Pinned Coil On Plug conversions - COP

hmm let me see if i can colossally screw this up. Been a few years now since i did the good old dc circuits topic in Tafe electrical but i'll give it a go. someone please correct me if I'm very wrong

Current draw of the coils in parallel would be 14 volts (assuming charging voltage with the engine running ) divided by the resistance of 0.75 ohms (Coils in parallel) would be 18.66 amps and 261.24 watts when the coils are 100% on
I=V/R
P=V*I
14/0.75=18.66 amps
14*18.66=261.24 watts

and the original current draw with the coil in series is 4.66 ohms and 65.24 watts
I=V/R
P=V*I
14/3=4.66 amps
14*4.66=65.24 watts

So we want a 14 amp current drop across the whole circuit to keep the fuses from blowing so we'll need to match the original resistance as close as possible. A 2.25ohm resistor would be ideal but that is not a size they make so a 2.2 is the closest one
to make the total circuit resistance 2.95 ohms which would end up making the current draw
I=V/R
P=V*I
14/2.95=4.74 amps
14*4.74=66.36 watts

Voltage drop across the resistor would be 2.2 ohms (resistor value) multiplied by 4.74 amps
Then power going through the resistor would be 10.428 volts multiplied by 4.74 amps
V=I*R
4.74*2.2=10.428 volt drop
P=V*I
10.428*4.74=49.43 watts

So that would mean voltage drop across the coils would be
V=I*R
4.74*0.75=3.555 volt drop
P=V*I
3.555*4.74=16.85 watts

So a 2.2ohm resistor of at least 50 watts would be needed?
OR if 6 ohm COPs existed they would give the correct resistance when wired in parallel.

 

You're correct, @TonyZXR. Another alternative is to add a resistor to each coil, this would mean 4.5 ohms each resistor. The voltage issue may come into it, though. A coil is a voltage converter, with the output being a ratio of the input. So, if the input voltage is only 3.55v as Tony worked out, then the high-voltage output is going to be a quarter of what it would have been if the whole 14V were applied to the coil. If they were in series, then the output voltage would be half of output of a single coil.

I've probably confused more people than helped, usually do. Sorry.

 

I was thinking maybe try 2 of these to try and fire the coils without overloading the tci when running them in parrallel. Then each coil would pull 9 amps each like how it used to in the original bike They`re rated at 100amps and switch at 0.5ms so it should switch fast enough for 190000rpm if i did my calculation properly



They`re also rated to multiple million cycles

 

Solid state relay @frank
1.2 ohm range ?

 

I wouldn't use it, @TonyZXR because my calculation says it is a 60degree delay at full revs. It seems the best way to do it is in series, having to seen the specs of the COP. Impedance is the other calculation we are leaving out, it is significant in the current draw.

 

Yep . Well it was good to get the brain going again haha

 

Ahh right yeah . yea series seems the simplist and most powerful setup

 

Just to throw the whole conversation sideways, the creation of spark power is a little more complicated. A coil (transformer) only creates an output when the input is changing - if you run continuous DC current through a coil there will be no output voltage. Now this is where impedance comes in. Impedance is the resistance created by a coil. My memory is not so good with AC impedance (black magic, they say stuff like impedance delays a voltage by quarter of a cycle and a capacitor advances a current by quarter of a cycle... I didn't do so well on this part of my uni). So the impedance, any use of capacitors in the igniter, and igniter cycle rate all add to the calculation. The strength of a spark is not merely in the current, but voltage is very important: it's the force that pushes the electrons across the gap. So for the best results, you need all the data and the calculations to work it out. In the meantime, static resistance should offer a reasonable guide. The igniter may have capacitors to help limit the current draw, as a safety net, but that isn't necessarily foolproof.

Speaking of uni, I should get back to it. (Hashtag I hate uni, don't know why I'm doing it)

 

I think the TCI (igniter) was fried and cooked the coils. The circuit shouldn't be complete until the igniter "fires" unless you have a short to earth. Not have the wires in front of me and a quick look at the zxr service manual, the coil inputs are infinite resistance (open circuit), so no current should flow until the igniter closes the circuit at firing. Which it might open and close a few times in a few microseconds. Just for fun numbers, redline is 114,000 degrees of rotation per second. No, I didn't count them

 

Yes, the primary and secondary windings are separate circuits. The current in the primary produces a magnetic field (greater the voltage and current in the primary, the greater the magnetic field), and the changing magnetic field creates a voltage/current in the secondary. As for timing, at full revs these bikes are nearly completing a full revolution of the crankshaft in 3 milliseconds; these electronics are in microseconds.