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Learn me something; ECU Power distribution, wiring schematic, custom wiring harness

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  • Learn me something; ECU Power distribution, wiring schematic, custom wiring harness


    So I am at the final leg of my VET swap and have done a fair bit of reading on wiring, etc. As it stands, I am on an ECUMaster standalone, have already spent way too much time getting comfortable making a patch harness and have tested the ECU and a few outputs. Everything seems to be working so far, so now I really want to dig into things.

    1) Power distribution setup. Essentially I need a power distribution block for +12V switch, Ground (I was initially going to the run several branches into 2 or 4, 14 AWG TXL wire tied directly to a crimped connector and bolted to the head), and +5V. One end of the spectrum is an ECUMaster or Haltech PDM, but those are circa $1500+, and I feel is unnecessary for a dual duty street/HPDE car. The other end, a simple fuse/relay distribution box. What does the SB recommend??

    2) Free/simple software for drawing up/laying out wiring schematic with appropriate symbols. Again, nothing too fancy and MS Paint I feel is a little.....primal for what I am looking for

    For a little context; SR20VET into a Z32 chassis. New sensors to include
    Haltech IAT
    LSU 4.2. wideband (that is what is compatible with this particular ECU)
    MAC 3 port for boost control
    H20 temp, Oil Temp, Oil Pressure sensors from ECU MAster
    Taarks Hall Effect sensor
    VVL/VTEC control (2 wire using a PWM circuit if I remember correctly)
    It's all being wired to a Mil Spec circular bulk head plug.

    I think that's it. Most of the sensors are straight forward being 2 wire.

  • #2
    I used a sealed Bussmann mini relay and fuse box. Easy and clean enough. I have all power for the entire car going through it.

    i did a wiring list by connector and wire color in excel with a simple wiring diagram for 12V, 5V, and sensor grounds in word art/shapes. Worked fine for me, and is easy to reference later.

    Dont let scope creep make an already big project turn into something you can never finish.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!

    DefSport Koni Sleeve and Spring Perch Buy!!!


    • #3
      Yep. Which is why a simple twin bussed fuse/relay box is what I am leaning towards. +12V, 5V and ground are all that matter. All other signal wires are pinned directly to he bulkhead connector.

      Mind sharing your spreadsheet (or link to where you got the busman)?? Seems that Amazone has a few options but WayTek also offers them cheaply. I am leaning to a bussed box for ease of everything


      • #4
        I got a bussed Bussmann box with 5 mini relays and ATM fuses on the other side. It used the same female connectors and seals as a Metripack 280 connector I believe, so I used some of those for higher power things like feeding power into the relay box and some of the outputs. I'd recommend making it all go to connectors so you can remove it for whatever reason without taking the whole wiring harness out of the car.

        The spreadsheet is nothing fancy, just lists ECU pinout, function, what color and gauge wire it goes to, and I put a length in another column to start building. For the diagrams, I measured out approximate branch locations, and labelled those, which is where I pulled branches off when wrapping. It all goes together pretty easily once you start at the ECU and go from there.

        If you're just doing a single connector's worth of stuff, not sure you'd need to go to that level of detail. Could just list the pinout of the relay box and connector and be done.

        Also, I didn't put 5V or sensor ground through the relay box - you want to only do power switching in the box. Let the ECU directly power your sensors via 5V and sensor gnd.
        '18 Chevrolet Volt - Electric fun hatch for DD duty!

        DefSport Koni Sleeve and Spring Perch Buy!!!