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Thread: WOT boost surging going from 15.5psi down to 12 back up to 15

  1. #1
    Potential Tuner
    Join Date
    May 2018
    Sydney, Australia

    WOT boost surging going from 15.5psi down to 12 back up to 15

    Just been dialing in my wastegate duty cycle values to suit 16psi on my 2014 xr6 turbo mk2 and under WOT i can see on my boost gauge the peaks at 15.5 and goes back down to 10 and back up to 15 all whilst im under wide open throttle. i can see the wastegate duty cycle goes from .73DC down to 0 which is obviously whats causing the drop in boost but i have a feeling there is another table or something i have forgotten about that is influencing this change,

    the car was dyno tuned 2 years ago made 330kw, since then it has had a new turbo core replaced and when that was done the wastegate actuator was over adjusted holding the door 5mm open, this explains why it used to be so laggy so now i have rectified that by setting it with a 7psi base spring and a half a mm of preload (found a 5 and 7 spring inside)

    anyone have any ideas or could have a quick squiz through my log and tune and give me some feedback, i am aiming for it to just hold close to 16psi for most of the time at wot.

    i have a gut feeling its something to dow with the on/off boost threshold, i havnt touched the values, it the only thing i can find that in my mind might be causing this?

    FYI this is my running gear
    turbosmart wastegate actuator with 7psi base spring, currently set to have a bees dick of pre load
    4 inch dump to 3 inch exhuast with high flow cat right through to factory rear muffler
    the usual injectors, fuel pump upgrade
    3inch intake
    full intercooler kit
    Last edited by Jungatz; 06-26-2019 at 03:23 AM.

  2. #2
    Tuner in Training
    Join Date
    Jul 2016
    Sounds like your desired boost and duty cycle tables are not correct. Tune in open loop first then back fill your desired boost table. There's a how to guide on the pcmtec forums, same principals apply to hp tuners

  3. #3
    Advanced Tuner
    Join Date
    Feb 2015
    Perth, Australia
    you're trying to tune in open loop boot without the under and overboost thresholds high enough and a constant wastegate DC

    either max them for full open loop or tune boost in closed loop