Quote Originally Posted by familyMAN View Post
Well, this isn't as easy as I hoped. The rpm pin on 3S ecu is not used at all in AEM 3S ecu. (It is however used as the rpm signal in a DSM ecu). So, I'll have to de-pin and switch it to another low side output. I "think" it should go on a low side ground driver, but since the 3S AEM EMS isn't actually made to send a tach output I have no idea if there are resistors and "crap" that should be in the EMS box to make it work. Waaay out of my knowledge base here.
Did you look inside the 3S version to see if it isn't wired up? It seems like the DSM has it ready, and it just needs to have the settings changed.

It might be easier to use another lowside ground driver from 3S EMS. That 3/2 ratio could be a pain to do outside of the ECU.

Since you used the 3S EMS, what power transistor and coils are you using, 3S or DSM?