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Registered
Join Date: Jan 2001
Location: Huntsville, AL
Posts: 31
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Ignition Testing
I would like to test the output of the CD box on my 71e and I don't have access to an ignition tester or oscilloscope. I am trying to diagnose a miss at high rpms. Will a mutimeters with a logging feature and pc cable work? Can anyone recommend one?
Scott |
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01-17-2002, 07:18 AM
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Registered
Join Date: Dec 1999
Location: TX USA
Posts: 9,804
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Scott,
I have not used any of the $79 to $99 data-logging DMMs, but I have my doubts about an A/D converter that only samples 4-7 a second for analyzing ingnition pulses. My somewhat expensive bench DMM can collect 1500 samples per second and send it to my PC for graphing or signal processing analysis of the waveform. And, my waveform processing scope collects 10 megasamples per second on a single-shot event. I feel comfortable using the scope, but I haven't tried using the DMM on signals that change as rapidly as CDI waveforms. The risetime of that SCR firing the main cap is less than one microsecond! A better test of your CDI-system would be to build an adjustable spark gap with sharp points. Bosch specifies a test load using a gap of 10 mm, or about 3/8". If your coil, powered by the CDI-unit can put out a spark that will jump 10 mm between sharp points, then you can be assured the output of the CDI-unit and the coil are both OK ... unless the output is intermittent! The 'Sharp Points' aspect of the spark gap is IMPORTANT!
__________________
Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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01-17-2002, 10:34 AM
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