Calibrating the tachometer for my Land Rover 200TDI

 18 Sept 2024

     As you may have read in the previous post I installed a tach for a diesel in my 109, sourced from Speed Hut. Then it needed to be calibrated.

So after a search online I settled on a laser driven tach to calibrate my meter. This was sourced from Jegs though there are many places selling the same device. I chose Jegs because it came with a 9v battery and it is a reputable company.

https://www.jegs.com/i/JEGS/555/W89719/10002/-1

I started by cleaning off the crank pulley face with acetone and applying a 3/4" of the supplied reflective tape. Then I started the engine did a quick peek at what the rpms were (720) and went about my business doing other stuff until the engine warmed up. I took around 15 min just to be sure.

However I failed at getting a stationary photo of the applied tape......my bad! I did get a pic of the tape being reflected by the laser.

The laser worked from almost any angle, I found it easiest to shoot through the PTO hole in the crossmember.

This way I could read it at the same time. That turned into a good thing as the memory on my device didn't work. I'm not sure if it's a factory thing or user error at this point.

Anywho it was reading around 744-743 rpms, my tach was pretty close!

As per the instructions I had to restart the engine whilst holding down the calibration reset button. Once the needle had swept to 6000, back to 0 and up to 1000 I could release the button. Holding down the button again allowed the needle to drop and I let go around 750rpms.

I killed the engine and restarted it and the tach went to 750! Success! It was calibrated. I have to remember to shut off tach power at every shut down and re-energize once the engine is running due to some issue with my car and the tach software.

Then I revved it to 3000 just to see what it sounded like, I could tell there was more in it, not ready to go there yet!

After shutdown I did one last thing. I upgraded the switch. I wanted just and on-off switch instead of an on-off-on switch, the new switch uses spade connectors vs tightening screws and having exposed power behind the dash.

It all works and looks good to me! I am shifting from 1-2 at around 1300  and the other shifts at around 1000rpms. When doing 35mph and going from 4th to 4th OD(Roamerdrive) I drop around 400rpms.