AutometerTach in 12a?
 

Hi guys,
Im sorry if this has been posted before - I did a search and couldn't find what I needed.
I'm interested in putting a tach and shift light in my car, and I remember from my old SR20 Nissan days that when you put in an Autometer Tach that you cut a certain # of wires depending on the number of cylinders you had. For those of you running a tach, did you have to cut wires for this purpose, and where did you connect the current lead to get RPM readouts?
Sorry for the questions - Im familiar with the suspension and bodys of these things, but the engines I'm still trying to play catch up on!

- Alex

from what i have read, the rpm signal comes from your trailing coil. maybe someone with more experience and knowledge will confirm and clarify. i hope this helps.

confirmed

So I figure you go to the trailing coil on the negative side.... What setting (# cylinder) do you set the tach to??

You use the 4-cyl setting on external tachs when dealing with a rotary.

It's determined by the number of degrees of shaft rotation between firing events.

yup - you guys were right. I wrote Autometer too (for some reason I didnt get the other posts) and was sent this from their tech support department -

Hi Alex,

On those engines, you'll want to connect your tach signal wire (green) to the negative side of the LEADING coil (NOT the trailing coil) will give you a 2PPR (or otherwise known as a 4-cylinder setting) tach output signal.

It's not to say that it's a 4 cylinder setting, it's really just that it's a 2PPR setting, that's the important part.