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

[Marc Swanson]

this is not an issue of a .7v static increase in feed voltage.  IMO, 
whats happening here is that under full load where the coils are drawing 
a good solid 15amps the aging voltage regulators fail to *hold* at rated 
voltage.

I haven't put a meter on it, but I'd be willing to bet thats whats going 
on here.



On 2/10/2011 6:51 PM, qshipq at aol.com wrote:
> 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
>
> Sent from my mobile
> __________________________
> John Cunningham
>
> US Mobile +1 (617) 750-5025
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>
> On Feb 10, 2011, at 12:27, qshipq at aol.com <mailto: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
>>

-- 
-----------------------------
Marc Swanson
M Swanson Consulting LLC

Email: mswanson at mswanson.com
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