Tachometer recalibration (1 Viewer)

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Oct 23, 2014
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Dominican Republic
Hello guys,

I have a RJ70 with a vortec V6 swap in it.

Since I add 2 cylinders to the engine the tachometer reads a false meassure, when the engine was at 2,000 rpms the tachometer reads 3,000 and so on.

I found some info on placing some resistors to the circuit on a hilux cluster and other guy made it with a potentiometer but nothing regarding a 70 series cluster.

I decide to make the jump, do it and document it to share with you.
 
First unassembly the cluster unscrewing all the bolts in the cluster, take out the front clear plastic and the black faceplate.

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Then unscrew the 5 bolts marked in the picture and it will loose the tachometer from the rest of the cluster

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In the back side of the tach, there are one red and one black wire soldered from the actual tach to the board.

Take the 10k potentiometer and solder it. You want to solder one wire to the middle terminal (usually labeled #2) and the other wire to either of the remaining two terminals (usually labeled #1 and #3). Polarity does not affect the result.

One of the soldered terminal have to be soldered to the black wire and the other terminal to the red as seen in the pictures.

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Then, install the tach in the cluster and test it. With the vehicle running and another tach to guide us, Turn the potentiometer to one side adjust the gain in the needle.

See the video adjusting the tach
 
I had to do a similar thing, but for the speedometer of my Prius. It was indicating a speed 10% greater than my actual speed (as measured with GPS, and road radars) because for some reason the previous owner decided to put smaller wheels. I couldn't find any information on how to reprogram the BCM, so I designed a small circuit that measures the frequency returned by the speed sensor, lowers it by 10%, then sends it to the speedometer. Now it indicates the correct speed.
 
I had to do a similar thing, but for the speedometer of my Prius. It was indicating a speed 10% greater than my actual speed (as measured with GPS, and road radars) because for some reason the previous owner decided to put smaller wheels. I couldn't find any information on how to reprogram the BCM, so I designed a small circuit that measures the frequency returned by the speed sensor, lowers it by 10%, then sends it to the speedometer. Now it indicates the correct speed.
Niiice!!!! Do you have any pictures or more information that you can share with us?
 
Niiice!!!! Do you have any pictures or more information that you can share with us?
I made more than a year ago a video on the project. At that time I didn't know yet whether it would work or not. The video can be found by going on YouTube and searching the keywords "Blue Moonshine Speedometer". Blue Moonshine is the name of my channel.
 
I made more than a year ago a video on the project. At that time I didn't know yet whether it would work or not. The video can be found by going on YouTube and searching the keywords "Blue Moonshine Speedometer". Blue Moonshine is the name of my channel.
Thanks, I'll look for it
 

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