romanian_miata

I have been reading for a while in here as well as MS forum but nothing to help me. I want to run fuel only and I am not sure how to get my tach signal.
I have a 2000 Miata. Is there a way to ge the tach signal from the coils (using a mod because of the wasted spark) or do I need to do the CAS replacement and the whole 9 yards just like the guys that control ignition as well.

I could not find anywhere info about direct coil signal (fuel only) when there are coilpacks (2) instead of one coil.

Any help is greatly appreciated.

arga

My wife's on the computer w/ the schematics but off the top of my head why not AND the two ignitor signals together? Another "better" option would be to check out MS SnE2. There were working on a stock solution for the 99/00 crank wheel and cam sensor. I haven't checked on that in a about a month, though. Don't know where they are on that.

MSSnE2 has a lot of potential. We need some guinea pigs.

Matt Cramer

You just need a tach signal that gives a constant number of pulses per RPM. You could even trigger it off of one coil's negative terminal and tell Megasquirt you have a two cylinder engine.

romanian_miata

Thanks Matt. This is the reply I was looking for. I read this post:

https://www.miataturbo.net/forums/sh...ad.php?t=10921

and thought that I needed the mod with the diodes just for reading the tach from a 2-coil pack.

Matt Cramer

You could do that mod too, but Megasquirt can get a perfectly good RPM signal from a single coil just as well. You just won't be able to run as many squirts that way.

romanian_miata

What do you mean by "won't be able to run as many squirts that way"....? I plan to run fuel only. I have done some more reading today. I forgot to mention that I have a MS II and I am note sure if I should go MS2Extra for fuel only and use the CAS for input or just use the negative coil. How do I find the negative for the one of the coils and does it matter which coil I pick?

Thanks again.

Matt Cramer

If you have the pulses off only one coil, you could set it to inject fuel once per crank revolution. With both coil pulses, you can inject twice per crank revolution. The coil you pick should not matter.