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JRSC spiking IATs and loss of boost

Discussion in 'Forced Induction' started by FLounder, Aug 31, 2010.

  1. FLounder

    FLounder power hungry VIP

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    ok so i finally got my ignition situation figured out and went back on the dyno today. no more missing at high rpms, but now the car is doing something else bad.... at higher rpms (6500 and up) the IATs spike up 50 degrees and the boost drops from 9-10 psi down to 6psi.

    it has never done this before, and it has been on many dyno runs on the 10lb pulley. the IATs will slowly rise with heatsoak after repeated runs, but not spike very high very fast like this. the belts are tight and not slipping. the IAT sensor is very new, only a couple hundred miles on it. im wondering if the blower itself is bad? man i am so frustrated with this build! any ideas of why or how this is happening?

    background info: built top and bottom b20vtec with JRSC at 10psi tuned on Neptune. motor runs great and pulls smooth and hard until about 6500 rpms or so.
     
  2. 99sidude

    99sidude Moderator Moderator VIP

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    Sucks to hear this. I haven't heard any stories of the blowers themselves failing. Usually the bearings in them will wear out. I think it could be a couple of things.

    -belt slipping at high rpm's (yes I know you ruled it out, but it can be hard to detect)
    -Bypass valve not operating properly.
    -Vacuum leak
    -Injector problem

    It's strange you had to upgrade your ignition. I had the exact setup minus .2l of displacement and it ran strong with stock ignition.
     
  3. FLounder

    FLounder power hungry VIP

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    me and my tuner are going to try to dig a little deeper into this, maybe this sunday... hopefully its a fixable problem. i will certainly check all the things you listed 99sidude, thanks.

    i still have stock ignition, ive just had to replace all of it. my car seems to like to eat distributors for some reason.
     
  4. Briansol

    Briansol Admins Admin VIP

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    you may simply be beyond the efficiency of the blower... it's simply blowing in heat at that psi level. You may need to consider an aftercooler.
     
  5. newb

    newb phresh VIP

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    This.

    I dunno how those bypass valves would react with a torn diaphragm, but its worth a check. Replace all your vacuum lines if theyre not new already. Zip tie the ends if you have to.
     
  6. FLounder

    FLounder power hungry VIP

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    I dont think it can be passed the efficiency of the blower...
    a few weeks ago i made some pulls where the ignition was breaking up but it did NOT drop boost and spike the IAT.... made around 250whp(not running right). got ignition fixed went back to dyno to try again, now its making around 220whp because of the boost drop :( we are running a massive fan right into the motor and a bag of ice melting on the supercharger manifold the whole time to keep heat soak to a minimum. this recent problem is not heat soak. the temp spikes up very high during the pull, and then cools back off quickly afterward. it has never done anything like this before on more than 15 dyno pulls.

    thanks for the input though guys, hopefully this weekend i can figure it out.
     
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