Switches or relays?

[Jim Blackwood]

That does get a little confusing. I'm not sure what the actual duration
of a single spark across the spark plug gap is. Maybe as you say, but
kinda like using your stopwatch on a lightning bolt. In this particular
instance there are two things: The flux across the gap is likely the
result of the original ionization charge followed by the decay of the
r/c circuit, and that flux continues only as long as there is sufficient
potential to maintain the ionized state. In concept it's not that much
different than the operation of a peak-and-hold circuit, except that
conduction generally dies off before it is switched off. As you say,
this conduction likely continues in both directions in an alternating
fashion, the reversals occurring at an extremely high rate, but one that
is determined by the r/c constant of the secondary circuit. Tho' I don't
know for sure, I suspect the MSD circuitry relies on a much slower
frequency in the primary circuit using positive feedback to maintain
amplitude until the signal is switched off. In this case, whether or not
the ionized field collapses depends on the relative frequencies, i.e.
does the original pulse last long enough for the second one to pick up
where it left off? Normally, I don't think this is the case, which means
that the ionizing potential of the second charge has to equal or nearly
equal the first. I base this on the need for a saturate-and-collapse of
the magnetic field, and on the sound the MSD makes when firing.

-----Original Message-----
From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org] On
Behalf Of Bruce
Sent: Friday, November 17, 2000 4:10 PM
To: diy_efi at diy-efi.org
Subject: Re: Switches or relays?



The only multispark jumps I've ever seen were the MSDs.   Granted been a
while since I had access to that good of scope, but I rather doubt any
oems do it.

The better ignition systems will give you a much longer spark.  ie, I've
seen some oem stuff extended form .5 msec sparks to .75 msec using a GM
HEI in place of a Bosch module. Bruce


----- Original Message -----
From: "Jim Blackwood" <jblackwood5 at home.com>
To: <diy_efi at diy-efi.org>
Sent: Monday, April 14, 1980 8:56 PM
Subject: RE: Switches or relays?


> Well, yeah at least in theory. Kind of depends on the decay rate how 
> many actual sparks bridge the gap.
>
> -----Original Message-----
> From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org] On 
> Behalf Of Bruce
> Sent: Thursday, November 16, 2000 8:39 AM
> To: diy_efi at diy-efi.org
> Subject: Re: Switches or relays?
>
>
>
> All the sparks are A/C.  Coil condenser oscillations, an all don'tcha 
> know. Bruce
>
>
> ----- Original Message -----
> From: "Jim Blackwood" <jblackwood5 at home.com>
> To: <diy_efi at diy-efi.org>
> Sent: Tuesday, November 13, 2001 9:58 PM
> Subject: RE: Switches or relays?
>
>
> > Normally that would not be the case, although it could be done. 
> > Usually
> one
> > lead of the coil primary will be switched while the other goes 
> > directly to positive. There is no intrinsic advantage in changing 
> > the polarity of the spark for a street engine, motorcycles have used

> > this system for at least
> 30
> > years. A multiple discharge would have sparks going in both 
> > directions
> (AC).
> >
> > Jim
> >
> > -----Original Message-----
> > From: owner-diy_efi at diy-efi.org [mailto:owner-diy_efi at diy-efi.org]On
> > Behalf Of Ron Schroeder
> > Sent: Tuesday, November 13, 2001 3:03 PM
> > To: diy_efi at diy-efi.org
> > Subject: Re: Switches or relays?
> >
> >
> > At 12:32 AM 11/9/01 -0800, you wrote:
> > <snip>
> > >** An analogy:  You seem to think the HV terminals are each the 
> > >equivalent of a stick welder's welding rod.  Instead, one is the 
> > >rod and the other is the ground clamp.  They trade off functions 
> > >with every
> spark.
> > >
> > >--
> > >Ludis Langens
> >
> > Hi Ludis,
> >
> > I hven't really looked into Wasted Spark much but I have a simple
> question.
> >
> > Does the drive to the primary trade functions too (reverse polarity)

> > every other firing?
> >
> > Ron Schroeder
> > WD8CDH
> > E. E. S.
> > wd8cdh at bnl.gov
> > rjs at bnl.gov
> > ron at 112motors.com
> > 631 344-4561 Day
> > 631 286-5677 Nite
> >
> > ----- End of forwarded message from owner-diy_efi at diy-efi.org -----
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