Ford Coil Triggered Gap Testing

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

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