[snipee90]

How would you go about coding your speedo to show the correct speed instead of being 3-5% faster than it should be

[marvinstockman]

I'd just use the computer in your head, which helps delay dementia.

[oVeRdOsE.]

yeah , quick search, there's at least 3 DIY

[e90yyc]

I’ve looked into this before and from what I’ve gathered it’s more nuanced and iterative than you’d think.

There are multiple speed readings in play:

Speedometer
Digital speed (if coded)
Cruise control

The DIYs floating around will explain. And I could have some of this wrong.

What I do know is that you can improve the accuracy of the DIGITAL speed reading with simple coding. But it’ll still be off actual/GPS speed. And the coding doesn’t impact the speedometer or cruise control speed, so it won’t agree to those either.

[TunafishE93]

https://www.e90post.com/forums/showthread.php?t=1696407

[mainbearing]

Yeah the speedo discrepancy is really annoying.

[TunafishE93]

Originally Posted by e90yyc

I’ve looked into this before and from what I’ve gathered it’s more nuanced and iterative than you’d think.

There are multiple speed readings in play:

Speedometer
Digital speed (if coded)
Cruise control

The DIYs floating around will explain. And I could have some of this wrong.

What I do know is that you can improve the accuracy of the DIGITAL speed reading with simple coding. But it’ll still be off actual/GPS speed. And the coding doesn’t impact the speedometer or cruise control speed, so it won’t agree to those either.

The link I provided adjusts digital and analog speedometer. Which in turn fixes the cruise control.

[Mike K]

NHTSA law that US cars must over report mph so most cars do this too. Only since GPS that anyone notices...

[TunafishE93]

Originally Posted by Mike K

NHTSA law that US cars must over report mph so most cars do this too. Only since GPS that anyone notices...

Yes definitely intentional. The odometer is dead on, so that tells me they programmed the speedo to read high. It was an annoyance to me, but coding fixed that annoyance. I didn't likr the curb lights on turns either, but luckily we can pretty easily code all these things to our likings.

[e90yyc]

Originally Posted by TunafishE93

The link I provided adjusts digital and analog speedometer. Which in turn fixes the cruise control.

Oh wicked! The coding I was thinking of was BC_DIGITAL_V_KORREKTUR

I will follow the steps in your post.

Most of the DIYs I’ve seen have been for Perfeckt Toolbox.