Speedo offset fix...
 

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... ;)

:thumbup:

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

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

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

My E30 was sloped up to an extra 6-8 km at a 100 then back down to be dead on at 200 km/hr. This may or may not be the same with the E53, I think some sluthing and testing may be in order! ;) Back in the day the dealer told me that the speedo was calibrated to be accurate at 200 km and as long as it was within 10% in between there was no problem.

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

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

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.. :-)

It's easy enough to get a few reference points of actual vs speedo speed and figure out if it's a linear ratio or a curve as mentioned above (where actual speed becomes speedo speed at 200kph).

I can pull up actual speed on my scanner or the hidden menu and compare at a few different indicated speeds. (I often describe some action I've done in my x5 at some speed and will usually say "I drove through this curve at an indicated 75"