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

[Marc Swanson]

What we are saying here is that 12v is insufficient for an ls2 coil to 
fire correctly at full boost (high cylinder pressure).  so once the 
alternator is effectively out of the picture, you're screwed.


On 2/10/2011 7:27 PM, qshipq at aol.com wrote:
> A WOT run takes 10 seconds at 15amp off a charged battery? You are then
> just back to the difference in feed voltages. I'd sure be interested in
> what's happening via measures. I'm still intrigued, not sold.
>
> SJ
>
>
>
> -----Original Message-----
> From: Marc Swanson <mswanson at mswanson.com>
> To: qshipq at aol.com
> Cc: jc at j2c3.com; s-car-list at audifans.com
> Sent: Thu, Feb 10, 2011 6:15 pm
> Subject: Re: LS2 coil adventures part 17...
>
> 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 <mailto: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 <mailto:jc at j2c3.com>>
>  > To: qshipq at aol.com <mailto:qshipq at aol.com> <qshipq at aol.com
> <mailto:qshipq at aol.com>>
>  > Cc: s-car-list at audifans.com <mailto:s-car-list at audifans.com>
> <s-car-list at audifans.com <mailto:s-car-list at audifans.com>>;
>  > mswanson at mswanson.com <mailto:mswanson at mswanson.com>
> <mswanson at mswanson.com <mailto: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
>  > China +86(0)136 6080 9560
>  >
>  > On Feb 10, 2011, at 12:27, qshipq at aol.com <mailto:qshipq at aol.com>
> <mailto: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 <mailto:mswanson at mswanson.com>
> Phone: (603)413-6833
> Cell: (603)512-1267
> Fax: (603)316-0372
>
> http://www.mswanson.com

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

Email: mswanson at mswanson.com
Phone: (603)413-6833
Cell: (603)512-1267
Fax: (603)316-0372

http://www.mswanson.com