BTD New Reader
July 19, 2016 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
July 20, 2016 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
July 20, 2016 1:02 a.m.

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

AWSX1686 Reader
July 20, 2016 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 HalfDork
July 20, 2016 7:59 a.m.

LS1 swap time is the obvious answer.

BTD New Reader
July 20, 2016 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 UltraDork
July 20, 2016 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
July 20, 2016 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
July 20, 2016 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
July 24, 2016 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

You'll need to log in to post.

Also on Grassroots Motorsports

GRM Live on Wednesday, June 28: The Science Behind Fasteners

10 hours ago in News

They hold all of your work together, but do you know when to use each type of fastener?

Action Cam Guide

10 hours ago in Articles

Capture your on-track memories with today’s latest and greatest

Reader's Ride of the Week: Troyer Modified Hillclimber

11 hours ago in News

It's a circle track car that's been convinced to turn left and right, and go up hills.

You Need This: Track-Ready 1991 Mazda Miata for $5500

12 hours ago in News

What’s better than a Miata? How about a Miata that’s ready for the track?

MX-5 Cup Racing: Live on Your Screen This Friday and Saturday

3 days ago in News

Catch all the action of the Global MX-5 Cup race at Road America live this weekend.

How to Run Compressed Air at Home

3 days ago in Articles

A guide for installing an air compressor and air tools in your home garage.

2017 Volkswagen Golf SportWagen TSI 4Motion

3 days ago in New Car Reviews

Say hello to the Volkswagen Golf SportWagen TSI S with 4Motion. It comes with a turbocharged 1.8-liter engine that is ...

You Need This: $1600 Street Racer Ford Festiva

3 days ago in News

It already has a GRM sticker and everything.

Get Your Subscription Combo Deals!

3 days ago in News

Get both our magazines for the price of one!

Your Projects: smokindav’s VW GTI Project

3 days ago in News

Love a good MK5 GTI? You might enjoy this build thread.

Wing It: Simple Talk on the Complex Subject of Aerodynamics

4 days ago in Articles

Whether sleek, boxy or somewhere in between, all cars interact with the air while racing down the track.

2018 Acura TLX V6 A-Spec

4 days ago in New Car Reviews

Acura is introducing something new for the 2018 model year: the Acura TLX V6 A-Spec. It's the highest trim level ...


Grassroots Motorsports Magazine

Subscribe Today

Also get your instant access to the digital edition of Grassroots Motorsports Magazine!

Learn More