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Old 09-14-2010, 07:26 PM   #1
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Default Boost spike/creep gheyness

Hey guys,

I'm having a problem with boost rising ~3psi over its setpoint between 4900 and 6000 rpm. This only started occuring after I put on a cheap ebay MBC, but (to my eyes) my logs look pretty noisy in that region too, so I'm not sure if electrical noise might play a factor also.

On my current tune, I reach a steady 11 psi by 4k. The MBC and wastegate do their thing, no problem. Once I get to 4900 though, something happens to cause a 3psi rise that only persists until 6000 rpm. After that, back to 11psi again (well, a bit less; my wastegate source is still the fitting on the turbo, so there's some drop across the intercooler). I can't quite wrap my head around what's going on, especially since the overshoot is windowed - I can make this happen all day, but it only occurs between 5k and 6k rpm. On either side of it, everything's working the way it should.

I attached some pics of logs, one showing stable boost at 11psi and 2 showing the spike once I hit 4900 rpm. The third also shows the drop back down at 6000 rpm.

Can anyone shed some light on what's going on?


*Relevant info: 1999, -S kit, 2560, ebay I/C, mbc, and bov, MS2 in parallel with 550 low ohm injectors, wastegate signal at compressor outlet, MS map signal from rear of intake manifold
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Boost spike/creep gheyness-good-boost.jpg   Boost spike/creep gheyness-boost-spike-2.jpg   Boost spike/creep gheyness-boost-spike-3.jpg  
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Old 09-18-2010, 07:13 PM   #2
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Shameless self-bump. ANY ideas? At this point I'll try anything that doesn't involve tranny hookers.
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Old 03-17-2011, 05:21 AM   #3
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Hiiiiiiiiiiiiiiiiiiiiii nick!

I'd suggest an electronic waste gate that will stabilize without dumping unnecessary pressure.

As far as windowing i would talk to dr smith about that, he seems to know a lot about windowing.
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