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Old 04-21-2010, 12:11 PM   #1
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Default 91 Harness Build - Which parts needed?

Folks: Been trying to scale the fairly sizeable (for me at least) learning curve involved with assembling a Megasquirt for my 91 Miata. Trying to make sure I understand and am capable of doing this before putting time and money to the test.

My biggest stumbling block is building my own harness. I think Option 2 in the following thread is for me. (How to make and install your own Diy MegaSquirt.) I understand I need a 48 pin connector as discussed in this thread. (My harness(48 pin) differs on a -95).

Do I need to simply purchase the following two components and wire them up with the wiring harness from diyautotune? That seems to make sense from the wiring diagram provided by Braineack in the 90-93 standalone wiring section. (I first assumed I needed the 64 pin connector.)

(1) 26 Pin Female connector (174516-6)
(1) 22 Pin Female connector (174515-6)

Thanks in advance for the clarification and all your contributions to this forum.
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Old 04-27-2010, 12:56 PM   #2
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Are you doing a standalone or parallel setup?
If you are doing a parallel setup you will need all the connectors Brain has listed since you will be making a harness that plugs into the OEM ECU and the existing wiring harness. For a standalone you only need the connector that looks like the ECU so you can plug it directly into the factory harness. The DIYAutotune harness then connects to the male 64 pin and the MS.

I have done two other MS installs on completely custom kit cars, but this will be a first for me too installing it int my 91. I just ordered the connectors and actually got two of the mail connectors and one set of all the female ones so I will have enough to make a standalone harness for my 91 and a parallel harness for my 97. It also happened that all the parts together was just 61c over the minimum order amount. I got the connector from onlinecomponents.com. They do not list the shipping when you place the order, but I got my invoice today and shipping was 8 bucks from AZ to SC. I know I wante to know that before I ordered in case they charged me something rediculous for shipping. They were also the only place that I could find that had the connectors in stock.
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Old 04-27-2010, 02:03 PM   #3
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Relte: Thanks for the reply.

I'll be doing a standalone install but I like your idea of ordering additional parts to cover future installs especially since many places have a minimum order. Thanks for the source.

With your clarification and more time reviewing the instructions I think I now understand the process. I think I was thrown off by knowing that my 91 ecu connector wasn't a 64 pin connector. I just couldn't figure out how I would know which pins on the connector to wire to. I think I just need to ignore a couple of blocks on the 64 pin connector, use the relevant diagram at diyautotune and count the pins! Here's hoping I don't destroy anything too expensive.

Anyway, thank you for your response and good luck with your build.
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Old 04-27-2010, 04:27 PM   #4
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Have you considered the DIYPNP? I built one, installed it and had the car running on it in a little over five hours. Here is a picture of the assembled unit. I had it apart again to wire in the launch control and to enable the fuel pump relay, which you will also need to do when you plan to remove your AFM.

91 Harness Build - Which parts needed?-photo0129.jpg
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Old 04-27-2010, 04:55 PM   #5
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I keep going back and forth between a DIYPNP kit and a regular kit.

If I'm honest, a DIYPNP is probably the best solution for me and makes more sense for the very small additional amount of money required.

I'll step back for a few weeks and re-evaluate when I've had a chance for things to settle in.

Thanks for the suggestion. You've probably sealed the deal for me.
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