LukeG

My current wiring harness is a bit of a hacked together mess with electrical tape. The coolant sensor can go from reading 200 degrees to 12 degrees simply by moving it around. Super sketchy and I'm fed up with it. I didn't wire this car up, but I'm tired of having issues with the wiring and winter is coming so it is a perfect time to redo the whole rat's nest.

I want to redo it right. Mil-spec would be awesome!

What wire should I be using and where can I get it? Something high quality with a lot of color options would be great. I think most wire available is cheap garbage and I'm okay with spending more for higher quality. I am also very good with a soldering iron.

Should I be soldering and using epoxy heat shrink or using a heat gun and butt connectors with solder in them? Or something else?

Is it possible to buy new single connectors if one looks rough?

Any advice on laying it out and removing things that are not necessary?

I absolutely despise electrical tape. That **** is disgusting. What looms do you guys recommend for protecting the wire bundles?

I know some of this is in the build threads on here and I'm digging through them now. Thanks ahead of time for any advice and PosCats will be generously awarded!!!

LukeG

Found an old thread on here with lots of good info and answers.

https://www.miataturbo.net/engine-pe...harness-73932/

So it seems like self-fusing silicon wrap instead of electrical tape is a go.

Removing anything unnecessary is not recommended.

Love the idea of getting a late model car's shiny new harness from the junk yard for the wire. Genius!

The McMaster Carr loom is apparently pretty good.

I was able to find new connectors on Rock Auto. Sweet!

Still curious about the butts... soldering and using epoxy heat shrink or using a heat gun and butt connectors with solder in them? Or something else?

AA-Ron

This is be your best reference on how to construct a motorsport wiring harness https://www.rbracing-rsr.com/wiring_ecu.html

I personally buy my wire loom, connectors (non Mazda), heat shrink, etc. from ProWire USA https://www.prowireusa.com/

I will warn you, building a harness isn't cheap. You will also need special crimpers if you want to use Deutsch connectors, which are standard in a motorsport wiring harness.

LukeG

PosCat awarded!!! Thanks a ton!

Holy **** that rb racing reference page is amazing!!! Will be spending my weekend reading that.

LukeG

Concentric twisted wiring... mind blown.

AA-Ron

@ThePass did a good writeup on how he wired his car. The only thing I would change is the Weather Pack connectors he used but I believe he is changing them over to Deutsch connectors too.

https://www.miataturbo.net/engine-pe...5/#post1399462

shuiend

iTrader: (24)

What year car do you have? What ecu? Diyautotune has a nice bundle for sale if you have a MS. Also you should not solder any wire in the car. Everything should be crimped together. Ballengier Motorsports should have a ton of the connectors you need.

My last piece of advice is goodluck, and don't **** up.

LukeG

Haha, yeah. ******* up is not an option.

Thanks on the crimping advice. Car is an Exocet with 1999 1.8L and Hydra 2.7.

Just out of curiosity, why is everyone saying not to solder? I figured that would be the best connection.

Roda

The argument is that solder/wires may become brittle and break in the high vibration environment. Most agree that crimping is better if done properly with good tools and parts. I used both Weathertech and Deutsch connectors on my MS install, and useable crimping tools can be found for reasonable prices. The Deutsch are better quality and seem to be the go-to connector these days.

If you do solder, use solder with lead (more flexible), use shrink wrap to support the joint, and properly strain relieve the wires. Also start with a good mechanical joint like a "NASA/Lineman's" splice.

Wiring is tedious work, but when done properly should last well.

As far as looming, I used the self adhering silicone tape and Painless split woven wire sleeving and am pretty happy with the results.

hornetball

iTrader: (4)

Solder is brittle and will crack under vibration. NEVER solder a connector end -- always high quality crimp. Good crimping tools are readily available and much cheaper than they used to be. Back in the day, you had to go to an aircraft parts store.

As for mending a wire or making a butt connection in the middle of a run, I always twist, solder and heat shrink those. Those don't see vibration or strain. Won't be an issue.

+1 to a quality harness is not cheap. If you have a Mazdaspeed membership, you can get brand new OEM harnesses with all connectors for many years of Miata. That might actually be a less expensive way to go and will save you untold hours and be OEM quality.

Roda

Very good points. I should have been more specific that connectors should NOT be soldered.

LukeG

You guys rock. Thanks for all the great info!

ThePass

iTrader: (3)

Regarding the frustration with inaccurate gauges, have a look at my old thread: ITT We discuss high quality gauges

Regarding custom wiring...

Read the RBRacing link two or three times, then google all the questions you have about details they didn't cover completely and after many more hours you should have most of what you need to know to build a proper motorsports harness.

The harness I built is entirely mil-spec except for the connectors. I originally shied away from doing Deutsch connectors because of the cost of entry for the tools (easily $500-$1,000). Then I discovered that Prowire USA (who I get 90% of my materials from and highly recommend) sells the pins for the Deutsch connectors in two versions: the traditional and truly motorsport grade "socket" style which takes the expensive barrel crimper tool, OR a more economical "stamped" style which can be crimped with a simple "B type" hand crimper like THIS ONE. I'm now moving over to DT and DTP connectors for everything new, and will go back and change out all the connectors on my existing harness at some point when I really feel like cursing at myself for several hours.

Keep in mind it's a tedious and expensive project. Assuming you want to do things right and not cut corners, there are a few places you can opt for something that costs a little less than the really baller version but it still adds up very fast. Ask someone about materials they think they need to do wiring and their list has about 3 items. The real list is shockingly long, especially when you start to look at all the different sizes of each thing that you need for different diameters, etc. The process of specing out and building your own harness will make you really understand and appreciate why motorsports wiring quickly adds up to thousands and thousands of dollars per harness between material and labor. To build my chassis harness and the other little auxiliary harnesses I did cost well over $1,000 because of all the various sizes of each material needed, tools I was buying for the first time, etc. and it was a 100 hour project.

Also, you need to write down everything. See the wiring lists I made in my build thread for an example. One wrong wire could lead to hours and hours of banging your head against a wall when things don't work right and you can't figure out why.

Davezorz

iTrader: (2)

The concentric twist is cool because the finished cable is limp and you will be able to route it easily in the car. The wires no longer want to wrap themselves in a tight coil when you are done. I was a little surprised how long it took to do, and I was just making a simple harness from the Passenger airbag to under the steering column. If your ego can handle it, ask your wife/girlfriend for help. Apparently the process is similar to braiding hair.

I used mostly the DIY Autotune wire bundle, which I believe is TXL type, I bought a few spools of TXL for any additional circuits I need. I also tired out a little bit of MIL-W-22759/16 that is recommended on the RBR racing page, and the difference in weight/bulk between it and TXL is much greater than I would have thought.

Another reason for Crimps over solder is that it can be hard to know when you have made a bad solder joint. If you take the time/spend the money to get the proper crimping tools and supplies (correct terminals, correct crimper settings, ratchet style crimper), it is much harder to mess up and pretty easy to check for problems.

engineered2win

I would recommend using something like the Lemo B-series connectors for anything that gets connected/disconnected a lot. They are rated for >5000 cycles, so they won't wear out anywhere near as quick as a standard motorsports connector. The Deutsch DTM is only rated for ~100 cycles, for example. They're available in solder cup or crimp connectors. The B-series solder cups are standard for datalogging onboard automotive crash tests and I've never heard of a test fail due to a failed connector (which is a big deal when a test is >$50k). I try to use them for stuff on the race car like camera power connectors, CAN ports, ECU comms/ethernet ports, etc that gets used multiple times over a race weekend. They're too heavy and expensive to use for generic engine harness connectors, but have their purpose and work reliably. Before anyone cries about soldering, use the crimp terminals if that makes you sleep better at night; they're industry standard for automotive and aviation testing and don't fail unless the strain relief is incorrect.

afm

iTrader: (3)

Just as an aside, a Daniels AF8 with a turret head that will handle 12-26AWG DTP, DT, and DTM solid contacts lists for $377, so it's not quite that insane

ThePass

iTrader: (3)

Can this also do Deutsch Autosport contacts?

afm

iTrader: (3)

Yes. Ideally you'd use a different $100 turret for smaller AS contacts (TH1A does all size 12/16/20 DT-series and some AS) but the results with the wrong turret will be miles better than the results of using a universal Delphi-style crimper on stamped contacts, since the indents will take the same form for a given gauge setting for any contact, regardless of which positioner is used.