what gauge wire for an alternator?

[BSeery]

I am wiring up a small (40 amp) altenator to my drag car. I need to run the 12 volt output wire all the way from the front to the back where the battery cut off switch is.

I looked at some 10 gage wire, but it seemed a bit on the thin side for 40 amp over that distance.
I looked all over M.Boro yesterday and NO ONE had 8 gage automotive wire around. Most people gave me the :screwy:look when I asked for it.

Any suggestions or ideas ?

[wax]

Audio Masters should carry 8 gauge and bigger wire. I could have sworn Radio Shack did as well.

[AaroNX]

I'd use 4 gauge if it was me. Not sure where you could get any in murfreesboro, but if you come to Columbia at any point I can get you some.

[Ashley P]

I am wiring up a small (40 amp) altenator to my drag car. I need to run the 12 volt output wire all the way from the front to the back where the battery cut off switch is.

I looked at some 10 gage wire, but it seemed a bit on the thin side for 40 amp over that distance.
I looked all over M.Boro yesterday and NO ONE had 8 gage automotive wire around. Most people gave me the :screwy:look when I asked for it.

Any suggestions or ideas ?

I'd say more like 4 gauge over that distance if it's the output wire. Question: do you have to wire the output wire through the switch, or can you run the control wire (low amp) through the switch? Do you have to follow NHRA guidlines? If you could run the high current to the starter cable, and the control wire through the switch you could use a 12-14 guage or whatever...

[BSeery]

I'd say more like 4 gauge over that distance if it's the output wire. Question: do you have to wire the output wire through the switch, or can you run the control wire (low amp) through the switch? Do you have to follow NHRA guidlines? If you could run the high current to the starter cable, and the control wire through the switch you could use a 12-14 guage or whatever...


I don't know if even running the control wire through the battery cut off switch will work. I think that wire just excites the field and gets it going. Once the alt. is producing power I don't think you can get it to stop producing by unhooking the switch wire, but I will give it a try.

I have it set up now that there is just the output wire from the alternator to the starter terminal, and a jumper from that to the 12v+ post of the 2 wire connector. It does not produce voltage right away, but once you rev the engine it then starts to produce power. I am not even using the switch wire.

I don't know that NHRA has a spec on how it's to be wired. They just say that when the switch on the back of the car gets turned off everything should die. As is now, mine keeps running because I am feeding power after the rear switch.
I was thinking the best way was to run the output back to the battery side of the rear switch.

[Slipstream]

Clickie! (http://www.powerstream.com/Wire_Size.htm)

Scroll toward the middle

You're looking for "AWG gauge" & "Maximum amps for chassis wiring"

I would take your 40 amps and multiply that times 1.5 for your peak current draw (saftey margin) that gives you 60Amps. The chart says 8 Guage wire is good for 73 amps. This should be more than fine. If you want additional margin of safety, go up to 6 guage. 4 guage is overkill. Make sure you get stranded copper wire.

[BSeery]

Thanks Slipstream, cool link.

I picked up some 6 gage. Talk about overkill!!! I only got that in case I couldn't find some 8 later on today. This stuff is thick, about as thick as my pinkey finger.

Still looking for 8, but I do have 6 to run if I have to. Won't have to worry about the car being underweight once I put 15 feet of that in there.

[Snake_Chaser]

I woulda went to Advance and bought some of the clear jacketed battery cable wire unless that woulda been too big for what youre wanting

[BSeery]

I found some 8 gage at Audiomasters. They sell it by the foot from the spool. Picked up 20 feet (plenty of left overs). It' way larger than any factory wiring I have seen, but I guess they are only going 1-2 feet tops.