Measuring boost back pressure

turbovan said
Are these results even possible? I thought the best you could hope for was slightly less back pressure than boost pressure. Could the bung be experiencing a vacuum effect due to its proximity to the wastegate? Or maybe the calibration is off since it hit -9psi? I just don’t understand lol

Either way, there must be a significant difference vs your first text. Thank you for posting this!
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I agree. It doesn’t make sense and there has to be something else at play. I logged about 5 runs and all but one showed negative numbers like this BUT one did show like 2-3psi of back pressure. The calibration of the sensor hasn’t changed. Next steps are to enable boost controller and add a little more boost and see what back pressure readings are.