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# Injector current calculation for proper wire size

### Practical Harness Construction - Club Level

Discussion and questions related to the course Practical Harness Construction - Club Level

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What is a good rule of thumb for sizing wire feeding injectors? I've got a flow rate table with offsets in uS for fuel pressures and voltages for my ID1050x's but I don't understand how to estimate injector pulse widths/duty cycle.

Thanks

You need to know the resistance of the injectors. Usually around 10-15 Ohm.

If you want to know the maximum current draw (always open), you take Ohm's law:

U = R * I

I = U /R

U = 12 V (example)

R = 15 Ohm

Therefore your current draw would be:

I = 12 / 15 = 0.8 A

As you can see, they don't draw much current continuously so your wire size does not need to be huge. I always use 22 AWG for the signal wires and 22 AWG for the supply wires which splice into a common 2x22 AWG wire 12V feed which gives me a theoretic 10 A for 8 injectors, for example.