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Old Sun, Aug-11-2013, 06:49:35 PM   #31
ocbaud
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Default Re: DIY: Eliminate Speedometer Error

just did this about 5 minutes ago. i'll have to test it out later on today

thanks for finding this!
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Old Mon, Aug-12-2013, 01:19:39 AM   #32
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Why does BMW do this???


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Old Mon, Aug-12-2013, 04:20:32 AM   #33
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Default Re: DIY: Eliminate Speedometer Error

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Originally Posted by lucad2 View Post
Why does BMW do this???
Seriously! It drives me nuts after having only owned the car for a few days, set the cruise at 80 and I'm getting passed by Priuses.

Anyways, thanks for figuring this out, terraphantm. I've gotta ask, is there a cheaper way to do this than BMW scanner? It's $650 with the proprietary cable which is a bit out of the average hobbyist price range for something as simple as changing the speedo calculation.
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Old Tue, Aug-13-2013, 01:40:12 PM   #34
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Default Re: DIY: Eliminate Speedometer Error

as an update. tested multiple speeds up to about 80mph and it is dead accurate with the gps program Speed Box on my work iphone.

thanks!
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Old Tue, Aug-13-2013, 02:47:27 PM   #35
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Default Re: DIY: Eliminate Speedometer Error

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If you're curious as to how the change works, the bytes I change are used as a ratio. 0x25 = 37; 0x23 = 35. 37/35 = 1.057, or a 5.7% error. I am not sure what the 0xC8 (200) value represents; I think it might be an upper limit to the allowed error (5.7% until the error reaches 20 km/h). That last byte is simply a checksum (XOR all the values together, and then XOR with 1)
I'm not 100% clear on this - does it eliminate the error altogether, or reduce the 8.9% error to a lower 5.7% error?


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Anyways, thanks for figuring this out, terraphantm. I've gotta ask, is there a cheaper way to do this than BMW scanner? It's $650 with the proprietary cable which is a bit out of the average hobbyist price range for something as simple as changing the speedo calculation.
Find a friend or a shop that has the scanner, will be cheaper to pay someone for the service rather than shell out for a scanner yourself.
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Old Tue, Aug-13-2013, 02:55:17 PM   #36
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Default Re: DIY: Eliminate Speedometer Error

There are pirated software versions you can find for under $100. Some people on bimmer forums have used them with success.

OP, if you have the real scanner version, would you be willing to lend it out so we can flash our clusters?
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Old Tue, Aug-13-2013, 04:12:25 PM   #37
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Default Re: DIY: Eliminate Speedometer Error

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Find a friend or a shop that has the scanner, will be cheaper to pay someone for the service rather than shell out for a scanner yourself.
Of course. My curiosity is really related to the cable itself, is that program hardware locked to some sort of proprietary cable?
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Old Tue, Aug-13-2013, 06:47:12 PM   #38
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Default Re: DIY: Eliminate Speedometer Error

Subscribed for when someone figures out how to make bmwscanner work with a USB ODBII cable (blue VAG-COM)
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Old Tue, Aug-13-2013, 06:54:22 PM   #39
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Default Re: DIY: Eliminate Speedometer Error

anyone in chicago area able to do this....I'll drive to you. (and toss you a few $$).
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Old Tue, Aug-13-2013, 07:01:54 PM   #40
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Default Re: DIY: Eliminate Speedometer Error

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Originally Posted by EYEHAVEYOU View Post
I'm not 100% clear on this - does it eliminate the error altogether, or reduce the 8.9% error to a lower 5.7% error?




Find a friend or a shop that has the scanner, will be cheaper to pay someone for the service rather than shell out for a scanner yourself.
non-M is 5.7%, M is 8.9%. My proposed change makes it 0% for both.
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Discussing DIY: Eliminate Speedometer Error in the Coding and Tuning Forum - Discuss all avenues of coding and tuning here! at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)