WG Jeep Geek - Tinkering with Jeep Electronics

[Hoobz]

Originally Posted by skipperau

Would these help with the speedo issue?

https://hmbe.com.au/speedometer-calibratior

Yes and no

It's complicated, well, for me to put in words.

Yes, it could possibly be used (assuming the ones you linked work on the same abs tone ring speed sensor (wheel rpm) signal parameters as the WJ/G's, I don't know) on a Jeep that has had diff ratios changed...but...only then would you be trying to give the tcu/ecu a reading it needs to compute/accept as correctly matching the output speed of the transmission (also possibly engine rpm and tranny input speed).

For example (using very simple whole numbers just to make it easy):
For the speed sensor on the output of the tranny showing 300 rpm, the abs tone ring (wheel rpm) sensor has to be signalling 100rpm if the stock 3.1 ratio diff gear from factory. If so no fault code.

Then you change diff ratio to 4.1.
Speed sensor on tranny output says 300, but now abs tone ring (wheel rpm) sensor is signalling 75 rpm. Now computer isn't getting the expected 3.1 tranny output to wheel rpm ratio and delivers fault code.


Soooo....ah easy...use one of those gyzmos in the links to proportionally change the signal coming from the abs tone ring rpm sensor (wheel rpm) of the new diff ratio to one the tcm ecu accepts. Yes, ecu tcu is happy. But...

...that doesn't factor in tyre diameter, and hence the speedo reading on the dash is up to shit, and reading wrong.

So yes, and no

It would work for both tcu ecu and speedo, if you increased (from stock oem) the tyre diameter by the exact same ratio you decreased the diff ratio by. Then it's a yes and yes.

Confused yet

It's pretty easy to follow if you draw pictures and stuff

If it was me, I'd just calibrate the abs tone rings rpm signal from the sensor to what the ecu tcu needs to read from stock. Then use a digital GPS speedo stuck near the dash, and ignore the oem dash speedo

Personally, I wouldn't go as far as to proportionally recalibrate the oem speedo ingoing signal using a micro processor. Couldn't be bothered finding that wire and extra programming

[skipperau]

Originally Posted by Hoobz

Yes and no



It's complicated, well, for me to put in words.



Yes, it could possibly be used (assuming the ones you linked work on the same abs tone ring speed sensor (wheel rpm) signal parameters as the WJ/G's, I don't know) on a Jeep that has had diff ratios changed...but...only then would you be trying to give the tcu/ecu a reading it needs to compute/accept as correctly matching the output speed of the transmission.



For example (using very simple whole numbers just to make it easy):

For the speed sensor on the output of the tranny showing 300 rpm, the abs tone ring (wheel rpm) sensor has to be signalling 100rpm if the stock 3.1 ratio diff gear from factory. If so no fault code.



Then you change diff ratio to 4.1.

Speed sensor on tranny output says 300, but now abs tone ring (wheel rpm) sensor is signalling 75 rpm. Now computer isn't getting the expected 3.1 tranny output to wheel rpm ratio and delivers fault code.





Soooo....ah easy...use one of those gyzmos in the links to proportionally change the signal coming from the abs tone ring rpm sensor (wheel rpm) of the new diff ratio to one the tcm ecu accepts. Yes, ecu tcu is happy. But...



...that doesn't factor in tyre diameter, and hence the speedo reading on the dash is up to shit, and reading wrong.



So yes, and no



It would work for both tcu ecu and speedo, if you increased (from stock oem) the tyre diameter by the exact same ratio you decreased the diff ratio by. Then it's a yes and yes.



Confused yet



It's pretty easy to follow if you draw pictures and stuff

No, all good, I understand. I'm a Marine Engineer and Ship's Captain, electronics and engineering are my life lol.

They have been used successfully for both regearing and going up in tyre size. The SpeedoDRD seems to be the favoured choice, the tuning process is pretty simple, work out how for out the real speed is compared to the indicated, for example -7%, set it to -7% and it adjusts to suit. It takes its feed from the tone ring input, reinterprets it to the new mathematical value and then tells the ECU the corrected value.
Now, if you change tyre sizes it has to be reprogrammed to suit but they are infinitely adjustable from +\-99%, it seems to be a fairly idea answer.
BUT! It wasn't suggested to remove your fun making your own module, I was thinking you could use the existing tech in it as a starting point for yours if you wanted. [emoji41]

Doug.


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[skipperau]

And nothing I said there is to suggest I'm telling you what to do, I can use and tune radars and radios, I work with 11L NA diesels daily but wouldn't know Raspberry Pi or Arduino if I fell over it for example, I'm here to learn. [emoji12]


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[Hoobz]

I must be missing something. Which could be because...big day and tired

From looking at the info in the links I don't see how it can both tell the ecu tcu the correct oem abs speed signal and have the speedo corrected, because the two are mutually exclusive, by differing ratio changes.

Adjust for correct actual speed (by factoring tyre circumference and diff ratio change) but then the ecu gets a wrong reading (by factoring diff ratio change only) and vice versa

Unless you change tyre circumference by the exact same ratio as the diff ratio change.


Formula comparison could be something like this, maybe?

Tone ring signal going to ecu tcm affect
Rpm= tone ring speed x diff ratio change

Speedo reading affected.
S= tone ring speed x ratio change x tyre circumference

[skipperau]

Originally Posted by Hoobz

I must be missing something. Which could be because...big day and tired



From looking at the info in the links I don't see how it can both tell the ecu tcu the correct oem abs speed signal and have the speedo corrected, because the two are mutually exclusive, by differing ratio changes.

No, it's likely I've missed something, there may be two modules , one for the TCM and that one for the ECU.
I'll have to see if I can find the thread again.


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[Hoobz]

Originally Posted by skipperau

And nothing I said there is to suggest I'm telling you what to do, I can use and tune radars and radios, I work with 11L NA diesels daily but wouldn't know Raspberry Pi or Arduino if I fell over it for example, I'm here to learn. [emoji12]


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I'm very beginner.

This thread is helping me very much. Making me think hard.

If everyone ads it will only help. Keep adding for sure. Awesome for you to stay.

The best way is for people to ask, suggest, comment and be peer reviewed. But, it takes a massive amount of humility to do it and risk being corrected, feel a bit silly, when that's exactly how we improve.

I'm throwing myself right out there, and anyone of you guys can certainly teach me when I'm going wrong. If we're all like that, then we'll all get somewhere and learn. And people checking the thread learn too.

I bet there's a few people looking at this busting to type something. They shouod go for it.

[Tyvokka]

I have speedodrd and it works fine with correction for the bigger tires by comparing speedo vs gps.

Anyway, I haven't actually read up on all the recent posts anf have no heads or tails on what's going on tbh.