How do you guys hookup the factory tach to your megasquirt system?
I'm installing MS II ver 3.0 with EDIS and a relay board and I'm trying to figure out the easiest way to hookup my factory tach to EDIS/ MS-II.
Connecting the tach to pin 11? (diagnostic or clean tach out) is "iffy", as per Matt Cramers post. The other option that has been recommended is fabricating a tach driver as per the megamanual on EDIS.
Thoughts? Comments?

 

What year is your car?

The 90-93 doesn't normally need the ECU to drive the tach, but will in your case since you swapped in EDIS and removed the stock ignitors which drive the tach. The 94-95 does and is looking for a 12v square wave. With the MS-1 Extra code the tacho output mod works fine to drive it. With EDIS and MS-II you'll probably need to do the EDIS tach driver as per the megamanual. Check it with a scope if possible to look for a 12v square wave signal...

 

The car is a 90 1.6. Wish I had a scope but don't have one...