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Ms3x install


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Well this'll be the next step and progression for my Z, so I thought I would start a thread talking about my MS 3X install. My intentions are to have MS 3X run my ignition on my triple Mikuni carbs for now. Eventually I will go fuel injected but now I'm working on putting a plenum together.


I have been studying the mega manual on a daily basis trying to figure out how I'm going to do my initial wiring. I do have a few questions if anybody can answer them about the wiring.


As far as the wiring for the fuse box on the main plug. The example schematic shows the coil on just one fuse; with a COP coils would you still have it on just one fuse?

The schematic also shows splitting the injectors between two fuses -will that work for our engine?


I plan on running wasted spark -coil on plug ignition, so I do I will wire the injectors like I do with sequential and use the software formatting to make it wasted spark?

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Batch fuel injection is a waste of fuel- okay:0

You might want to rethink that statement. Of course, sequential would be optimum , but batch works just fine.

I will eventually set up a sensor for the cam, but it is on the bottom of the list right now.

A wasted spark and batch injection will be light years ahead of my dizzy and carbs for now.

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For simplicity I would run one fuse for the coils and split it off into the six wires using a junction block or something. It's all up to you though, if you think you need 6 fuses and have the room for them, have at it.


I'm not really familiar with MS3x, I'm not sure if you can just use the software to run wasted spark COP. Hopefully someone from DIYautotune will chime in. I have a feeling you will have to wire them like you would for MS1/2, pairing 1+6, 2+5, 3+4 to output 1, 2, 3.


There's two fuses for the injectors because there's two injector drivers. To keep everything separate, I went with two fuses when I rewired my engine recently. I ran with a single fuse before that. 



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Thanks for the reply. The MS3x is capable of sequential spark and fuel, but for now it's all going to be batch- and that's where it gets a little foggy. I wasn't sure if I needed to spread the load of the circuits out to more than 1 fuse for the coils .

This was also my question for the injector power circuits; was there a reason for showing the injectors split up into 2 fused circuits ( 4 cylinder example on megamanual )

I know the MS3x will run wasted spark, but do I wire the coils paired like you said or is the wasted fire all done with the software.


Back to the megamanual

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I ran one fuse for six low-z injectors and one fuse for the six GM truck coils.

I believe I ended up with 1 7.5A fuse for the injectors and 10A for the coils,

but I may have that backwards.  I started with 7.5A for both and blew one

during a hard pull through 2nd & 3rd.  This is with full sequential ignition

and injection.


I chose to use one fuse for each due to a limited selection of compact

ATC fuse boxes.

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Thanks Sam,

I was just getting ready to post that I found the answer. It says in the manual to wire wasted spark COP the same as just COP. Like you said, it's all done in the firmware.

One circuit makes it easy for the coils.

Are you running 2 fuses for the injectors?


Yes, but I am running 12 high-Z injectors. You should be able to get away with 1 fused power supply.

Edited by Sam280Z
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  • 2 months later...

Well I haven't done much lately except for fixing squeaky urethane bushings.

I did manage to finish up a prototype(sounds official) for my D585 bracket. This is pretty much a finished product, but might need some tweaking once I install spark wires. It was tougher than I thought trying to find room for all this; plus the fact that Delco couldn't have made these coils anymore unsymetrical in shape.  I didn't want to reroute my heater hose and it will run under the bracket. The bracket attaches with the 2 bolts for the heater hose. I plan on using studs for mounting and it will be easier to utilize the block for grounding spots ,since there are so few.

I bought a complete set of coils and diced and spliced the harness to make a six banger set-up.The connectors just clear all obstacles.

  The spark wires might be custom or stock. The stock wires might work by just looping the extra length of wire-if you can picture that.


MS power; I have kept an old 82zxt harness that was in amazing condition and I have been canning parts from it. I have pictured what i think is the main starting circuit relays or the main relays off of the zxt. The fuse terminal block with the two leads I will use in line from the battery to the main relay. I'm betting it's a 60 amp for the zxt. The two relays mounted together should be perfect for the main and the fuel relay. The battery power will come from a 10 guage wire from the + battery.

I will use another ganged fuse block like the one pictured on the inner fender which will be powered off the main relay. That will be dedicated for the MS.

The ganged fuse block that is  already installed will be just for accessories since it is powered straight off the alternator.   


Question regarding ignition input. I stare at the schematic that was supplied by DIY and I am having trouble interpreting how the ignition should tie in. They show power parallel to the battery +. Are they just implying that you need a hot wire from your ignition for the relay? I might be over thinking this. 




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I have enough to make at least 3 or 4 more, but it's nothing special at all. Just 1.5" square aluminum notched with a hole saw to allow the round coil to sit flat. The bitch has been getting them situated that I can run the spark wires. This might not be my last version before it's all over. I need to get some stock wires from the JY and see how it goes. It would be nice to just order off the shelf than to make custom sets.

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