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Thread: LT1 24X 411 PCM conversion - all of us please step inside

  1. #41
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    I've been having issues for the past few years with getting a 383 LT1 setup to work right in closed or open loop maf with the LS1 ECM. No matter what i do the car fouls out the back cylinders really badly. We've searched everywhere multiple times for vacuum leaks and found nothing. The o2's will just randomly go crazy and cause huge fuel swings and always foul out 7 & 8. I haven't tried open loop SD yet because it's been quite a while since I've messed with the car but I want to get the thing running right so he can run some mile events with it. It seems to idle smooth and drive fine until it fouls out the plugs in a matter of 10-20 minutes.
    2000 Camaro SS M6
    11:1 Stock bottom end
    76mm Altitude compensator

  2. #42
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    JasonS5555 can you send me a copy of your tune. I have a 96 lt4 24x. Thanks

  3. #43
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    Quote Originally Posted by Nitroused383 View Post
    I've been having issues for the past few years with getting a 383 LT1 setup to work right in closed or open loop maf with the LS1 ECM. No matter what i do the car fouls out the back cylinders really badly. We've searched everywhere multiple times for vacuum leaks and found nothing. The o2's will just randomly go crazy and cause huge fuel swings and always foul out 7 & 8. I haven't tried open loop SD yet because it's been quite a while since I've messed with the car but I want to get the thing running right so he can run some mile events with it. It seems to idle smooth and drive fine until it fouls out the plugs in a matter of 10-20 minutes.
    i have found you have to run them in full SD open loop only. also work on your transient fueling as well. This will help the rear plug issue. As soon as fuel trims kick in , the car looses it;s damn mind.
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  4. #44
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    Does anyone have a base LT1 tune that I can start from, or even stock LT1 injector pulsewidth and offset tables? I just installed the 24x system and am starting the tuning process. I began with a combination of some tunes I've found out there but everyone seems to be using difference injectors and heads and the car is running like crap at idle.

    My car is a 96 LT1 with Headers and a K&N CAI.
    Thanks,
    Last edited by LT1 Formula; 07-09-2016 at 09:18 PM.

  5. #45
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    did you remove the 02 sensors from the system completely? running maf, or SD? 28 lb injectors?
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  6. #46
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    Quote Originally Posted by Area47 View Post
    did you remove the 02 sensors from the system completely? running maf, or SD? 28 lb injectors?
    02 sensors are still in the system, wideband is installed on bank 2 about 8in past the narrowband injector. SD right now, stock 24# injectors.

    I found the offset table for the stock 24# injectors from a 96 impala base tune that a friend of mine had. If anyone sees any issues or if this doesn't match your stock 24# injector offset data please chime in.

    96 LT1 Impala Battery Voltage (VDC) vs Injector Offset (?sec)
    VDC usec
    0 305
    1.6 305
    3.2 7782
    4.8 7782
    5.2 7782
    5.6 7782
    6 5890
    6.4 3754
    6.8 2991
    7.2 2502
    7.6 2045
    8 1770
    8.4 1556
    8.8 1434
    9.2 1312
    9.6 1160
    10 1038
    10.4 916
    10.8 824
    11.2 702
    11.6 580
    12 488
    12.4 397
    12.8 305
    13.2 244
    13.6 214
    14 183
    14.4 153
    14.8 122
    16.4 61
    18 0
    19.6 0

    Checked continuity for injectors/coils and swapped my coil packs from one bank to another. After cleaning the plugs the car runs smoother but I'm chasing a high idle issue now (1500RPM) even when commanded to 900. Car will barely run at 900 if I manually lower the IAC counts. Reset IAC and nothing changed. Checked for vacuum leaks but will check again tonight as well as for bad grounds. I did not change the cal during the process. I will post my log file when I get home from work.
    Last edited by LT1 Formula; 07-12-2016 at 07:29 PM.

  7. #47
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    per previous notation. remove the factory wideband sensors completely from the vehicle. Unplug them and put them on a shelf in the garage. You will not make the car run worth a damn with those in there, or hooked up to the ecm, period. you MUST run the car on wideband feed back trim error only. once the trim error is dialed in to where you want it. you're good to go.

    It will run like a whole new animal once it is dialed in correctly. {without 02 sensors}
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  8. #48
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    anyone ever have issue doing a SD tune and not getting proper map signal (kpa) with a 2 bar

  9. #49
    Senior Tuner Frost's Avatar
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    Quote Originally Posted by Area47 View Post
    per previous notation. remove the factory wideband sensors completely from the vehicle. Unplug them and put them on a shelf in the garage. You will not make the car run worth a damn with those in there, or hooked up to the ecm, period. you MUST run the car on wideband feed back trim error only. once the trim error is dialed in to where you want it. you're good to go.

    It will run like a whole new animal once it is dialed in correctly. {without 02 sensors}
    No idea what's happening there.... I've only tuned maybe 10 of these setups (and don't do it any longer because you can't get the time paid for) but outside of the 3 race cars, all of the rest ran closed loop without issue. The last few were big cam'd, high SCR strokers and they ran better than many LS1s do (as far as driveability here). Of the 7 street cars, 5 of them ran MAFs, 2 SD, and all were CL.

    I honestly have not seen the issue that you guys are talking about. I'm not saying that I don't believe..
    Steve Williams
    TunedbyFrost.com


  10. #50
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    Quote Originally Posted by Frost View Post
    No idea what's happening there.... I've only tuned maybe 10 of these setups (and don't do it any longer because you can't get the time paid for) but outside of the 3 race cars, all of the rest ran closed loop without issue. The last few were big cam'd, high SCR strokers and they ran better than many LS1s do (as far as driveability here). Of the 7 street cars, 5 of them ran MAFs, 2 SD, and all were CL.

    I honestly have not seen the issue that you guys are talking about. I'm not saying that I don't believe..
    The last two i did, both of them freaked when the narrowband sensors were plugged into the system. One was an Lt1 car from hell {giant cluster of poo} and the other was a 98 vortec truck. Both did not like the 02 sensors being plugged in what so ever. Both maf based actually. Worked better for resolution.
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  11. #51
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    Ever think of putting the 411 pcm o2 sensors in place of the old old sensors? acdelco # 213819 for a 2002? I know when I did a 1996 vortec swap, I checked, and the thing had the same o2 sensors from a 2002, and it ran fine. Maybe they aren't the correct o2s or a cheap offbrand o2 that the 411 doesn't like... I have good luck with the acdelco # listed..
    Thanks,

    Dustin

  12. #52
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    Starting to fool around with tuning my 24x-396lt1 in a couple of days.
    Ricardo
    1996 A4 FBody with LS7 swap

  13. #53
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    Hi, new to the site! Hope it is ok to post this question since I found this thread while searching for info for my issue.
    I have a LT1 383 with the 24x system and I am getting a P0332 knock sensor code. This is a bank 2 knock sensor code, and I understand the 24x is only supposed to use one knock sensor, so I have to assume this is a faulty code that was not taken out by the tuner ( I bought this already tuned and do not have the ability to change the tune yet). I figured I could install a resistor into the wire coming from the PCM tied to ground to simulate the 2nd knock sensor and keep the SES light from coming on. Does anyone know what the resistance is of the needed knock sensor and which wire to tie into on the PCM? I was told the PCM originally was from a 2001 z28.
    Thanks for any help!
    Last edited by drptop70ss; 10-13-2016 at 10:20 PM.

  14. #54
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    After recently doing a conversion on an LT4 Hot cam and using the 2002 L31 knock sensor and tables. I had to zero out {B6244}, {6246}, and {B6247}. I then reduced the entire {B6245} by 50% and {6250} and {B6255} entire tables by 75%. Knock retard now works properly.

  15. #55
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    Quote Originally Posted by Wickmtrs1 View Post
    After recently doing a conversion on an LT4 Hot cam and using the 2002 L31 knock sensor and tables. I had to zero out {B6244}, {6246}, and {B6247}. I then reduced the entire {B6245} by 50% and {6250} and {B6255} entire tables by 75%. Knock retard now works properly.
    Where are the tables you are referencing? I'm not having any knock issues except where you might expect to see knock. I used 2 sensors for a 96 impala SS.

    I am doing my 24x system now (finally) and when I went closed loop trims were off, bucking @ 1900-2000 and idle jumps around when coming to a stop. Wasn't doing any of that OL with the WB connected.

  16. #56
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    I referenced the tables in the post.

  17. #57
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    I was getting no knock reporting at all. Other tuners have seen the same issue. What worked for my set may not work for others. My particular engine is probably different than a lot of other engines out there.

  18. #58
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    I'm having a similar issue as one of the other posts here. My 7 and 8 are always darker than the others and I'm thinking they are just fouling.. the car will run great and then somewhere didn't he line it will run real bad. 7 and especially 8 are dark. Assuming this is causing my miss bc if i ride it out and get on the throttle hard it will clear up?
    Input?

  19. #59
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    Quote Originally Posted by Area47 View Post
    The last two i did, both of them freaked when the narrowband sensors were plugged into the system. One was an Lt1 car from hell {giant cluster of poo} and the other was a 98 vortec truck. Both did not like the 02 sensors being plugged in what so ever. Both maf based actually. Worked better for resolution.
    Mine runs great with the factory L31 02 sensors and closed loop! If you start with a LS based tune YOU MUST change the injector bank table to match the L31 van. The 02s and wiring also have to be in the correct location left and right. If those steps are not taken I could see the PCM trying to trim the wrong cylinders and banks and the engine running like poo!

  20. #60
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    To improve on what I said about the closed loop, I ran two years on a tune that was done with narrowbands only. Put a wideband on it and it was very close to being perfect anyway.