MicroSquirt.com read only forum (Jan.15,2018)

I was about to crank my engine over for the first time after the install but now i'm not so sure after reading this:

MegaSquirt needed one signal per ignition event, but the timing was not critical.

MegaSquirt-II needs one signal per ignition event, but this signal MUST occur at the advance offset with respect to TDC.

So you CANNOT use the negative side of the coil to trigger MegaSquirt-II because the coil already has timing advance built in, and using it for a timing signal will screw up the total advance severely. You must use the appropriate distributor or crank wheel for your ignition module.

My plan was to trigger off the (-) coil driven by pertronix. The distributor is a stock 009 with centrifugal advance. I understand how the dizzy advance can screw up the triggering of injection. Should I not bother and wait till the weekend to get a timing light, lock the stock dizzy and wire it up for spark too?

'73 porsche 914
MS II V 3.0

I just use the tach signal that is generated by the ignition control module. Not sure if you could do that in your case or not.

you could keep using your mechanical advance if you use a VR sensor (instead of coil) to provide the MS2 with its RPM signal

Yes, you can trigger off your existing coil -ve terminal if you're only
controlling fuelling because it's not very important when the fuel is
injected, BUT, if you then decide you want ignition timing control under
MS-II control you'll have to trigger it differently, either hall effect, optical
or Variable Reluctance sensor from the cam or (preferably) the crank.
Dave.