Procharger Debug: MAF Location, Tune or Other?

Discussion in 'Forced Induction - 5.0L V8 Engine' started by AZtrophy, Sep 11, 2019.

  1. AZtrophy

    AZtrophy Member

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    Hey everyone. I'm new to the S550 platform/the forum and was hoping to get some of the experts here to help focus my debug efforts.

    In my case there are a few things going on:

    1. On cold start, the car idles @ 750rpm but after ~20 seconds it dips down to ~500 and rises up to 1k+ before settling at 750 again. It may repeat the cycle at varying times thereafter.
    2. When warm, the idle still varies quite a bit with vacuum bouncing between -17inHg to -20+inHg & AFR between 13.x to as high as an instantaneous ~16.x, based on the gauge cluster readout.
    3. Under moderate throttle the car will begin to build boost and without modulating the throttle, will bounce back to somewhere around 3psi, never really seeming to rise above 6psi (again, at partial throttle). As you can imagine, the car bucks a ridiculous amount during this process.
    4. WOT seems to perform as expected though I just got the car so testing hasn't been exhaustive.
    I plan to have the car re-tuned to enable Flex Fuel, likely by Lund. Prior to doing so, I would like to have any potential hardware based issues fixed. Which leads me to the question... do you guys think the likely culprit here is:
    1. MAF located in FMIC
    2. Tuning related (ie. early tuning issues per the referenced thread)
    3. Vacuum/boost leak (I suspect that the variations in vacuum and AFR are more likely a symptom of the issue rather than the cause, but what do I know?)
    4. A combination of these
    5. Something else entirely?
    Thanks in advance!!

    [Background Info]
    I recently purchased a 2015 GT with a stage 2 Procharger (P1SC) setup. I also have a Charger Hellcat (PD supercharger vs centri) so I'm used to entirely different driving characteristics.

    The car seems to have been a relatively early S550 build (Procharged in June 2015) then sold to the guy I bought it from who only put ~2k miles on it over the next 3 years.

    I've been reading as much as I can on the forums and it seems that the early tunes had some bucking issues, but that was also fixed around the same time* the build was performed. *(June 1st per the referenced thread).

    Supercharger Config (P1SC Stg2)

    • FMIC MAF location
    • 4.13 pulley
    • Tial BOV (Q 50mm)
    [/BG]
     
  2. Roush05

    Roush05 Well-Known Member

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    The weird boost build and drop sounds to me like an issue with the bov and how it is actuating. Vacuum leak could cause this. My idle does a similar thing as your but I am not on the Procharger tune so I am not sure if it's related. MAF location doesn't really cause problems unless you are wastegated and even then only sometimes.
     
  3. Crackerjack17

    Crackerjack17 Well-Known Member

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    My stg. 2 runs perfect, idles perfect, etc. Lund tuned. Maf in intercooler. Stock procharger bov.

    Your on a 4.13 pulley? On pump gas?
     
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  4. OP
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    AZtrophy

    AZtrophy Member

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    I plan to do a smoke test tomorrow to check for leaks.

    I know that there are plenty of people running with a similar setup and no issues. I was leaning toward the tune since it was done so early but again, wanted to give the car the best shot at running properly before having Lund chase ghosts in the machine.

    I appreciate the responses. I'll update after the leak testing.
     
  5. ahl395

    ahl395 Well-Known Member

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    I would guess vac/boost leak or BOV issue. If you dont find anything there datalog and send to Lund.
     
  6. SheepDog

    SheepDog Well-Known Member

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    Sounds to me like the vacuum source to the BOV isn't hooked up properly or at all. The boost pressure may be opening the BOV prematurely if there is no vacuum/pressure source to the top of the valve. This would explain a slightly lean condition because you have a disconnected/broken tube to the intake manifold, and the issue building boost because there is no pressure on the top of the valve to help the spring hold it shut. Worth a look anyway. Any trouble codes?
     
  7. OP
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    AZtrophy

    AZtrophy Member

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    No codes and unfortunately, I didn't get to the smoke test today. I did however build the tester so it should be a go tomorrow barring any other complications.

    Ordered some Quik Latches too just in case I need to remove the front bumper and happen to break the clips. As you guys know, the BOV is pretty well tucked in there so this seems likely.

    Yup, so it's probably a good thing that I've been babying the car due to this other issue. Called up Procharger today and they estimate that it's likely making about 15psi at full boost. :shock:
     
  8. 80FoxCoupe

    80FoxCoupe Well-Known Member

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    I have ran a 4.0 on my stg2 p1sc on pump 93. I did add octane booster at the track just to ensure full timing of 18deg. Looking at logs without octane booster, may pull a degree at times or may not.
     
  9. sloride

    sloride Active Member

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    How much boost with that pulley? Anyone got a sense for what ballpark boost each incremental pulley change nets. I currently have the P1X on my 2016. Running the 4.75 pulley making about 9-10psi. Tune is Happily running 19deg of timing with 93 and about 10oz of Boostane per tank. What size pulley would I need for 11-12psi? Thanks
     
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  10. whatsup62

    whatsup62 Well-Known Member

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    Depends on what RPM you are taking it to - the 4.63 on your set-up should add approx 1psi. I have the D1X and running 4.5" pulley. On E85 and see 15psi at 7500 rpm.
     
  11. sloride

    sloride Active Member

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    I run it to 7500rpm as well. Maybe I’ll try the 4.63”. Don’t want to chance near 15psi on pump gas. Thanks!
     
  12. 80FoxCoupe

    80FoxCoupe Well-Known Member

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    No idea on boost numbers.
     
  13. OP
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    AZtrophy

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    The Procharger rep gave a rough rule of thumb of 1psi per 100mils/0.1" in pulley size. If that is indeed the case, then either the 4.63" on the low end or 4.5" would theoretically put you into the range you are after. (Assuming 6-rib based on 4.75" which isn't offered on the 8-rib)
     
  14. OP
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    AZtrophy

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    Smoke test was inconclusive. I don't think the volume of smoke making it through the system was sufficient for leak detection. Going to modify the DIY tester and try again, this time after pulling the front bumper so I can put eyes on the BOV.
     
  15. sloride

    sloride Active Member

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    thanks for the info just ordered the 4.5”. Not a big deal if a little to much boost for my comfort. I can always tailor timing since I’m tuning it my self.
     
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