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  1. #1
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    94 zj ecu turbo tunning help ?

    last year I planned on turbo charging my 94 grand cherokee 318 v8. I bought a GT35 turbo, and planing on setting it up after my punched out cat, BUTTTT with all the research I've done and ****ing headaches, I can't find out how to tune the computer? The best Idea I have is to a, get a computer/ wire harness out of a 98 dodge ram or make it carburated. if any of you have an easier way PLEASE shoot. thanks guys..... Kevin

  2. #2
    Forum CONDUCTOR Man Z88Z's Avatar
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    There never really was anything available for OBD1 besides the MP PCM (Mopar Performance engine computer) which is fairly limited

    Your best/easiest/cheapest routes might be to go with either the OBD2 Jeep/Dodge PCM or go with MS(megasuirt) or an aftermarket setup. I believe MS is considerably cheaper than FAST, ACCEL, etc.

    B&G did offer custom flashing of OBD1 PCMs for a while but I believe it turned into a "maybe, sometimes, if they feel like it" kind of thing - plus you'd have to send it out to them, and send it back to them for any additional modifications for changes or if the tune wasn't right etc.


    Updating to the OBD2 Jeep/Dodge PCM and tuning it with SCT might actually be a good way to go, but I'm not sure exactly how far you have to take it to get it to "meld" with the OBD1 wiring. Still a bit of work to it I think...

    We did have someone (cmsch180) that was planning to do just that and seemed to have worked out most of the problems with mating the two systems (OBD1 and OBD2) but I don't think he's posted in a while.

    Among the problems were: I believe you have to double up on some sensors to satisfy both the OBD1 dash cluster and the OBD2 PCM. OBD1 cluster gets straight analog input (I think that's the right way to say it) to power oil pressure, tach, etc - whereas on OBD2 Jeep clusters that info comes from the PCM through a databuss.

    That, and we weren't sure whether or not the OBD1 security system would be able to disarm the OBD2 PCM. I believe OBD2 PCM gets it's arm/disarm signal from the BCM (Body Control module/computer) and no one was ever really sure if the OBD1 signal would disarm the OBD2 PCM - but I think if you use the Dodge PCM without the security feature programmed in it might not be a problem. (Dodge doesn't use a BCM)

    FlyinRyan does SCT tuning - he might have a better idea of what's involved in some of that.

    I'm finishing up converting my 93 to OBD2 but I went the really hard way and just converted the whole thing to 98 spec front to rear. But to do that you pretty much have to go with late style door panels so you can use the late ZJ door modules. ya there's a lot of BS involved in doing that.


    You could go the carb route, but you'd have to work out a way to keep some of the sensors in there to operate the OD/lockup on the 46RH. Simpler than if you had a 46RE but still some work to it - although someone does make a kit that will operate OD/Lockup on the RH with no computer at all! I believe that's PATC aka transmissioncenter.net or something like that.
    Last edited by Z88Z; 05-11-2013 at 02:02 AM.

  3. #3
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    Short of a standalone, your best bet is to swap to OBDII. I am working with a customer now making this transition in a YJ , but that is a different animal, and he is not concerned with CELs and such, he just wants it to work. Not everyone can afford that kind of freedom.

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    Yeah i think ill go the wrought or swapping for an OBDII. probably out of a dodge truck of sorts? newer the better I've heard? I'm not quite sure yet but i may just swap the 318 for a 415. but if i did this, id make it manual. $ is in volved for that so i may stick that plan for the future. I did an 2WD axle swap on'er now and setting er up for race. i appreciate the imput guys, I may just mess around with this turbo somemore on this engine? its just been a pain in the ass! O yeah, what size injectores would you reccomend? I've got 24LB but believe I'd need like 34/36LB? + an additional inline fuel pump? probably run 10 12 LBS / boost.

  5. #5
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    Quote Originally Posted by 94jeepgrandcherokee View Post
    Yeah i think ill go the wrought or swapping for an OBDII. probably out of a dodge truck of sorts? newer the better I've heard? I'm not quite sure yet but i may just swap the 318 for a 415. but if i did this, id make it manual. $ is in volved for that so i may stick that plan for the future. I did an 2WD axle swap on'er now and setting er up for race. i appreciate the imput guys, I may just mess around with this turbo somemore on this engine? its just been a pain in the ass! O yeah, what size injectores would you reccomend? I've got 24LB but believe I'd need like 34/36LB? + an additional inline fuel pump? probably run 10 12 LBS / boost.
    Depends on how functional you want it to be. I am speculating here, but my thoughts are if you just want OBDII engine control, a Ram PCM and harness would likely be your best bet as many came with few options. If you wanted something that would be most compatible with your ZJ though, I would imagine a OBDII ZJ PCM/harness would be the best plan of action, and then flash the trans out of it via SCT . On that note, I'll know more about flashing the trans out this week as I'm tuning 3 different Dakotas that are pre-2000 (i.e. same PCM essentially as the 5.9 ZJs) and have either gone TKO or 727 this week.

    Injectors are going to be heavily dependent on boost level, displacement, fuel system....

  6. #6
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    most of my experience with doing this is with VW's, How hard would this be with a ZJ? just the motor and maybe will show a cel so I know if something's going wrong. I am looking for a new to me zj and a cheery 94 5.2 came up along with a nice 5.9.

  7. #7
    Forum CONDUCTOR Man Z88Z's Avatar
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    Quote Originally Posted by impulse byer View Post
    .... I am looking for a new to me zj and a cheery 94 5.2 came up along with a nice 5.9.
    Well if you want easy, it's a no brainer.

    If you get the 5.9 (or any OBD2 96-98) you can go right to tuning via Ryan ^


    The early ZJs might be cheaper but then you have to go through all that ^ wiring and/or hybriding just to get it to where it's OBD2 and tuneable.

    BTW does this thing have to pass any emissions inspections? Ryan can probably accommodate you if it does - but way easier if you don't have to deal with it.


    If you're going with something other than the RE trans on a late ZJ, you can use the PCM from a Dodge truck (seems some work and some don't - or maybe people just got bad PCMs from the junkyard) or you can just let Ryan do his thing on the Jeep PCM as he's pretty sure he can delete/shut off, the auto trans stuff. (from what I've seen though, trans related faults don't affect engine performance - but see what Ryan says on that)

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    1998 Grand Cherokee 5.9 Limited
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  9. #9
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    Quote Originally Posted by Z88Z View Post
    Well if you want easy, it's a no brainer.

    If you get the 5.9 (or any OBD2 96-98) you can go right to tuning via Ryan ^


    The early ZJs might be cheaper but then you have to go through all that ^ wiring and/or hybriding just to get it to where it's OBD2 and tuneable.

    BTW does this thing have to pass any emissions inspections? Ryan can probably accommodate you if it does - but way easier if you don't have to deal with it.


    If you're going with something other than the RE trans on a late ZJ, you can use the PCM from a Dodge truck (seems some work and some don't - or maybe people just got bad PCMs from the junkyard) or you can just let Ryan do his thing on the Jeep PCM as he's pretty sure he can delete/shut off, the auto trans stuff. (from what I've seen though, trans related faults don't affect engine performance - but see what Ryan says on that)
    Well I do have etesting and here's the trouble 1997 and older only get a 2 speed idle test no scanning . 1998 and newer get a "readiness check" the plug in the obd2 port and check your vehicle’s emissions control systems are working properly. sorry to hijack.

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