Re: Maximum input voltage for "can" style (Lucas/Bosch) ignition coil (fwd)

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Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Fri, 19 Aug 2005 17:15:01 -0700
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Maximum input voltage for "can" style (Lucas/Bosch)   ignition 
    coil (fwd)

At 03:16 PM 8/19/2005, you wrote:


>         I have another "coil" which was new to me.  Came from some Ford
>product.  There are actually three separate coils with separate
>primaries.  Both ends of the HV windings have connectors for regular
>spark plug wiring, leading me to suspect that this is from a V-6 and one
>lead from each side of the HV winding goes to a plug, with the primaries
>commutated in some way to serve as the distributor.  Coils appear to be
>quite a bit less capacity than the GMHEI.
>
>Ed

Yep.. so called "distributed ignition", which is becoming very popular: no 
more distributor or rotor to replace/fail.  As you note, the individual 
coils are physically smaller. They each run at a lower rate of course, and 
they probably have different leakage inductance. Since they could "charge" 
slower, they could have more inductance, reducing the current requirement 
for the same stored energy, or, maybe they use a capacitor discharge, so 
all they need is a 100:1 transformer (with a closed core?) and they don't 
need the extra inductance to store the energy.

As an aside, there's also very clever ways to detect misfires and knocks 
when you have a coil per cylinder.  You can look for the ionization of the 
gas in the cylinder (measure the current across the sparkplug before/after 
firing, basically).  The technique was described (and patented) by Fiat 
back in the late 60s or early 70s, so it's certainly off-patent by now.