NAPA coil

[ndutton]

Thanks Neil....on the ball as usual

Not so much. I'm simply regurgitating info found in Kelly's epic Coil Input thread.

I'll add this though: resistors are necessary only on coils of insufficient internal resistance in the first place. We know A-4 electronic ignition requires coil resistance of around 4Ω so if we consciously decide to buy a deficient 3Ω coil we'll need a resistor to make up the difference. If we select a 4Ω coil there's no need for extra parts - - and extra connections.

Joe's comment is spot on that Pertronix's own coil didn't pass muster despite their advertising that it was "the perfect match for their ignitor ignition." Maybe it is on your Chevy but no way on our A-4.

[Mo]

OK Neil.
So it would be easy to pick up a coil with 4 ohm resistance....I'll do that and keep it aboard. If you remember, I took the EI off my spare engine about 1/2 way through last season. It had an external resister as well as coil...so I put it all on there... like you, no problems.

[ndutton]

Finding a 4Ω coil at the local auto parts boutique might be more difficult than you think.

Clerk: What make and model car is it for?
You: Not for a car, it's for my boat.

Clerk: I can't access the computer without inputting a car make first.
You: Not for a car, it's for my boat. Can you pull up the internal resistance specifications? I can choose from there.

Clerk: I can try. In the meantime, would you like to purchase an air freshener or some lemon Go-Jo hand cleaner? They're on sale.
You: No thank you, all I need is a coil.

Clerk: What make and model car is it for?
You: Aaaarrrgggghhhh

[Mo]

We have a guy at "Diesel Auto Electric" here in Dartmouth. He's been there as long as I can remember...and he knows A4's as well. Literally a wiz behind the counter. Jim will come up with one

[roadnsky]

...A question I have for the group is how warm should these coils be after running for an hour or two in an enclosed engine space?

Neil-
Before I put in my resistor (Echlin ICR 5500) I shot a temp of 200° plus after about a 30 minute run.
Aimed right at the "O" on the FLAMETHROWER label.

[ndutton]

Before I put in my resistor (Echlin ICR 5500) I shot a temp of 200° plus after about a 30 minute run.

YIKES & GADZOOKS
What was the temp after the addition of the resistor?
What is your alternator output voltage?
Is your Flamethrower epoxy or oil filled?
What is the coil resistance? I have the same one (oil filled). It's spec'd at 3Ω but actually measures 3.3Ω

What time of year? Maybe important in your case.

[roadnsky]

YIKES & GADZOOKS

Exactly

What was the temp after the addition of the resistor?

Only "shot" it twice. Both times around 110°

What is your alternator output voltage?

At idle (750rpm) is 13.57
At cruise (1700rpm) is 14.20

Is your Flamethrower epoxy or oil filled?

Epoxy

What is the coil resistance? I have the same one (oil filled). It's spec'd at 3Ω but actually measures 3.3Ω

Don't have the notes with me but remember it being 3.1 or 3.2Ω

What time of year? Maybe important in your case.

It was in the summer, so admittedly higher because of the environment.

[ndutton]

Well sir, you passed the quiz. The only comment I have is oil filled coils are more tolerant of heat than epoxy. In your environment you might consider it when it's time for replacement.

[roadnsky]

...The only comment I have is oil filled coils are more tolerant of heat than epoxy. In your environment you might consider it when it's time for replacement.

Yeah. Found that out too late in my case.
I have a spare coil. But you'll never guess what it is.

With the resistor on there now, I don't plan on needing a coil for some time...

[Mark S]

Got the ICR 5500 and will install it and the coil when next at the boat. The NAPA guy told me the resistor goes between the coil and the points, or Ignitor in my case. Makes sense to me. You guys who use the resistor, is that where you put it?

Mark

[hcrisp]

Resistor

The resistor's purpose is to reduce the current TO the coil is my understanding.

[roadnsky]

Got the ICR 5500 and will install it and the coil when next at the boat. The NAPA guy told me the resistor goes between the coil and the points, or Ignitor in my case. Makes sense to me. You guys who use the resistor, is that where you put it?

Mark

Mark-
I put mine in front of the coil.
I believe someone else put it before the EI.

There's a discussion about it in the marathon coil thread.

[roadnsky]

There's a discussion about it in the marathon coil thread.

Ok, found it. Neil quoted here in his post #113 in the COIL/RESISTOR thread:
"My resistor is installed just ahead of the coil. One resistor terminal gets the ignition wire from the switch, the other goes to the coil +. Here is the scanner I have.

Full disclosure:
Thatch emailed me a Pertronix diagram he uncovered that showed a ballast resistor. On their drawing the Ignitor module positive (red wire) is connected ahead of the resistor whereas mine is connected after the resistor. My way delivers lower voltage to the ignition module but I don't think it's any big deal. Pertronix specifies 8-16 volts range for their Ignitor so I think we're good either way. Without accurate measurement yet I estimate I'm running at 11 - 11.5 volts to the coil and module (after the resistor). I was unaware of their drawing when I installed my resistor, just did it without regard for the module. It's working fine though, starts instantly and runs smooth.

Stewing on it overnight I think I prefer the slightly lower voltage to the module. It might prolong its life. This is pure speculation. I could just as well start a thread next week on module failure, who knows?"


Here's the page:

http://www.moyermarine.com/forums/showthread.php?t=5748&highlight=coil+input&page=3

[ndutton]

Here's the installation drawing I mentioned.

Installing the resistor in the black wire from the ignition module has the same effect of reducing the voltage to the module, contrary to the published instructions. Either way you do it please know that the resistor can be overdone. At around 9 volts to the coil it ceases to function properly. This is why it's important to get the resistor right, enough but not too much. The ballast resistor calculator found in numerous posts eliminates the guessing. It's based on real world testing on an Atomic 4 and builds in a modest 15% safety factor.

[Dave Neptune]

Fwiw

I have the Indigo E/I and after running it for around 10 years without a resistor, I called Tom for an opinion. He asked me to try a resistor on mine to see if I could detect any "cold starting or while running issues". The E/I hot feed is on the resisted side with the coil. I never did check the voltage, I just installed the resistor supplied to me. I have been using it for a bit over a year now and did not notice that I had made any changes at all. The E/I will work will with lowered voltages, as long as you stay within suggested voltages. I absolutely did not notice anything and I must say it did suprise me a bit.

Dave Neptune