[s-cars] LS2 coil adventures part 17...

[qshipq at aol.com]

 John
It's been a while since I've had ignition training and study.  I'm thinking without looking that a .7v increase in feed voltage might affect dwell by such a small fraction of a millisecond, I just find it incredulous that it could solve a damn thing.  Better yet, maybe a comparison to spark plug gap could be a better correlation to the problem.  Somewhere I have a SAE paper on spark break up voltages.  If the LS2 at 40kv is breaking up at high rpm, a reduction in gap OR going to a laser iridium (not the 'regular' iridium) OR even a platinum plug seems a better/complementary solution.  With such a narrow margin of dwell gain on a 5ms LS2 charge time, this fix using a VR, just doesn't seem like a long term solution...  And/or change your plugs quite often?


No misunderstanding, VERY intrigued is all.

My .02

Scott J

 

 

-----Original Message-----
From: John Cunningham <jc at j2c3.com>
To: qshipq at aol.com <qshipq at aol.com>
Cc: s-car-list at audifans.com <s-car-list at audifans.com>; mswanson at mswanson.com <mswanson at mswanson.com>
Sent: Thu, Feb 10, 2011 2:27 pm
Subject: Re: [s-cars] LS2 coil adventures part 17...


Scott - 


Still think we just have a small misunderstanding. I'm far from saying OEM coils won't work in fact I'd bet my left compressor wheel that a new OEM setup woulda done me fine. So my point is very definitely not that LS2 is the only solution that woulda worked, just that this seems to explain why LS2 did not work before on my particular car vs a other one sitting right next to it. 


Fully agree about curiosity about logging but sadly no... I said to marc I wish I had a nice logging digital Oscope to watch waveforms under boost during the whole process. I do have a logging DMM setup somewhere but didn't occur to me to try to rig it up... And not sure if its sample speed is fast enough... Also tough to wire that up to the coils for on-road WOT pulls but prob coulda done it at tue ECU side...


JC


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On Feb 10, 2011, at 12:27, qshipq at aol.com wrote:



 

 JC thanks for the followup.  It makes no sense to me whatsoever in light of what 3B guys are running with a dizzy and stock single coil and 12.7/13.8VRs, but in the end, I say you do what works.  Did you have a way to log the voltage and miliamps at the coils before and after the mod?  

That LS2 Coil is a beast, which is why I'm having a really hard time believing a 14.5V feed is the really the problem, or that a 14.5VR install is the solution.  More specifically, my bet is that 14.5 VR overcomes another problem, not solved.  I've seen ocilliscope runs of the LS2 coil with some pretty impressive gapping, but then again, I didn't pay attention to what the feed voltage was.  

I'm intrigued, but not sold.

Thanks for the details

Scott J