I have installed a digital NOS WOT/window switch, #15982, on my 1988 Camaro. The rpm readings are erratic, strange or not linear?

When idling the readings are the same as on the Autometer gauge, but when rpm rises the NOS is showing values about twice the reading on the Autometer.
Both unit are connected to the same point, the white wire going to the coil.
If I program the NOS to 16 cylinders it shows correct rpm above idle but half the idle rpm.

Can the NOS unit be picking up some distortion, bad signal or something else?
What can affect the tach signal?
Are there any better places to connect a tach? With better signals?

Can I connect the NOS unit somewhere on the ECM to get a better reading?

I feel a bit nervous to use it as a nitrous controller if rpm readings are off.





Further testing has shown that the readings are correct at idle. Above idle to 3500 rpm the readings are doubled and above 3500 rpm the readings are correct again. Tried with different wire routings so I dont think it is noise in the tach signal.
Maybe the unit is not functioning right?

BR

 

Problem solved.

Instead of connecting it to the tach signal from the coil I connected it to the ECM tach signal. Now it works as it should.

 

Good to hear you figured it out. Can't wait for the weather to break, so I can work on the next phase of my car.