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What coil to use with Lumenition PMA50


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I have a Lumenition PMA50 Optronic kit which I plan to fit to my TR2. I have fitted several Lumenition kits to my classics over the years and in fact my wife's Spitfire 1500 has had one fitted since the 1990s.

My problem is that the instructions state 'Suitable for coils or coil/ballast combinations of not less than 3 ohms and also states:-

'Not suitable for low resistance (i.e. less than 1 ohm) electronic ignition coils.

It then shows a diagram with a coil and ballast resister included. These coils which have ballast resisters are usually 1.5 ohms.

Although I am reasonably competent with car electrics I find this somewhat confusing and slightly contradictory.

Can anyone help please?

Regards, Colin

Edited by Colin Fairhurst
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If it states not less than 3 Ohms then I would take that as definitive Colin. Since the TR2 has no mechanism for switching a ballast resistor anyway, why not just go with that?

Of course, you could use a lower resistance coil as long as the ballast resistor is always in circuit so the total is always 3 Ohms or greater, and perhaps that is what the diagram is showing. There is no benefit in doing that but it might be shown for those cars which have ballasted systems as standard.

 

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19 minutes ago, RobH said:

If it states not less than 3 Ohms then I would take that as definitive Colin. Since the TR2 has no mechanism for switching a ballast resistor anyway, why not just go with that?

Of course, you could use a lower resistance coil as long as the ballast resistor is always in circuit so the total is always 3 Ohms or greater, and perhaps that is what the diagram is showing. There is no benefit in doing that but it might be shown for those cars which have ballasted systems as standard.

 

Thanks for that Rob. Do I take it that the 1.5 ohm coil and the 1.5 ohm resister add up to a total 3 ohms for the Lumenition module?

It would be relatively easy to connect a ballast resister in series with the 1.5 ohm coil and a separate 12 Volt to the Lumenition module from the ignition.

I was also thinking about the Voltage. A standard coil would have 12 Volts approx. all the time and the ballast resisted coil would be at 7 to 9 Volts when the engine is running.

Regards, Colin

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I'd take a LUCAS Sports coil DLB 105, Moss nr. TT2981, 3 ohms ,40000 volts.

You will be happy with.

When using a 1,5 ohms coil you need a ballast resistor also same 1,5 ohms , this must be bypassed by a relay while starting the engine.

Thus you get higher voltage to the coil's primary circuit which provides high voltage at the lead to the distributor then and that helps better engine starting ( improved igniting energy) under severe conditions ( e.g. in wintertime).

Right after release of the start button the ballast must be again connected in series  with the coil, thus 3 0hms again system voltage.

 

hope this is of help

Wolfgang

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1 hour ago, Colin Fairhurst said:

It would be relatively easy to connect a ballast resister in series with the 1.5 ohm coil and a separate 12 Volt to the Lumenition module from the ignition.

 

Yes it would be easy to do that but as I said, there is no benefit and a TR2 should never have a ballasted coil anyway. Just fit a 3 Ohm coil  as Wolfgang says.   

Alternatives to the Lucas coil -which has mixed reviews - are the Bosch 027 blue coil or the  Pertronix Flamethrower 40511 (oilfilled)  or 40611 (epoxy filled). 

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1 hour ago, r-fox said:

I'd take a LUCAS Sports coil DLB 105, Moss nr. TT2981, 3 ohms ,40000 volts.

You will be happy with.

When using a 1,5 ohms coil you need a ballast resistor also same 1,5 ohms , this must be bypassed by a relay while starting the engine.

Thus you get higher voltage to the coil's primary circuit which provides high voltage at the lead to the distributor then and that helps better engine starting ( improved igniting energy) under severe conditions ( e.g. in wintertime).

Right after release of the start button the ballast must be again connected in series  with the coil, thus 3 0hms again system voltage.

 

hope this is of help

Wolfgang

I do understand all that but what about the effect of the voltage on the module, that is, 12Volt standard coil or 6 to 8 Volt ballasted coil?

I have read that there are different types of Lumenition Modules and that some are designed to operate at less than 12 Volts.

Edited by Colin Fairhurst
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The PMA 50 installation information is quite clear. 

https://www.gsparkplug.com/media/wysiwyg/technical-information/lumenition/PMA50_installation.pdf

The PM50A unit needs a 12 V supply on the red lead. The coil voltage has no bearing on that. 

The diagram labelled '2' shows a coil with a series resistor (which I think has confused you)  but as I said that is depicting a car with a ballasted ignition as standard. In your case use a 3 Ohm coil without a resistor.

The problem with low resistance coils is nothing to do with voltage - it is the current drawn. If the resistance is too low the current will overload the switching  component in the module and burn it out.  

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Colin, I have a Lumenition MS4 Mega Spark coil, with ballast resistor and instructions. This coil was specifically intended for use with the Optronic PMA50 module. It had very little use before I changed to an Albertronic 123 Ignition distributor (with which I am delighted) and is now surplus to my requirements. If interested please PM me or it's going on ebay.

NB This coil is suitable only for a -ve earth vehicle.

Tim 

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1 hour ago, RobH said:

The PMA 50 installation information is quite clear. 

https://www.gsparkplug.com/media/wysiwyg/technical-information/lumenition/PMA50_installation.pdf

The PM50A unit needs a 12 V supply on the red lead. The coil voltage has no bearing on that. 

The diagram labelled '2' shows a coil with a series resistor (which I think has confused you)  but as I said that is depicting a car with a ballasted ignition as standard. In your case use a 3 Ohm coil without a resistor.

The problem with low resistance coils is nothing to do with voltage - it is the current drawn. If the resistance is too low the current will overload the switching  component in the module and burn it out.  

OK, Thanks for that. I understand now.

One problem is that when I google something very often there are a lot of ill-informed opinions which can confuse things.

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