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Trying to figure out the best size wire to power a walbro 450, I've read that 10awg is ideal to reduce voltage drop, but I would like to run tefzel wire and the largest readily available locally seems to be 12awg, would that suffice? Total length of about 4m. From what I can see the pigtail that comes with the pump seems to be 12awg.
I run 12 awg tefzel for pretty much every in tank fuel pump. Owner always seems to eventually want to upgrade and then you're already covered if they are only use 340's "for now".
Since I don't know what PN pump or what pressure the pump's going to be running at, lets pretend its worse case and call it 20 amps (which would be like 100 psi)
M22759/32-12 has a resistance of 2.02 ohms per 1000 feet, or in your case of 4M this is 0.0265 ohms. This equates to a voltage drop of 0.53V, or 3.6% of 14.4V which is right at the limit of what's generally considered acceptable in low voltage DC circuits.
In reality you're likely to run a lower pressure and the amp draw could be as low as 12 amps for an N/A engine with no major fuel flow restrictions.
Feel free to check my math as I'm up past my bedtime.
12 gauge tefzel is fine for that pump, distance, with typical voltage.
You may also be able to double up on the wire, to half the voltage drop.
Also, don't forget to make sure the ground path, and the power supply to the relay/PDM is also sized correctly.
