Coil input information

[joe_db]

Unless your A4 is wired other than stock, it was designed for a 12 volt coil. When I bought one from the local Western Auto the parts guy asked if the engine used a ballast or not and looked up the part # for a 12 volt coil.
BTW, going from the Indigo system to points seems to have ended my endlessly burning out coils

[swallace11]

Hot Coil

Have read above discoveries with interest. I changed to Pertronix EI a few years /ago and also bought Moyer stock coil, said to work with EI, ie 3 amps. Big improvement, but was concerned about how hot the coil got. Coil ran hotter than adjacent engine block and could be touched only momentarily.

Two years ago switched from ammeter in start panel to voltmeter to discover 15-16v. My original regulator started to ooze black mastic sealant. This was about time that Shawn recommended the adjustible voltage Transpo through ASE which I also installed and gave 14.2 out of box and was a direct bolt on replacement. Also resulted in full battery charging, 12.8 volts at rest. Based on others experience above, I'm still concerned about the coil heat, so have now ordered a 0.8 external ballast resistor to suppliment just in case. Can't measure coil temperature but hoping to note cooler to the touch operation. Was also thinking of wrapping the coil with aluminum with fins folded in for greater head dissipation.

[Mo]

Don Moyer,s coil thread.

Swallace,

This is a link that Don Moyer wrote. It's worth a read.

http://www.moyermarine.com/forums/showthread.php?t=171&highlight=filled+coils

[sastanley]

wow - 4 amps!

Mo, thanks for posting that..if you read the details, it has the same info that Neil recently found regarding max amps, but Don wrote that piece in 2005!

I dunno why I didn't see it before.

Maybe we need Admin Bill to add extra tags to anything Don Moyer writes, so that when we do a search on a particular subject in the forum, his comments are always at the top of the list.

It would probably save us newbies a lot of trouble.

[ndutton]

Yeah Shawn, had we simply followed Don's treatment we could have saved a lot of grief.

Which brings me to my Pertronix gripe - not their product but actually their customer support.

Problem 1
You and I independently approached them with your recent coil overheat and failure. I actually cut and pasted your data set and sent it to them as if it were my own. Their responses were from different techs/engineers and were completely different from each other!! This did not instill confidence that they had any idea what was going on.

Problem 2
They specify a 4 amp maximum system current with their Ignitor electronic ignition product. They recommend their 3 ohm Flamethrower coil for this system, "The perfect match." They have to know every 12V alternator in the civilized world puts out 13.8 or more volts. So their recommended system results in at least 4.6 amps, contrary to their own specification!! To adhere to their spec we have to use a resistor which they don't mention anywhere visible. If they do it's three layers deep in some tech troubleshooting page.

OK, that rant is done. I'm feelin' a huge sermon coming on over Pam's shyster mechanic.

[Mo]

read it last spring.

Hey Guys,
I'm no electrical wizard. I remembered reading it last spring and thought that swallace could gain some info regarding oil filled coil heat. You guys are the ones doing all the testing and to be honest, I'll suck up the information that you guys come up with.

[67c&ccorv]

This has turned out to be one of the more interesting and informative threads in a while thanks in large part to Neil and Mark and others. Good shot Kelly! Since the coil (automotive type) is designed to run on 9 volts it seems we have a large voltage cushion to work with. I will do the math as recommended by Neil to see where I fit in the equation. 40K volts? Are we headed back to the Drags?

SStanley: "Yup....flying down the creek at 2,000 RPM!"



Actually...it does sort of remind me of a drag race Hanley and Shawn.

You know that part of the race I mean Hanley - where you look on one side and the guardrails are flashing by at light speed...and then you look at your closely matched opponent and it seems he is gaining/losing on you by a snails pace.

I think they call it a paradox...or something like that!

[swallace11]

Hot Coil

Thanks much Maurice for pointing this out. I now remember reading this FAQ sometime ago. I've been through all the major systems on my A4(Tartan 30) and it is running extremely well. Smooth idling, easy starting, steady 160 deg temp. 115 compression. On a recent 100 mi trip, had to motor part way and got about 0.55 gal per hour at 5.25 kt. To keep it that way I try to keep up on small improvements such as external ballast resistor if making system more fail safe. With 4 ohm coil, seems the safety factor is already built in. This thread has provided a great learning experience.

[Carl-T705]

Perhaps the answer lies in powering the ignition off a hot lead from the battery or key switch rather than directly off the alternator where the voltage would be more consistent.

[hanleyclifford]

Perhaps the answer lies in powering the ignition off a hot lead from the battery or key switch rather than directly off the alternator where the voltage would be more consistent.

Good point. The voltage coming right off the alternator is going to be the highest in the (dynamic) system. Moreover, it is "dirty", that is ahead of the noise suppressor and possibly subject to spikes. Ignition should be tapped well downstream of the alternator - I run mine from the main buss bar thru a toggle and then an oil pressure switch.

[Triton106]

I am reading this thread with more than passing interest given my own coil/alternator issue. I also converted to EI a couple of years ago.

It seems that all of calculations in the postings here assume that the coil (-) is 0v or ground. However, I noticed that while my coil (+) is 17.4v (which obviously is too high) the coil (-) is approximately 9.2v. I am not sure if that is what it should be or it should be 0v. I traced the coil (-) wiring - one wire goes to EI (-) and the other goes to the tach. Is the tach or the EI (-) suppose to be grounded?

In my case, my coil was recently fried. The alternator is putting out 17v as mentioned. I still have not found out the root cause. If it is even implied that EI could be cause I am going back to points, condenser system. I still have a new set as back up.

[Kelly]

Which brings me to my Pertronix gripe...

Problem 2
They specify a 4 amp maximum system current with their Ignitor electronic ignition product. They recommend their 3 ohm Flamethrower coil for this system, "The perfect match." They have to know every 12V alternator in the civilized world puts out 13.8 or more volts. So their recommended system results in at least 4.6 amps, contrary to their own specification!! To adhere to their spec we have to use a resistor which they don't mention anywhere visible. If they do it's three layers deep in some tech troubleshooting page.

I'm glad you said it first, Neil. I don't have enough confidence in my electrical knowledge to call someone out on the subject, but in the back of my mind I was thinking the same thing. I thought I was walking the golden path by matching my Pertronix EI to the recommended Pertronix coil...then comes along the math behind the Volts, Amps, Min., and Max. and now we're back to cobbling something together to be within specifications. Sheesh!

Thanks for expressing with words my secret grievances.

Shawn-

can you measure the static resistance of the coil

3.3 Ohms

Also, measuring as per the Pertronix recommendations: 11.6 Volts at coil+ with the starter switch on run.

[joe_db]

FYI: Coil current would only follow the I=V/R formula with the points (or electronic equivalent) closed and the engine OFF.
I don't want to bore you all with the details of inductance and what is essentially a high frequency AC system, but the only good way to actually know what the coil current is would be to actually measure it with the engine running.

I always thought it would be nice if someone made an "old low RPM engine electronic ignition" that used less dwell than a modern system. Not saying this is an issue, but it seems like it could be.

[sastanley]

Thanks Kelly..just trying to build a little database in my head for these things. I never bothered to measure my 'bad' coil before it went bad, so I was wondering if my 3.3 ohms I was reading was similar to other coils or if burning up the coil had changed the resistance from 'stock'. When I get back to the boat, I will measure the resistance of my new Flamethrower that has never been used for comparison.

Never made it to the boat this weekend (man, the weather here on the US East Coast has been awful!) so, no new news to report.


Cheers!

[edwardc]

... (man, the weather here on the US East Coast has been awful!) ...

I am so THOROUGHLY SICK of rain!