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

Fri Feb 11 06:28:35 PST 2011

On 2/11/2011 9:16 AM, qshipq at aol.com wrote:
> Isn't that a better primarily a function of spark plug gap?  SAE 
> 2001-01-0245.  This is where some before and after measures would have 
> helped.  I look at a 5ms LS2 coil at full charge,

"full charge" changes after every spark event, so in the milliseconds 
between events where the input voltage is dropping your available spark 
energy is also dropping.  If I had more time to play I'd be happy to 
hookup my scope to the input power lines to show what happens to the 
line voltage, but I don't.  If I let everything be a science experiment 
I'd have no time to get real work done ;)  It was broke, we changed one 
variable and it fixed it.  thats scientific enough for me.

> and think a VR of 13.7 vs 14.5 isn't going to affect charge time much 
> at all.  Put another way, that's such a small change, I'd be concerned 
> that with any increase in spark gap, the 'problem' comes back.
>
> My point being, I believe there is another underlying problem if a .7v 
> increase in VR rids one of ignition hesitation.  Not trying to bust 
> yer balls, just massively intrigued by this logic train.
>
> 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 6:29 pm
> Subject: Re: LS2 coil adventures part 17...
>
> 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 <mailto: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 
> <mailto:mswanson at mswanson.com>>
> > To: qshipq at aol.com <mailto:qshipq at aol.com>
> > Cc: jc at j2c3.com <mailto:jc at j2c3.com>; s-car-list at audifans.com 
> <mailto: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> 
> <mailto: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> 
> <mailto:jc at j2c3.com <mailto:jc at j2c3.com?>>>
> > > To: qshipq at aol.com <mailto:qshipq at aol.com> <mailto:qshipq at aol.com 
> <mailto:qshipq at aol.com?>> <qshipq at aol.com <mailto:qshipq at aol.com>
> > <mailto:qshipq at aol.com <mailto:qshipq at aol.com?>>>
> > > Cc: s-car-list at audifans.com <mailto:s-car-list at audifans.com> 
> <mailto: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> 
> <mailto:s-car-list at audifans.com <mailto:s-car-list at audifans.com?>>>;
> > > mswanson at mswanson.com <mailto:mswanson at mswanson.com> 
> <mailto:mswanson at mswanson.com <mailto:mswanson at mswanson.com?>>
> > <mswanson at mswanson.com <mailto:mswanson at mswanson.com> 
> <mailto: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?>>
> > <mailto: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> 
> <mailto: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 <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