 10s for sure, but longevity trumps speed for me. I may do the lower or at the very least pin the stocker. Plus around here they are taking the rollcage issue pretty seriously at the race tracks. My personal best is 10.79 @ 128.50. Car is 4650 lb;s with me in it. It just blows peoples minds man....what a car.
     
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  12. jvm728

    jvm728 SRT Hellcat Supporter Gold Supporting Member

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    How many aftermarket twin screws have a clutched pulley
     
  13. Rick@Metco

    Rick@Metco Gold Member Hellcat Supporting Vendor

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    None.
    And other factory-supercharged applications like the Lightning, Cobra, GT500, ZL1, CTS-V, and Z06 use fixed (non-clutched) pulleys.
    The IHI-manufactured blower used in the HC application has been offered on performance European cars for years, and during that time many enthusiasts replaced the OEM pulleys with fixed units.
    I'm not here to convince anyone of anything, just stating some facts. There is some degree of risk associated with any performance upgrade, and the choice is yours to make.
     
  14. Bstudey01

    Bstudey01 Gold Member

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    My E55 had a clutched pulley from the factory on the twin screw supercharger. Replaced with non clutched pulley and had zero issues for the 30K miles I put on it.
     
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  15. Rick@Metco

    Rick@Metco Gold Member Hellcat Supporting Vendor

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    ^ That is exactly the type of application I was referencing when I mentioned the European supercharged cars.
     

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