'Big Cap' ignition upgrade: coil question

[johnbendik]

I'm in the last stages of the 'Big Cap' upgrade, and I'm using a coil (BWD E92P from Advance Auto) that has a measured resistance of .5 ohms.  My stock coil has a measured resistance of 1.5 ohms, and I presume it has the standard inline resistor from the starter solenoid.

I'm trying to figure if I need to put an additional 1 ohm resistor in line with the coil to compensate for the resistance difference.  What do you guys think?  As I understand it, the problem is the potential of doing damage to the ECM?

Thanks in advance,
JB

[eaglefreek]

I would consider it.  My understanding is that the ICM(Duraspark) is what would be damaged.

[IowaEagle]

I agree extra resistance would be good.

[Jurjen]

With the standard resistor wire still intact, the coil needs to be at least 1.5 Ohms.
If the resistance is lower, the ignition module gets to hot.
I have by-passed the resistor wire (1.35 Ohms) as well and have a 3 Ohm coil instead, so far this has kept (the still original) ignition module happy.
Edit:
Putting a resistor in line is good for the IM, but the voltage over the the coil will drop to about 20% of 12V. I would try to find a 1.5 Ohm coil.

[IowaEagle]

Thanks Jurjen.

[johnbendik]

Thanks, Jurgen.  I took your advice and switched the coil out for a 3 ohm Pertronix, and bypassed the resistor.  Although I'm now having some other ignition problems (I'll start a new post for that), I can verify that I am getting a healthy spark.

I found that out the hard way: I was carefully disconnecting spark plug wires from the cap (one at a time) while the engine was running, to figure out which cylinders weren't firing.  I accidentally got my meaty, low-resistance thumb between the plug wire and the cap, with my thumb about an inch from the cap.  The spark jumped the 1 inch gap and lit me up like a Christmas tree.

JB