Coils sparking 6 times each stroke

[David.wynne.jones]

Hi guys, 

I've gone from a wasted spark set up to coil on plug, and the ignition timing is super inconsistent, its firing every 5 or 6 times every 720 degrees when it's supposed to happen once theoretically. It's a stock Mitsubishi GTO with a 6g72 and the only difference is there are 6 coils instead of 3 coil packs. Obviously, the signal wires are wired individually to the ECU and the power and ground are grouped and wired appropriately, it is set up for sequential ignition. The triggering is picked up fine, the RPM is being read accurately, the trigger wires are shielded, and the offset is correct. 

I can't find any other explanation for the inconsistent and random timing of the sparks. I've attached the base map, I've changed the dwell settings up from 1ms to 5ms, still no changes. 

An interesting note is when the coils which are from a Mazda premacy are bench tested, they don't seem to care whether the signal is a pulse or not. I've tested a dwell time of 1-5ms and also held the signal high for a few seconds and it sparks away the whole time, almost as if it has its own self discharging. Not sure how any other coils work but thought it was interesting.

If the ignition timing was every 120 degrees it would somewhat make sense, but its 5 or 6 sparks per 720 degrees which makes no sense to me. A low or high dwell only changes the spark energy, no change to the timing of them. It's very peculiar and the only other explanation I can think of is that the ECU could potentially be faulty, surely not...

A_Mitsubishi GTO G4 Xtreme.pcl

[Adamw]

3 hours ago, David.wynne.jones said:

I've tested a dwell time of 1-5ms and also held the signal high for a few seconds and it sparks away the whole time, almost as if it has its own self discharging.

That would be pretty unusual.  I do believe there is a GM LS2 coil that does self discharge if over dwelled but it is pretty rare for any coil to do that. 

Get a cheap LED test light and connect it to the ignition output would be a quick option to confirm there is only 1 flash per cycle.  

[David.wynne.jones]

Thanks for the reply Adam,

I did also think it was weird, but clever also. I was actually testing it with a 12v signal too, after I realised it was probably wanting a 5v signal... pretty solid coil

I put a small led in the output of cyl 1, videoed it, and played it again in slo-mo, pretty much six pulses per tdc. I think the Mitsubishi GTO trigger option in that version of PC Link could be wrong. I'm going to try again tomorrow on 1 tooth per TDC.

The 6G72 (1992) crank angle sensor is actually on the cam also, it is a 3-tooth disk, so 3 teeth on the cam = 120 degrees each on the cam x two = 720 degrees.

Hopefully the trigger 2 options pick up the cam angle okay, it is a 3 short 1 long disk, unsure if the cam pulse or cam level is best, probably try both and see which one has a trig error.

I saw another post on the forum who had a gto running on the gto trigger option, I really doubt the trigger option is wrong, but I know the red xtreme ecu I have is pretty old.. who knows

[Adamw]

1 tooth per TDC mode wont work with 2 trigger 2 teeth.  With the GTO and EVO trigger modes we actually use both the rising and falling edges of trigger 1 effectively doubling the resolution.  One thing I have seen before with the evo trigger mode on a G4 ecu is it not initialise properly during setup, when this happens you get massive trigger errors reported during cranking.  So if you are not getting trigger errors counting up while cranking then this probably isnt your problem, but just in case I would suggest doing this to reinitialise:  Change trigger mode to "Subaru V1-6" - make sure trig 1 & 2 change to reluctor.  Do a store, then power cycle.  Change trigger mode back to GTO, store, power cycle, check ign again.