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Why is it necessary to rewire inj. harness to factory spec?

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  • Why is it necessary to rewire inj. harness to factory spec?

    Hi guys,
    If I am using high impedance 550cc rx-7 injectors with the 88na ecu, do I need to rewire the harnesses to factory spec or can I just run them off of 2 wires from the ECU?
    What is the point of rewiring it anyway? The ECU doesn't care if it has a Romulator plugged into it instead of the regular chip? Is it only needed if you are running low impedance injectors with dropping resistors and if fyes, then why?
    Thank you
    Viktor G
    13.729 @ 102.90
    http://z31.com/board/print_profile.php3?user_id=872

  • #2
    z

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    • #3
      Resistor location

      So if I am running low impedance injectors and put a resistor in series with each one, after the harness splits, I will be ok, right?
      I just don't want to revert to factory wiring because I have opened the harnesses up a while ago and cut out all the wiring that was not used to make the wiring harness smaller.
      Attached Files
      13.729 @ 102.90
      http://z31.com/board/print_profile.php3?user_id=872

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      • #4
        not sure how it works, but if you do that make sure to ohm the harness at the ecu. if you put 10ohm resistor at each injector with the post recall wiring it would add up to 30ohms and if you put 3 ohm resistors to keep the ohms low at the ecu, then the injectors are now at ~6omhs each. thats probably why you need to revert and do each one individualy. i think.

        alex
        Attached Files
        Must Go Faster, Faster Untill The Thrill Of Speed Overcomes The Fear Of Death.

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        • #5
          SupSay Z wrote: if you put 10ohm resistor at each injector with the post recall wiring it would add up to 30ohms
          no, but that's how you're supposed to do it, only I suggest lower ohms, my measurements of 87T vs. 88T yielded 7.6ohm difference... so anything between 5-10 will work, stay on the lower end if you can

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          • #6
            z

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            • #7
              zmech made me feel better about putting 10ohms in mine. Drove it today. quite fun...
              My beloved Z:1987 2+2 NA2T w/30a swap.
              My black sheep: 88ss parts car (pretty much stripped and gone)
              207k miles and counting. Turbo'd since 155k.

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              • #8
                resistors will create "lag" that's why I suggest lower ohms, and the reason you need any at all are precisely to avoid burning out the ecu, but as there is almost 8ohm difference between sets that's a big current delta, one that might be larger than necessary

                just fyi but the dodge caravan injectors were 14.7ohm which is even higher, so I'm sure when it comes to "high" and "low" they are all over the place

                dsm injectors were measured at like 2.4ohm so adding 10ohm resistors would be 12.4, 87T are 4.8ohm so you'd be at 14.8, unless you used smaller ones

                measure first then purchase

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                • #9
                  SupSay Z wrote: not sure how it works, but if you do that make sure to ohm the harness at the ecu. if you put 10ohm resistor at each injector with the post recall wiring it would add up to 30ohms and if you put 3 ohm resistors to keep the ohms low at the ecu, then the injectors are now at ~6omhs each. thats probably why you need to revert and do each one individualy. i think.

                  alex
                  Yes, I figure I would have to add the resistors at the 2 wires that are feeding the injectors at the ECU.
                  The injectors on post-recall wiring are in parallel, so if I add a 10ohm resistor to each one, that will only be 3.3ohm total drop (plus a little resistance from the injectors) and burn the ECU.
                  13.729 @ 102.90
                  http://z31.com/board/print_profile.php3?user_id=872

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