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

[qshipq at aol.com]

 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 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 
> China +86(0)136 6080 9560 
> 
> 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 
>> 
 
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