Speedometer correction, the easy way!

[OldFaurt]

OK, So this guy at work got me all worked up over Arduino stuff and since I needed some "EASY" speedo calibration, I got to bustin some code and low & behold,
I got a working model! I want to embed full opto isolation in & out to make it bullet proof but the code works! Since I am a PCB Design Engineer, it is not only going to be pretty, but easy as well. Now I am working on a mod so you can crank a knob to set it against your GPS! Bring your rig up to "GPS" speed, then crank the knob to match, YOUR DONE!
It will work from stopped to OMG! and can be adjusted for tire wear & will also fix odometer at the same time. If it fails flip 1 switch and it is stock!
Anybody interested?

[4.3LXJ]

I am sure you will have some takers. I assume it is OBDII only. What would it run?

[bluedragon436]

seems like a fun way to incorporate the Arduino into the XJ!! I think I'll just stick with the speedometer gear swap.. I don't think my XJ likes having add electronic upgrades very much..

[Carves]

Simple plug in, stand alone item ?? .... or integrated into the labyrinth of dubious, chrysler electrics ??

Keen to see what you come up with .. :popcorn:

[Brasscatz]

interested :)

[nickyg]

Here's my easy speedo calibration check.

1. Firmly press the gas pedal to the floor.
2. Count to 50432. That's 70 MPH.

3. Firmly press the brake pedal to the floor.
4. Count to 50432 That's 0 MPH.

[OldFaurt]

I am sure you will have some takers. I assume it is OBDII only. What would it run?

No, it hooks up between the speed sensor on the transfer case and cable, corrects the pulse rate. it corrects the odometer, Speedometer and also effects AW4 shifting as this signal also goes to the Controller.

[OldFaurt]

seems like a fun way to incorporate the Arduino into the XJ!! I think I'll just stick with the speedometer gear swap.. I don't think my XJ likes having add electronic upgrades very much..

It does not get added to the electronics, it measures the pulses coming from the sensor and modifies them faster / slower to match reality. The vehicle electronics see a correct sensor output, so, no code thrown by ECU.

[4.3LXJ]

Just a stupid question, the WJ and other vehicles from 99 up use the same speed sensor circuit to operate antilock brakes. A sensor at each wheel and one on the TC. Any idea how that would be affected?

[OldFaurt]

Simple plug in, stand alone item ?? .... or integrated into the labyrinth of dubious, chrysler electrics ??

Keen to see what you come up with .. :popcorn:

If I can source the connectors, you will unplug wire from sensor, plug this into sensor then attach cable to the corrector. Then you route a cable up into the console so you can adjust the Speedometer using a GPS and a knob. Turn until Speedometer reads 60 Mph when the GPS does. The speed will be correct throughout the whole range of speed.

[OldFaurt]

Here's my easy speedo calibration check.

1. Firmly press the gas pedal to the floor.
2. Count to 50432. That's 70 MPH.

3. Firmly press the brake pedal to the floor.
4. Count to 50432 That's 0 MPH.

Dang NickyG, you take all the fun out of Product development,

[OldFaurt]

Just a stupid question, the WJ and other vehicles from 99 up use the same speed sensor circuit to operate anti-lock brakes. A sensor at each wheel and one on the TC. Any idea how that would be affected?

In a case like that I might have to make a version to keep from messing with the balance
between those two systems. The sensor on the TC would most likely be used just for reference in say a traction control system the uses the Anti-lock brake system to slow a spinning wheel to transfer power to wheels with traction. In that case the correction device would not cause an issue.

[4.3LXJ]

The reason I ask is that they all seem to share the same circuit. So I don't know. Might get a WJ one of these days and putting 33s on it would mess up the speedo.

[OldFaurt]

The reason I ask is that they all seem to share the same circuit. So I don't know. Might get a WJ one of these days and putting 33s on it would mess up the speedo.

If you can put 33s or drop 4.10:1 ring/pinion in it without on the Jeep without messing things up, this won't hurt anything as bot of those things change ratio of signals from wheel sensors vs TC sensor!

[4.3LXJ]

Yes, I know I can match the gear ratio as close as possible. But it still may not be right on. Just thinking out loud

[OldFaurt]

Yes, I know I can match the gear ratio as close as possible. But it still may not be right on. Just thinking out loud

The way this will work is just like the sensor,
The sensor uses 2 or thee wire but the signal is the same.
There is a ground wire and a wire pulled high. when the sensor turns it grounds that wire 8 times for each rotation. The corrector watches that signal and creates a signal just like it but faster or slower as determined by a potentiometer. Turn it clock wise and the speedometer will read a higher speed, counter clockwise and it will read slower.
I am going to try to make it plug and play so if it fails you unplug it, plug the cable onto the sensor and you have the same old slightly off speedometer you had before.

So unless you want to drill a hole to hard-mount the pot, there will be ZERO vehicle modification.

[4.3LXJ]

OK, sounds good

[OldFaurt]

Well, the project is coming alone delightfully.
Right now it is going to use a pot to adjust the speedo.
I have the code all worked out, now I am sourcing Automotive grade components.
The device will be small and can be put in the centre console.
I think I have even found some connector sets so it will hopefully be very simply plug -n- play.

Will keep you updated!