BTD New Reader
7/19/16 11:27 p.m.

To make a long story short:

Building an Exocet. Mechanically, it's pretty much finished. The only hurdle that's really holding me up is the wiring. I HATE wiring and the difficulty is compounded by the fact that the PO and a local shop managed to hack up the stock harness a good bit. This makes tracing issues a royal PITA. I'm also impatient and dislike reading wiring diagrams. This is holding up my whole build.

Other engines (looking at you Chevy LS) have dozens of options for abbreviated and stripped down harnesses designed specifically to get the engine running with minimal wiring. Example: LS Swap Harness. No power windows, no A/C, no emissions stuff, no stereo, no airbag modules. Just the wires needed to make the engine run. I want this so, so, so badly for the Miata engine but can't find anyone who makes such a thing.

Honestly, I'm shocked. I figured there would have to be plenty of market given the number of Miata race cars that would love to lose 20+ lbs of wiring from the car.

So, I come to the only place on the internet that knows everything about everything with a question:

Does anyone make a PNP harness for a Miata that includes only the wires required to get the engine running (and maybe lights/gauges)?

Dietcoke Reader
7/20/16 1:00 a.m.

Miata race cars don't use miata computers, so there is no need for such a harness. They will all use aftermarket management with its own harness.

Dietcoke Reader
7/20/16 1:02 a.m.

You're probably best off starting with a megasquirt setup and wiring the lights/signals/tails from scratch.

AWSX1686 GRM+ Memberand Reader
7/20/16 7:52 a.m.

Just give me the exocet, I'll make my own harness for it and you can have my 97 miata. Simple. ;)

Andy Neuman
Andy Neuman HalfDork
7/20/16 7:59 a.m.

LS1 swap time is the obvious answer.

BTD New Reader
7/20/16 8:11 a.m.
Dietcoke wrote: Miata race cars don't use miata computers, so there is no need for such a harness. They will all use aftermarket management with its own harness.

This still involves creating a harness from scratch, which requires either merging with the OEM harness or sourcing plugs to build your own. With the prevalence of something like a Megasquirt PNP setup, I'm just surprised that there isn't a pre-fabbed solution. I have no problem running an aftermarket ECU if that's what it takes, but that's still a lot of wiring that I would rather leave to a professional rather than DIY.

If I could buy a MS with a plug and play harness, not just a PNP ECU, I would do it in a heartbeat. AFAIK, that doesn't exist for the Miata - hence the post looking for one.

(EDIT: Jeez! Even DIYAutotune does a PNP harness for the LS engines Right here)

LS swap adds an easy $5k to the cost of the project.

Robbie GRM+ Memberand UltraDork
7/20/16 8:46 a.m.

If you have a hacked wiring harness, the easiest solution to get er running might be to just buy a complete wiring harness from a scrapper. I got all 4 NA harnesses complete and uncut (and even labeled!) with a bunch of parts I bought for an engine swap from a guy who buys and parts wrecked miatas here in chicago. I could probably even track him down if you need.

When I met him to pick up the parts, he was very knowledgeable. He could tell me all the plugs and whether they are necessary or not and would likely be willing to mark them for you, and then you just leave the rest unplugged.

Zeitgeist Reader
7/20/16 9:13 a.m.

I agree with Robbie. Get an unhacked harness and plug it in then at least enjoy driving the Exocet while you continue to look for an expert to help cut down your harness or a pre made harness. I too hate wiring and wire diagram tracing but my Exocet had a bad ignition switch I had to trace and I cut some of the extraneous stuff out already. It isn't as horrible as I expected but I still don't like it with more to go. Driving sure makes it worth while. Where are you located?

BTD New Reader
7/20/16 10:17 a.m.

Robbie, could be an option. PM sent!

I'm in Colorado, I've been chatting with Flyin Miata and they're an option that still on the table. Also talking with some local Spec Miata shops that are open to doing a standalone harness.

LanEvo Reader
7/24/16 8:20 a.m.

You can buy complete wiring harness kits from Painless and others. Not terribly expensive and a lot easier than building a chassis and engine harness from scratch

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