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

Shameless self-bump. ANY ideas? At this point I'll try anything that doesn't involve tranny hookers.

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.