Re: Ford Coil Triggered Gap Testing

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Luc by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ludev-at-videotron.ca>

Hi Terry all,

I don't think you have any gain in using a bigger cap than a 1.5
to 2 uF, it not take a lot of current to magnetize the core or
the ignition coil and for best output what you need is fast
collapse of the magnetic field. With a bigger cap you will have
more energy than it's necessary and you will slow the discharge time.

Cheers,

Luc Benard

P.S. Tx Terry for the nice test.

Tesla list wrote:
> 
> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> 
> Hi All,
> 
> I hooked up a version of Marc's Triggered gap circuit at:
> 
> http://hot-streamer-dot-com/temp/MetlickaGap.jpg
> 
> My version has some MOVs and a line filter added just to control things a
bit:
> 
> http://hot-streamer-dot-com/temp/CoilTest/CoilTest.gif
> http://hot-streamer-dot-com/temp/CoilTest/P7310004.jpg
> 
> I put a 40kV Tek6015 probe on the hot lead going to the Ford coil and a
> Pearson 411 current monitor on the hot lead too.  These show the voltage
> and current waveforms going to the ignition coil.
> 
> http://hot-streamer-dot-com/temp/CoilTest/Coilin1.gif
> http://hot-streamer-dot-com/temp/CoilTest/Coilin2.gif
> http://hot-streamer-dot-com/temp/CoilTest/Coilin3.gif
> 
> 700 volt spikes (I have 240 volt MOVs on the input side of the line filter)
> and 27.5 amp peaks with a 5MHz ring :-O  So there is some substantial noise
> there!!
> 
> I looked at the output of the dimmer (input side of the filter) too:
> 
> http://hot-streamer-dot-com/temp/CoilTest/DimmerOut1.gif
> http://hot-streamer-dot-com/temp/CoilTest/DimmerOut2.gif
> http://hot-streamer-dot-com/temp/CoilTest/DimmerOut3.gif
> 
> The filter and MOVs clean the voltage waveform up nicely but the current is
> still messy as is probably expected.  However, the 5MHz signal is gone.
> Now a little 50-100kHz ring but that would not be noticed ;-)
> 
> I looked at the AC in from the AC line:
> 
> http://hot-streamer-dot-com/temp/CoilTest/ACin1.gif
> http://hot-streamer-dot-com/temp/CoilTest/ACin2.gif
> 
> Not really too terrible.  The impedance of the line is very low at say 60Hz
> but it is like an open (inductor) at say 100kHz.  The MOVs probably help
> keep the voltage spikes down but the current spikes are still pretty high
> at around 27 amps.
> 
> I put a 20uF PFC cap in parallel with the AC line:
> 
> http://hot-streamer-dot-com/temp/CoilTest/ACin3with20uFcap.gif
> 
> That really knocked down the current and cleaned things up.
> 
> I tried putting the cap on the dimmer output side but that was not a good
> idea ;-)  Got 76 amp spikes then!
> 
> http://hot-streamer-dot-com/temp/CoilTest/20uFonDimmerOut.gif
> 
> I also tried a 5 ohm big power resistor but that did not really do much.
> 
> http://hot-streamer-dot-com/temp/CoilTest/5OhmonDimmerOut.gif
> 
> I need to rewire things now that I know what I am dealing with.  Probably
> move the filter back on the AC line input side and add MOVs where it is
> now.  I also need to look at how the coil is "grounded".  A GM coil may be
> better since the secondary is isolated from the primary but the capacitance
> between the coils is still high...
> 
> Hope this is not real confusing, but your getting the raw results as they
> happen :-))
> 
> BTW - The Ford coil now runs cool with the 1.5uF cap as opposed to the 15uF
> cap.  Probably like 1/100 the power :-))
> 
> Cheers,
> 
>         Terry