Yellow Jackets Ignitor Module and general ignitor module questions

[phatmonk]

Yellow Jackets Ignitor Module and general ignitor module questions

Hi All,

Keeping this short, I'm chasing a misfire when on boost.

Replaced the plugs.  Interesting found BCPR7ES-11 in there from the last mechanic, no big deal.  Anyhow, replaced with BCPR6ES-11.

The air box has been out/in recently, Will check it's gone back on properly tomorrow with some light.  Maybe it is un-metered air.  I hope it's not the AFMs, been through 6 sets...

But, I have a feeling it is the 20+ year old coil packs and/or ignitor module.  Found this (awesome!) video on how to test the ignitor module, again I'll give it a crack tomorrow.

So, here are a few quesitons:
 

 

 

 

[admS15]

Those plugs have a 1.1mm gap. Try decreasing the gap to 0.7 -0.8 and see if misfire goes away.

[phatmonk]

Sort of off topic-ish.. sort of.

24 minutes ago, admS15 said:

Those plugs have a 1.1mm gap. Try decreasing the gap to 0.7 -0.8 and see if misfire goes away.

I've skimmed the threads, people going from 1.1mm to 8mm gaps and vice-versa fixing problems (or not!).  I figured that having a timing tune and exhaust with no extra boost keeping the stock 1.1mm gap would be fine.  Anyhow, I hear you and it is on the list.

[V28VX37]

Here's my misfire diagnosis thread for some inspiration: http://www.sau.com.au/forums/topic/326043-resolved-misfire-in-r34-gtt-rb25det-neo/

Also in the early days I had a significant breakdown beyond 4000rpm, which turned out to be a broken CAS

[phatmonk]

Ummm.. not sure what happened.  The finished post is here:

 

 

[MrStabby]

The more power/torque you make the more difficult it is for the spark to jump across the plug gap. Missfire on boost is classic underpowered ignition. So you either need to add more electric power to the plugs, or make the gap shorter. Since closing the gap is free, its a good place to start for diagnosis. You can also inspect the plugs while they're out to see if they are consistently coloured, which should help diagnose if some coilpacks are weaker than others. Also check that the coils are seeing the full ~14.5V, because less volts on the primary solenoid means less volts at the secondary solenoid and therefore less volts at the plug.

[phatmonk]

Thanks @MrStabby and @V28VX37.  Somehow this double posted mid typing.  Here is what I found (and posted in the other thread here):

Testing as per the above, pins (cylinders) 1 to 6 tested at 500 ohms +/- 10 ohms per pin.  What raised an eye brown, the video tested at 8 Mohms.  The two units are waaayyyy different but who knows which one is right.  It would be good for some more results.

Testing in reverse. each pin read open - sweet.

Here is where things start getting interesting.  Quoting the electronics buff who's multimeters we used, we were testing the "forward junction voltage on the base emitter" - this isn't covered in the above video and honestly, nfi, but it sounds good.   Pins 1 to 5 read 1.2v.  Pin 6 read 0.6v.  Testing across three multimeters and a transistor reader, this was consistent.  Then, all of a sudden, all pins started reading 0.7v.

So, something is wrong here and I ordered a refub unit.

[V28VX37]

Yeah I've tried measuring stacks of coil packs over the years, typically none the wiser. Hunting random misfires is part of the game owning an RB, I never had any issues with my previous LS1 even though it pushed more power naturally aspirated than my RB does with forced induction...