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Mil-Spec type wiring as for car audio speakers.

EFI Wiring Fundamentals

Discussion and questions related to the course EFI Wiring Fundamentals


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Zac/anybody,

Not sure if you would know the answer to this, but I do quite a bit more Audio work then wiring motorsports, but still do both. I am wondering if I can run a pair of 18-22 gauge mil spec wire instead of a 16-18 gauge speaker wire? Running mil spec wires would be easier and smaller. I know it will cost more, but I am not worried about that right now. I am just wondering if it would be ok? Or if the mil spec wires will be prone to engine noise coming through the wires because it is thinner?

Thanks,

Dave

G'day Dave :-).

Will be absolutely fine. In motorsports, you often run smaller power supply wires in parallel because its easier to build the loom with two 20awg wires as opposed to one 16awg one, and you might be limited on the size of wire that can fit into the connector at either end also.

The insulation on wires, be it TXL or Tefzel doesnt help with radiated noise, any noise will pass through it like it doesn't exist, so if you're finding problems there, I'd try using shielded cable instead :-).

Zac,

given electricity takes the path of least resistance wont one wire take more load than the other?

so you wont actually get 2 times the current capacity?

genuinely asking as i always thought this was a big no no.

Yeap, you're spot on, but as a bit of current starts to travel down one wire, it will cause a voltage drop across that wire... so the current will be more inclined to to flow down the other wire, which will then have a voltage drop induced across it, so the current will want to travel down the other wire.... Rinse repeat, and equilibrium will be reached and the same voltage drop is seen across both wires.

Its like connecting two resistors in parallel, but the resistors are really low value, and if your crimp connections are good, and the wires are in good condition, you'll get very, very close to two times the current capacity.

There is absolutely an argument to be made that if one of the wires is damaged, the other wire will be required to take the entire circuit load, and this could be a dangerous situation... However proper construction techniques, and twisting the wires to hopefully ensure that if one of them is severed, they both are, will limit the danger.

Totally illegal in building wiring though, don't do it there. In fact, don't do any building wiring at all, its a real bore!

Yup, the current flow is in reverse proportion to the resistance, when in parallel. so if one wire has 1% more resistance, then the other will carry 1% more current - it isn't a case of all going through the lesser one.

They use parallel conductors in the electricity industry for both HV (11kV, 33kV etc and LV (400V) circuits, i.e to supply a transformer or switchboard where it would be impractical to run one very large conductor. Each conductor is tested separately before being connected up.