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Tefzel Vs. TXL Amperage

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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The manufacture of my fuel pump indicates that 14-17 amps are needed depending on the pressure. I keep finding conflicting information but I'm trying to determine a comparison of tefzel vs txl amerpage ratings.

The thing I learned about wiring, is that wires don't really have amperage ratings.

Asking what is the amperage rating of a wire is like asking how much water a balloon can hold... there isn't one answer, or the answer can change depending on the circumstances. So, that's why you're getting conflicting information. But the funny thing is that more than one of them is probably correct.

What wires do have is temperature ratings. Tefzel is rated for 150C and TXL is rated for 125C. And you use those ratings in your specific use case to figure out how much amperage you can safely put through them.

The simple formula is: Ambient Temp + Temp Rise < Max temp rating, and leave some headroom at that.

But you also have to consider if the wire is bundled or not, the size of the bundle, and altitude also affects how the temp rises. So you have to de-rate based on those factors.

Or you can use the shortcut method I do, and just use the Deutsch connector ratings. It works because almost every circuit will have a DT or DTM connector in it. And for Tefzel wire those connectors will be the limiting factor anyway.

24awg: 3A

22awg: 5A

20awg: 7.5A

16awg: 13A

12awg: 25A

These are reasonable numbers for Tefzel wire. But they are probably too high to be safe for TXL in many cases. I don't have a rule of thumb for TXL to offer you.

Here's a good temperature rise table to refer to:

https://www.is-rayfast.com/news/wire-cable/temperature-rise-by-current/

Very good post, Matt, but still only part of the equation and, in context, maybe not that important.

Vince, here the current 'rating' is only part of the issue. You should also have the voltage, which will be across the pump from where the wire and grounds are connected, for the flow and pressure ratings of the pump. In this case, what may have the current capacity may still introduce a significant voltage drop - and that will cripple the pump's efficiency. I'd suggest going a couple of sizes, at least, on the wiring's 'rating', to ensure you're actually getting the benefit of the pump - and don't forget the ground side.

Different electric motors have different characteristics, but a rough guide is the power is to the square of the voltage - eg, if 14V across the pump (healthy alternator and decent wiring) is 100%, then 11V (which is not uncommon) is ((11/14)^2)*100%, or only 61.7%. Even a simple 10% drop from the wiring is a mere 81% of what you could have.

What make and model pump is it, I should be able to find the voltage chart for it?

Matthew and Gord,

Thank you for your input!

I will be running a 16V system with a Magnafuel Pro500 fuel pump. Carbureted application so only needs 25-36psi from the pump. I'm fine with running 14 AWG but would ideally like to run 16, if possible, to decrease the overall size of the harness.

With that pump, and running a 16V system, I expect you aren't running an a alternator?

It states the current of 13A is at 12.5V, which would be the voltage across the pump (+ve to -ve terminals), and with a nominal 16V you have 3.5V drop acceptable loss in the wiring, etc.

The wiring options you're looking at should have a voltage drop Vs current Vs length, in some form, so you should be able to match a gauge for your total wiring length and current while matching the voltage drop that's acceptable. Then check the maximum current it's rated to - there will be a fudge-factor, depending whether it's in a loom where the heat is trapped, or if they're independent and in the open air which will allow cooling.

Do you already own the pump(s), or are you still looking, because there are several points I don't like about their "spec's" for the pump and their "rating". I don't doubt their effectiveness for the most part, but like all other manufacturers that just give a "xxx power" for their product, there are a lot of unanswered questions and generalisations.

I am running a 16v alternator. I do not own the pump and I am not married to it. However, it is readily available at the racetrack as many people run it. That's why I was interested in running one. In case I have issues.

"Or you can use the shortcut method I do, and just use the Deutsch connector ratings. It works because almost every circuit will have a DT or DTM connector in it. And for Tefzel wire those connectors will be the limiting factor anyway.

24awg: 3A

22awg: 5A

20awg: 7.5A

16awg: 13A

12awg: 25A"

I can use the following math?

2x 22 awg =10A

3x 22 awg = 15

and so on?