Author Topic: Twin Coil  (Read 296 times)

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urkrajnc

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Twin Coil
« on: April 06, 2018, 04:36:02 PM »
Hey guys. I'm still running "old type" of coil (rotor and distributor cap) and now I'm wondering where is the difference between this two?

https://www.ebay.co.uk/itm/Fiat-126-IGINITION-COIL-PACK/183085350694?hash=item2aa0bcbf26:g:NpUAAOSwwgRai9Vs

and

https://webshop.fiat500126.com/tuning/ignition/twin-ignition-coil-_cornered

As I understand (yes I did search on forum and didn't find proper answers) if I use coil from bottom link I need series resistor to work as it should, but what about the first one?
Do you maybe know if there is possible to buy coil from first link anywhere new? I can't found it any where. Also when I checked on this web page (photos) he used the coil from first link.

Thank you all for help.

p.s. if I put the topic in wrong section I apologise so please moderators to move it to the right one. Thanks

urkrajnc

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Re: Twin Coil
« Reply #1 on: April 09, 2018, 03:39:37 AM »
Anyone?  ::)

Xylaquin

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Re: Twin Coil
« Reply #2 on: April 09, 2018, 08:23:09 AM »
Sorry, I didn't comment on this because I'm not entirely sure... but I've always understood the second link is a BIS coil only, I've never seen it on an aircooled.

urkrajnc

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Re: Twin Coil
« Reply #3 on: April 09, 2018, 10:07:15 AM »
If you check on link its says:

This product fits the following models:
Fiat 126 (1972-1987)
Fiat 126 BIS (1987, 1988, 1989, 1990, 1991)

The thing is that is quite expensive with series resistor so Im wondering to get something cheaper :)


urkrajnc

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Re: Twin Coil
« Reply #5 on: April 09, 2018, 07:12:45 PM »
Thank for the answer. I had it on my car yes, but somehow get "damaged" and doesn't work anymore. That's why I change it for single coil with rotor and distributor head.

The second link you send me is the same like user @michaelodonnell500 did on his car. I'm looking more "plug & play" thing :D
http://club126uk.co.uk/forum/index.php?topic=10797.msg79714#msg79714

And on this one I still need series resistor don't I?
https://www.126fan.sk/eshop/index.php?main_page=product_info&cPath=16&products_id=187

Thanks

michaelodonnell500

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Re: Twin Coil
« Reply #6 on: April 10, 2018, 01:24:00 PM »

The second link you send me is the same like user @michaelodonnell500 did on his car. I'm looking more "plug & play" thing :D
http://club126uk.co.uk/forum/index.php?topic=10797.msg79714#msg79714


I am planning to make a plug and play adapter kit for this.
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thepuddlejumper

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Re: Twin Coil
« Reply #7 on: April 11, 2018, 10:51:35 PM »
I have the same double output coil on all of my 500’s and 126’s fortunately no problems so far, they look to be original as well. I have searched the tinternet to find replacements to no avail. I am not into auto electrics and ballast resisters are Aiian to me so I am concerned at having to modify and use these replacement twin coils.

Ralph

drcdb15

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Re: Twin Coil
« Reply #8 on: April 13, 2018, 12:21:56 AM »
I think there may be some confusion here arising from the terms used - twin coil, coil pack etc.

In early ignition systems, when costs were high and reliability low, a 'single coil' like this one:  http://www.motozbyt.net/audi/9696-cewka-zaplonowa-fiatalfaromeoaudicitroenladapeugeot-.html

was used to create a high voltage to send to the spark plugs. However, it generated only one high voltage at a time, since it had only one coil. As the engine had X spark plugs, a distributor was used to send the generated high voltage to each spark plug in turn. So a 'single coil' fed to all of the spark plugs through a distributor. In a 4 cylinder engine each spark plug only received every fourth spark that the coil was generating.

As time went by, manufacturing became cheaper and more reliable, and it became feasible to make a "coil pack" - this is simply a bunch of individual coils, all packaged together in a single 'box', and there is one coil for each spark plug. So a V8 engine, for example, might have an "8-coil pack" and a 2 cylinder engine might have a "2 coil pack", also called a "twin coil pack" or just "twin coil".

Because each spark plug has its own coil, there is no need any more for any distributor mechanism - which not only reduces manufacturing costs but also improves reliability, since there is now no rotor carrying a high voltage.

You still need some sort of trigger to make sure the high voltage is generated at the correct time for each cylinder, so you still have a "distributor", but this is now a LOW voltage sensor rather than a high voltage rotating contact, and all it does is rotate to indicate engine position, sending a trigger voltage to the coil pack to 'fire' each coil at the correct engine position.

It doesn't matter which system you use, but obviously if you have the old system single coil you will still need an old style distributor, with the HT leads going from the distributor to the spark plugs. If you have a twin coil pack, then you still have a distributor, but without HT leads. In this case the HT leads go directly from the coil pack to the spark plugs.

If you look at the pictures, you can see in the red car the old system, the HT leads come from the brown distributor cap on the side of the engine, to the two spark plugs. The single coil is on the right, hidden behind the rear light, but you can see the central lead from the distributor going towards it.

On the blue car, you can see the twin coil pack mounted on the right of the body, and the two blue HT leads going straight from each one's individual coil inside the coil pack to its respective spark plug. Notice there is no HT lead to where the distributor would have been on the 'red' engine.

As the wiring diagram on the Axel Gerstl advert shows, it is wise to use a ballast resistor with the twin coil pack. It is not essential, and if you google this topic you will find great discussion about the pros and cons of using  ballast resistor. The theory is to do with battery voltage at start up, and early coils being designed to operate on 9v rather than 12v - the resistor stopped the coils being overloaded. My own view is that the resistor MIGHT do some good, but will NOT do any harm, so if it runs OK with the resistor fitted then leave it in place.

This history and explanation comes from Burton Power, who do tuning stuff for Ford (hence the mention of Ford engines):

Why do some ignition systems have a ballast fitted where others do not?

Originally, all ignition systems did not have a ballast fitted which meant that the ignition system used a 12v coil with a 12v feed from the battery via the ignition switch. Such a system works fine when an engine is running, but problems can occur when starting the engine. The starter motor draws a huge current from the battery leaving less energy to create a spark across the spark plugs. The result is a weaker than normal spark which is not ideal for starting an engine. This problem is worsened by colder temperatures and/or a worn starter motor which will draw even more energy for starting and leave even less energy for sparking. To overcome such a problem, ignition systems were changed to run a lower voltage coil (usually 9v), and these coils could still give the same output as the original 12v coils. In order to run such a coil, the 12v ignition feed runs through a ballast, reducing it to 9v at the coil. To assist starting, a 12v feed (usually from the starter) bypasses the 9v ignition feed, giving the 9v coil a 12v feed. The result is a better than normal spark which is ideal for starting, particularly on cold damp mornings. As soon as the engine has started, the 12v feed is cut and the coil will run on the 9v ignition feed.

How do I know which ignition system is fitted?

Ballast ignition systems were introduced in around 1970. Virtually all Ford models from this date should have a ballast fitted. To find out for sure, use a multimeter to check the voltage on the positive wire of the coil with the ignition on. Around 9v means you have a ballast, around 12v means you don’t.




thepuddlejumper

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Re: Twin Coil
« Reply #9 on: April 14, 2018, 09:55:00 PM »
Just to clarify the coils I have look as a normal coil but have two outputs one to each of the plugs not the distributor.  The distributor is not connected to the spark plugs and both spark plugs fire at the same time. This is not a traditional distributor ignition system I think it is called a lost spark system but don’t quote me on that.

Ralph

michaelodonnell500

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Re: Twin Coil
« Reply #10 on: April 16, 2018, 03:43:28 PM »
I have the same double output coil on all of my 500’s and 126’s fortunately no problems so far, they look to be original as well. I have searched the tinternet to find replacements to no avail. I am not into auto electrics and ballast resisters are Aiian to me so I am concerned at having to modify and use these replacement twin coils.

Ralph

Ralph - I'm almost a year into using a modern fiat coil like this one:

https://www.ebay.co.uk/itm/NEW-Ignition-Coil-Pack-for-FIAT-PUNTO-SEICENTO-STRADA-1-1-1-2-16V-121/253292083688?hash=item3af96279e8:g:z1gAAOSweM1aI8iX

And a ballast resistor like this one:

https://www.ebay.co.uk/itm/Micro-Dynamics-Balast-Resistor-For-Aftermarket-Coils-Race-Rally-Motorsport/310998474507?hash=item4868f41f0b:g:tHcAAOSwaNBUeSRC

I have fitted an accu spark system (standard points will work fine)

No problems since I bought the proper ballast resistor.
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urkrajnc

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Re: Twin Coil
« Reply #11 on: April 16, 2018, 06:54:14 PM »
Thank you @drcdb15 for detailed explanation!

Thank you also @michaelodonnell500 for the links and explanations in all threads.

I bought the same "setup" as you have at the moment (@michaelodonnell500) but with 1.5 ohm ballast resistor - now I just have to get back home, install it and give a try :)

Thank you all guys!