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Overboosting Mhd . v8 stage 2+

Discussion in 'Troubleshooting' started by White335xi, Jan 1, 2018.

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  1. White335xi

    White335xi Lurker

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  2. Cheezy

    Cheezy Lieutenant

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    I dont see any over boosting
     
  3. White335xi

    White335xi Lurker

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    around 3200 rpm i hit 15 psi when the boost target is set at 12.5
     
  4. Cheezy

    Cheezy Lieutenant

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    Yeah seems typical. You lag then you hit boost and you get a slight spike then throttle closures fix that and it goes back to normal. OTS Tunes cant expect perfection. Its probably not slowing you down any.
     
  5. RSL

    RSL Corporal

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    Boost mean is over 21psi at initial peak. It's probably how your running it (starting at 3100rpm in 4th gear), but if you have inlets or outlets, they're not helping the issue. It essentially goes from vacuum to full boost in 200pm. Might try 3rd gear instead and see if it has any better control, but yeah, OTS map is one size fits all, some better than others.

    https://datazap.me/u/ramirezmatthew/log-1514766041?log=0&data=3-5-6-18
     
  6. White335xi

    White335xi Lurker

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    Throttle closures happen when overboosting, So a custom tune should fix this?
     
  7. veer90

    veer90 Lieutenant

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    549
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    Rye, NY
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    e90 335i 6MT
    Looks like boost mean is measured at the charge pipe pre-TB, and boost is measured at the manifold post-TB. DME is doing its job closing the throttle with overboost.

    Have you messed with the wastegates / turbos at all?
     
  8. White335xi

    White335xi Lurker

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    No. But this is the 2nd motor on the car with turbos included. Stock turbos btw
     
    Last edited: Jan 2, 2018
  9. RSL

    RSL Corporal

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    I didn't check the IATs before, they'd be a potential factor if WGDC/PID was tuned at/for higher DA, but looked at earlier logs with warmer IATs and seems something else might be going on. What MAP sensor do you have and what flash-time options do you have selected?

    21.5psi boost mean flat line through 5000rpm @ 39% duty cycle on stock turbos isn't reality. Not only that, it stays at 21.5psi mean after you let off the throttle while calculated boost drops, so seems like either a MAP sensor reading problem or a conversion issue.

    https://datazap.me/u/ramirezmatthew...ata=3-5-6-18-31&solo=29&zoom=19-47&mark=43-41
     
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  10. White335xi

    White335xi Lurker

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    Oem map sensor, can a cracked o ring have anything to do with it? Also I have wasgate rattle fix for the options.
     
  11. RSL

    RSL Corporal

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    I assume you mean MAP o-ring. Doubtful, but should certainly replace it if it's torn or cracked. Maybe flash again without the rattle fix set first and double check no other flash time options are accidentally selected.

    The log you posted in this OP isn't that bad and looks like it could be somewhat normal initial overshoot for cold weather (denser air), but some of the ones from a week or 2 ago, boost mean (MAP readings) don't seem very plausible. Mostly closed throttle plate safety would help keep boost mean higher, but still seems like a lot. You might try a Stage 1 or non-FMIC map and see if anything changes with it or even go back to a v7.1 that seem to have less forceful meeting of boost/target. If nothing else, might eliminate the throttle closures and see if that's mostly or entirely the boost mean/overshoot problem.
     
  12. White335xi

    White335xi Lurker

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    Alright I’ll see if replacing the o ring does anything. Here’s a log from two days ago with the v7 stage 2 fmic. I’ll see if Changing the map to stage 1 or even stock & see if the issue remains. https://datazap.me/u/ramirezmatthew/log-1514848290?log=0&data=3-18-22&solo=3&mark=54-35-43
     
  13. RSL

    RSL Corporal

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    Same issue on v7 map, may just be too damn cold to work well with the OTS PIDs, which are probably tuned nowhere near your DA (~20F and almost 15psi ambient). Higher density = easier to boost = overshoot = throttle closure = larger pressure differential between the charge pipe and manifold.

    Try a stage 1 and/or non-FMIC map, but I think you'll have the same issue on most/all in varying degrees until it warms up or you get custom map with PID dialed in specific for your car/environment.
     
  14. White335xi

    White335xi Lurker

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    https://datazap.me/u/ramirezmatthew/log-1515105559?log=0&data=3-5-6-11-12-18-22
    stock map, "stage 0".. still same problem. Any other reasons that can cause this? Can a bad boost solenoid be it?
     
  15. dyezak

    dyezak Major

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  16. White335xi

    White335xi Lurker

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    t
    even if i flashed back to stock?
     
  17. dyezak

    dyezak Major

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    You probably wouldn't notice a thing if flashed back to stock either way. There's so much headroom on this cars in stock trim it takes a SERIOUS problem to become visible.
     
  18. White335xi

    White335xi Lurker

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    I still overboot while stock, i wouldn't think it would be a tune problem. Throttle closing too, not sure what to be looking for.
     
  19. dyezak

    dyezak Major

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    Oh dude, then you definitely have a problem with your dikfer.
     
  20. White335xi

    White335xi Lurker

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    Whats that?
     
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