| Stock turbos, selin intake, pmuch full bolt ons, and a SZ tune. I've boost leak tested several times, car will hold 4-5 psi for 25-30 seconds until it tapers down to 1.5-2 psi. (No one is really clear if this is normal or not) It will hold the 1-2 psi almost indefinitely. I cannot find or hear any leaks, but i do hear some minor air turbulence inside the motor. The boost is VERY predictable for a lower duty cycle setting around 10-10.5 psi. It builds quickly and holds without any spike that I have seen. It's just when I try to get a setting for something closer to 14-15 psi that this happens. Engine has 99K on it, stock turbos had zero play, zero oil during the last inspection this past winter. No weird noises, zero smoke. Ton's of preventative maintenance done over the past two years b/c im sort of out of my mind. Car has been looked over and tuned by SZ, but didn't really have time to look at this boost issue, or it didnt show itself on the dyno. With a Blitz Type-R (compact version) I have tried gain as high as 15 and as low as 1. Duty/Set stays constant at 53. I have more pulls trying to tweak this then I feel like mentioning. 3rd/4th gear (partial throttle >3500rpm) --> Boost spikes to 16, immediately falls to 12, then picks up to 14 and holds til redline. 4th gear (starting ~3000rpm) --> Boost builds to 14.5, immediately falls to 11.5-12, then picks back up to 14ish and holds til redline. 2nd gear pulls have a massive spike to 16-17 even with the gain set at the bottom. Increasing the gain past 6-7 just causes a larger spike before the giant falloff in 4th. I have been trying to figure this out for months and it is driving me nuts. Anyone seen behavior like this from stock turbos ? It's not the end of the world, but I have a feeling the boost should respond differently. I can't really find any resources that help explain this.. been looking forever.
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