ignition coils replace with GM twin spark coil?

Has anyone ever replaced the original XJ coils (my bike I am working on is a YICS 650 bike from 1982) with the dual plug distributor-less coils from GM? They are only 10 bucks new on Ebay and I would guess 5 bucks each at the breakers.

I understand that the XJ coils have a resistance value of 2.5 ohms. And the GM coils are 0.5-0.8. If I added a resistor (often called a ballast resistor) to make it up to 2.5 or 3.0, that should solve the problem of possibly damaging the transistor module (ignitor).

However I was also wondering about putting in a direct 12 volt supply from the starter so that while under cranking from the starter, it bypasses the resistor and gets full voltage from the battery when starting?

I think I can get away with mounting both coils on the frame just under the tank, exposed... but if painted gloss black as the frame, it should go un-noticed by most...

anyone done anything with the GM coils? I know that the TCI unit (ignitor) could be replaced with GM HEI modules but my ability with electrics is somewhat limited to inventing new swear words.... I was hoping to just replace the coils, make em fire as hot as possible, re-gap the plugs to 50 thou... and help the bike to start. I do have all the Taylor rubber plug ends for the coils, the wire crimp on connectors and the solid copper wire.

I also have a few spare GM coils so all the parts are here except the ballast resistor (which is a devil to buy as most adverts on Ebay telling me about the coil they sell do not have the resistor values posted.)

Thanks in advance for any help you might offer...
Mike....
mikestp@yahoo.com

 

I didn't use GM ones, exactly... I used Hitachi distributorless coils from a Saturn. Their primary resistance is closer to the XJ coils (2.2 Ohms, IIRC), though I'm actually driving them from a Microsquirt ECU. I mounted the coils up under the tank, where the originals used to be.

Adding a resistor to low impedance coils will not work. You'll lose too much energy in the primary circuit.
You could also look, though, at using Miata coils, which have their own energizer built-in.

 

Chacal/Len sells a dyna coils conversion kit.

Gary H.

 

I haven't looked at that part of the bike yet. I might be pleasantly surprised they will fit in the original position under the tank. Your coils look like the standard GM coils. Did you measure the impedance of the coils? And what year Saturn? A 4 cyl or a 6?

 

And that coil kit is available for what? 30 dollars? If I can fit the GM coils in and figure out the proper impedance I can do it all for under 30 bucks.

Thanks for the info.... But I am hoping for a cheap alternative.

 

I understand.

Gary H.

 

I found the 2.2 Ohm (again, assuming I remember correctly) resistance by measuring them. I don't recall measuring the impedance... and, if I did, I don't remember what it was, or at which frequency.

It was a four cylinder Saturn, maybe an SC2? No idea what year. Pulled them from a you-pull-it junkyard here about six years ago.

 

They look to be 1995 to 2001. Cool that you measured them at 2.5 They would be a bolt in replacement. They are available at breakers for about 10-25 bucks. And if my 650 frame is the same as yours, it fits in the frame . Perhaps with a bit of welding filing etc. Seems to be a nice update to the old stuff..
Sorry ot mention impedance. It is the same as resistance in a dc circuit. I should only really mention resistance. but my electrics are fairly poor. I am able to design DC circuit bards (I designed some IBM clone computer motherboards.. IBM AT 286, modems, and video cards in 1984). At that time all was 5 12 volt DC.
Simple in my opinion compared to my old Luxman stereo.... lol

 

Impedance is significant in coils, as they are quite inductive and are run at frequencies from 15 to 150 Hertz. I just don't know or remember what the inductance is of these primaries. Since the resistance is similar to the original coils, though, and the voltage is the same, I would expect similar inductance as well.

Looks like the yard where I got them would charge $10.99 each for these today.

I had to solder the primary side wiring into the connector on the bottom of these, as they plug into a base plate. I'll see if I can double-check the resistance this evening or tomorrow.

 

Ooop... Sorry. I was definitely misremembering. I found a post where I posted my original measurements:

I measured the two coils at about 5mH and .25 Ohms, so 3.4msec max dwell per the calculator. These will not match with a TCI.

Maybe try the Miata coils?

 

I did this same modification of using GM coils on Honda CM400 twins. They have a 0.5-0.8 ohm rating. The original Honda coils are rated the same. I was able to gap the plugs at 50 thou and boy did it make it easier to start. I am hoping a similar situation here. Although I will need two coils instead of just one for the Honda twin. I am just worried about the resistance values to match up. I can get to the breakers in a week. I can test the coils before I buy em...

 

Here is a quote from a thread.... Miata coil ratings. They too are in the same area as the GM coils
factory manual:
Resistance (primary): 0.78 - 0.94 ohms
Resistance (secondary): 11.2 - 15.2 K ohms

 

Not the old old ones... the newer ones that have built-in igniters. Those could be triggered with a dummy load resistor in parallel.

Edit: Just remembered also that the Denso setup in my 2002 4Runner had built-in igniters and was set up for wasted spark. The issue there, though, is that one side is COP and then there's a wire that runs to the "other" plug. Electrically it would work. Mechanically, it might be a bit weird to mount.

 

The units I see on Ebay are the coil on plug type. I dont know what years Miata might work? I will do some searching...

 

I think all the built-in igniter ones will be COP. There may be some EDIS type setups where you could use the igniters built-in to the coil pack plate, but that will probably make mounting difficult.

 

These (VW new Beetle 1998 - 2001) are cheap, and have built-in igniters. Not sure whether dwell is controlled internally or externally, though. You would want internal dwell control.

http://www.ebay.com/itm/Ignition-Co...ta-L4-2-0L-/291495836732?fits=Make:Volkswagen

 

How about this as an alternative coil? Dont know the voltage output, but the 3 ohm is the right range... Also would require two items....

http://www.ebay.com/itm/Harley-Igni...ortster-85-99-Repl-H-D-31614-83-/291550823287

or this item:
http://www.euromotoelectrics.com/EDL-IGNCoil30D-p/edl-igncoil30d.htm

 

The second one looks pretty good. Hopefully 20% higher resistance doesn't make too much of a difference.

 

outa stock and discontinued....dammm