Size of wire??
 

When wiring like say a electic fuel pump is it an advantage to usr bigger dia wire or can bigger pull more juice???? thanks in advance for any help bryan

Re: Size of wire??
 

If your wire size is to small and the distance from the powersource(usually the battery) to the pump is fairly long you will have a drop in amperage. The pump manufacturer will usually give you a recommendations as to what size wire to use but in no case should you use a wire size that is smaller than the wires on the pump for optimum pump output as well as preventing the pump from overheating.
It's all about Amps not voltage your gonna get 12 volts but the Amps will drop due to small wire size and distance !!

Re: Size of wire??
 

Install a relay inline with the pump and you will not have to use large wire.
http://www.painlessperformance.com/Manuals/50102.pdf

Re: Size of wire??
 

The longer the wire the greater the resistance. Double the length of the wire and you double the resistance of the wire.

The larger in diameter the wire the less resistance in the wire. You can't go too big.

The resistance of the wire adds to the resistance of the circuit overall. As resistance goes up, current goes down.

12-14 gauge wire should be more than sufficient for a fuel pump in any race car. The smaller the gauge the larger the wire.

Re: Size of wire??
 

Thanx Gary--thats what I was trying to say!!! I know what it is just not how to put it down on paper--Comp 387

Re: Size of wire??
 

We run a dedicated fused hot wire from battery t o a relay (10-12 gage) and then to pump. Relay is switched thru ignition switch and then separate . switch on dash (14-16 gage). Fuel pressure seems steadier even with Holley or Mallory 140 with this direct set up.

Re: Size of wire??
 

Electricity is like water, ya just need a bigger hose ;)

Re: Size of wire??
 

When using a relay you should be carefull how you mount the relay and in what direction, so that on accell the G-forces does not shut the relay off! Just a FYI

Re: Size of wire??
 

Do not forget the ground side of the wiring needs to be just as large as the power wire.

Re: Size of wire??
 

I also pull a large ground from the battery to a ground strip terminal and then pull to the other accessories. I don't trust just grounding to the frame...

Re: Size of wire??
 

And depending on your computer(if using one in your car), if everything is chassis grounded, you will have nasty litle transient spikes all over the place..

Chassis ground what isn't sensitive and set up a separate ground with out chassi interference.

If you arent using a computer in the car, just chassis ground everything with good heavy ground wire.

David
The New Hemi Guy.

Re: Size of wire??
 

wow thanks for all the great input now i think i need to rethink some of my wiring...... thanks to all bryan

Re: Size of wire??
 

Bryan,

Just to be clear on the relay's. You still need a large wire on the main power into the relay and out to the pump. I use 10 or 12 ga. depending on length of run, on the cars I wire. You can then use 14 16 ga on the switch wires. I use relays on the fuel pump, water pump, and electric fan. I also put fuses on everything. Some like circuit breakers, I like simple with fuses.

Also, as several have said, make sure you ground everything. I probably over kill this, but I use ground straps on the heads to block on alum head combo's, block to frame/cage. I chased a grounding issue on a car years ago, and swore to never miss that step again!

Good luck.

Ken

Re: Size of wire??
 

as far as grounding straps go USE THE BRAIDED STUFF- do not use solid core

Re: Size of wire??
 

Define juice? A wire twice as big in diameter will have 1/2 as much resistance or twice the conductance. See OHMS LAW.

http://en.wikipedia.org/wiki/Ohm's_l...of_Ohm.27s_law

Basically voltage = current times resistance or current = voltage divided by resistance. Resistance is measured in ohms.

Re: Size of wire??
 

OHMS law???

That has been our problem, we have been using "Murphy's law" all this time!

David
The New Hemi Guy