Speedo offset fix...

[wpoll]

In a thread about re-coding the temp gauge to be more representative of actual engine temps, the discussion turned to fixing the factory configured speedo offset.

I've been researching this a little and while there is a lot of info. on doing this on other BMW platforms, there's not much for the e53. Knowing that the e53 was based on the e39, I researched e38/e39 solutions. Having downloaded my e53 IKE EEPROM contents and reviewed the hex data dump, I can confirm that it seems that there may be some similar speedo offset data in the same locations as for the e38/e39 platform: -

0x00b8 0f
0x00b9 33
0x00ec f0
0x00ed cc

0x0260 0f
0x0261 33
0x0294 f0
0x0295 cc

I still need to confirm that these values are in fact the speedo offset, how the offset is represented and what checksums are involved. And then what should be entered to remove the offset...

Watch this space...

[80stech]

[Emory39]

Originally Posted by wpoll

0x00b8 0f
0x00b9 33
0x00ec f0
0x00ed cc

0x0260 0f
0x0261 33
0x0294 f0
0x0295 cc

so replacing the first two number of that hex line should do the trick?

[wpoll]

Originally Posted by Emory39

so replacing the first two number of that hex line should do the trick?

No - it's more complicated than that. But only slightly so.

[Ohsoslow]

How much of an offset are you going for... would be nice to half it.. save $35 every 1000ks

[wpoll]

Originally Posted by Ohsoslow

How much of an offset are you going for... would be nice to half it.. save $35 every 1000ks

Tax evasion...? Who would do that...?

[andrewwynn]

Originally Posted by Ohsoslow

How much of an offset are you going for... would be nice to half it.. save $35 every 1000ks

I'm curious about this thought. This offset changes the speedometer display not the odometer. Do you pay by the km that you drive? Entirely too logical of a way to have people pay for the roads they wear out that will never take off in the USA. (people have proposed using GPS in the car but as that would also help prove who causes crashes they have blocked that legislation of course)

[wpoll]

Originally Posted by andrewwynn

I'm curious about this thought. This offset changes the speedometer display not the odometer. Do you pay by the km that you drive? Entirely too logical of a way to have people pay for the roads they wear out that will never take off in the USA. (people have proposed using GPS in the car but as that would also help prove who causes crashes they have blocked that legislation of course)

Ohsoslow and I were making a joke about road tax evasion. Here in NZ roading is paid for by a levy on fuel and when this was introduced (decades ago) when most passenger cars ran on petrol and most agricultural equipment ran on diesel. To avoid penalising farmers this levy was only applied to petrol sales - road users of diesel vehicles pay this levy seperately via a system called Road User Charges. You have to pay in advance for blocks of distance you intend to travel. I usually purchase 5,000km or 10,000km blocks ($312 and $625 respectivily). This once really only applied to the transport industry but with the massive increase in diesel-powered private vehicles, many of us now pay RUC on top of our fuel costs.

And yeah, the coding changes we are discussing don't affect odometer readings.

[andrewwynn]

Is the offset a % or like a slope eg 42 @ 49 and 73 @ 70 etc.

[wpoll]

Originally Posted by andrewwynn

Is the offset a % or like a slope eg 42 @ 49 and 73 @ 70 etc.

I was hoping it was a simple ratio, with the two values being the numerator and denominator of the ratio - so in effect a percentage change factor. But as suggested by 80stech, there may be some other mechanism here I have yet to discover.

The simple ratio used in the e46 is easy to follow (thanks to TerraPhantm at e64 fanatics): -

0x25 = 37(dec)
0x23 = 35(dec)

37/35 = 1.057, or a 5.7%

But is seems our e53 is more complex and BMW love to store simple values as complex sets of integers. I'm try to figure out what they have done here in the e53 (or at least on mine - I'll get the version of the IKE next time I connect up).

I'm going to have to get setup with NCS Dummy to get a dump of the module functions and to confirm the hex locations. I have NCS Expert but have never bothered with NCS Dummy - now seems a good time.. :-)