Coil Voltage Question
Thread Starter
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Coil Voltage Question
I have a 45k volt coil on my cars ignition system. To get this 45k volts out of the coil, does the coil have to have the full 12 volts to the coil. I know I have a resistor wire running to the coil and the voltage is down coming into the coil. This has got to affect the output. Any thoughts on this? Would running a full 12 volts to the coil help?
Just curious.
Just curious.
Racer
Joined: Nov 2002
Posts: 307
Likes: 0
From: Denver Colorado
Re: Coil Voltage Question (Eddie 70)
Yes, a full 12 volts to your "hot" coil will help. But if you have a breaker points distributor, the 12v's will make the points wear fast, due to arching.
Your "resistor" wire voltage to your coil, except during start up cranking, will be about 8 volts.
You may want to try a Petronics, mine seems to work great, (had it wired up for about a week now). I wired a direct 12v from the "switched" side of fuse box(ignition side) in back side of dash to coil. I have the "high powered" Petronics coil as well, and seems to do just fine with the constant 12 volts.
Good luck!
Your "resistor" wire voltage to your coil, except during start up cranking, will be about 8 volts.
You may want to try a Petronics, mine seems to work great, (had it wired up for about a week now). I wired a direct 12v from the "switched" side of fuse box(ignition side) in back side of dash to coil. I have the "high powered" Petronics coil as well, and seems to do just fine with the constant 12 volts.
Good luck!
Thread Starter
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Re: Coil Voltage Question (Bill Oxley)
Bill, thanks for the input. I have the Pertronix on mine also. With the key in the run position, I have a little over 6 volts. I think I will run out there and get me a 12 volt signal and see if it makes any difference to my car. It always starts fine and seems to run fine.
Anyone else got any input?
Anyone else got any input?
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Re: Coil Voltage Question (Eddie 70)
:nono: A full 12V would help the coil burn up. Some aftermarket coils are made to handle the full 12V. Most stock coils will not. That resistor wire is there to protect the coil as continuous operation puts 12V on primary side of coil, which is shorted to ground while distributor rotor is between contacts inside cap (sparkplugs). That higher voltage with nearly no resistance draws max current the coil can handle and heats things up.
Now the full 12V is used when starter solenoid is energized (resistor wire bypassed). But only for short period during start-up to produce more spark for ignition. And aftermarket CDI boxes can run full 12V because they control the coil power.
Now the full 12V is used when starter solenoid is energized (resistor wire bypassed). But only for short period during start-up to produce more spark for ignition. And aftermarket CDI boxes can run full 12V because they control the coil power.
Racer
Joined: Nov 2002
Posts: 307
Likes: 0
From: Denver Colorado
Re: Coil Voltage Question (cardo0)
I agree with cardo0, but Petronix recommends you use a coil than can take a contineous 12 volts. They call theirs the "Flamethrower". That's what I have to go with my Petronix, works great, good crisp spark!
Drifting
Joined: Mar 2003
Posts: 1,608
Likes: 3
From: Canberra AUSTRALIA
St. Jude Donor '05-'06
Re: Coil Voltage Question (Bill Oxley)
I had a similar voltage problem. Turns out the wiring from both the start and run circuit both had partial breaks in them. I fixed the wire problem and I also have the Pertronix electronic "points" and the flamethrower coil. Now it runs great.
Before I found the wiring problem the car would "stutter" when I stomped on the gas. You need to check the voltage at the points when someone is starting the car (ie key turned to start) and when the motor is running. IF the start voltage is below 12 volts then you may have a problem with you wiring and or ignition switch. The ignition switch is about $20 but it is a pain of a place, on top of the steering column under the dash. On cars as old as ours it is worthwhile replacing anyway if you are in the area working on somethin else.
If you want to see if the voltage is causing a problem then hotwire your car by running a lead from the alternator to the coil. This will put +12 volts directly on the ignition circuit. BE CAREFUL as once you start the car you cannot turn it off without removing this lead. If the car runs smoother and doesn't behave like it is has a carb problem then time to check the wiring.
Good luck.
Before I found the wiring problem the car would "stutter" when I stomped on the gas. You need to check the voltage at the points when someone is starting the car (ie key turned to start) and when the motor is running. IF the start voltage is below 12 volts then you may have a problem with you wiring and or ignition switch. The ignition switch is about $20 but it is a pain of a place, on top of the steering column under the dash. On cars as old as ours it is worthwhile replacing anyway if you are in the area working on somethin else.
If you want to see if the voltage is causing a problem then hotwire your car by running a lead from the alternator to the coil. This will put +12 volts directly on the ignition circuit. BE CAREFUL as once you start the car you cannot turn it off without removing this lead. If the car runs smoother and doesn't behave like it is has a carb problem then time to check the wiring.
Good luck.
