Re: Pertronix Ignitor Inside Info.

[Darrel Kline <darrelk@domain.elided>]

The good John Landry responded:

>I guess I don't understand what you mean by "put out" in referring to the
>Ignitor.  I mean, the voltage is a product of the battery or alternator which
>has passed through the coil's primary windings and then into the Ignitor.
The
>Ignitor and similar electronic ignition systems (like the Holley gold box I
>suppose) simply ground out the coil's primary windings in a controlled
>fashion.  They don't amplify the primary coil current do they?  Or maybe they
>do?  I assumed the resistance of the coil is what controlled how much current
>gets through.  I mean, if the resistance is .5 Ohms, then you'll get a
heck of
>a lot more current than if the reactance was say 10 Ohms.  Like any switch,
>electronic, mercury, mechanical or otherwise, it can only handle so much
>current.  Thus the restriction on the coil resistance by Pertronix.

Bear with me :-)
The only way to increase current is to lower the resistance or increase the
applied voltage. 
The Holley and Prestolite are similar to *most* of the electronic ignitions
of that time in that they use a transistor to open the circuit when the
pickup sensor aligns with one of the reluctor teeth.  I believe the
transistors in these systems are configured so that only battery voltage is
applied to the coil...But it would be very easy to design a circuit which
would apply more voltage to the coil primary for increased current flow.
A good example is the MSD6 which uses a step-up transformer to bump up the
voltage, and then a capacitor to store the energy. The voltage applied to
the primary is 460-480 volts!
The GM HEI is another system that only delivers battery voltage to the
ignition coil, but the difference is the coil's .5 ohm primary circuit. Now
it's obvious that if you apply 14 volts to .5 ohms the current is going to
get out of hand...so the HEI module has a current limiting circuit, which
limits the current to 6 amps.
Really what I was trying to find out was how much *power* the Ignitor can
supply to the coil.  I mean you look at it and it's small, so you wonder
how many amps it can handle. Taking the HEI example into consideration, you
can see that if I had just asked how much voltage (which can vary) the
Ignitor applies to the coil it wouldn't really answer the question of how
much power it can handle...Because even if it applies a lot of voltage, or
is compatible with a low resistance coil (which it isn't), it still may
have a current limiting circuit.

>Are you saying that you would expect the Ignitor to amplify the voltage prior
>to it passing through the coil?  

I *was* thinking that the Ignitor probably did step up the voltage.
There's obviously a definite advantage to increasing the voltage applied to
the primary, namely increased voltage *and* current at the plug.   

>I realize that current flows from negative to
>positive, so I suppose what I think I hear you saying makes sense.  

Are we talking Conventional current flow or Electron flow? :-)

> The Pertronix Engineer did say something about a typical breaker-point
>ignition system wave form peaks at maybe 200 volts.  He said in
>comparison, the Ignitor wave form peaks at around 400 volts.  I don't
understand what this >means, because how could breaker-points yield >higher
voltage?  Wait... could >this be a function of the condenser releasing
stored voltage?

I don't think the 200-400 volts results from the condenser, but because the
primary and secondary are wired together at the tachometer terminal.
Something to think about.

>Take care,
>John

Regards,
Darrel Kline
Colorado Springs
1980 Scout II