Wiring - New Build

fastd · #1 (**permalink**) 05-23-2021, 11:55 AM

Hello all,
Looking for some guidance with respect to wiring another project I inherited. Something isn't right with it all.

I think, among other things, it may have to do with the wire gauge sizes and I am trying to piece it all together:

Running a 4 gauge wire from the 185 amp alternator (150 amp at idle) from the front engine compartment all the way back to the trunk - that's about 13.5' to a one terminal of kill switch.
From that same terminal, running a 2' 1/0 gauge cable to the positive side of the battery.

From the other terminal, running a 1/0 gauge 13.5 ' cable back to the front that connects to the starter.

With holley terminator X Max EFI (draws about 50 amps) and both fans running (drawing about 30 amps) I am getting the following voltage readings:
Alternator: 14.3 (before the fans come on its 14.6)
Battery: 14.0
Fuel pump: 13.3

At a minimum, I think that 4 gauge from the alternator to the kill switch should be increased to 1/0 also.

When the engine gets up to 205 degrees, just above where the second fan comes on, it likes to stall abruptly. I am waiting for a tuning date cause it's running rich.

Any comments are much appreciated...thank you!

sunman · #2 (**permalink**) 05-23-2021, 01:51 PM

Change out the #4 like you think. It sounds like your 12 volts is dropping to low to run EFI when second fan kicks in. Just a guess but your wire is to long/to small for sure with that amp draw on the charging circuit. Or just a suggestion I think a shortened alt wire should go down to the starter terminal that is on the disconnect side of cut off switch just for safety. Shorter wire might fix prob without going bigger

twobjshelbys · #3 (**permalink**) 05-23-2021, 03:14 PM

Quote:

Originally Posted by sunman

Change out the #4 like you think. It sounds like your 12 volts is dropping to low to run EFI when second fan kicks in. Just a guess but your wire is to long/to small for sure with that amp draw on the charging circuit. Or just a suggestion I think a shortened alt wire should go down to the starter terminal that is on the disconnect side of cut off switch just for safety. Shorter wire might fix prob without going bigger

And if low voltage after the fan is the problem then it's more likely the alternator capacity than wire size/IR drop.

sunman · #4 (**permalink**) 05-23-2021, 04:10 PM

#4 wire is rated at 85 amps max. Are you pulling power from alt terminal or starter? You are pulling 80 or more. Your alt can put out 185. When amps go up volts go down. That happens when your #4 carry’s more than 85. You probably have a fuel prob or something else but you really need to be on switched side of disconnect. I think it’s a rule. Check out the thread above this one about disconnects

fastd · #5 (**permalink**) 05-23-2021, 05:33 PM

If I disconnect my 4 ga wire as it current is, and then reconnect the 4 ga from the alternator to the starter directly, that should probably solve my voltage issue but I don't think my kill switch would work any longer though...

TwobjShelbys:
I don't think that that is the issue; I actually upgraded the altnerator from 175/100 at idle to 185/150 at idle; it's a bit better but something still isn't right...

sunman · #6 (**permalink**) 05-23-2021, 06:12 PM

It should work. Positive should go to one disconnect terminal and everything else on the other. If you have more wires on the disconnect terminal than the alt move them to switched side. You got the starter terminal switched so alt would be too. This is just about having switch wired right tho. On the stalling it could be a warp in the flux field for all I know

fastd · #7 (**permalink**) 05-23-2021, 08:02 PM

Great; thanks; that sounds like it could work; I'll come back after I try it.

sunman · #8 (**permalink**) 05-24-2021, 05:28 PM

I think to be Race legal you need have a disconnect on negative too

twobjshelbys · #9 (**permalink**) 05-24-2021, 06:15 PM

Quote:

Originally Posted by sunman

I think to be Race legal you need have a disconnect on negative too

Not according to this topic on battery disconnects. See reply 13 which excerpts from the regs.

Battery Disconnect Switch

sunman · #10 (**permalink**) 05-24-2021, 06:33 PM

I have always had one on positive only too. Great that’s one less part I need to get and zip tie down. Party On

fastd · #11 (**permalink**) 05-30-2021, 10:51 AM

Hey all.
I put the battery cable to one post on the kill switch and everything else on the other side and that didn't work.
When the car is running and I turn the kill switch to off, the car keeps on running...
Seems like I need to run another 1/0 cable from the alternator to the kill switch (instead of running it from the alternator to the starter where is meets the 1/0 wire from battery/kill switch) unless anyone has any other ideas.
Thanks.

1795 · #12 (**permalink**) 05-30-2021, 11:01 AM

Something like this is what you need.
https://www.googleadservices.com/pag...gQIARBY&adurl=

It is designed to kill the battery and the alternator. Without the dual type kill switch the alternator keeps charging the system.

Jim

sunman · #13 (**permalink**) 05-30-2021, 01:36 PM

Dual switch upgrade on the list of parts I have to get. I have to admit l toasted an alternator one time by disconnecting the battery and the motor kept running. Just for the info, do you have a one wire alternator?

fastd · #14 (**permalink**) 05-30-2021, 05:54 PM

Quote:

Originally Posted by sunman

Dual switch upgrade on the list of parts I have to get. I have to admit l toasted an alternator one time by disconnecting the battery and the motor kept running. Just for the info, do you have a one wire alternator?

Yes; it's a one wire alternator.

fastd · #15 (**permalink**) 05-30-2021, 06:07 PM

It seems that that switch (Flaming River Combination Battery and Alternator Kill Switch) that 1795 linked to might not work with a 1-wire alternator...

https://www.youtube.com/watch?v=khP0e6MBl-8

sunman · #16 (**permalink**) 05-30-2021, 07:54 PM

Good to know, that video makes it clear. I would/will put a 175 or 200 amp Megafuse block right off of and close to the switch terminal to protect that alt wire. The motor to chassis ground should be at least 1/0 also. Thanks for the update

fastd · #17 (**permalink**) 05-31-2021, 08:21 AM

Quote:

Originally Posted by sunman

Good to know, that video makes it clear. I would/will put a 175 or 200 amp Megafuse block right off of and close to the switch terminal to protect that alt wire. The motor to chassis ground should be at least 1/0 also. Thanks for the update

I did remember to also change my ground wire from 4 ga to 1/0 ga.

Sunman,
I'm not sure I understand the issue you are addressing though...you need a megafuse to protect your the 1 wire? I don't understand the connection between the 1 alternator wire (mine is a GM style alternator, it's 4 pin with just 1 white wire) and the 1/0 gauge wire I am running to the positive post of the alternator...

sunman · #18 (**permalink**) 05-31-2021, 09:49 AM

The 1/0 positive post alt wire is hot all the time and should be fused if it goes to back of car. You can’t use starter terminal it’s connected to car power on switched side of disconnect. The white exciter wire power circuit would be switched with second points in dual switch. I’m thinking you have a CS130D by the 4 pin plug. My 12SI alt was a true one wire only