Author Topic: Twin spark coils.  (Read 8712 times)

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michaelodonnell500

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Twin spark coils.
« on: March 28, 2017, 10:14:29 PM »
I was looking for a twin spark coil last week and the prices are a bit steep.

Other twin spark coils are available and they are still cheep so I thought I'd test one out to see if it works.

I bought one of these from eBay as they are very common and low cost. Better quality ones are available.



This has a plastic connector rather than 2 male spade connectors so I will need an adapter in the long run.

I tested it and it worked. Car started fine and ticked over as normal.

I will need to modify the bracket to bolt it in place. It's not a straight swap, but it is a low cost alternative and if you ever got stuck at the side of the road you could pick this up from eurocarparts and hold it in place with a few cable ties!

I've started making a bracket by removing the bracket from the old one:







I'll post an update once I've modified the bracket and done a few miles on it.


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Rusty's Uncle

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Re: Twin spark coils.
« Reply #1 on: March 29, 2017, 08:22:48 AM »
Nice one Michael  :)
After burning out two brand new £45 twin spark coilsas many weeks last year I got straight on ebay and got one of these for £9.28 .
I then remembered that in a lot of parts I bought last week there is a 126EL ignition set up. Guess what it uses that same coil pack. Also has the connector but sadly the two wires have been cut with only about 6mm left but I will be able to solder onto them.

DEYAN IYI

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Re: Twin spark coils.
« Reply #2 on: March 29, 2017, 10:44:54 AM »
Hi!

In case someone is replacing the single coil to double, do not forget to use an external resistor. The models with the double coil power it trough a sky blue cable  of 1.7 Om resistance, if I remember well.

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Deyan

mintex

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Re: Twin spark coils.
« Reply #3 on: March 29, 2017, 10:34:10 PM »
Nice one  :good:
Dave

michaelodonnell500

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Re: Twin spark coils.
« Reply #4 on: April 09, 2017, 07:01:18 PM »
I've welded up the bracket to hold the coil so the cinq/panda coil now use the 126/500 bracket.

This coil measures 0.7ohm which is a bit low. I've read a number of different manufacturers websites which all, irritatingly have different opinions as they are written for different reasons.

Firstly.
Aftermarket distributor manufacturers require the coil to be at least 1.4ohms to prevent damaging the points.  So I have bought a 1 ohm ceramic resistor to bring my coil up to 1.7ohms.

Secondly
Ballast resistor.  I don't believe they are needed on a 12v coil. I have read that they were required on 9v coils. The extra current available upon starting allows a stronger spark while the starter is cranking and during colder months. Once the ballast has warmed up the resistance increases allowing the 9v to run in a 12v circuit. This is not the case for 12v coils because they cannot draw more current than they can handle in a 12v circuit.

I haven't used a ballast resistor in the 5 or so years my twin spark coil was fitted. The coil is now dead because I left the ignition on for 2 hours. I would recommend doing that, it creates a lot of smoke and it stinks!

I will test this new coil with and without a ballast resistor to compare results.

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« Last Edit: April 09, 2017, 09:08:07 PM by michaelodonnell500 »
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michaelodonnell500

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Re: Twin spark coils.
« Reply #5 on: April 20, 2017, 09:21:31 PM »
Here is the 1 ohm resistor I boughtalong with a few leads I made up to bridge between the new coil and the existing wiring.



I'll make some better wiring up soon, this was just to allow for a simple test.

The lead on the right connects via the resistor to the ignition.  The lead on the left connects to the distributor.


I took it out for a spin tonight and it ran fine. So far so good. I'll be using it from now on so I can update with some progress.

Once I've made up a connector lead I'll draw up some instructions on how to make a connector adapter to fit this coil without modifying the wiring loom.



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« Last Edit: April 20, 2017, 09:24:10 PM by michaelodonnell500 »
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michaelodonnell500

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Re: Twin spark coils.
« Reply #6 on: April 22, 2017, 05:14:19 PM »
Here is the 1 ohm resistor I boughtalong with a few leads I made up to bridge between the new coil and the existing wiring.



I'll make some better wiring up soon, this was just to allow for a simple test.

The lead on the right connects via the resistor to the ignition.  The lead on the left connects to the distributor.


I took it out for a spin tonight and it ran fine. So far so good. I'll be using it from now on so I can update with some progress.

Once I've made up a connector lead I'll draw up some instructions on how to make a connector adapter to fit this coil without modifying the wiring loom.



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Well that didn't last long! I've had 30 miles or so out of the new setup before it died on me.

The 1 ohm ceramic resistor failed which then caused the points to arc with the excess current going through them. The condenser may have failed too but I haven't tested it I just swapped it for a known good one.
I filed the points back, set the gap, redone the timing then put it all back together.

This time i have fitted a ballast resistor.  The last resistor may not have been rated for the current that was being drawn through it.

On the plus side the coil survived the battle!

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Gadge

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Re: Twin spark coils.
« Reply #7 on: April 22, 2017, 05:56:08 PM »
Ahh that's ashame. Could it have been a dodgy resistor?
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michaelodonnell500

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Re: Twin spark coils.
« Reply #8 on: April 23, 2017, 07:38:13 PM »
It may have been. I'll check the specifications first.

I might try and replicate it on the bench so I can test it off the car. Redoing the points at the side.of the road is a nuisance I'd rather avoid!
I've been out for a few small drives with the ballast resistor and it seems to be working OK.

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Rusty's Uncle

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Re: Twin spark coils.
« Reply #9 on: April 23, 2017, 08:53:00 PM »

I might try and replicate it on the bench & I've been out for a few small drives with the ballast resistor and it seems to be working OK.

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Good to hear that you two are getting along OK  ;D

michaelodonnell500

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Re: Twin spark coils.
« Reply #10 on: April 23, 2017, 08:58:31 PM »

I might try and replicate it on the bench & I've been out for a few small drives with the ballast resistor and it seems to be working OK.

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Good to hear that you two are getting along OK  ;D
It's been a rocky relationship but we're working through it.

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Gadge

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Re: Twin spark coils.
« Reply #11 on: April 23, 2017, 09:14:50 PM »
Its a good trial I've often looked at these newer style coils and wondered if they would work on the older cars. Just out of interest what could potentially happen if you didn't use the resistor?
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michaelodonnell500

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Re: Twin spark coils.
« Reply #12 on: April 24, 2017, 04:20:53 PM »
once the resistor blew I was running it without a resistor! It allowed  too much current through the points which caused them to arc and stop working. It may have killed the condensor too but I've not tested it yet. I'm not sure when the resistor blew so I'm not sure how long it was working without one.

the modern coils I have measured are all below 1 ohm.
Anything below 1.4 ohm will damage the points unless you add an appropriate resistor or add contact-less points (Accu-spark etc.)

I'll keep going with this and should be able to put together a conversion kit once I've ironed out all of the issues!
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drcdb15

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Re: Twin spark coils.
« Reply #13 on: April 26, 2017, 10:22:09 PM »
once the resistor blew I was running it without a resistor!
Not quite sure I understand this - if the resistor blew, as in vaporised hence infinite resistance, in effect it acted as a fuse and that should have stopped the igntion completely. If the car kept running, presumably the resistor must have short-circuited to zero resistance?

You've probably seen these items already, but if it might be of any help, there is info on what resistance values to look for and the wiring for a standard set-up:

First a quick explanation of how a ballast system works
When a car is first started, the oil is thick and the engine is cold and hard to turn, so the starter will draw a large amount of current. Whilst cranking, you may notice the lights dim as the engine turns, this also means that the coil is robbed of current which in turn causes a reduced spark that will make the car hard to start. Often you will find the car starts at the very moment you let go of the key as this is the point it full voltage returns.
To overcome this the ballast ignition was developed. The car is fitted with a coil that runs on a reduced voltage. The coil is then fed through a ballast resistor or wire that reduces the current to the correct voltage for the coil.
Now the clever bit. When the engine is cranking the starter solenoid feeds the coil directly with 12 volts, bypassing the resistor. Although the car is cranking and all the voltage is reduced throughout the electrical system, the coil is receiving more volts than it requires which compensates for the voltage drop, thus giving a full spark.
How to test
Most people will tell you to test the feed for the coil. This tells you nothing - it will always show around 12 Volts because there is no load on the system, the resistor has nothing to resist ! ( unless the points are closed )
If there is no ballast resistor visible you may have a ballast wire inside the loom. To test for it proceed as follows:
Check voltage of battery with volt meter
Remove the wires from the negative side of the coil ( negative earth cars )
Connect a temporary wire from the negative terminal of the coil to earth
Turn ignition on ( nothing else switched on )
Now check the voltage on the coil, put red probe on + side of coil and the - probe to earth
If the reading is less than 80% of battery voltage there is portably a resistor in the system. If it is more than 80% you probably have a standard system
Remove the temporary wire and reconnect wires .
If your reading is less than 80% you should use a ballast coil , AccuSpark Blue
If you reading is more than 80% you should use a non ballast coil , AccuSpark Red
 
As a final note :
A standard 12 volt will only have a single 12 Volt feed to coil
A ballast system should have 2 feeds. One resisted feed and a second full 12 volt feed when the starter is engaged
Do I have the correct coil ? Testing your coil
To test coil set voltmeter to Ohms, test between -and + terminals. A reading of around 3 is a standard coil, a reading of around 1.5 is a ballast coil.
Removing Ballast resistor
What do do if you wish to remove the ballast system and go with a standard 12 Volt system ?

If you have a visible resistor you just need to remove the resistor and join all the wires.

If you have a ballast wire in the system proceed as follows:

Remove the 2 feeds into the coil and tape up
You can run a new wire from the coil to the back of the ignition key
You can also take a feed from the fuse box. This must be switched by the key and be on the live side not the fuse side. To test, it should still work with the fuse removed


1973/126

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Re: Twin spark coils.
« Reply #14 on: April 26, 2017, 11:47:04 PM »
 I`m running a standard bis twin coil on our air cooled with no resistor and haven`t had a problem so far.
 Also on one of my later air cooled cars that was originally fitted with a twin coil there was a condenser connected to the coil as standard.
 The 126Fan guys have it listed on their web site.
 http://www.126fan.sk/eshop/index.php?main_page=product_info&cPath=16&products_id=112&language=en
 And here is a picture I found on the internet. Ignore the rest of the stuff in that engine bay:)
 
1972 Fiat 500
1980 Fiat 126