EDIS coil packs: Sparkplug with or without resistor?

[Philip Lochner]

This is one of those threads that can easily prompt a lot of speculation. I hope will not happen in this case.

I've been converting the Chrysler 440 in my Jensen to EFI using MS-2. Phase 1 was to get just the ignition running with MS-2 reading a 36-1 trigger wheel off the crank
pulley and then controlling 4 BIP373's directly which were firing the EDIS 4-post coil packs. While the car was running on carb (with MS doing ignition only) I had NGK BP6S spark plugs with dwell of 3ms. Whilst I suspected this might be on the high side, the car ran fine for continuous 1hour+ drives on several occasions over several months.

When phase 2 (EFI) was being implemented I changed the spark plugs to Chamion RJ12YC, because I always had it that these coil packs really need to fire into plugs with resistors.

Then, once the car ran again (now on EFI), it would let me down by the road side after longer drives (40min+). Eventually I realised that the ignition module (with the 4 BIP373's) was overheating, resuling in these IGBTs shutting themselves down for protection.

NOTHING changed from the carb setup to the EFI setup EXCEPT for the plugs being changed to another WITH resistors.

Can anyone tell me why the change to resistor-plugs would suddenly cause the ignition module to overheat when it was apparently fine when running resistorless plugs??

I have since reduced the dwell to 1.5ms and now its running nice and cool.

[DonTZ125]

Dwell is on the primary side, plug resistors are on the secondary side, and never the twain shall meet. If your switch to R plugs made your drivers overheat, then something else was at work that hiccuped at the same time.

[kjones6039]

Phil,

FWIW.... I doubt that changing to resistor plugs would have any effect on the IGBT coil drivers.
I have run both the EDIS module and the IGBT drivers. I found that resistor plugs were essential for proper operation of EDIS but I doubt their necessity when using IGBT drivers. Additionally, I am still using the same Ford coils as I used with the EDIS system (now driven by IGBT) at ~3ms dwell without issue.
Therefore, I must concur with Don, that something may have occurred that that was contemporaneous with, but not related to the plug change.

Ken

[DonTZ125]

Point of pedantry - a BIP373 is not an IGBT, but rather a 3-stage Darlington. The old VB921s were IGBT, which is probably how the habit of calling every heavy driver transistor an IGBT developed.

From everything I have ever read or heard discussed on the topic of resistor plugs, I would recommend them for each and every installation be it EDIS or otherwise. There have simply been too many horror stories of inexplicable malfunctions and wild misbehaviour that simply dried up and vanished when resistor plugs were installed.

[kjones6039]

Don,

Your point is well taken. I got locked in on my setup (using IGBT's) and Phil's BIP373's got lost in my dissertation.

I continue to agree with you, in that Phil's issue is not likely to be caused by changing to resistor plugs.

Ken

[Philip Lochner]

Look I know I'm a blond, and I have done the most amazingly daft things but this time I am stumped. I also thought that what happens on the secondary side could not affect the primary side- certainly not to this extent.

I have read somewhere that resistored plugs will produce a longer spark duration than non-resistored plugs. Could that have anything to do with things?