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
I would consider it. My understanding is that the ICM(Duraspark) is what would be damaged.
I agree extra resistance would be good.
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.
Thanks Jurjen.
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