Easy way to get an rpm signal ?

[prebordao]

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 ?

[Chuck.H]

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

[prebordao]

No sensors, CIS.

[ewave]

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.))

[DRACO A5OG]

+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.

[prebordao]

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