Oem tach use with megasquirt

[1SIKSIX]

There is probably a simple solution to this, so instead of spending too much time searching ill ask here. What signal does the oem cluster need for the tach? Since i started using ms2 the tach runs at half speed/ not work at all. The cluster board was just rebuilt by programa and functions properly. I run an msd6a ignition and ran that signal wire to the cluster with no luck today. I know others have had issues. Car is 89 635. Probably same issues e30 people having.

[bry195]

3 pulses per rev. I'll let you know in a couple days when I set mine up.

[1SIKSIX]

3 pulses per rev. I'll let you know in a couple days when I set mine up. wonderful. My tach hasn't worked since i made the switch. The wiring diagram shows a resistor.

[dburt86]

i never had an issue with the tach with my ms2 or my ms3. Just tacho from the MS to the tach pin on the harness side

[rf900rkw]

the tach signal mimics an old points distributor. 2 pulses per rev for a 4cyl, 3 pulses per for a 6 cyl. The actual output is a 50% duty 12V square wave.

http://zeeasylum.com/albums/bimmerforums/scope-ign.jpg

[bry195]

so its just a 12 volt square wave at 2 or 3 pulses per rev? when you say duty it leads me to believe they are evenly spread over each rotation. am I reading that correct?

[tptrsn]

8 pulses for a V8 then, or do we know? (M62b44)