Volts to coil - Team Camaro Tech
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post #1 of 126 (permalink) Old Apr 5th, 10, 07:10 PM Thread Starter
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Volts to coil

hi all i have the pertronixs 1181 in my stock 327 2bbl, im reading 6.8 volts with stock wires and a 45000 flame thrower, it runs great but they say to run 12 volt, wire from fuse box ignition i tried this and runs the same. great, but im reading14 volts, is this still ok for my motor,will i get better perfomance this way? thanks in advance
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post #2 of 126 (permalink) Old Apr 5th, 10, 07:24 PM
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Re: volts to coil

You're fine on the 14 volts. You should see at least 13.8 volts at idle and around 14.4 volts with the car running at speed.

If your new system calls for 12 volts, then you should run 12 volts or else you will not be getting rated coil voltage. The old points system used a cloth covered resistor wire that drops the voltage down. If you are using that to supply your new ignition then you are shortchanging yourself. If you had a hotter setup than just the stock 327 you'd really see some issues. Inside the car on the fuse block, you will see a terminal labeled "IGN" and a male spade connector next to it. Make up a 12 or 14 AWG wire with a fuse and use that to supply your new ignition setup.

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post #3 of 126 (permalink) Old Apr 6th, 10, 09:06 AM
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Re: volts to coil

Actually, the cotton insultated resistor wire doesn't impact voltage. It's not a voltage regulator. It impacts (reduces) current.

But agree. Bypass the resistor wire and run full current with a good 14g braided wire to the coil from a 12v source. As suggested above, the IGN port in your fuse panel is perfect for this.

Last edited by Straight-line-69; Apr 6th, 10 at 01:40 PM.
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post #4 of 126 (permalink) Old Apr 6th, 10, 01:48 PM
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Re: volts to coil

Quote:
Actually, the cotton resistor wire doesn't impact voltage. It's not a voltage regulator. It impacts (reduces) current.
In correct..
A resitance reduces the voltage...
Electriity is like water thru a pipe...except the amount of power (watts) (volume per minute drawn) is determined by what is drawing the elecrons.
The coil will draw a given wattage, with the voltage down it means a higher current because the source Battery (like a water pump) is higher than the requirement.
V x A= W
With higher current the coil runs hotter, and so does the resitance wire.

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post #5 of 126 (permalink) Old Apr 6th, 10, 06:02 PM Thread Starter
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Re: volts to coil

thanks all for the reply,will i get better performance or gas milage doing this,or is the stock hook up will be the same, i know the ign wire from the fuse panel will give me more voltage this way.
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post #6 of 126 (permalink) Old Apr 6th, 10, 06:43 PM
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Re: volts to coil

Quote:
Originally Posted by Straight-line-69 View Post
Actually, the cotton insultated resistor wire doesn't impact voltage. It's not a voltage regulator. It impacts (reduces) current.
You are correct in that it results in reduced current, but only on the ignition components not the entire circuit and it does so by limiting voltage to reduce wear on the components once the engine is running. The system gets full voltage only on startup from the starter relay.

Resistance in a circuit introduces voltage drop. Potential measured from source to neutral or ground is full potential. Measuring at any point within the circuit to ground with resistance between the source and measuring point will result in a lower reading than full potential.

For instance, measure voltage directly at your battery. Then measure voltage at your fuse block. The small bit of resistance in the wire is enough to cause a voltage drop so you should read slightly less voltage at the fuse block if your meter has enough resolution. The resistor wire used for points systems was used specifically to drop voltage at the coil.

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TKO 600-Moser 3.42-Detroit Truetrac
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Last edited by Steiner; Apr 6th, 10 at 08:13 PM.
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post #7 of 126 (permalink) Old Apr 6th, 10, 09:44 PM
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Re: volts to coil

Wrongo. If you have a voltage meter, measure for yourself. With the the ignition key in the 'on' position (engine off), and assuming the points are in a dwell position, you should have over 12v on the coil end of the resistor wire. If not you have issues.

Again, the cotton insulated resistor wire is not a voltage regulator.

The applicable Ohm's Law is:

I = V/R

I = Current (amps)
V = Voltage
R = Resistance (ohms)

Last edited by Straight-line-69; Apr 6th, 10 at 10:51 PM.
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post #8 of 126 (permalink) Old Apr 6th, 10, 11:08 PM
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Re: volts to coil

Quote:
Originally Posted by Straight-line-69 View Post
Wrongo. If you have a voltage meter, measure for yourself. With the the ignition key in the 'on' position (engine off), and assuming the points are in a dwell position, you should have over 12v on the coil end of the resistor wire. If not you have issues.

Again, the cotton insulated resistor wire is not a voltage regulator.

The applicable Ohm's Law is:

I = V/R

I = Current (amps)
V = Voltage
R = Resistance (ohms)
The reason you measure 12V with the points in dwell position is because you are measuring across an open circuit at that point and will read battery voltage because there is no load. It is the same as if you unplugged the ground from a light on the car. You would read 12V on both sides of the light bulb. When running normally or when closing the points, the circuit is closed and the voltage drop from the resistor wire (or ballast resistor in other models) becomes apparent.

To use your Ohm's Law example, you can plainly see that decreasing voltage will decrease current. That is why a calibrated resistor wire (or ballast resistor in some cases) is used on points. In order to limit the current across the ignition components under normal running conditions, the voltage supply is limited except when starting the car.

There is no argument as to current being limited (in the ignition components....the resistor wire dissipates current as heat thus the cloth covering instead of plastic). The argument is over the statement "Actually, the cotton insultated [sic] resistor wire doesn't impact voltage."

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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Last edited by Steiner; Apr 6th, 10 at 11:19 PM.
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post #9 of 126 (permalink) Old Apr 6th, 10, 11:48 PM
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Re: volts to coil

I mention the total wattage depends on what is drawing it
A low voltage coil is different to a 12v coil....
put 12v on a 6v coil it will heat up and the car will stop till it cools down
And visa versa will do the same expept it takes longer than about 20 mins

I think some of you had better go back to your basic high school phyisic books

My Spelling is not incorrect...it is creative

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post #10 of 126 (permalink) Old Apr 7th, 10, 12:02 AM
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Re: volts to coil

Quote:
Originally Posted by Steptoe View Post
I mention the total wattage depends on what is drawing it
A low voltage coil is different to a 12v coil....
put 12v on a 6v coil it will heat up and the car will stop till it cools down
And visa versa will do the same expept it takes longer than about 20 mins

I think some of you had better go back to your basic high school phyisic books
Your saying putting 6 volts through a 12 volt coil will do the same, just longer?

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post #11 of 126 (permalink) Old Apr 7th, 10, 05:11 AM
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Re: Volts to coil

Dwell Angle: The dwell angle is the number of degrees of rotation of the cam/distributor during which the points are closed.

All coils are 6 volt coils, a reduced voltage is needed to prevent overheating.

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post #12 of 126 (permalink) Old Apr 7th, 10, 01:16 PM
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Re: Volts to coil

Brother Steiner (and others), I see how you arrive at your faulty conclusion; that the cotton insulated wire to the coil is a voltage limiter or reducer or regulator. But again, this wire plays no role as it relates to voltage.

And again, I=V/R. It's 'current' that's being reduced by the cotton insulated wire, not voltage, which is a constant.

If you had a voltmeter on the end of the lead to your starter (the big red wire from the battery), you should show 12v (~) with the starter disengaged (open circuit). Correct? Once you engage the starter, the volt-meter would show a reading of 8-10 volts while the starter was turning the crank. Correct? With the use of this big 1g braided copper wire from battery, there's not a lot of resistance (some) but no added resistor is built in, yet there's a significant voltage drop as the component (any electronic component) is under a load? Correct?

12v is still being supplied. Correct?

Back to the coil. The coil sees 12v between each dwell period. Obviously, if you're measuring the voltage at the coil with the engine running, your meter will show a lower reading than 12v. That will be case with or without a resistor (or resistor wire) in place. Again, test this yourself by substituting the resistor wire with a larger 14g braided jumper wire with no resistor. With the engine running (or not), you'll get the same voltage reading (with a voltmeter) without the use of the resistor wire as with.

The reason the engineers at Chevy added the jumper wire from the starter to the coil, is to provide full 'current' (no resistor) to the coil while the current-hogging starter is engaged. Otherwise the spark plugs would have inadequate spark during cranking. Voltage is the same regardless.

Also, a voltmeter is used to measure voltages in a steady state, which our ignition systems are not. Think of the points as a crude switch in an inductive system. If you instead used an oscilloscope to measure voltage, you would see 12v being supplied to the coil by the resistor wire.

FWIW

Last edited by Straight-line-69; Apr 7th, 10 at 02:36 PM.
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post #13 of 126 (permalink) Old Apr 7th, 10, 01:46 PM
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Re: Volts to coil

Quote:
All coils are 6 volt coils, a reduced voltage is needed to prevent overheating.
They maybe in the US, but when in NZ with cars from all around the world, we have 12 and 6 volt coils, both look idententical except on the bottom...1 has 12 yje other a 6 in the part number.
A common issue with our coast gaurd resuce is people put an engine in a boat, use the old coil, no ballist resister (a ceramic block with heavey resistance wire inside) then break down off shore and wounder why.

Holden GM cars do not have a resistance wirem but a ballisy resistor on the firewal
But still use the same std loom colour coding as Chev.

Another note, if you change to 12V you also need to change the capacitor t prevent premature wearing (burning) of the pionts...and if you change the length of the coil to dizzy wire this will also cause premature wear of points
If the pionts hammer has the dag, capactor is rated too high ....if anvail, too low
Check that, Im not 100% sure have it around the right way...been a few decades since messing around in that area.

My Spelling is not incorrect...it is creative

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post #14 of 126 (permalink) Old Apr 7th, 10, 02:04 PM
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Re: Volts to coil

Geeesh. Ohm's law is Ohm's Law. It is just a relationship. If you have a length of wire (unless it is some very special wire) the resistance is fixed. The higher the voltage the lower the current. Period.

VxA=W is not Ohm's Law. It is Joule's Law. That is simple DC power (work). For a piece of equipment that does a fixed amount of work the amps increase if the volts decrease. A 1 HP motor (746 W) can only do so much work. Raise the volts, the amps go down. Period.

Ohm's Law is mis-used a lot.

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post #15 of 126 (permalink) Old Apr 7th, 10, 02:10 PM
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Re: Volts to coil

Lol

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