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Old 03-16-2012, 08:04 PM   #5568 (permalink)
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Originally Posted by jackbauer View Post
I have a special version of the code that supports tach input with 2 pulses per rev (4 cyl). Its accurate to about 150rpm and has saved me on many the occasion from an overspeed. The hardware is comprised of a 4v7 zener , 2k2 resistor and a .1uf ceramic on one of the icsp pins (forget which one!). A later code also has brake input in a similar fashion.
Ahh, a "did something screw up" check is less demanding than trying to track RPM accurately enough to report over OBD2 and use for constant-RPM operation (cruise control or PTO/idle mode).
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