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flightlead404 flightlead404 is offline
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Join Date: May 2015
Posts: 802
RPM Input Frustration

I've reach a state of high frustration trying to get reliable, indeed any,
RPM pickup.

As a reminder, I'm attempting to pick up from the TD output of the 6-pin Bosch CDI unit

Car was running beautifully before I began this effort, there's nothing whatsoever wrong with the ignition. If I swap the stock WUR back in it fires straight up and has good idle speed, timing, and idle AFR.

I've tried every combination of OPTO, VR1, and even VR2 with either + or - to the TD output and the other side either floating or grounded......nothing.

Occasionally I've got weird, unreliable, and unrepeatable results, but nothing I can use. The stock tach remains connected and functions correctly throughout.

Anyone got any ideas?

Try some sort of circuit off the coil negative to tame the voltages? Maybe sort of inductive pickup with a 1N25 opto isolator and a pullup resisitor to +12? **** anything!
Old 12-18-2016, 06:11 PM
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