No subject

Thu Nov 20 11:46:45 EST 2003

last link below, it looks like the primary of the coil is unmodified.
The dI(t)/dt is the same (about 8.0 amps / 3 milliseconds) so
the inductance of the primary coil is the same as stock.
There is a lot more ringing on both the primary and secondary,
probably because of a reduced coupling factor between the
primary and secondary. Older coils used with mechanical points
tended to have looser coupling and more ringing, but the trend
with more modern systems has been to go with more coupling.

I would be most concerned about the first overshoot on the
primary where the voltage goes negative and the current has
a reverse spike. The driver stage (PSO transistor) has to absorb
this spike. Usually there is some amount of internal protection
provided to clamp a reverse voltage, but if the energy of the
spike is high enough and consistently applied, it could degrade
the lifetime of the PSO.

I still like the idea of exploring different options for the igniton,
but the stock system is quite good so it'll be that much harder to
improve on it. Somewhere I still have an SCR (silicon controlled
rectifier) designed for high power radar pulse modulators that
I was going to use in making a killer capacitive discharge ignition
with years ago, but somehow I never got around to it.

Speaking of high power ignitions, it amazes me how huge the
dual magnetos are in top fuel dragsters. They have spark currents
over 40 amps (vs. about 1/20 amp in typical passenger autos).
Of course, a single misfire could leave enough nitro behind
to cause the engine to explode on the next cycle. So I guess
some overkill is worthwhile.


----- Original Message -----
From: James Murray (LMC) <James.Murray at>
To: <s-car-list at>
Cc: 'Bruce Mendel' <brucem105 at>
Sent: Monday, January 27, 2003 5:40 PM
Subject: [s-cars] Ignition System Improvement?

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Back in December there was a small thread from Bruce M. about "Hi-Energy
Ignition Systems", interested I contacted to see
if they had anything for the AAN engine since they had nothing posted on
their web site. The rep said that 1 of the Engineers previously modified a
set coilovers for an UrS4 friend in Germany, but it was a 1 time deal, and
need confirmation from the Engineer who performed the surgery. I recently
heard back from the Ignition Solutions and said they could do it again,
priced at $875 for 5 new coils with warranty, or they could modify your own
coils (I don't know the price) but I would imagine around $275 since 5 new
coils costs around $600.

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