Gregory Kirk wrote:
>
> Trevor Boicey wrote:
> > > This happens as soon as the rotor swings around to an electrode inside
> > > the cap. Boom! A sparkplug ignites.
> >
> > That's simply not true. The voltage will not "sit" on the rotor
> > waiting for the proper gap before firing.
> >
> > The voltage appears at the rotor when produced by the coil. It
> > will either arc to the metal if the metal is close, or nothing
> > will happen. It will not "sit and wait" and screw up your timing,
> > that's simply not possible.
> >
> Actually, as I understand it (please correct me if I'm wrong) the coil
> is in essence a large capacitor, whose fucntion is to hold a charge
> until such time as there is a path to ground. So the charge would in
> fact sit ( in the capacitor, not the rotor though) until the rotor came
> around and made contact with cap, wich provides the charge in the
> capacitor (ignition coil) with a path to ground ( via the spark plug).
>
> Boom, plug fires.
>
> Greg
The ignition coil is a transformer and a collapsing magnetic field in
the primary, caused by the opening of the points, induces a voltage in
the secondary (many more turns of wire than the primary, so many more
volts) which will cause a current to flow if a closed circuit can be
found. The very high voltage will jump air gaps in a 'closed' circuit,
if they are small enough (the rotor to cap and plug gaps). If they
aren't, the secondary voltage collapses without any current flowing.
The coil doesn't store energy at all, and certainly not like a capacitor
does.
PaulH.
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