Wire ampacity/ wire sizing g

Hello, I'm looking for a definitive way to determine proper wire size for TXL wire. A lot of the material I found online lean towards a larger than needed size. Any help would be appreciated.

The definitive way is to do your own testing. Determine the maximum current in your environments the wire can take before melting the insulation, or raising the resistance.

Is there a particular load or type of loads that you are questioning? Are we talking about a Starter Motor, Cooling Fan, or a sensor supply?

I find that connectors are often the limiting factor. Their limits are often clearly defined, and the size wires the terminals are designed to support give you a clue as to what size wire would be required.

Hello, I've been building a lot of harness' lately using tefzel and when it comes to fuel pump/fans I've always used 12ga. Asked a lot of people about it and heard different things about using 14ga or even 16ga for fuel pump wires on shorter runs (less than 5ft). I saw on the wiring fundamentals diagram that around 16ga is good for the 20A outputs. I just wanted some clarity on if a 14ga or 16ga would be sufficient enough for fuel pumps drawing 20A for runs around 5ft or less. Appreciate any comments on this!

The only definitive way to do this is to methodically test in your specific environment.

Short of that you can just refer to the deign spec ( SAE: J1128 TXL ) of the wire and hope that their vendor complies with it.

Most people just use rule of thumb numbers and add a safe de-rate factor.

I've been using this as a general reference for years Remington Copper Hook-Up Wire Ampacity