N55 e90 Overboost MHD 2+ E50

machinehead

New Member
Dec 11, 2020
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2011 e90 335xi N55 PWG AT
VRSF catless downpipe, 340 LPH LPFP BMS charge pipe, XHP stage 3, turbosmart VR9 dual valve, wastegate rod adjusted to 5.5 inches of vacuum fully closed.
I've tried all the maps from one through two plus, and have always gotten an overboost with throttle closing that feels like massive hesitation since day one, at the moment I'm sitting at stage two plus e50 blend map, went from stock diverter valve to TurboSmart VR9 dual valve to try to eliminate the diverter valve as a problem for over boost, the problem actually got worse with the new diverter valve, adjusted wastegate so it's fully closed at at 5.5 inch of vacuum now heading Max boost 24.5 PSI and even with throttle closure did nothing to reduce the boost on a 3000 to 3500 RPM pull. stock MAP sensor.
with stock diverter valve and stage two plus 91 octane tune, would see a peak of 24 psi boost on initial throttle opening, then would taper down below target boost, now it's maximum boost throughout the pull, even with throttle closure.
I welcome any ideas.
 

machinehead

New Member
Dec 11, 2020
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What issues were you having before you adjusted your wastegate rod? What turbo are you running?I assume it's not stock hitting 24.5psi.
Overboost has always been the issue since tuning. Yes 24 psi on the stock turbo, but only for the inital throttle response, then it tapers.
 

Zeezul

Lurker
Nov 26, 2016
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Holiday, FL. 34691
Overboost has always been the issue since tuning. Yes 24 psi on the stock turbo, but only for the inital throttle response, then it tapers.
Have you tried a new map sensor and/or throttle body actuator? Also, are you hitting 24.5psi in 3rd gear into 4th as well? Somethings definitely going on with your throttle body hardware or it's a tuning issue.