Easy way to get an rpm signal ?
 

I would like to get an rpm electric signal for a project i'm considering: idle management.
As i a have pertronic similar ignition (no points) can i get a useful signal from there ? I believe the points are replaced by a hall effect switch. Can i "hijack" the signal, maybe through an optocoupler ?

You don't mention what car you have, but on the 3.2 engines there is an RPM sensor that is unused, except maybe for factory idle/CO testing. It's right under the throttle body, with a little rubber cap on it. This is not connected to anything but an extra sensor on top of the flywheel. I can't remember if it's a reference (once per revolution) or a speed sensor (a lot per revolution, can't remember exactly).

Chuck.H
'89 TurboLookTarga, 334k miles

No sensors, CIS.

Easy. Grab it from the electrical connector to the Tachometer. The signal goes from battery voltage to ground, either 3 or 6 pulses per engine revolution. (This is on a 3.2L, but I suspect it's there on a CIS engine too.))

+1 you can place a piggy back spade at the back of the tach.

I did that for the speed sensor for my navi system off of the speedo.

Yes, so simple. I have another thread going on about my jumping tacho and there i realized i could use it like this.