I was wondering what gauge wire the engine harness is made of along with the front harness. Im going to be diving into some stuff soon and want to buy the correct gauge wire. Im thinking 12 but im not entirely sure.....

 

Look at Rywire :

I don't know Ryan personally, but for a new harness, that's a pretty good deal.

 

I know about them. Im not interested in buying a new harness. The one I have now is fine. I also dont see a point in that one for our car. Its not like the engine harness is really that visible after you make it a single turbo type harness. I just want to know what thickness the wire is on the stock harness.....

 

Each wire in the engine harness will carry a different amount of current, so they are not all the same thickness. If I had to guess, most of the wires are probably 18-20 AWG (AWG stands for 'American Wire Gauge'), with some of the thicker wires (such as the single wire that carries +12V power to all 4 injectors) appear to be closer to 14-16 AWG. It's very unlikely this will be documented in the factory service manual, and wiring is important so you shouldn't trust my memory... it's been years since I had the engine harness out of my car.

If you have a spare harness you can easily determine the OEM wire thickness by cutting and stripping a length of wire using a decent set of wire strippers, for instance if the copper fits correctly in the 18 AWG section of the wire stripper it's likely you're working with 18 AWG wire.

Most people consider two or three important factors when choosing wire gauge:
Current capability; nearly everyone understands that thicker wire (lower AWG like 10 or 12) can safely handle more current than thinner wire.
Size; thinner wire takes up less space... if you tried replacing every wire in the OEM engine harness with 12 AWG the bundle would be at least twice the original size and would not fit through the firewall grommet.
Weight; some people might consider the wiring harnesses to be heavy. It's probably possible to save a few pounds off most racecars by ditching 'unnecessary' wiring or replacing existing wires with fancy MIL-spec / aircraft-spec wire.

One other thing that needs to be considered when choosing wire gauge is the pins or connectors you will be crimping onto the wire. An example of this is the red/blue/yellow crimp connectors found at most auto parts stores (which aren't the best thing to put on a racecar, by the way). A better example is the OEM ECU connectors which use two different sized pins, and although the large pins might work when crimped onto a 22 AWG wire, the small pins won't fit onto a 16 AWG wire and even if they did they would not insert into the plastic connector properly.


Wiring is not easy, it is a skill most good mechanics don't have and there isn't a ton of documentation about it online. In addition to experience, the right tools are very important when it comes to wiring, similar to fabrication there are some jobs that simply can't be done properly without the right tools. One of the best ways to learn the correct procedures and tools and components to use would be finding someone local to help you. Your original question is quite basic, so I'd suggest you keep it simple while you are still learning... don't try to replace a ton of wires all at once or delete things from the harness unless you're absolutely sure they are unused.

 

^ Yup

 

Cool. Thanks for all the advice. I wouldn't consider myself a newb or anything. Im just planning on doing a wire tuck and i may need to extend some wires. So i wanted to buy the correct gauge when doing so. I have a ''professional'' soldering iron that i will be using. The weller wesd51. I also have all the appropriate tools needed to fumble with wires. I will be working very carefully as i learned a tremendous amount from my last wiring venture. Take a look ay my earlier threads if you want.

I will be moving 1 wire at a time and testing everything as i go so the end result is a working tucked harness. I already made my harness a ''single turbo harness'' the correct way. If i take my time, i should be just fine with this. If need be, i have a few friends that have done this job plenty of times to include making their own harness from scratch.

But like i said before, i just wanted to know what gauge wire the wire harnesses were so i could buy the correct spare wire.

 

i ended up buying this.... theres an instructional video and everything. i also just realized its SWG and not AWG. i hope thats not a big deal...

 

It's cheaper than a harness from Mazda and they make both a single turbo harness & a simplified sequential harness.

I have the simplified sequential harness myself for RHD and it's a beauty.

-Geoff

 

it depends on what the wire does. the high amperage stuff uses larger wires than the low amperage stuff.

 

The thing with the rywire harnesses, its JUST the engine harness. There are still 2 other harnesses that need to be addressed: The charge harness and the entire front harness. I found a better solution to this issue. I got like 15 spare wire harnesses for the fd that i will hack up if need be.

 

the other harnesses live a much easier life...

i've found though if you have the right tool and a little practice, depinning the connectors is actually really easy, so if you need to replace a few, its actually not bad at all.

 

Im not replacing anything. I will be EXTENDING wires if need be to accommodate the wire tuck.

 

Although I don't personally agree with doing a 'wire tuck' for the purpose of making the engine bay look pretty, you might as well try to do a good job of it. Soldering is generally a bad idea when it comes to automotive wiring, non-insulated crimp splices would be a better idea. When most people think 'crimp splices' they picture the ones with yellow/blue/red plastic on them that can be bought at most auto parts stores. Those are insulated butt splices and they most people use the wrong tool to crimp them which ends up resulting in an unreliable crimp. Non-insulated or uninsulated splices are just metal without any plastic on them, if you use the notched end of a crimping tool you can generally make a nice solid crimp that will be reliable enough to withstand the vibration that tends to damage solder joints over time. In a pinch, you could wrap this splice in good electrical tape for insulation (just like Mazda wrapped the non-insulated splices that in the OEM harness, for instance the +12V injector power wires). If you want something that will be a bit cleaner looking you can use double-wall (aka epoxy-lined) heat shrink tube. The only trouble with heat shrink sleeving is you need to plan ahead since it is a tube that must be slipped over the wire.

My main gripe with wire tucks is you are adding at least two new splices to each length of wire that you want to extend... one connecting the old wire to each side of the extension wire. Each new connection is a potential point of failure, especially since the average person doesn't have much experience building wiring harnesses or crimping splices. The cleanest and most reliable method of extending a harness would be to remove the entire 'old wire' and replace it with a single longer wire, complete with new pins crimped at each end that will allow it to fit in the original connector... unfortunately it's difficult to find most of the pins that Mazda used in their harnesses.
My other gripe with wire tucks is people sometimes move the wires out of the way just for looks, and this often results in the wiring harness being more difficult to service than the original setup. Not that Mazda did a brilliant job or anything, but again the average wire-tucker has probably spent less time considering the wire routing than the Mazda engineer(s) who were assigned that task.

 

Sad face to a wire tuck? Thats a first.

 

Can I suggest instead of doing this to an old (and most likely heat-embrittled?) wiring loom, you would better spend your efforts on removing the existing loom, then unwrapping it from all the brittle plastic sheathing, check for damage, and then re-wrapping it with heat resistant wrap, and laying it down nicely in the stock position again?

This way it will give you near factory reliability, and you wont have it as a source of a problem for years to come.

Besides, the factory engine bay is so busy, and the wiring runs underneath most things so much, that "tucking" the loom wont achieve much of a visual difference, nor is it going to add reliability or serviceability to a car that you intend to daily drive. I wouldn't be adding more potential failure or problem points to the car.