INFO:MSD 6AL Points Trigger/OEM Tach/Duraspark/HEI

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

 72FordGTS wrote:

Todd mentions he used the TFI coil with .5 ohm resistance in his setup with an HEI module.  The HEI modules need a low resitance coil.  Coil selection seems to be very important for the module to work properly.   

Here is some comparisons on an HEI module firing different coils.  As you can see, the higher resistance coils produce much less energy.  This results were performed with a standard GM HEI 4-pin module, which limits the current to about 5.5-6.0 AMPS.  Some aftermarket HEI modules have higher current limiting of 7 amps or more. 

This is a 0.5 Ohm coil.  Notice that the module hits the almost 6.0 amps, then levels off.  This is the current limiting feature in the HEI coil.  

This is a 1.5 Ohm coil.  Notice the coil takes longer to reach it's peak, and it only peaks at about 3 amps.  This is more like the power on a points ignition that has a resistor wire limiting the current.

This is a 4.0 Ohm coil.  It probably doesn't have enough power to fire a plug.

Great info showing huge differences with minute resistance changes. I examined just about every part of my ignition system, from testing distributor cap coil terminal/rotor button resistance(HUGE variances between manufacturers), magnetic pickup, testing plug wires, even spark plug resistance varied widely between resistor plugs for my application(Autolite 45, Champion RF11YC and the NGK WR5's I am currently using(least resistance). 