Aftermarket Engine Harness
 

Does anyone know where/who would make an aftermarket engine harness for my '99 turbo motor?

The car is a full prep race car and only needs the engine harness and ecu plugs.

I have an extra factory harness, but I'm worried about cutting it apart and messing something up. I'm a nut and bolt/driver type of racer and not a fan of wiring etc.

Thx guys

No one.

There's nothing wrong with the OEM engine harness. Use it.

You either hack up the spare stocker and hope it works, or pay someone serious money for a custom one.

Spec miata guys would beg to differ.

Are they allowed to change them?

Spec Miata guy told me both the NA and NB Miata were "overbraked" from the factory and that I should ditch my "silly overwight 4 pot willwood calipers and enormous rotors" and instead run stock 1.8 brakes with Hawk Blacks.

Spec Miata guy told me I didn't need to ever check the shims on my solid lifter BP4W head.

Spec Miata guy told me to put Mobil 1 in my 5 speed.

Spec Miata guy told me that a stock ECU with the crystal changed out would give me better results than a megasquirt & wideband ever would.

In summary: So why don't you go ask the Spec Miata guys?

My :2cents:: Stock harness is fine. Get a wiring diagram and meter and cut out the shit you don't need/want and reloom it. Nothing is going to fit/work better than the stock harness.

If you feel the need to build your own, or pay someone a silly amount of money to do so, Ballenger Motorsports and Eastern Beaver can get you all the connectors you will ever need. If you built a "full prep race car" then something like an engine/ECU harness should be trivial.

step 0, buy a proper ratcheting crimping tool with multiple dies
step 1, buy all the OEM connectors you need with pins
step 2, buy motorsports/milsepc grade bulk head connectors with the correct amount of pins for things passing through the firewall
step 2.5, buy a power management system of your choice
step 3, buy proper automotive rated wiring in many different colors and stripe patterns and gauges, adhesive lined shrink wrap, and your choice of wire protectant material.
step 4, buy approximately 5 gallons worth of beer
step 4.5, acquire label making machine.
step 5, make time in your schedule enough to consume 5 gallons of beer and to wiring, make space to layout shit over 2 miatas worth of space
step 6, mix parts listed above in correct proportions.

SM guys are not held in high regard around these parts, so you're going to have to elaborate a little bit. What do SM guys not like about the factory engine harness?

I can see where he's going with this. Nothing is worse than trying to run a standalone on a wiring harness that some moron had previously fucked with.

And the factory wiring harness is larger than it needs to be.

However, if there's nothing wrong with your particular harness, then there's nothing wrong with your particular harness.

I've had issues with my factory harness. for a few reasons I believe.

1) It's going on 25 years old.

2) its been in the car for 320k miles

3) allot of time has been spent on tracks.

4) Its been fucked with, wires removed, re purposed, and added.

Exactly.

Each of those are things that would make me consider building a new harness.

All of them at once? New harness time.

I can tell.....There seems to be a growing contingent of people(myself included even though I don't race SM) that are having misfire/stumbling problems solved by replacing the harness. '99 is the most affected model. I have no idea if it "is" the harness itself or connectors or something else but replacing the harness "fixes" the problem. I'm sure many of them would replace their harness if they could.

My point being the oem harness may be ok but that doesn't mean one couldn't make, or have one made, that is better.

99-00 conectors that are in front of the valve cover are subject to bad connections, weather pack kit or better connectors solve that. Don't ask me how I discover that fact...

Redo the loops and put them near the firewall while you're at it.

You can buy a decent quality generic harness on fleabay or from summit for less than $200 - and that is for the whole car. An engine-only harness is likely to be a fair bit less.

Installation is a big job though and as was said, you end up having to carve up an OEM harness for the connectors and pigtails, or source new connectors which can be a challenge for some of the more unusual connectors.

My race car has a custom harness. I didn't build it but the PO must have spent weeks building it and putting it together. I probably wouldn't be so patient. I would hunt around for a good uncut harness, cut the unnecessary circuits out of it, and replace the dodgy harness with that. They are getting harder to find (especially engine, injector and ECU harnesses for certain models like 96-97 NA8) but they are still out there if you are patient and look hard enough.

custom wiring system
 

I dunno. I think a lot can be said for a custom wiring system, especially one with a single waterproof connection at the firewall that would be the only thing to disconnect when you take your engine out for work. Plus, we seemed to have left a lot of "extra" wiring laying around that could have been used as ballast. Or mouse food.

Thank you Cordycord for showing how much extra crap wire there is in these cars. Any chance you can tell me who made yours? Or would you make me one?

We make them in-house for the Catfish. Each one is different, so price is dependant on what's involved. Shoot me an email if you really are interested.

This is one of those things I go back and forth on.

1) Buy an unmolested wiring harness and yank everything not necessary

2) Over the span of a couple months, research and acquire the necessary motorsport centric connectors, wiring, heatshrink, snazzy loom, pins, firewall one port quick disconnect. Try to justify the baller RacePak Smartwire power control module. Run wiring to the trunk for superficial reasons and weight transfer. Cry as I wrap my brain around getting the lengths and routing 100% correct. Develop alcohol addiction. Pour gasoline on the car and dance around the flames in a fit of anger when everything doesn't work.

The OCD leans towards option 2. The sensible tells me not to fuck with it till I have issues and revel and seeing positive numbers in my bank account.

If you ever do Option 2, please take videos. :)

For the former portion of option 2 of course, not the latter!

Drunken mechanic YouTube videos could be a fun new series I could start... :rofl:

I'm slowly perusing most of Option 2 on my other project (sans racepack) and I believe you are about right on that one.

PCMs are baller but cost big $$$... If you do it right, you can use a standard blade fuse box with resettable blade circuit breakers, or even those breaker panels they use for RVs. Mount your fuse box or breaker panel in the dash so it is accessible and your circuits can be reset from the drivers seat.

Well wehre I used to work, MoTeC, we would charge around 5-6 grand for an engine harness.

Figure 3 grand in parts to do it yourself (Deutsch Autosport connectors, Mil-spec wire, DR-25 heatshrink, etc) plus a month of planning/work to get it all done.

So just use the stock harness is what I am saying unless you love wiring like I do haha.

$3k in parts for an engine harness wtf?

We don't work for MoTeC, so we can charge about half that price. :) In the world of used Miatas, this is big money. Hell, it's a spare car! In the world of professional racing, this is a weekend tire budget, or Ricky Bobby's bbq bill. If you're setting up one of Emilio's Race Pack systems it will cost even more. And that would make it even better. And will give you more options and accessories.

That said, most guys can get away with taping up their extra plugs...

Pm sent cordycord... Thx man

A lot of that is the cost of the motec power management system. But some of those detsch connectors are over $100 a piece. Honestly if I was going to rewire a real racecar these days it would have some sort of PMS, not sure it would be motec but it would have one unless it was a ridiculously simple car that required 8 fuses and 2 relays or less.

Ok that makes more sense. I was thinking just engine harness.

It looks like we'll be doing one with a RacePak SmartWire system soon. It makes this wire layout even simpler.

Yeah...simpler is the idea for sure.

I did a firewall connector on my car awhile back, excuse the wad of spaghetti that it turns into as I hadn't finished everything on the build at this point the picture was taken but I just wanted to protect the wires from chaffing as I moved things around.

https://www.miataturbo.net/attachmen...ine=1412831236

My best advice I can give is plan out everything you want to run in your car, and buy the right connectors the first time. Nothing hurts more than having to buy a $90+ connector twice...

Yep. Also think about future expansions that you even MIGHT want. Mostly things like data which can consume lots of ports. Or even move that off to a separate harness, and where to route that.
Even for a simple harness from scratch it's easy to break a grand in parts alone just when talking OE level stuff not even mil-spec that's standard on professional race cars. . I'm redoing some of the wiring in my car to make it more weather proof. $250 to delcity later I've got some of what I need, but not a single sensor connector yet.

1. This is a solid option but will take a lot of time, research and care. As the insulation ages, it tends to embrittle with time and the copper can corrode, sometimes invisibly (beneath insulation). Some connectors may require replacement, especially going back far enough. The older the car is, the less functional this option is.

2. This will cost you a TON of time, effort, planning & cursing. Figure over 100 hours for a typical inexperienced person to do everything. You will need to spend more time than you thought mastering crimping and more money than you thought in tools, connectors, sleeving, heatshrink, etc.

In trade parlance, the Smartwire system is a PDM (Power distribution module). They are fantastic where the Motec one is a benchmark able to control # of retries, amperage limiting, failure notifications. It has limp-home functionality to bring a car back to the pit/paddock during the race instead of outright failure. As a general rule, they exceed the scope of a low cost vehicle or street car.

Ballenger Motorsports could build a harness but this is a difficult issue. We could do a proper, made in USA harness and sell it for something like $1,200. We could do a little more volume and get an off-shored one made with some knock-off components for about half that. If we got 20-50 people together who were willing to make this choice and sign up for an identical harness, we could release a product. The Miata community is small, doesn't like spending money (except for a few select racers), and often wants a lot of custom variation. So I'm not sure on this point. Maybe a poll thread and checking with people. I suppose the Spec Miata people would want the product too.

At present we track Miata's and love them, so we offer product to make it easier for people. It isn't a profitable endeavor but Miata's are a lot of fun and some of the parts are also used on higher volume applications.

Yeah. In the pro world, often a tiny short harness for something like an ignition/injection subharness can run $5k using specialty products and methods.

The problem with getting a harness from you thats made for everyone is that we all have different setups and need different wires of different lengths and other varying requirements. Its not like jim bob's carb'ed camaro where there's thousands of cars out there with essentially the exact same wiring requirements.

+1

Even wiring from the same model year will be different based on the options list. 100 hours for a complete job seems a bit low, actually.

I know. Hence my word choice "and often wants a lot of custom variation."

It may be possible to subharness the sections that tend to have variation as a workaround. This and the year to year variation is the big problem to get around.

Yep. Also why I said "Figure over 100 hours" rather than figure 100 hours. It is a hugely larger task than the average enthusiast realizes in time, cost, labor, research, etc. I've seen skilled go,go,go type mechanics thwarted by this sort of project due to the planning & paperwork necessary. It requires several new skills and validation to get acceptable results.

There is sort of an open question of is there someone who has a product and then the issue of whether an individual should make their own harness from scratch. I think we at least covered the issues for the purpose of answering the thread.

Sounds like the Miata crowd should get in touch with one of the companies that does custom Honda harnesses. What you're all asking for is readily available for most popular Hondas, with tons of customization available.

Call up Rywire. they already make custom harnesses for the 13B:
Mil-spec Tucked 13B Harness (FD3S/Rx7)

Basically what I'd be happy with right now is an engine harness that went to a bulk head fitting on the firewall and a harness from there to go to my ecu of choice. Single point of disconnect from all the low current connections on the motor. An Anderson style connector for the alternator/starter/battery line as well. There's 3 options of wiring harnesses for just the engine side.

It's worth a look. Anyone have a complete engine harness they can mail to us for evaluation to make a product?

errr well, stock there isnt an engine harness its kind of bastardized into the rest of the harness. If you were on a couple months ago I could have hacked one off of an early 95 model right at the fire wall, just cut straight through. Without cutting wires someone would end up sending you like more than half the car's harness.

NB have a separate harness, for engine controls at least. NB1 and NB2 don't differ that much (except ignition).

Just to make the "truth" even less obvious.


When I swap engines back and forth, the OEM harness is not that bad, but all-in-one contact at the FW would not hurt (with provisions for all the small extra stuff). The OEM connectors are not designed for that many connect/disconnects.

You can make a venn diagram for racers and experts. not all racers are experts, not all experts are racers.

You would be amazed how many "pro race engineers" don't have a clue, and refuse to listen to reason because they are a "professional racing engineer". before you listen to anyone in the paddock make sure they run at the front, or built the car that does.

Im using a microsquirt module and its 8' harness in my project, not complete.
Very basic, but more than capable.

Other things like defrost, wipers, and lights will be wired through push to reset fuses and any associated relays (starter)


If your starting from scratch, you REALLY don't need to over complicate things.


What ECU are you running? That will have the biggest impact on how you wire it.

Third time I've typed this now.

I'm in the process of building one, slowly, probably one circuit at a time. There are a couple reasons for this. First is to learn how to do it; I'd like to build a purpose built at some point. Second, two of the previous owners made some interesting wiring decisions that leave me concerned about reliability (including one who has posted here about how you don't need to do it). Third, I spent about half an hour after a track day trying to figure out why my tail lights didn't work. I'm 6'5" tall. The less time I have to spend looking at breaker panels in the footwell the happier I am.

So far I've only installed the data system, which meant fabricating a bunch of custom cables. One side had AIM's crappy, soldered, non motorsport connectors. The other DTM connectors. The AIM stuff took way longer, cost substantially more and was a way bigger pain. The DTM stuff was cost effective, easy, robust, and a pleasure to use. I know which way I want to go in the future.

I've taken a few cost cutting measures. I'm only using one color wire. It'll take a little longer to ring stuff out in the future, but I can live with that. I'm also not using expensive heat shrink. I'm using normal stuff for long runs, with marine grade adhesive backed stuff at either end. It works for the car's purpose and is available at Harbor Freight. Under the hood will be DR-25. Breakers and switches are replacing the fancy PDM systems. Maybe not as nice, but plenty of top level cars used them for a long time.

All together I have about $25 in wire, $60 or so into a nice set of used DMC crimping tools, maybe $30 in DTM connectors, and maybe $15 into heat shrink and something like $10 for switch and breaker. No it's nowhere near an entire car, but I suspect I'll only be in the $1000 range unless I go crazy with AutoSport connectors instead of MilSpec stuff.

If you're in Northern California I can even help you out with tools.

Oh and Ballenger Motorsports (post here as vtjBallEng) and ProWire USA can get you most of what you need. Digikey is good for switches and breakers.

Aircraft spruce and dell city are also options when looking for switches realys and breakers. But I have to say, for individual relays the delphi/packard relay kits that B motorsports sells are clean as fuck compared to the relay kits from dell city.

This is what we took out of Bruce's stock wiring harness. It represents painstakingly identifying each wire, confirming the color code, checking continuity and then physically unwrapping the shrouding and pulling it out.

Over and over and over...

I just did the same thing to the mx6. Sucked. I could have built a new harness faster.

Rywire told me no thanks awhile ago.

Plus goddamn 1. :bigtu: