Ignition coil

Farmer42

Club Member
Hi all

I have a dilemma with my ignition coil.

A couple of weeks ago, my coil packed in and I thought it was a good opportunity to upgrade to a Flamethrower coil. I am running a 260Z with the E12-80 280ZX electronic distributor. I couldn't see what the resistance was on the old coil but I know it didn't have a ballast resistor attached. Couldn't get a reading on it when I tested it.

All the indications from reading and the advice given was leaning towards a 3 ohm coil so I bought one. However, I fitted it and the car turned over and over before eventually starting and then ran like a dog - coughing and spluttering. All the wires were checked along with the spark plug gaps & all fine. Tested the coil resistance with a multimeter and it showed 3 ohms.

Luckily I had borrowed an OEM Nissan 280ZX coil off Huw to get me to JDM day at Combe whilst I was awaiting delivery of the Flamethrower and the car started & ran great off that. Tested it and it was 1.5ohms. Again no ballast resistor was used.

Question is, do I persevere with what should be the correct 3ohm coil and if so should I be setting anything on the engine to compensate or do I return it and go with a 1.5 ohm coil? Would it wreck the electronics on the dizzy by doing so?
 

toopy

Club Member
1.5 ohm coil for electronic ignition is correct, 3 ohm is high performance points coil, but it should still work, just wouldn't last as long.
 

nospark

Well-Known Forum User
Farmer
I have similar to you. 240z with 280zx dizzy (e12-80 module) and no ballast resistor. I bought a petronix flamethrower 3 ohm coil based on the advise of old threads on this forum. It gives stable firing with a timing light BUT it acts like a rev limiter at just over 4,ooo revs when everything just boggs down. Since your post i have done lot of reading and have found other threads where it happens on this setup.

Go to xenonzcar.com and read the 280zx FSM. The section on the ignition module is interesting but what seems to be most relevant is the OEM coil is 0.84 to 1.2 ohms. So I am really wondering why some people say 3 ohm on a e12-80 module set up when the FSM a coil with a much lower resistance is what is required. More reading for me but i am going to dump my 3 ohm coil.
 

Farmer42

Club Member
Interesting!

So why does all the advice and previous threads (& even the description for the Flamethrower coil on MJP website given by Mr F) point to a 3ohm coil for electronic ignition?

Did a bit more reading. The MSA website recommends a 1.5 ohm coil with a ballast resistor for factory electronic ignition i.e. an E12-80 system. Other information suggests that using a 1.5 ohm coil without a ballast resistor will burn it out quicker which is possibly why mine died in the first place. Other info suggests using a 3ohm coil but considerably widening the spark plug gap although it doesn't say by how much.

Confused.com!!! :conf2::EXTRAconfused:
 

toopy

Club Member
A 3 ohm coil should work perfectly well with points or electronic, but as above, not always the case it would seem, 1.5 ohm is optimum tho for electronic in the case of 280zx ignition.
The ballast resistor only comes into play when starting, for points it helps, for electronic it does nothing or is a hinderance!
 

jonbills

Membership Secretary
Site Administrator
A 3 ohm coil should work perfectly well with points or electronic, but as above, not always the case it would seem, 1.5 ohm is optimum tho for electronic in the case of 280zx ignition.
The ballast resistor only comes into play when starting, for points it helps, for electronic it does nothing or is a hinderance!
I think it's the other way around - on the points distributor. the ballast resistor only doesn't come into play when starting. when running, the ballast resistor is in play, so the points burn out less quickly.
Or, put the other way round, you don't have to have a ballast resistor at all with points, as long as you enjoy changing points very regularly.
 

toopy

Club Member
I think it's the other way around - on the points distributor. the ballast resistor only doesn't come into play when starting. when running, the ballast resistor is in play, so the points burn out less quickly.
Or, put the other way round, you don't have to have a ballast resistor at all with points, as long as you enjoy changing points very regularly.

Your right Jon, my bad! :)
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
The ballast resistor is a starting aid. When starting it's out of circuit allowing max (over) voltage at the coil and hence a bigger spark. When running it's in circuit and 'dropping' voltage across it so as not to overheat the coil.

I've tried to measure the 'primary' (low voltage circuit) resistance on my coils today without reaching a conclusion. I have three meters including a 'Fluke' digital meter. I just couldn't get reliable readings, will try again and report back. If I had to guess I'd say my Sam has a 3ohm coil and my blue car virtually no ohms! Both have 280ZX Dizzys. Ridiculous and no help so I'll get to the bottom of it when I have replace batteries and tested fully.
 
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nospark

Well-Known Forum User
The e12-80 module has roughy 5 "programmed" functions, including a duty cycle. It needs to "see" 12v hence the ballast resistor is removed (which would give 9v at running) . The e12-80 module likes a 0.84 to 1.02 ohm primary resistance coil because the currents and voltages match the modules' duty cycle. The primary coil windings builds up magnetic saturation, gets cut abruptly and transfers the very high voltage to the secondary windings and on to the spark plugs. Remember Voltage= resistance x current. The module in theory is designed to handle 12v/1ohm=12amps.
With my presently fitted 3ohm coil, the engine hits 4,200 rpm the engine revs go no further. This is because the modules duty cycle doesn't match the expected/designed resistance/current and can't saturate and cut the electromagnetic force in the coil in the correct way. In simple terms your electronic control module whether its e12-80 or and aftermarket module needs to match the resistance and voltage of the coil to they are both singing from the same hymnsheet.

I am not experienced in autoelectrics so someone might say my observations above are incorrect. I've just done some reading the past few days and just put a bit of what i've learned.
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
The resistance of my coils are 1.5ohm and less than 1 ohm. Both work fine (no ballast).
 

AliK

Vehicle Dating Officer
Staff member
Club Member
The e12-80 module has roughy 5 "programmed" functions, including a duty cycle. It needs to "see" 12v hence the ballast resistor is removed (which would give 9v at running) . The e12-80 module likes a 0.84 to 1.02 ohm primary resistance coil because the currents and voltages match the modules' duty cycle. The primary coil windings builds up magnetic saturation, gets cut abruptly and transfers the very high voltage to the secondary windings and on to the spark plugs. Remember Voltage= resistance x current. The module in theory is designed to handle 12v/1ohm=12amps.
With my presently fitted 3ohm coil, the engine hits 4,200 rpm the engine revs go no further. This is because the modules duty cycle doesn't match the expected/designed resistance/current and can't saturate and cut the electromagnetic force in the coil in the correct way. In simple terms your electronic control module whether its e12-80 or and aftermarket module needs to match the resistance and voltage of the coil to they are both singing from the same hymnsheet.

I am not experienced in autoelectrics so someone might say my observations above are incorrect. I've just done some reading the past few days and just put a bit of what i've learned.

What are those 5 functions?
 

Farmer42

Club Member
Rob

Do your coils get hot and are they the Pertronix Flamethrower coils? A couple of sites that have them online say that the 1.5 ohm coil will overheat unless used for racing or high revs.

I eventually managed to get a reading out of my old knackered coil and it was 1.2ohms. I was running that without a ballast resistor and it was getting very hot to the point that the oil was leaking from the front. I think it was a bosch coil. I have been doing some more research and all the literature (Haynes Manual, FSM etc) says to use a 1.5ohm with ballast but that the dizzy module needs the full 12 volts.

I need to do something soon to replace the borrowed coil but I am minded to avoid the Flamethrower. I have a ballast resistor from when I had the points dizzy so I will try it without first but if the coil starts getting hot, I will try the resistor & post up the results.
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
Getting hot - don't know but both have been driven many miles as they are.

What makes a coil a 9v coil or a 12v coil? I need to research. If you are running a 9v (ballast) coil on 12 volts that might be the problem?
 

jonbills

Membership Secretary
Site Administrator
Or if your regulator doesn’t work and you’re running it at 18 volts [emoji849]
 

nospark

Well-Known Forum User
Ali, go to xenonzcar.com and go to the 280zx factory service manual. There is a section in the manual on the e12-80 module.

You will be hard pushed to find an aftermarket/branded coil with a primary resistance of 0.84 to 1.02 ohms. I tried hard. Also, Nissan no longer supply. The USA/Japan might be a source. A couple of years ago I replaced what I thought was my dodgy 280zx coil (the car cut out once on a dual carriageway) with the Flamethrower 3 ohm . Thought it must be "better". Recently put my old 280zx coil back on the car (it reads 1.2 ohms on the multimeter). Car now revs better and up to 6,000rpm where the tired lump starts to shows its age. So thanks to Farmers original posting i have learned about coils and sorted out what I thought was just a tired old engine problem.
 

jonbills

Membership Secretary
Site Administrator
To add a little info to this thread.
I have an epoxy filled flamethrower coil. It is 1.8 ohm. Works great with my 280zx dizzy.
I used to use the Pertronix/Aldon ignitor with the same coil but didn’t run well above 6k revs which I’m pretty sure is down to Pertronix - I think I’ve used other coils too to no avail.
4e5078c9277ce0047e5f5cd4d6535b73.jpg
 

Farmer42

Club Member
Jon

I notice you have a ballast resistor underneath. What is the voltage from the positive to the coil when it's running (9 or 12) and the voltage at the negative on the ballast? It would be interesting to see if a lower voltage is needed to protect the coil but still supply the dizzy with 12 volts.

Also, just in case I need to wire one in, how is it wired? Is it ignition wire (b/w) to negative on the ballast, from the negative on the ballast to the dizzy module and then from the +ve on the ballast to the -ve on the coil?

Thanks
 

jonbills

Membership Secretary
Site Administrator
Jon

I notice you have a ballast resistor underneath. What is the voltage from the positive to the coil when it's running (9 or 12) and the voltage at the negative on the ballast? It would be interesting to see if a lower voltage is needed to protect the coil but still supply the dizzy with 12 volts.

Also, just in case I need to wire one in, how is it wired? Is it ignition wire (b/w) to negative on the ballast, from the negative on the ballast to the dizzy module and then from the +ve on the ballast to the -ve on the coil?

Thanks

Hi Paul, the ballast resistor is really only there as a handy post for all the terminals and the original looks [emoji3] all the wires are at the same end so about 11.75v from memory. Here’s the wiring
49337ce2ac02b9afd016f57c602b9154.jpg


So the dizzy supplied off the coil (although I do keep meaning to move the dizzy supply back to ballast resistor post to keep it logical and separate)
 

Farmer42

Club Member
So, finally cracked it!!:party:

I returned the 3ohm Flamethrower and bought a Lucas DLB110 1.5ohm coil for £16 which was supposed to be the equivalent of the OEM 280ZX STC-30 coil. I looked for an OEM coil but they appear to be discontinued although you can get an equivalent aftermarket one from the States for megabucks.

Fitted it up without the ballast resistor and had the dizzy supply from the +ve on the coil. I then reset the spark plug gaps to 1.1 mm which was supposed to be the correct setting for the coil and a 280ZX dizzy. It turned over a fair few times before starting but didn't run great and felt down on power. The coil also got quite hot.

I then fitted up the 1.6ohm ballast resistor with the +ve supply to the dizzy connected to the -ve side with the feed coming from the black/white ignition wire and the green/white connected to the +ve and the other b/w to the +ve on the coil as shown in Jon's pic above. The -ve on the coil went to the -ve on the dizzy.

It started ok but I still felt a lack of power & a slight misfire so I tried resetting the spark plugs back to 0.9mm.

This worked a treat. It started first time and runs sweet with no power drop and no bogging down on higher revs. Even the Tach still worked!!:hurray:

Ran the car for around 45 minutes what was a fairly hot day on Sunday and the coil felt a lot cooler. Same again last nite on a 2nd trial run. There was a slight voltage drop between the ballast resistor and the coil but normal voltage on the feed to the dizzy. The voltage increased to the +ve on the coil when the ignition key was turned to start indicating that it was bypassing the ballast but dropped again when on normal ignition position when the engine was running.

It seems therefore that 12v coils prefer less voltage when they are running as has been said before in this thread and that the ballast does a job. A 3ohm coil with or without a ballast resistor does not run a dizzy with a E12-80 module (or it didn't in my case!).
 

toopy

Club Member
Glad it's all sorted, :thumbs:

There's obviously something unique about your car/dizzy/wiring that requires the ballast resistor to be retained, mine was removed when i replaced the dizzy and coil as per the usual advice for this upgrade, and it's worked fine since day one!
 
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