12V key ignition wire

73' mach 1

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Need to tie my Sniper, cd box and distributor to a 12v key ignition. Where is the best place inside the car to tie into? I spoke to the guys at Holley and they said it's pretty low current. Maybe 2 amps max. So whats a good spot to tie into? Thanks

 

Fabrice

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If you mean the Sniper pink wire, the green red wire right after the ignition key is what I've used before the next junction. Also on a 73 harness.

 

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If you mean the Sniper pink wire, the green red wire right after the ignition key is what I've used before the next junction. Also on a 73 harness.
Is that the same red/green off the starter solenoid?

 

73' mach 1

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And yes the pink wire. I have 3 total though. Distributor, CD box and Sniper.

 

Fabrice

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Don't recall the circuit exactly (it's been more than 2 years), but it works fine on mine. I do not expect your cd box to be an issue.
In case you need crawl under the column, since this wire is THE wire for the system, the connection must be really solid. (was almost number 1 cause of failures of installs)
I suggest you remove the chair. It's done in seconds and really makes a massive diff to work fine and secure there.

Edit:

Oh and while at it, place on the blue wire (+ pump) a switch there before it goes to your inertia switch and finally to pump. As the sniper primes on key on, it's always been annoying not be able to disconnect the pump when you need test other things non sniper related. I'll correct this soon.

 
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Don C

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The red with green stripe wire that is connected to the "I" terminal on the starter solenoid is after the the resistor wire and has a reduced voltage. When the starter is activated it feeds full battery voltage to the ignition coil.

You need to connect to it under the dash at the ignition switch before the resistor wire.. An alternative is to use the Pertronix relay that is activated by the reduced voltage on the red/green striped wire under the hood and the power feed is connected directly to the battery, supplies full battery voltage at all times and doesn't place an additional load on the ignition switch. The downside is having one more item that can fail.

PerTronix 2001 PerTronix Ignition Power Relays | Summit Racing

 

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The Pertronix is just a relay, so any good brand such as Hella would work. I like the Directed Electronics 8616 relay because it is much smaller. However, the amps loading is lower at 10 amps so it would work depending on the application. In EFI and CD applications the ignition wire is typically just used as a trigger. The heavy load goes through the wire connected to constant battery. I used this relay for my EFI application.

https://www.amazon.com/gp/product/B000CJ05WW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

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You are  totally right Tony, but in case of the Sniper, Holley provides a well designed quality harness with relays so there is no need to add anything more to the circuit. 

 

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The only thing I'm using relays for are my Fans and the one Fabrice mentioned that's already in my harness for the pump. Everything else is fused going to the battery.

 

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Personally for my Holley EFI I ran a relay that is activated by the terminal wire at the solenoid. This way the Holley gets power directly from the battery since I have heard that these Holley kits can be very cranky if the power isnt nice and clean or if there is any RFI. I had actually been looking at picking up some RF blocking wire loom just to go through things and make sure to eliminate any chance of RF.

 

73' mach 1

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Personally for my Holley EFI I ran a relay that is activated by the terminal wire at the solenoid. This way the Holley gets power directly from the battery since I have heard that these Holley kits can be very cranky if the power isnt nice and clean or if there is any RFI. I had actually been looking at picking up some RF blocking wire loom just to go through things and make sure to eliminate any chance of RF.
Yes. Most of the issue stem from things being too close to the coil. I've mounted the sniper coil away from everything.

I also have braided EMI shielding to put over the wires. Just a matter of cutting sleeving and re-sleeve. Good solid grounds are important. 

 

tony-muscle

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Yes. Most of the issue stem from things being too close to the coil. I've mounted the sniper coil away from everything.

I also have braided EMI shielding to put over the wires. Just a matter of cutting sleeving and re-sleeve. Good solid grounds are important. 
Do we know how far from the coil is it recommended to run wires to reduce the chances of EMI interference?

 

73' mach 1

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Do we know how far from the coil is it recommended to run wires to reduce the chances of EMI interference?
I don't have that information. I work with spectrum analyzers. Would be awesome if I could use one and see how much interference is generated. Although I'm guessing this is more of a voltage thing vs frequency. 

 

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I don't have that information. I work with spectrum analyzers. Would be awesome if I could use one and see how much interference is generated. Although I'm guessing this is more of a voltage thing vs frequency. 
Can you with the spectrum analyzer run a powered wire next to the coil and see how close you can get before you start detecting frequency changes from the coil? The powered wire may have to be connected to a battery not connected to the car's charging system to avoid any other interference. In any case you will be detecting if there is any difference as you move the wire closer to the coil. I am thinking all this from a theoretical aspect since I have never used a spectrum analyzer.

 

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Most of the EMI comes from the spark plug cables. The ignition coil does a good job of shielding the EMI producing coils in the metal can. Using good quality carbon resistor or helically wound spark plug cables help, but do not eliminate, all of the EMI. Do not run any wiring parallel to spark plug cables. Even spark plug cables are not immune, running spark plug cables very close together or touching for any distance will causing cross firing. Keep wiring away from the distributor. Shielding helps for inductive EMI,  but doesn't stop the EMI traveling through the wires from other circuits. This is why most sensitive electronics are connected directly to the battery, the battery is an excellent filter of both inductive and capacitive voltage spikes. This is why most EFI systems  (as well as other sensitive systems like computers and audio systems) just use the wire from the ignition switch as a trigger to turn the unit on, but receive their main power directly from the battery. Ungrounded shielded braid may actually increase the EMI in the shielded wire by a capacitive action, so make sure the shields are well grounded. Aircraft engines use completely shielded ignition systems, including the magneto, spark plug cables, and spark plugs, with multiple grounds on the shields. Most military engines are well shielded. The generators we had to power our electronics had completely shielded ignitions.

 
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73' mach 1

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Can you with the spectrum analyzer run a powered wire next to the coil and see how close you can get before you start detecting frequency changes from the coil? The powered wire may have to be connected to a battery not connected to the car's charging system to avoid any other interference. In any case you will be detecting if there is any difference as you move the wire closer to the coil. I am thinking all this from a theoretical aspect since I have never used a spectrum analyzer.
These things are pretty sensitive. Depending what you set your center frequency for you can read anywhere from 9khz all the way up to 40Ghz! Essentially you could put a paper clip on the input and it acts like an antenna so like I said Depending on what you set the center frequency for you'll see everything in the air in that band.

 

Fabrice

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light green or green with red, yes. I think I recall 2 of same colour come at the switch. You need ofc the one that gets powered once the key is turned on.
And you need to Y split it before the next junction. I'd really solder this connection and thermo sleeve it. I call it THE wire because it's really the one you want to be reliable ;)

 
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