renns

Does the leading coil ignitor provide dwell control? A forum search seems to indicate no, but info in the following article apparently contradicts that.

http://www.teamfc3s.org/info/articles/demystifying.html

In figure 8 it appears that coil charging begins prior to receiving IgT signal. In other words, the leading edge of the 5v signal from the ecu (IgT) is not used, while the trailing edge triggers the firing event. Can anyone shed some light on this? If not, it's test time. Thanks.

WAYNE88N/A

I think the ECU "cuts" the signal voltage to collapse the coil field, which in turn produces the voltage surge (it's been a while since the basic electricity school, sorry)...anyway, that's why the "trailing" end of the 5v is what appears to trigger the event....

renns

What I'm wondering is if the _arrival_ of the 5v IgT signal is critical. In cases where the ecu controls the coil charge time, the leading edge is typically used to begin charging, and the trailing edge to trigger the firing event. These ignitors are 'dumb' in that they respond directly to ecu input, and don't control coil charge time on their own.

In other cases the coil charge time is determined at the ignitor, and it turns itself on at an appropriate interval before the next expected firing event, and then waits for the trailing edge of the ecu signal to fire. These are 'smart' or 'intelligent' ignitors, in that they provide the charge time control, and only look for a trailing edge signal to time firing. I'm wondering into which category the FC coils fall.

RETed

Almost all electronic ignitors already do this - yes, they do control dwell control over the coil itself.


-Ted

renns

Thanks for the info.

renns

Testing by others indicates the FC trailing coil ignitors provide dwell control, while the leading do not. Apparently modern ecu's with adequate processing power take over all control of coil charging, and change dwell based on operating conditions. This eliminates the need for a 'smart' ignitor. Details can be found here:

http://www.nopistons.com/forums/inde...ST&f=8&t=40326