MS v3.0 wiring w/ MSD - step 50a or 50b?

[trwebb26]

When assembling a v3.0 board with the plans of using an MSD box for ignition - do you use hall/opto wiring (step 50a) or "trigger off of the negative terminal" (step 50b)?

 

http://www.megamanual.com/ms2/V3assemble.htm#input

 

I ordered my megasquir pre-made and I'm not sure if they wired it correctly for my application.

[z-ya]

So you plan on driving the MSD with the distributor, and then triggering the MS off the MSD? You want to drive the MS with the MSD tach ouput. I would lean towards the negative coil trigger configuration.

[trwebb26]

But is says that you can't control ignition if you use that method (configuration 50b). I'm thinking that the only correct way is by configuration 50a (optically).

 

My problem is that I expect it to have been wired by the 50a configuration - but my board has the 50b.... ???

[Forrest]

Whether or not you use optical/hall or VR is your choice for the input of the tach signal. You could use MSD as the output for either input. You need to specify which input you want to use.

 

Either way, don't worry - it's very easy to change those jumpered settings.

[trwebb26]

If I understand it correctly - there are three choices for input...

#1) Hall/Optical that takes the square wave input from a Hall sensor, optical sensor, or points (installation 50a in the manual)

#2) triggering off the coil - but only if you are not controlling ignition timing (installation 50b in the manual)

#3) VR takes the AC signal from a variable reluctor sensor and converts it to a square wave for use by MegaSquirt (installation 51 in the manual).

 

I'm trying to decide if I should be using option #1 or option #2