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Twisted Harness Q's

EFI Wiring Fundamentals

Discussion and questions related to the course EFI Wiring Fundamentals

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I was reading this document about the twisted harness and some questions popped into my head! First of all filler wires do you terminate them?

Do you add binder in each layer or only at the final layer?

When you plan your layers the inner one is the longest and the sorter the outer?

If you need to splice grounds and voltage supplies for sensors were do you splice them?

If your ECU doesn't have round autosport connectors is it possible to have a harness like this?

How do you plan junctions for this kind of harness?

The document specifies 20% more cable length from the measurements you take is this a general rule and does this apply as you add layers one by one?

What about shielded cables do you twist them the same way as the others or this is not possible?

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No, there most likely wont be terminal pins to terminate the filler wires to, they should get secured behind a connector or at a branch point though.

Planning the layers comes down to wire size. That TE COP document says to put your smaller wires in the inside, working towards your outer layers. I build mine to opposite to this however, with my larger conductors (usually shielded wires) in the center, working outwards to the smaller conductors.

I make my splices directly behind the ECU connector if possible. They should always be at a connector, or a branch point, so they can be strain relieved and your harness sections dont grow or shrink along their length.

Yes, it is possible. Superseal 1.0 connectors are common for aftermarket electronics, and you can get backshells for them to accept a molded boot shape.

Planning junction positions is the same as for a standard harness, I try and minimize the number of them, and will over branch out a harness then run a few of the smaller branches next to one another till they need to deviate. The branch points take the most time, so if you can minimize their number, do so!

The 20% if a rule of thumb. I do this, and find it doesnt give an unacceptable level of wastage. Must better to have to snip 100mm off a wire than be 5mm too short!

Have a look at this facebook post I did a while ago (Before I worked at HPA). I talk about how I've constructed the core out of the shielded wiring there :-).

On my own search for inf about concentric twisted harness I found this page:

Good read.