Speedometer calibration vs GPS

[bkirk]

It seems pretty simple to me - your issue was the speedo reading too high. The device you installed to fix it is hijacking the data from the diff to speedo, to make the number (which represents your speed, aka distance over time) appear lower. This is making your odometer read lower too, since it is seeing the car travel less distance.

Which is probably a felony. We aint no snitchez here though... Wheres CalAgent when you need some street talk??

So the million dollar question is.......if I remove the hardware device, is there a tested method of using the software method to alter just the speedometer? I read that things still needed to be tested on that method. While I don't have access to a Windows device, I'm sure I could scare one up if I had to. But I hadn't heard of anyone actually making the changes for just the speedo.

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While I hate doing projects twice, removing the device is pretty simple, but coming up with a plan to fix it via software will likely take far longer than the install and de-install. Once I hear of a plan to adjust the intentional BMW speedo inaccuracy, I will give it a shot.

[BimmerBreaker]

It will likely take some experimenting to figure out how to calibrate it properly. Ive been in this community 10+ years now and never seen someone care so much about the speedo calibration as you. Thats not a knock against anyone - just pointing out that since nobody has cared about it in the past, it hasnt been looked into a whole lot...

The first page has a good post from 328i M Power (Abel). He would be the one Id talk to about this stuff, he is very good with these types of things. I ask him for help whenever diesel engines stump me and my inpa install...

I would start by getting the INPA pack installed on a spare laptop and then go from there. The calibration can be done, I am quite sure of it, but youll need the INPA tools to do it. Most notably NCS Expert. Start by installing that so by the time the knowledgable people post some ideas, you are already in a position to try it

[bkirk]

I have begun the process of drinking the Grape Kool-Ade by ordering the USB-ODB cable and the ODB to BMW 20 pin cable. I have also downloaded the INPA software zip file. Now to find a Windows machine.......so far the Grape flavor is great...........

My fascination with a corrected speedo is just part of my automotive OCD.......

[BimmerBreaker]

If you set your calibration way off, you can do 0-60 in 1 second. Thats hypercar territory. Just sayin...

[bkirk]

If you set your calibration way off, you can do 0-60 in 1 second. Thats hypercar territory. Just sayin...

Maybe I can set it to 88 miles per hour and then I won't need 1.21 gigawatts of power to go back to the future.

[rf900rkw]

The divisor might just be a signed 16bit number. If so, set it negative and pass that DeLorean.

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Maybe I can set it to 88 miles per hour and then I won't need 1.21 gigawatts of power to go back to the future.

Dammit, ya beat me to it.

[ThatZ3Guy]

If you set your calibration way off, you can do 0-60 in 1 second. Thats hypercar territory. Just sayin...

Haha, faster than that new M8!

[bkirk]

Just a bit confused on the Windows / INPA software setup. I will get my hands on a friends old Windows laptop this weekend. He is done with it, so I am going to wipe his old software and get a clean copy of Windows running. I have ordered the USB/OBD cable that is linked, along with the 20 pin to OBD connection cable. Once I have the laptop and have transferred the software over, I've read about needing to perform surgery on the cable, since I will only be using this on a 1999 Z3 2.8L.

There appears to be a number of exe files on the downloaded files, so I will have to sort through those to see what needs to be installed. While I was reluctant to mess with the software settings on the vehicle, if I'm going to do it I might as well figure out what all I can see and/or do. Any pointers on what to install or what to avoid will be appreciated.

[ptony101]

I do believe the E46 based clusters can be coded to take the speed signal, as well as tach temp etc, from the CAN bus. But then you would need to have the ABS module spit the info out on the CAN bus.

Yes, there is a function in my KMB daten file for selecting the "abs_sensor" as the road speed signal source. The option that's currently active however is "reed_kontakt", so still the diff sensor. A quick look at the wiring diagrams indicates the ABS module is connected to the DME, which is on the CAN bus. So, maybe it's talking already. Interestingly, CAN Bus is "aktive" for Tach, Coolant Temp, Gear Symbol and Fuel Consumption (also some non descript functions called CAN-BUS INSTRUMENT x).

We were the last with the diff mounted sensor. E38 and up just used the ABS for everything. And the way BMW did it was cute. It sorta makes sense, but it's still a PITA at times. They didn't blend the wheel speeds and come up with a master VSS signal. No. And they didn't want to have the entire car shut down for a failed wheel sensor. So they cooked the signal from each of the four sensors and distributed it throughout the car. DME might get the right rear. Cluster the left front, cruise the right front, radio, climate, nav, trans.... You could pretty much predict which wheel sensor was bad just by noting what did and did not work in the car and having the distribution list.

Clever engineers, designing in a bit of fail safe by using different sensors. Just an FYI, the training module I have shows that for E38, 39 and E53, the left rear wheel ABS sensor feeds the cluster and is used for distance and speed.

[ptony101]

Just a bit confused on the Windows / INPA software setup. I will get my hands on a friends old Windows laptop this weekend. He is done with it, so I am going to wipe his old software and get a clean copy of Windows running. I have ordered the USB/OBD cable that is linked, along with the 20 pin to OBD connection cable. Once I have the laptop and have transferred the software over, I've read about needing to perform surgery on the cable, since I will only be using this on a 1999 Z3 2.8L.

There appears to be a number of exe files on the downloaded files, so I will have to sort through those to see what needs to be installed. While I was reluctant to mess with the software settings on the vehicle, if I'm going to do it I might as well figure out what all I can see and/or do. Any pointers on what to install or what to avoid will be appreciated.

Where did you download the files from? Most of the INPA program collections are packaged with everything you need and come with instructions that should be followed exactly. I'd stick with that for now. There might be some extra stuff but there are inter dependencies that are critical and not always obvious. To me at least.

Whether you need to modify the cable depends. Typically, what you need to do is bridge pin 7-8 in the ODB cable. really simple. It may not be necessary because it's already done. There's also a chance the 20 pin adapter might have the corresponding pins bridged inside it.

[bkirk]

Where did you download the files from? Most of the INPA program collections are packaged with everything you need and come with instructions that should be followed exactly. I'd stick with that for now. There might be some extra stuff but there are inter dependencies that are critical and not always obvious. To me at least.

Whether you need to modify the cable depends. Typically, what you need to do is bridge pin 7-8 in the ODB cable. really simple. It may not be necessary because it's already done. There's also a chance the 20 pin adapter might have the corresponding pins bridged inside it.

I downloaded from the link provided in an earlier part of this thread that listed the specific cables, etc. Since I have the 99 2.8 L which is the E36, its unclear to me after I get the software running where to find the data elements that deal with the speedo. But I have a few steps to go before I get to that.

[rf900rkw]

Clever engineers, designing in a bit of fail safe by using different sensors. Just an FYI, the training module I have shows that for E38, 39 and E53, the left rear wheel ABS sensor feeds the cluster and is used for distance and speed.

Actually I would more say stupid engineers because they guaranteed that any wheel sensor problem will result in something in the car failing. Cooking a master signal by combining, comparing, and rejected outliers is the industry standard and doesn't end up with random subsystems dropping out.

And you're magical training manuals have been on the internet for many years. Read them all. Quote them often.

[BimmerBreaker]

The INPA install pack from the Z3 diagnostic thread should have instructions and the install .exes are in part 1, 2 and 3. Do them in order and itll be fine.

[328 Power 04]

I downloaded from the link provided in an earlier part of this thread that listed the specific cables, etc. Since I have the 99 2.8 L which is the E36, its unclear to me after I get the software running where to find the data elements that deal with the speedo. But I have a few steps to go before I get to that.

The pack I have there will work perfectly with your Z3 2.8 Coupe, and all the data you need is already bundled. You need the obd cable (INPA K+DCAN is good) no bridging required, plus 20-pin adapter.

I have been very busy with work, but will try to assist a bit when I can.

[ptony101]

Actually I would more say stupid engineers because they guaranteed that any wheel sensor problem will result in something in the car failing. Cooking a master signal by combining, comparing, and rejected outliers is the industry standard and doesn't end up with random subsystems dropping out.

True.

[bkirk]

The pack I have there will work perfectly with your Z3 2.8 Coupe, and all the data you need is already bundled. You need the obd cable (INPA K+DCAN is good) no bridging required, plus 20-pin adapter.

I have been very busy with work, but will try to assist a bit when I can.

Cables are ordered from eBay per the provided link. My friend gave me his old Windows laptop but it turned out to be an old Windows XP version that didn’t work with the software.

I bit the bullet and installed BootCamp on my new MacAir along with the latest version of Windows 10. Once the cables arrive I will finish the install and get back with any questions.

I suspect my questions will revolve around which data element will need adjusted to correct the speedo without affecting the odo.

Thanks.

[ptony101]

I suspect my questions will revolve around which data element will need adjusted to correct the speedo without affecting the odo.

Thanks.

That's the million $$ question. Actually, that's only the $500k question. I can see the parameters that could affect it. The other $500k question is "can it be adjusted by NCS Expert?" and "what values would work?"

[bkirk]

That's the million $$ question. Actually, that's only the $500k question. I can see the parameters that could affect it. The other $500k question is "can it be adjusted by NCS Expert?" and "what values would work?"

I guess I didn’t realize that I was going to be a guinea pig, but so be it. After I completed the hardware mod to the speedo, the reaction was such that I thought there was another proven approach.

I’ll get the INPA software running once the cables arrive but it certainly sounds like I will need the collective knowledge of the group to determine what data element to monitor and/or modify.

[bkirk]

The pack I have there will work perfectly with your Z3 2.8 Coupe, and all the data you need is already bundled. You need the obd cable (INPA K+DCAN is good) no bridging required, plus 20-pin adapter.

I have been very busy with work, but will try to assist a bit when I can.

Loaded my MacAir laptop with BootCamp and an up-to-date version of Windows 10. Ran all the installation programs and configurations in Win XP compatibility mode and all seems to be running as expected. One of my two purchased cables showed up today, the USB-16 pin OBD2 cable. That allowed me to finalize Com port settings.

I need to read more of the included files to figure out how to use the software for for the INPA and NCS Expert software do I need a vehicle specifc configuration file? I plugged in to the passenger compartment OBD port and nothing crashed, but I saw nothing change with the INPA software (readings, etc) and the NCS Expert software seemed to want a Profile file.

UPDATED: Reading PDF for NCS Expert now, will attempt to get connected later.

[ptony101]

Loaded my MacAir laptop with BootCamp and an up-to-date version of Windows 10. Ran all the installation programs and configurations in Win XP compatibility mode and all seems to be running as expected. One of my two purchased cables showed up today, the USB-16 pin OBD2 cable. That allowed me to finalize Com port settings.

I need to read more of the included files to figure out how to use the software for for the INPA and NCS Expert software do I need a vehicle specifc configuration file? I plugged in to the passenger compartment OBD port and nothing crashed, but I saw nothing change with the INPA software (readings, etc) and the NCS Expert software seemed to want a Profile file.

UPDATED: Reading PDF for NCS Expert now, will attempt to get connected later.

If not already in your software download (it should be) get NCS Dummy. It's like a decoder ring for NCS Expert and daten files. There's a NCS Expert profile you can download too. Search for "ncs dummy - taking the expert out of ncs expert". Its on this forum. The user guide is extremely helpful in understanding what's going on.

[ptony101]

I guess I didn’t realize that I was going to be a guinea pig, but so be it. After I completed the hardware mod to the speedo, the reaction was such that I thought there was another proven approach.

I’ll get the INPA software running once the cables arrive but it certainly sounds like I will need the collective knowledge of the group to determine what data element to monitor and/or modify.

I'm right there with you but needed to do a lot more research on some of the data fields before I was willing to start coding. I also wanted to make a chart of actual vs. speedo readings, which i was finally able to do this weekend. So now I have my baseline and may try to re-code in the next few days.

To reiterate what I posted before, I'm pretty sure that the function that most likely affects the offset (called TACHO_OFFSET) is protected by NCS. You can't even read the actual value stored in that memory location with NCS, much less change it. At least that's what others have found when trying to fix the speedo on later series.

The one chance i think we have using NCS is a function called TACHO_SKALA_ENDWERT (SPEEDOMETER MAXIMUM VALUE). The choices are Europe, US and Japan. That's possibly significant because Japanese speedo's are reportedly 100% accurate from the factory. Sooooo, maybe just changing this will change the scaling factor for what's displayed on our speedo's. I'm game to try.

[bkirk]

I'm right there with you but needed to do a lot more research on some of the data fields before I was willing to start coding. I also wanted to make a chart of actual vs. speedo readings, which i was finally able to do this weekend. So now I have my baseline and may try to re-code in the next few days.

To reiterate what I posted before, I'm pretty sure that the function that most likely affects the offset (called TACHO_OFFSET) is protected by NCS. You can't even read the actual value stored in that memory location with NCS, much less change it. At least that's what others have found when trying to fix the speedo on later series.

The one chance i think we have using NCS is a function called TACHO_SKALA_ENDWERT (SPEEDOMETER MAXIMUM VALUE). The choices are Europe, US and Japan. That's possibly significant because Japanese speedo's are reportedly 100% accurate from the factory. Sooooo, maybe just changing this will change the scaling factor for what's displayed on our speedo's. I'm game to try.

We will be a team of two trying to figure this out! But first I need to get my 20 pin to OBD connector cable on Thursday (eBay delivery date). Right now with my laptop connected to the OBD2 port I'm not sure anything is working yet. When I run INPA I'm not sure I'm seeing anything meaningful and frankly I'm unsure what I should be doing with it.

When I run NCS Expert, I get so far as choosing the EWS module and then get an error "VIN Faulty" and can't seem to get past that. I tried multiple profiles and even manually entered my VIN, but still got the same error.

What is the difference between running the software via the OBD port versus the under the hood 20 pin port?

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By the way, this past weekend after determining that the odometer is also reset by the hardware fix for the speedometer, I then attached my Bluetooth scanner to the OBD port and went to the "Dashboard" functions to see what it was reporting as speed. While it displays the speed in a digital format with a decimal place, it was dead nuts on to the GPS (iPhone) and the speedometer indicated speed, which still has the hardware chip attached and its is subtracting 5.7% off the diff sensor......

So I'm not sure where the OBD port reading of speed is coming from, but until I remove the hardware fix I'm uncertain if it is affecting what the OBD port is reporting.

[ptony101]

We will be a team of two trying to figure this out! But first I need to get my 20 pin to OBD connector cable on Thursday (eBay delivery date). Right now with my laptop connected to the OBD2 port I'm not sure anything is working yet. When I run INPA I'm not sure I'm seeing anything meaningful and frankly I'm unsure what I should be doing with it.

When I run NCS Expert, I get so far as choosing the EWS module and then get an error "VIN Faulty" and can't seem to get past that. I tried multiple profiles and even manually entered my VIN, but still got the same error.

What is the difference between running the software via the OBD port versus the under the hood 20 pin port?

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By the way, this past weekend after determining that the odometer is also reset by the hardware fix for the speedometer, I then attached my Bluetooth scanner to the OBD port and went to the "Dashboard" functions to see what it was reporting as speed. While it displays the speed in a digital format with a decimal place, it was dead nuts on to the GPS (iPhone) and the speedometer indicated speed, which still has the hardware chip attached and its is subtracting 5.7% off the diff sensor......

So I'm not sure where the OBD port reading of speed is coming from, but until I remove the hardware fix I'm uncertain if it is affecting what the OBD port is reporting.

I've never tried to run INPA through the OBD port but a couple of things to consider. First, the cap for the 20 pin under the hood has to be on for the OBD port to work. Then, the only module you can read through the OBD is the DME. EWS is not available through it.

I believe the reason you were getting true speed from the Bluetooth OBD reading is that the DME gets speed info from the DSC module, which uses a wheel speed sensor (right rear), not the diff sensor.

[BimmerBreaker]

When I run NCS Expert, I get so far as choosing the EWS module and then get an error "VIN Faulty" and can't seem to get past that. I tried multiple profiles and even manually entered my VIN, but still got the same error.

Check what files are present in the "Daten" and "Sgdat" folders of your NCSEXPER folder

Does INPA work? Try talking to the engine through the OBD port in the car in INPA (for other modules youll need the 20 pin round port adapter)

I think our resident diagnostics software expert is pretty busy these days but im sure he will chime in when he gets a chance.

[bkirk]

Check what files are present in the "Daten" and "Sgdat" folders of your NCSEXPER folder

Does INPA work? Try talking to the engine through the OBD port in the car in INPA (for other modules youll need the 20 pin round port adapter)

I think our resident diagnostics software expert is pretty busy these days but im sure he will chime in when he gets a chance.

The Daten directory has 112 files in starting with BR_REF.DAT through Variable.DAT, the SGDAT directory has 1991 files in it starting with 00EK9284.IPO through Variable.DAT and there is an E36 directory for my 1999 Z3 2.8 L Coupe too.

I will wait until the 20 pin cable/connector shows up, but it was unclear to me if I was actually connected to the car in anyway, software wise. The cable was connected but the INPA software gave no clue as to be connected and the NCS Expert only gave the indication of connection by shoot an error on the VIN.

Dumb question, but when connected with INPA or NCS Expert, what should be displayed indicating a connection?