Bosch CDI Tach Circuit
 

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Hello, I am having a little difficulty figuring out the tach circuit on the bosch 6 pin. I was originally told that the 150 ohm resistor (R8) connected to ground would bleed off enough current to create a tach signal. The current coming off the tach signal would also feed into C3 so is that what causes the spike to drive the tach? IE C3 absorbs a lot of current and then slowly releases it into R8. I am thinking I could connect the gate of an SCR in parallel with the main SCR in an MSD or any other CDI box then put a .0068 uF capacitor (to match C3) connected to a 150 ohm resistor (to match R8) then connect that to ground. I could hopefully put this little circuit inside the MSD box etc, hook up a 6 pin plug to it, and then have a plug and play replacement CDI for pretty cheap.

Let me know if you think this circuit would work, any help is greatly appreciated!