Burken01

iTrader: (88)

hey all, I've been searching and reading all day about different fuel wiring setups and there is a lot of mixed reviews, opinions, etc... I will post pic's so people can actually see what I'm talking about..

shown below is my racetronix 98 hotwire kit as an example

ok on typical hotwire setups you have a 10 gauge inline fused hot wire off the battery/alternator that connects to a relay...





then it runs down and connects to a 40 amp relay



then it travels another 1ft or so and connects to the bottom of the "yellow" bulkhead wire line that will connect to the top of the fuel tank, these are 14 gauge wires..



then the yellow bulkhead goes into the top of the tank



then connects to in my case a 255 walbro using their supplied 14 gauge wire pigtail



ok now to my question to the electrical guru's out here..

whenever someone say's to upgrade the stock fuel wiring and to add a 10 gauge hotwire and relay when you add a high performance fuel pump never talks about changing out the wiring that connects to the yellow bulkhead which is 14 gauge, or the 14-16 gauge "intank" wiring direct to the pump..

wouldn't that defeat the purpose of running the 10 gauge in the first place,

to just connect it back to the stock bulkhead/ intank wiring?

walbro specifies 10 gauge in their online instructions when adding an extra pump but still supplies 14 gauge wire pigtails?

I was told the smaller gauge wire at the "end" won't cause enough power drop due to Ohm's law...

But I've hear conflicting info from other threads here saying something different..

I just want it done right sorry for the rant

smokeshow

iTrader: (17)

In a nutshell...yes. I always just use wire that matches the size of the pigtail on the pump. Never had an issue.

Burken01

iTrader: (88)

Even if the Intank wiring is just a short span compared to the 15ft of 10 gauge from the alternator?

smokeshow

iTrader: (17)

To be honest, that answer is a bit complex... If you were to hook up a time domain reflectometer at the end of the 10 gauge, you'd see increased resistance at the pigtail of the pump harness. So does current encounter more resistance through the smaller wire? ...sure. But there's really no need to dig that far into it. The length of the wire from the engine bay to the fuel pump is not long enough for power consumption of the wire itself to be an issue to the extent that larger wire is necessary to handle an increased current demand. Some good quality copper wire matching the gauge of the pigtail is sufficient. That said, I've used stock wiring for aftermarket fuel pumps countless times on vehicles used as daily drivers. Not a single problem.

Burken01

iTrader: (88)

Ok I'm still new to wiring but can kind of understand your point. A little

So the whole "hotwire" 10 gauge is a big conspiracy? Lol

smokeshow

iTrader: (17)

Not conspiracy, just peace of mind that the insulation won't melt off. It really just helps people who have setups that demand a lot of fuel over a long duration. Current draw increases with fuel flow, so if you have a pump that's just about maxed out it might push the limits of the wire if held at a high duty cycle.

Burken01

iTrader: (88)

This makes a lot of sense now that you say it like that..

I was just curious as to what's the point to upgrading half of the fuel wiring to 10 awg and leaving the other half stock 14-16 awg...

I'm doing a triple walbro setup for my turbo build and don't want to skimp out..

smokeshow

iTrader: (17)

Ideally, you'd upgrade all of the wire. As long as the wire itself can handle more than the fuse it is connected to, there is no need to worry. 10 gauge per pump would be a waste on a walbro 255; I'd just stick with the pigtail size. You'd be hard pressed to get one of those pumps to need all of a 20a fuse

Burken01

iTrader: (88)

Ok I already bought 10 awg so ill use that for the fused power line at least.. And I should be fine with the stock 14 awg intank wires only if each pump receives they're own alternator/battery source right?

smokeshow

iTrader: (17)

Yes, that will be fine.

Exidous

iTrader: (11)

It's not a conspiracy.

Scroll down for chart

The current capacity drops over distance given a consistent gauge. Is going from 10 to 14 a little extreme yes but ANY long run for an aftermarket pump should be as much 10ga wire as possible.

Burken01

iTrader: (88)

Thanks for the link, so technically even at 20 ft and 10 amps or less (walbro 255) I can run 12 gauge wire..

ZL1Killa

iTrader: (17)

the point is not to create a fusible length of wire and instead have a fuse serve a purpose.

Uneverknow

iTrader: (1)

Not sure if this helps you but you always want to use the larger wire closer to your source of power to reduce resistance. If you were to use the smaller wire by the source and larger further away it would not really help you. Smaller wire cannot carry a larger current without creating heat ( which stated before can melt the insulation from the wire and create a fire) another way to look at it is from a hose on a fire truck, you wouldn't put a garden hose on the truck thinking you can get enough water through it to have a fire house further down the line. As you see your only going to be able to flow as much water as the hose from the truck. Hopefully this all makes sense.

Burken01

iTrader: (88)

Yea I get it, I just wanted to know why nobody does a 10 gauge from battery to pump, the "hotwire" kit still connects to at least 4 ft of the stock wiring.. 10 awg to 14 awg bulkhead wiring to 18 awg in tank pump wiring

I'm going to run 10 awg from battery to top of tank, then connect it to teflon/ptfe 10 awg that goes directly to pump, a true "hotwire" kit