battery kill switch
Thread Starter
Race Director
Joined: Sep 2001
Posts: 14,686
Likes: 753
From: NEwhere Ohio
battery kill switch
Ok. I got a moroso super duty kill switch. It has 2 prongs.
I have relocated my battery to the pass rear compt.
Our batteries have 3 positive wires. If I understand its like so:
1 big one to starter
1 little (8 gauge) from alternator
1 little (8 gauge) to ignition
Do I wire the alt wire to the batt side of the switch and the ignition wire to the open/starter side...?
Goal is to kill the motor if the switch is thrown.
This way the alternator can't backfeed the ignition and keep the car still running if the ignition switch is thrown.
Does this sound right? How do you guys wire these things? 93 lt1
I have relocated my battery to the pass rear compt.
Our batteries have 3 positive wires. If I understand its like so:
1 big one to starter
1 little (8 gauge) from alternator
1 little (8 gauge) to ignition
Do I wire the alt wire to the batt side of the switch and the ignition wire to the open/starter side...?
Goal is to kill the motor if the switch is thrown.
This way the alternator can't backfeed the ignition and keep the car still running if the ignition switch is thrown.
Does this sound right? How do you guys wire these things? 93 lt1
Melting Slicks
Joined: Mar 2002
Posts: 3,108
Likes: 126
From: S.L.C. UT
You could also use it as a fuel cut off if you tie it into your fuel pump wiring. My fuel pump is externally mounted below the tank, so when I put one on my car, I will probably use it to cut the fuel since all the wiring is right there.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Ok. I got a moroso super duty kill switch. It has 2 prongs.
I have relocated my battery to the pass rear compt.
Our batteries have 3 positive wires. If I understand its like so:
1 big one to starter
1 little (8 gauge) from alternator
1 little (8 gauge) to ignition
Do I wire the alt wire to the batt side of the switch and the ignition wire to the open/starter side...?
Goal is to kill the motor if the switch is thrown.
This way the alternator can't backfeed the ignition and keep the car still running if the ignition switch is thrown.
Does this sound right? How do you guys wire these things? 93 lt1
I have relocated my battery to the pass rear compt.
Our batteries have 3 positive wires. If I understand its like so:
1 big one to starter
1 little (8 gauge) from alternator
1 little (8 gauge) to ignition
Do I wire the alt wire to the batt side of the switch and the ignition wire to the open/starter side...?
Goal is to kill the motor if the switch is thrown.
This way the alternator can't backfeed the ignition and keep the car still running if the ignition switch is thrown.
Does this sound right? How do you guys wire these things? 93 lt1
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
The idea of a battery kill swich is to cut the motor in case a car on the track is upside down with the throttle stuck open, the driver knocked out, and fuel leaking from the tank. The emergency personnel can just shut off the motor by hitting or turning the switch in the back of the car instead of reaching through the window, around the driver's upside down body feeling for the keys with the car about to explode. It is an NHRA requirement if the battery is located away from the stock location behind the firewall.
Thread Starter
Race Director
Joined: Sep 2001
Posts: 14,686
Likes: 753
From: NEwhere Ohio
What you are describing will work to shut off the motor. You will still have a hot wire going from the battery to the alternator. Ideally, you would want a 4 prong cutoff to cut off power to the battery and the alternator or fuel pump. I cut the fuel pump on mine so the motor will definitely stop and there are no hot wires after the switch. I think some members don't understand that the motor can still run after the battery connection is cut because the alternator can keep the electrical charge to the motor.
Im not sure if the alternator being backfed by the battery when the switch is thrown off (instead of charging the battery like usual) will cause any issues..
Im also worried about my racetronix 'hotwire' 255 liter/hr walbro setup. It has a hotwire coming directly off the alternator output to ensure voltage supplied to fuel pump is at a maximum. This is important for my supercharged setup.
Im going to see if I can relocated that 'hotwire' to the starter cable + or 'open' side of the switch so that the fuel pump will be 'killed' also.
I just need to make sure I dont defeat the purpose of the 'hotwire' by doing that.
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Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
I do have some concern about the wire to the alternator still being 'hot'. I like the idea of just everything being shutdown. Moroso makes a 'super duty' 4 prong switch with an alternator 'kill' hookup terminal. But heres the 'dumb' part: The alternator hookup (on the superduty switch) is only rated at 20 amps. Way too wimpy for a street car's 140 amp alternator. They have some relay kits to get around that (via Painless products), but to me thats just too many parts..... Also the super duty switch is just too heavy for me. Its overkill.
Im not sure if the alternator being backfed by the battery when the switch is thrown off (instead of charging the battery like usual) will cause any issues..
Im also worried about my racetronix 'hotwire' 255 liter/hr walbro setup. It has a hotwire coming directly off the alternator output to ensure voltage supplied to fuel pump is at a maximum. This is important for my supercharged setup.
Im going to see if I can relocated that 'hotwire' to the starter cable + or 'open' side of the switch so that the fuel pump will be 'killed' also.
I just need to make sure I dont defeat the purpose of the 'hotwire' by doing that.
Im not sure if the alternator being backfed by the battery when the switch is thrown off (instead of charging the battery like usual) will cause any issues..
Im also worried about my racetronix 'hotwire' 255 liter/hr walbro setup. It has a hotwire coming directly off the alternator output to ensure voltage supplied to fuel pump is at a maximum. This is important for my supercharged setup.
Im going to see if I can relocated that 'hotwire' to the starter cable + or 'open' side of the switch so that the fuel pump will be 'killed' also.
I just need to make sure I dont defeat the purpose of the 'hotwire' by doing that.
Melting Slicks
Joined: Mar 2002
Posts: 3,108
Likes: 126
From: S.L.C. UT
Again, I have the same Moroso 4 prong 250 amp cutoff you're talking about. I just used the big terminals to cut power to the battery and the small terminals to cut the fuel pump (easy because the pump is in the back anyway). This way, if the motor is running and the switch is on the off position, the battery is cut, the fuel pump shut's the motor off and the alternator will not be running to supply electricity to the motor.
That is the best way to do it.
