MSD Blaster II coil very hot

[flatbill]

I have an MSII V3 unit and I was running a Summit clone of the MSD 6 Box. MSD Blaster II coil. The coil has 1.1 ohms resistance. The generally suggested dwell setting is 25.5 ms. It usually ran OK but for a number of reasons, I pulled the MSD style stuff and went to a straight trigger from the MS. I found that the coil and the heat sink side of the MS were getting really hot. This was with a 2.5 ms dwell. The motor would run very badly when it warmed up. I dropped the dwell to 1.0 and it seemed better. I took a drive and I almost didn't make it back home. I finally had to boost the dwell to 2.5 to get home. And by the time I made it home, it was running lousy again. After I was home a while, maybe 5 or so minutes, I checked the coil temp with a thermocouple on my meter and the coil was at around 150 degrees. The MS heat sink was also really hot.

A friend suggsted that the coil was pulling too much current and causing the overheating. He suggested that a ballast resistor might help. I added a 0.6 ohm ballast resistor that I happened to have and set for 2.5 ms dwell. I ran the motor for a while and the coil and the MS seemed to be running much cooler. I need to get it out and run it to get the coil temp to level off and see where it is.

The MSD literature says that with an electronic ignition no ballast resistor is needed with the Blaster II coil.

Any suggestions as to ballast resistors, dwell times, coil temp, MS temp, can I really use this coil, etc would be greatly appreciated. Maybe I just need to reinstall the box and run it. I am trying to get rid of "one more thing to go wrong" on my motor.

Thanks, Billk

[Bernard Fife]

fb,

150 Fahrenheit isn't unusual for a coil. 150 Celsius is a bit hot, but not hugely so. You should ask MSD about the coil's dwell, but a ballast resistor is not the answer with electronically controlled coils (the ballast resistor is just there to prevent over current with point type triggers that have ineffective current control at low speeds.

Lance.

[flatbill]

Not only was the coil getting hot, but also the heatsink side of the MS was too hot to touch. I'm afraid that I'm going to burn something out. Thanks for the reply. When I added the resistor both the coil and the MS got cooler. Billk

[Matt Cramer]

Sounds like you're running too much dwell, but that 1.0 isn't enough.

[flatbill]

I just got back from about an hour running. Its hot here, over 100 degrees. I have had trouble with it running rough. I tried raising the dwell from 2.7 to 2.9 to see if it would smooth out. No. When I got home I checked the coil temp with an IR gun and got 184 degrees. It is pretty hot under the hood though. I think I am going to try another coil to see if I can get the temp down. I'm pretty much just stumbling along here. I will see about getting a data log posted and the msq.

When I raised the dwell from 1.0 to 2.5 it helped for a while, but started running rough again pretty soon.