Injector wires

[tmsnyder]

This is on the GM TBI ECM '747

The wires in the factory harness to Injectors 1 and 2 are twisted into pairs with 2 12V supply wires.

I assume this is to prevent the signal from creating noise in the surrounding sensor circuits as the injectors 'fire'.

Is the twisting required ? I haven't seen this mentioned in any of the supporting documents I've reviewed including schematics from GM.

Did you do this, or see it in your harness? Or were the wires run straight?

Thanks for any insight.

Todd

 

[Keith V]

twisting is always better than not twisted for signal wires as far as I know. Maybe some specialised case it isn't?

 

[tmsnyder]

twisting is always better than not twisted for signal wires as far as I know. Maybe some specialised case it isn't?

This is in a stock factory harness from a junk yard.

Just curious b/c the injector wires are different than the other wires, seem stiffer, and so when twisted together they really stay twisted.. Almost like solid strand wire but they are stranded.

 

[billvv]

Twisted-pair signal conductors are used to protect the signal from external noise rather than vice versa.

 

[tmsnyder]

Twisted-pair signal conductors are used to protect the signal from external noise rather than vice versa.

Yes I'm aware. But highly doubt that the injectors need to be protected from electronic noise. I would be more inclined to think the opposite is true.

Be that as it may,....

My question is, for those with fuel injection, are your injector wires twisted?

 

[billvv]

Mine are twisted (OEM GM TB harness).

 

[pvfjr]

Twisted-pair signal conductors are used to protect the signal from external noise rather than vice versa.

When it comes to emissions vs susceptibility, things tend to work both ways.

With twisted wires, there will be some destructive interference in the emitted fields. That's a good thing.

This page has four graphs of E-field radiated emissions for 0, 5, 10, 40 and 100 twists per meter. The results are nothing short of amazing.

https://medium.com/@emianalyst/effect-of-cable-twisting-on-radiated-emissions-66edb16bec1c

One gotcha is that this works best for "far field" as it takes some distance for the lines to blur, if you will. It will be frequency dependent as well. I'm not sure what the slew rate of the injector waveform is, but since they're pretty low impedance, I assume it's a good strong driver circuit. I'd be curious what the main frequency component is.