mfi shutoff with msd tach ??
 

how do most people deal with the shutoff relay
when they install MSD ignition??
obsolete it or is there a way to trigger the relay from the MSD tach???

The RPM transducer(speed Switch) needs a RPM signal. It usually gets it from the CDI from the same wire that goes to the distributer. With the MSD you do not have this signal wire anymore. On my 69 I ran the tach output of the MSD to the RPM transducer rpm signal(black/purple wire). It worked. I measured the voltage output to the micro switch and it is on (12 volts)over 1500 Rpm and shuts off at 1300 Rpm. Try it. I bet it works.

cool, thanks, wasn't sure if the transducer and the msd were compabitle

it's been a while, but finally got it hooked up like you described... works like a charm...

I found it very useful to have a manual over-ride switch for the shut off solenoid, especially when the car was cold. The solenoid tended to cut off the engine when cold. I connected the manual over-ride across the microswitch. This may not be relavent to your conditions, but thought it useful to consider.

I incorporated the switch in a little control/LED monitoring box attached underneath the ashtray. Sorry dont have pics, car in workshops.

Yep, the MSD tach driver is a square wave, works perfectly.