Coil input information

[roadnsky]

Jerry - Would you mind posting some voltage readings for that resistor, both sides - after warmed up and running, batteries full. Thanks, Hanley

Hanley-
I'm back from my trip and got to the boat today and ran some numbers.
I know that you're riding out SANDY right now, and have bigger concerns than resistor/coil numbers, so I'll wait until you pop out the other end.
Lemeno when you're back with us.
God's Speed...

[RobH2]

Yes, definitely need to get back to this later. We've been out of power for 5 hours in Baltimore. Running on generator for a few minutes. I'll check back in a few days. I hope everyone's boat is safe.

[roadnsky]

Ok, back to Coil Stuff...

Hanley-
It seems that you are back among us safe and sound, so here are the promised numbers from my coil, post resistor install...

My FLAMETHROWER Coil read @ 3.3Ω before I installed the 0.85 Resistor

AT REST / No Ignition:
BATTERY = 12.67v
COIL B4 Resistor = 7.9mv
COIL After Resistor = 7.8mv

IGNITION ON:
BATTERY = 12.57v
COIL B4 Resistor = 11.18v
COIL After Resistor = 9.04v

ALT ON @ 1000rpm:
BATTERY = 14.29v
COIL B4 Resistor = 13.57v
COIL After Resistor = 12.24v

ALT ON @ 1800rpm:
BATTERY = 14.30v
COIL B4 Resistor = 13.66v
COIL After Resistor = 12.45v

ALT ON / Idle @ 800rpm:
BATTERY = 14.29v
COIL B4 Resistor = 13.59v
COIL After Resistor = 12.23v

Zero differences starting or running that I can see.
Hope that helps.

[Ball Racing]

I noticed a fair ohm change between a hot running coil, and one that is non running and at outdoor temp.

So,, should you always ohm test for your resistor at non running temp, or get a ohm reading after running for a while.

Mine runs great right now, and can run hours at low speeds, no problem.
But after I switched out to EI , and started measuring coils, and resistors I noticed the change in ohms at the coil when warm.
Just something I have been meaning to post about for the last year or so...

[ndutton]

Daniel,
Would you say the difference in resistance is significant? Is this with a new coil or one that's been around the block a few times, perhaps even with an overheating episode in its history?

This is one of the reasons we built in a 15% safety factor in the Excel calculator. It's always nice to have a little cushion. Our recommended target amperage was 3.4 amps rather than the 4 amp maximum. As I said previously, the target amperage was chosen arbitrarily by me, a seat of the pants guess and a place to start testing. Thus far there hasn't been a reason to change.

While we're talking about it, lemme tell ya there's a certain level of risk coming out so strongly with this EI/coil resistance study and recommendation. It was based on a very limited testing sample and was contrary to the manufacturer's technical advice. It's been a couple of years since we published our opinion and I've been dreading the report that hasn't come yet, the report of a failure with this setup. Of course I hope it never comes but there's always the possibility, y'know? Nothing's guaranteed.

[hanleyclifford]

Thanks for those numbers, Jerry; it seems that the Flamethrower is comfortable cruising just over 12 volts. Is it hot to the touch after cruising at that voltage?

[Ball Racing]

Daniel,
Would you say the difference in resistance is significant? Is this with a new coil or one that's been around the block a few times, perhaps even with an overheating episode in its history?

I put a new coil on with the points and ran for a couple of months or so and then switched over to EI.
I don't believe I ran the EI without a resistor. So the coil should have been good.
I can't give the exact numbers as I didn't write them down, But I am thinking I saw from a third to a half of ohm or more difference when hot.
I may have posted some of this somewhere, anyway, just wondering with all this testing, if ohm testing @ warm running conditions were tested, or should be base line, and not cold.
And should a coil ever change ohms when hot even if less or up to a half ohm?

[ndutton]

Hmm, very interesting. A half ohm variation in a coil that measures 3.3 ohms (the typical Flamethrower story around here, 3 ohms specification that actually measures 3.3 ohms cold) calculates out at a 15% variation. There's that 15% figure again. If Moyer coils experience the same half ohm variation we're talking 11%.

I'm assuming your resistance is less at higher temperature and therefore the amperage would be higher and again, by 15%. Maybe the safety factor is keeping us in the good graces of the coil Gods.

All the resistance measurements I made were at ambient temperature. I never considered a coil's resistance would change with temperature. I should qualify that, I mean a coil that hadn't been abused with overheating and the resultant internal damage. We're talking good components here.

[roadnsky]

Thanks for those numbers, Jerry; it seems that the Flamethrower is comfortable cruising just over 12 volts. Is it hot to the touch after cruising at that voltage?

No. Not hot to the touch. Gun shows 110-120°
Unfortunately, to get a fair temp reading, I'll have to wait until next summer.
Right now the weather here is "perfect".
Sorry guys in the North East...

[roadnsky]

Neil, how do you have the ballast resistor wired in, looks like your coming off the + side of the coil to the resistor.
Where is the other side of the resistor going, maybe ignition switch ?

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 +.

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?

Neil-
My response to Mo yesterday on the other thread got me to thinking...
(I know, that smell is the smoke coming outta my ears)

With my BUSS BAR set up for the mass of coil wires, I realized that
my resistor is wired such that the EI is still getting full ignition voltage.
(PRE Resistor)
I haven't noticed any issue since adding the resistor in-line.
Starting, idling, cruising ALL seems to be normal.

Based on your comments (above) from last year, I'd like to hear thoughts about my set up, now that we're a year down the road...?

[ndutton]

Funny, as I was reading the earlier comments you quoted in your post I forgot they were mine.

What you didn't say but I'm assuming is your coil is getting voltage filtered through the resistor, right?

I have no reason to alter my opinion after all this time. My EI unit has lower voltage than yours but both are within the manufacturer's specification and they both perform well. My continued preference for lower EI voltage is pure speculation unsupported by any testing.

[roadnsky]

Yeah, I'm using the same resistor you are.
Wired one post from ignition and the other post to the coil + terminal.

My EI gets it's voltage (red wire) from the Positive Terminal on the Buss Bar.

I suggest we keep each one wired this way and see what time tells us?

[smosher]

Whats important is to reduce the current flowing through the coil. The resistor can be before the + or tied to the - side of the coil. The Goal is to get the amps down to less than 4 and the primary circuit to 4 or more ohms

I have a .8 50 watt ballast resistor connected between the - side of the coil and the black wire from the EI Ignition. My current flow through the loop is at 3 1/2 amps.

Steve

[ndutton]

The reason I think it shouldn't make a difference is the switching load through the EI is still at the lower voltage because it goes through the coil.

[roadnsky]

Whats important is to reduce the current flowing through the coil. The resistor can be before the + or tied to the - side of the coil. The Goal is to get the amps down to less than 4 and the primary circuit to 4 or more ohms

I have a .8 50 watt ballast resistor connected between the - side of the coil and the black wire from the EI Ignition. My current flow through the loop is at 3 1/2 amps.

Ahhhhhhh, I get it now!
Steve, both mine and Neil's resistor are also 0.85

The reason I think it shouldn't make a difference is the switching load through the EI is still at the lower voltage because it goes through the coil.

Agreed Neil.
Thanks guys