Proper Wire Size?

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jrcr_15

jrcr_15

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I am in the process of installing my Fitech FI on my Duster. I am using Fitech Dual Hyperfuel in-tank pumps and wanted some opinions on the wiring.

I have read about voltage drop / resistance increases when wires are run long distances.

Obviously, I am going be running a power wire from the EFI unit at the front of the car right back to the gas tank. The fuel pump wires coming out of the unit are 14GA and the wiring diagram on the fuel pumps also call for a 14GA to the + terminal. Based on the length of the car and the size of the wire, do you feel this is a cause for concern? Should I go a bit larger towards the pump?

Also, the batteries for the car are located in the trunk. I am going to run that wire right back there also. So same question, is this sufficent?

Thanks to anyone who can help,
Jim
 
You need to know the amp draw of the pump under full load. Based on what you just said, as example (14) I would lean heavily to 12

Google/ search for a wire size chart but make sure it is for 12V auto/ marine AND NOT 120VAC. The "normally accepted drop" for 120 AC is usually higher than what you want here
 
I was hoping you would reply, you are always so helpful! Thank you.

I found this:

upload_2018-7-19_23-29-59.png


I read that Fitechs typically are about 15 amps, so based on this chart above, 14 should do the trick?
 
The thing is many charts don't address where they "came from" or what "acceptable voltage drop" they were based on. This one here for example indicates 12 would be more acceptable, but this chart ALSO does not see to answer those questions LOL
12 Volt Wiring: Wire Gauge to Amps | Offroaders.com

The calculator on this page actually calculates based on the drop "you say" is acceptable

Wire Size Calculator

For myself, I tend to want to go WAY overboard. In fact I would likely use no12 in this case

"Somewhere" and assuming that wire claiming to be some gauge or another actually IS that size.........."somewhere" there are charts showing wire gauge vs resistance / 100 ft. If you can find that and decide what drop is acceptable, you can actually plug that in and figure it yourself.
 
By the way, I see you are using trunk mount battery. What I would do, here, is put a relay back there in the trunk, and feed the relay/ pump off the battery which will shorten the load wire. Then you can just trigger the relay with something like no18!!
 
I ran a relay on my race only car with trunk mounted battery but you lose this......

The FiTech ECU for Go EFI systems has a special driver circuit that will drive the fuel pump directly, which means that an external relay is not needed. This driver circuit allows both PWM control (pulse width modulated), and direct internal relay drive of the fuel pump. This allows the voltage to be reduced when the fuel demand is low, such as at idle and light cruise.
 
The important wire in this case is not the fuel pump wire sizing, it's the alternator charge line!

Make that wire BIG!

You can source off the battery to relays in the trunk area to fire your accessories.
 
All good points above!

Last year i upgraded my alternator and upped the wiring and did the MAD bypass so i am confident that my electrical can handle it.

I am also going to use a slightly larger wire for my main power to the unit to help reduce resistance and and kind of volt drop, but no relay.

Ill have to do some measurements and make a final choice on wire size.
 
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