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jpnovak jpnovak is offline
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Join Date: Apr 2000
Location: Austin, TX
Posts: 7,472
The GM HEI signal is a sine wave as the tooth passes the variable reluctor. The stock Porsche tach is expecting a square wave signal. You need a converter circuit to make the signal compatible.

See here for some documentation on the signal output.

General Motors 7-pin HEI Ignition Control
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Jamie - I can explain it to you. But I can not understand it for you.
71 911T SWT - Sun and Fun Mobile
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classicautowerks.com - EFI conversion parts
Old 10-16-2009, 07:44 AM
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