Hi Tom,
Here is a copy of a previous post. I have tested 5 Ohm coils and expect they should work just fine. In fact, if you read the DynaTek Installation Guide, they recommended the 3 Ohm coil not be used like we use them without a ballast resistor.
HI Joe,
Yes, I have. I’ve tested the 5 Ohm and various 3 Ohm coils.
Per DynaTek, recommended dwell for 5 Ohm → 10 mSec - 12 mSec. Recommended dwell for 3 Ohm → 8 mSec - 10 mSec.
I’ve tested with the recommended dwell as well as “un-limited dwell” (un-limited dwell, like a typical AeroVW secondary ignition) both coils. One thing that saves the coils with un-limited dwell is the fact that the alloy used for the primary has a very strong positive coefficient of thermal resistance. So, as they get hot the resistance increases pretty quickly. And they do get hot. With dwell control they don’t heat much at all.
The 5 Ohm coils should work just fine in our application and draw less current. If you read the attached document, and read between the lines, you will see that DynaTek recommends against using 3 Ohm coils in our application without a “one to two Ohm ballast”. I tested a 5 Ohm, in air, at room temperature, and it kept firing down to 5 Volts with only 8 mSec of dwell. Two mSec below recommended minimum.
Also, back when GPAS was still around, they had this to say about keeping the coils cool.
"NOTES CONCERNING USE: The coils must be mounted in a position where you can direct cooling air on them. If mounted on the back of the accessory case, the coils must be insulated from the case. They must be grounded to the engine. The maximum operating temperature of the coils is 180°F. degrees. Keep them cool.
Merry Christmas to you as well. And to all the Sonex community.
DC1-1-Installation-Guide.pdf (68.9 KB)
Wes
Wes
1 Like