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Thread: 97 Jeep 2.5 Turbo - Srt4 MAP- Positive pressure wall

  1. #1
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    97 Jeep 2.5 Turbo - Srt4 MAP- Positive pressure wall

    Ive turbocharged my 1997 Jeep TJ 2.5 4cyl. 95-98 JTEC

    New to tuning.

    Commanded Open Loop- Temperature Increased- O2 sensors off
    Full and Part Throttle PE off
    Map Multiplier halved from 244 to 122
    As per Map output voltage at KOEO calculates to 98kpa baro
    Ive gotten the jeep to run and idle, still rich afr approx 12.5 but takes the throttle well and revs freely in neutral.
    When i drive it, and log my afr is rich until I lean on the throttle past 30% or so and spikes super lean.
    This spike coincides on the log with a drop in Injector pulse width.
    My Base fuel Table is set slightly above the stock tune at the same new calculated pressure level.
    This lean out is at 30% inj duty cycle and right at KOEO Barometric pressure.\

    What am i missing?
    Thanks In Advance if someone can help me out.

  2. #2
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    How exactly did you get it to run with the 2 bar? I halved my fuel and spark tables to make it run with the 2 bar and it wouldn?t run at all.
    I?ve got a 99 Jeep Wrangler 4.0 turbo

  3. #3
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    The map multiplier must be reduced and now your base fuel table must be scaled down. If it is halved then barometric pressure will be at say 52kpa now instead of 105kpa. You can play with it to get better control of pre boost drivability if you are only running low boost.

    I still can?t get mine to run properly once it comes under load. So I may have a problem with my map or wiring.

    Let me know if this works for you please!

  4. #4
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    See I tried that and I was running into idling problems. It would start than die. All I did was halve the spark tables and fuel tables to match the halved MAP data that was present. I can shoot you my tune file if you want.
    Also does your VCM scanner work on your jeep? I can get my jeep to perform only in wide open throttle in boost right now my changing my WOT enrichment FYI

  5. #5
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    Can you post current tune and data log?

  6. #6
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    Current good running tune. I cant log anything, scanner does not work for my jeep.
    Attached Files Attached Files

  7. #7
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    Are you commanding open loop? I have my 02 sensors off. And no PE, I will post a tune tomorrow, it?s late here. Cheers

  8. #8
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    I am not commanding open loop. The idea is to stay closed and when I get the 2 bar to work I want to make a closed loop tune. I have the multiplier factor I want to use now so when I get the jeep to run with the 2 bar I will input the wot multiplier in the tune and ramp from there.

  9. #9
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    @MSJeepTJ Where is the MAP Multiplier at?

  10. #10
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    you are running bigger injectors right?

  11. #11
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    I have tried the map multiplier at many different ranges. From 108 to 195 and in the 140 range seems to have worked best so far. I?m still running the stock injectors, do you think that?s a problem? I can only see 30% duty cycle peak on my log. Although sometimes the pids are unreliable

  12. #12
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    your best will be to just do 122, and change the map normalizers to reflect the new scale, stock injector only go so far, you should install bigger injectors

  13. #13
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    I found out my main problem is the computer keeps going into limp mode because of too low voltage when koeo. Is there a way to disable this?

  14. #14
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    Quote Originally Posted by MSJeepTJ View Post
    I found out my main problem is the computer keeps going into limp mode because of too low voltage when koeo. Is there a way to disable this?
    low voltage from the map?

  15. #15
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    you need to post tune file and log

  16. #16
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    This is my current tune with stock map and a check valve to bleed the boost to the map.
    Its crude but its where i'm at right now.

    Thank you
    Attached Files Attached Files

  17. #17
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    Mack Jeep 1997 2.5 MS TUNE 4.5.hpt

    This is my 2.25 bar map attempt

  18. #18
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    MSJeepTJ post your stock tune as well so we can see what you did. I've never seen a 2.5 JTEC file besides yours.
    If in doubt, multiply everything by 1.1.

  19. #19
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    If you are still hitting the wall... I was doing the same.

    First... for giggles, unhook the battery after every reflash. I had an issue that between flashes, the map voltage would go haywire unless I unhooked the battery each time. This solved a lot of issues and let me get back on track.

    Now on the positive pressure side of the map.. fatten it up a LOT. Positive pressure takes a lot more fuel and it'll feel like its hitting a rev limiter almost. My last file before I popped the headgasket on my 4.0, it was finally taking some boost but at ~3psi, injector duty cycle was over 70%.

    Now throw another +15% to the 0 to positive pressure side of the map. You may want to pull some timing out of it as well for the time being just to be on the safe side. Going lean coming into boost with timing that is fairly high for boost.. tends to pop headgaskets. Ask me how I know. Lol

    If you are coming into boost and AFRs don't drop below 12.. let out of the pedal. I would shoot for mid 11s.. 11-11.5 seems to be the safe area. Even with a TON of fuel thrown at mine, it was still coming into boost at 12.5:1 on the wideband (which I believe is what cost me the headgasket). I've probably added 40+% to the positive pressure side of the map by now.

    Reset your battery.. then do KOEO log of the MAP sensor. I'm currently running the multiplier around 190 which basically split the map in half. Idle would be around 25-30kPa.. KOEO was around 65kPa... That left me with 65-105 for boost. I may need to tweak that a bit but I'm only planning on 5-6psi when done.
    Last edited by Mr4btTahoe; 06-08-2020 at 01:49 PM.

  20. #20
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    this is related to baro changing after each key cycle,the scale multi set to 190 giving a reading at koeo 44.8 kpa with a gm 2bar map , i change map 5v lo limit to 50 and is working, I also made changes to min valid initial baro to 6.5898 KPA and default invalid Baro to 55.3657