Re: Is the GM HEI module necessary?

Posted by Pinhead on Jul 14, 2011; 7:10pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Is-the-GM-HEI-module-necessary-tp3165080p3170062.html

Hmm very interesting. What coils are you using? What is the primary resistance of your GM coils? And what was the primary resistance of the stock coils?

Take a look at these charts:

Stock Coil, ~4.5 ohms
http://www.pcbwerks.com/pics/iggy14.jpg

GM DIS Coil, Wells C849, ~0.4 Ohms
http://www.pcbwerks.com/pics/iggy18.jpg

These show the current flowing into the coils. The point where the graph "flattens out" is where the coils are said to be fully saturated. Longer dwell and more current draw does nothing to increase spark energy and only unnecessarily heats the coils and drains the electrical system.

Notice how much longer it takes for the stock coil to saturate when compared to the GM coil.

Basically, I use the HEI modules because the Honda reluctor/HEI module combination produces the perfect dwell for the coils. Any extra dwell simply causes wasted heat and excess power draw from the electrical system. The spark isn't any hotter with extra dwell.

I assumed that the stock modules are optimized for the stock coils, thus having an unnecessarily long dwell time.