help calibrating tachometer 4cyl to 6cyl

[Spektrewing386]

I already have a variable resistor in place of the gain resistor (which controls sweep). Now I have my insturment cluster apart and 2 tachometers ghetto hooked up to the tachometer leads inside the insturment cluster. One tachometer I have is the original 6 cyl tach from the car the engine came from and the other is my 4 cyl tach that belongs to the car im calibrating it for.

Now I'm trying to calibrate the tachometer by adjusting the variable resistor and comparing the needle to the 6cyl tach readings while holding the accelerator at a certian RPM. But that is way hard because the higher up the RPMs I go the greater the error in the calibration shows.

Does anyone in the Atlanta area specialize in tachometer calibration?

Does anyone in the Atlanta area have a function generator (square wave capable)?


I'm willing to pay for help with this.

[Spektrewing386]

anyone?

[green91]

Tachometers count pulses, resisting the line won't do you much good. What you would need is a way to reduce the amount of pulses by 1/3

[Spektrewing386]

Tachometers count pulses, resisting the line won't do you much good. What you would need is a way to reduce the amount of pulses by 1/3

Yes I know how tachometers work.
what i did was replace the "gain" resistor with a variable resistor.. this controls sweep. I know this is correct because I am able to control the sweep of the needle by adjusting the resistor. I have done this in the running car. Thing is it takes a while to get it fine tunned and keeping a steady RPM is hard and the fumes can get bad.


Now right now I have my computer acting as sort of a function generator. Using a sound tone program I can output a wave through my computer to my stereo system to act as an amplifier for the signal. And I can then output that signal to the tachometer. And I can exactly control my tachometer from my computer screen by sending different freqencies.

Now I just need something to act as a rectifer to only send the + pulses. I have an old tachometer that reads both + and - sides of the wave and it works flawlessly with my computer setup.


So yes you can control amount of pulses, but that is much hard to do... to trick the V6 components to send a I4 like signal. Or you can let the tachometer accept the V6 signal and adjust the "gain" resistor to make it as if it came from the factory that way.

[Kaiser]

You're probably going to have to get an aftermarket tachometer and wire it in. If you did, it would be much easier than what you're trying to do now.

[green91]

On your cluster is it possible to simply swap the tach assembly only?

[Spektrewing386]

no, the other tachometer does not fit in the cluster. And the faces arnt the same so you cant swap circuit boards.