Coil and TCI question

[Ivan]

Time to start looking at a new set of coils for me. This weekend I had the wires from 1 & 2 fall out of the caps, and I am getting shy on wire to trim up. I am beginning to think that my low rpm dead spot is ignition related as well.

So, my question is this:

I can pick up a 4 cylinderr DIS coil pack from a junk yard for $30 or less. Something off a subaru or a neon or a ford 2.3 might work well. Do I need a specific load on the primary circuit to keep the TCI healthy? Obviously too little load will fry any circuit.

I figure the DIS coil packs will have some more bite than the stock XS stuff, and I wont have to wait for a week on shipping.

[randy]

You need 3 ohms total for each coil circuit. Early models have 1.5 ohm coils + a 1.5 ohm ballest resistor. Later models have 3 ohm coils , no ballast resistor.

[Ivan]

Any idea how much power they consume in the case that I might need to add a resistor?

[randy]

No way to tell how much power your NEW coils will draw. What the old coils draw has nothing to do with it. Match the ohms.

[XSPastor]

Fall out of the caps?! Did you screw them in?

[Ivan]

Fall out of the caps?! Did you screw them in?

Yeah, fell out. Well, not on their own, but removing the cap from the plug was enough of a jostle to seperate it.

I did indeed screw it on, and despite my best efforts including dielectric grease, judicious torque on the cap, meditation, consulting with politiicians, rabbis and an indian chief, the 28 year old wires corroded. You'd think they'd last longer than that. Go figure. I was able to trim a bit off and do a quick fix, but I am running out of wire, and I suspect the coils may be on their way out, since I still get a random sputter under load. I alone have put 20,000 miles on it and that in its self would be a work out for old coils. I have no idea how many actual miles it has, since it has a 160 speedo on an 81.

As far as needing to know the power requirement, Randy is right about needing to measure it on the new ones. I need to start thinking BEFORE I start typing.....

[bikerphil]

I've experienced an off idle stumble before and it was related to frayed red/wht wire at + side of coils and poor connection at ballast bypass. I thought at first it was carb related, but after re-doing the connections, it went away for good. The coils seem to like full voltage at launch.

[tw1980]

The load or( power draw) of the coils is determined by the impedance(resistance).The lower the resistance the more load that is placed on the tdi.As the coils charge the impedance increases.If the new coils don't charge as fast as the originals the load may be increased on the tdi and may damage the unit.Look up the specks on the replacement coils and compare inductance and impedance.If they are within 10% they should work. Terry

[TopCatGr58]

Hey Ivan,

If I can deduce from your comment about 160 mph speedo on an 81, you have an 81 XS....since it's not in you signature, then you need the 3.0 ohm coils. There is a tech tip about putting new wires in old coils. Just need to get some new solid wire core wires.

As for the coil packs, IIRC, they are single output, one for each cylinder. Trying to run a parallel set of triggering wires to 2 coils for 2 cylinders off of one TCI trigger wire will cause a considerable drop in resistance even IF the coils are 3 ohms, and would still possibly fry the TCI! If you can find some dual output wasted spark type coils that use 1 trigger wire, then you would be ok.

REgrettably, it's been posted that MikesXS is currently on backorder for the cheaper $35.00 high output coils, they have a new HIGHER output coil, but its' almost twice the price!
T.C.

[Ivan]

TC, you don't have to deduce, my bike year and model is in my profile, snugly nestled right where you told me to put it back when I joined.

Coil packs from most DIS cars are waste spark types. Just like the ones the bike has. They are just ganged together. Some of the newer stuff uses coil over plug type stuff where there is a small coil that fits on the plug. The Subaru, Neon, and the Ford 2.3 coils are all two coil units that have paired wires, although it is hard to tell from the looks of it. I think they would be more compact and have higher output than our normal coils. I also like the idea of easily replaceable wires. I have read the tech tip on replacing the coil wires, but I am guessing the coils are probably ready for a rest as well. In my automotive wrenching days, I ran into a lot of coils going weak, and causing cold stumbling issues and hiccups and such.

Its all just a thought right now. I still need to find time to get to a salvage yard and find something suitable, then figure out connections and mounting and such.

tw1980,you're talking capacitor there not coil. The time to reach a full magnetic field is usually what a dwell adjustment is about, and we don't get that adjustment in an electronic ignition. On a scope, the coil primary has a more or less constant voltage until the trigger when it is stopped by the module or points. IIRC there is a small initial surge that lasts a few micro seconds, but is negligible.

[tw1980]

No Ivan, TC is right on with his advise and the theory that I posted is correct.Our bikes fire two plugs at one time.If you have some specs on other coils that might give better performance without increased load on the tdi I'm ready to mount them up.But I need specs to feel safe. Terry

[tw1980]

Sorry Ivan I should have explained better.It's when the coil starts charging that concerns me.If it takes longer for the field to build.It may increase the current draw through the tdi.It would be cool if you could find coils that decrease load on the tdi and increase spark.Sorry I don't have an inductance meter any more or I'd take some readings for you.You might start out by using a resister in series with the coils,1 or 2 ohm.It will lower the Q of the circuit but will limit current draw.I woke up thinking about this. Terry

[Ivan]

Well, I guess that 12 years as an auto technician and the whole ASE certification thing were just a weird dream.

[tw1980]

Sorry didn't mean to insinuate you weren't well versed on the subject.I was just adding my 2 cents worth and thought I didn't explain what was churning in my little brain.

[Ivan]

I'll try and explain tonight after work on the home computer. Writing out lengthy posts is a pain on my little HTC Touch Pro.