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Thread: MPS 3 Gen 2 Nose dives / cuts out on WOT

  1. Default MPS 3 Gen 2 Nose dives / cuts out on WOT

    Hi guys hope you can help me my car seems to cut out pretty harshly on WOT in 3rd or 4th gear at about 4k-5500 revs.
    I have an TIH and what looks to be a SRI as the only mods. I initially thought it was the stock tune so I bought myself an APv3 and re flashed with stage 1 +98 ots.
    My car is a lot more responsive and goes a lot quicker but it kept the harsh cut out.
    I am unsure what's best way to diagnose this any suggestions?

  2. #2
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    Probably over boosting? @LittleredMPS, you read this on my AP down at the castle.

  3. #3
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    Use the ap to get logs?
    Guessing over boost or hpfp not keeping up
    Last edited by SarcasticOne; 02-08-2014 at 04:24 AM.

  4. Default

    I'll do data log sometime this weekend. Just say it is over boosting what would be the fix

  5. #5
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    After checking HPFP psi like Sarcasticone said, you may have a air leak.

  6. #6

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    Check plugs/gaps also. If the above suggestions don't help

  7. Default

    Woo! finally got some logs of it happening. Please let me know what you think and how I could stop it from happening

    Thanks for all your help in advance
    Attached Files Attached Files

  8. #8
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    HPFP pressure is fine. Looks like boost cut, but why? check for a air leak.
    Last edited by RedDjinn; 02-08-2014 at 10:48 PM.

  9. #9

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    Lots of boost there for a stage 1 + sri tune. Hitting 19psi by 3300 rpm? Doesn't a stage 1 target like 16? Hitting boost cut seems likely.

  10. Default

    Lachlan - yes thats what it says on the OTS comments, how would i keep it down

  11. #11

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    Can you post which exact map you are using? Maybe download a new one in case something got messed up/corrupted/mislabeled?

    The tune should target a certain boost at a certain rpm (you can look at the 'boost target table' if you downloaded ATR). Looking at a S1 tune, the boost limits have throttle close at 17.5psi and fuel cut at 18.5psi by the look of it. Looks like you might be getting fuel cut when you hit over 18.5psi? Someone with more ATR knowledge then me can probably explain how these limits interact.

    If you are consistently over boosting then there is probably something mechanically wrong that you need to find and fix, rather than a problem with the tune. Try RedDjinns suggestion first, boost leaks suck.
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  12. Default

    Attached is the map I've used (standard OTS) I put it through ATR and it corresponds with what you said regarding target boost & fuel cut.

    I'll check for leaks today, hopefully find one and that would be the fix. If not would upping the boost cut to say 19.5 be a problem the logs show it sits at just below 19.5, or would that be a silly idea?
    Attached Files Attached Files

  13. #13
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    datalog 2 fuel pressure drops below 1600psi briefly at 4.131... but as has been said, it's a boost cut issue...

    you could raise boost cuts (from 18.5psi) but i'd suggest a slight lowering of wastegate duty cycles

    Click image for larger version. 

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    select from APP from 68.75% to 100% in the RPM range you want and decrease it by 4-5 (press "-" to lower it by 0.5), save and re-load the map

    other options is a basic custom OTS map (freektune or stratified) or a full custom tune (same companies once again)
    Newbie FAQ My Build Thread
    From stock, to GT3071, to substantially less modded, many lessons learned!
    3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings

  14. Default

    Will try lowering the wastegate duty cycle and let you know.
    Just out of curiousity what would that do in terms of performance / boost? sorry first time mucking about with tuning so I'm learning as I go and you seem to be a fountain of knowledge!

  15. #15

    Default

    Could upgrade your HPFP and then run a stage 2 map. My ots one targeted 19.5 may. Upgrade the internals regardless if you looking at playing with your tune

  16. Default

    That's my next mod for sure. Going to put together some money for it, how much you think it'll cost? I'll take a few pics of my intake as I have no idea which one it is it came with the car lol. I'll probably start another thread in a different section once I get my tax return happy to dump it on mods lol.

  17. #17
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    Quote Originally Posted by iwannagiv View Post
    Will try lowering the wastegate duty cycle and let you know.
    Just out of curiousity what would that do in terms of performance / boost? sorry first time mucking about with tuning so I'm learning as I go and you seem to be a fountain of knowledge!
    In short, it reduces boost, both how quickly it builds, and the amount it can hold, have to find that happy point...
    Quote Originally Posted by iwannagiv View Post
    That's my next mod for sure. Going to put together some money for it, how much you think it'll cost? I'll take a few pics of my intake as I have no idea which one it is it came with the car lol. I'll probably start another thread in a different section once I get my tax return happy to dump it on mods lol.
    About 450 shipped...
    Newbie FAQ My Build Thread
    From stock, to GT3071, to substantially less modded, many lessons learned!
    3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings

  18. Default

    Just done a datalog after decreasing the wastegate duty cycle as suggested, still does it, looking at the logs looks like the peak boost got to 20+psi... Not happy.

    I will look into any air leaks tomorrow, any other suggestions I want to have this car run smoothly and don't want a rod shooting out
    Attached Files Attached Files

  19. #19
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    Check you plugs and plug gap as previously mentioned.

    Sounds exactly like a car I once had where its plug gaps were incorrect.

  20. #20
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    Quote Originally Posted by bd581 View Post
    Check you plugs and plug gap as previously mentioned.

    Sounds exactly like a car I once had where its plug gaps were incorrect.
    Nah, it's boost cut... Hitting 19+ psi for an extended period of time, map has cut set to 18.5

    Weirdly he dropped wgdc and boost went up... Am heading to work now, so will have to look when I get home to compare the 2 logs...

    However, I wouldn't stress too much, there's no knock being shown...
    Newbie FAQ My Build Thread
    From stock, to GT3071, to substantially less modded, many lessons learned!
    3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings

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