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      12-12-2017, 11:55 PM   #1
champignon
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Coding out Speedometer "adjustment"

BMW (as you probably know) intentionally sets its speedometers to read HIGH by several to more miles per hour over the correct speed. The error/over-estimation of speed is variable, it reads more "optimistically" the faster that you are going. They do this as a "safety feature." Dealers will generally refuse to code this out. I personally find this design of BMW to be beyond annoying.

Using Carly and some other tools, one can code out the "speed correction" on the digital speedometer, on the E82/E88 1-Series cars, including the 1M. I have done this on all 3 of my 1-Series cars. I have confirmed the effectiveness of this coding numerous times with gps readings. The analog speedo "correction" and the cruise control reading "correction" cannot be coded out on North American cars. So, if I am using the cruise control on the freeway, I will end up setting the desired speed at several mph over what I really want, then adjust it down or up after referring to the (now correct) digital speedo on the car.

On my own cars, the 135i coupe and the 135is convertible read at least several mph over true speed in the uncorrected setting; the 1M is more true to the actual speed, but still reads about 2 or 3 mph fast. As I said, I have coded this out on all of these cars, to the extent that I can.

From what I have been able to read on at least the Carly for BMW website, it appears as though this speedometer "correction" cannot be coded out on the F87 cars, including the M2. Is this correct? To what extent have you measured that your M2 speedometer(s), analog and digital, over-estimate the actual speed that you are travelling at? Have any of you M2 owners found a way or ways around this?

Thanks.
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      12-13-2017, 12:08 AM   #2
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Might want to post this down in the electronics / coding forum instead of the general section...
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      12-13-2017, 12:56 AM   #3
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Quote:
Originally Posted by ZPrime View Post
Might want to post this down in the electronics / coding forum instead of the general section...
I'm surprised that this would be considered such an esoteric topic as to warrant that. If I posted a question on coding out the intentional speedo error on the 1M in the 1M forum, there would be 10 responses within a day.
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      12-13-2017, 08:45 AM   #4
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So say your going 60, the Speedo (how bmw codes it) may say 65?
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      12-13-2017, 09:02 AM   #5
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Quote:
Originally Posted by bmwizgoat View Post
So say your going 60, the Speedo (how bmw codes it) may say 65?
Get out your smartphone and install one of those gps-based speedometer apps, or use a Garmin GPS, or do both, then compare the speedo reading to the true reading on you GPS device or smartphone. Do this several times to be sure you don't have an errant GPS-error reading. Also, when you pass through one of those "courtesy" radar things telling you to slow down, look at the mph or kph that the device shows you vs. what is on your speedo.

Unless the M2 is a wholly different animal than any BMW I have knowledge of made in the last 10 or 15 years, your BMW speedo will read several to as much as 6-7 mph higher than your actual speed, depending on how fast you are going. Try it.
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      12-13-2017, 09:11 AM   #6
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Quote:
Originally Posted by champignon View Post
Get out your smartphone and install one of those gps-based speedometer apps, or use a Garmin GPS, or do both, then compare the speedo reading to the true reading on you GPS device or smartphone. Do this several times to be sure you don't have an errant GPS-error reading. Also, when you pass through one of those "courtesy" radar things telling you to slow down, look at the mph or kph that the device shows you vs. what is on your speedo.

Unless the M2 is a wholly different animal than any BMW I have knowledge of made in the last 10 or 15 years, your BMW speedo will read several to as much as 6-7 mph higher than your actual speed, depending on how fast you are going. Try it.
A week ago or so, I drove down a street with a speed sensor reading. I was not going that fast but I noticed it was off a few mph faster than my speedometer. Didn’t think much of it but maybe this is true!
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      12-13-2017, 09:46 AM   #7
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@champignon you are correct

US
BMW speedometers read +3 MPH over actual.

This has been the case for several decades , even my E30 M3 did this.

I'm fairly confident that the reason for doing so was to prevent any concerns regarding lawsuits and speed limits. Essentially, with a 3 mph higher reading than actual, the driver can never blame receiving a speeding ticket on " speedometer error ".

BMW isn't the only manufacturer that does this, however, their adjustment may be one of the largest.

On cars that will show exact speed, this can be confirmed by displaying the actual speed from the on board computer ( which picks up its signal from the differential in most cases ) vs the speed on the speedometer gauge. The gauge is programmed to show 3 mph higher.

On many late model US vehicles , the actual speed display is not able to be shown in the OBC. This can be coded in. On some models the large digital display for speed can also be coded to work.

The speedometer needles however CANNOT be changed in BMW analogue dashes. In other words, this means that while one may be able to code the dash to display the actual vehicle speed, the needles on the gauge will always read + 3 ( unless one were to attempt to physically alter them- something I would NOT recommend).

Whether this can be changed in future digital
dashes is unknown.


On my 1M I had my car coded so that the OBC will display the actual speed. It is nice to know the actual speed I am traveling, at times. I will say that in the 1M you have to learn to look at the OBC for speed as opposed to the speedometer. In some E9x M3 I've seen that there is a large digital display with MPH. I haven't coded my X1 but if either option is available ( adding actual speed to the OBC , or adding digital speed display to the dash) I would like it.
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      12-13-2017, 11:46 AM   #8
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This has nothing to do with BMW design or a BMW-specific safety feature, and if you find it beyond annoying you'll need to stop buying European cars. European law stipulates that speedometers can't show speeds less than the actual speed and they can't show more than 110% of actual speed plus 4 km/h.

Actually, you may need to stop buying cars altogether and discover the joy of mopeds. I believe even US manufacturers are allowed a % variation based on the total range of the speedometer used in the car - I think a US car with a 150mph speedo is allowed up to a 6mph variation above a certain speed, might be 55mph. I saw something in Car & Driver about this, has to do with the engineering standards followed with respect to speedometer accuracy in the USA. Bottom line - this is not a BMW-specific thing.
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      12-13-2017, 11:48 AM   #9
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I don't know if it's the same with BMW, but with VAG the way this is done is to alter the sample rate from the sensor, but this also slows the odometer down accordingly. The difference between the odo and speedo remains constant.
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      12-13-2017, 05:03 PM   #10
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Quote:
Originally Posted by afwares View Post
This has nothing to do with BMW design or a BMW-specific safety feature, and if you find it beyond annoying you'll need to stop buying European cars. European law stipulates that speedometers can't show speeds less than the actual speed and they can't show more than 110% of actual speed plus 4 km/h.

Actually, you may need to stop buying cars altogether and discover the joy of mopeds. I believe even US manufacturers are allowed a % variation based on the total range of the speedometer used in the car - I think a US car with a 150mph speedo is allowed up to a 6mph variation above a certain speed, might be 55mph. I saw something in Car & Driver about this, has to do with the engineering standards followed with respect to speedometer accuracy in the USA. Bottom line - this is not a BMW-specific thing.
Actually, the rule is that although a certain amount of upward bias is allowed, the regulations state that cars (at least any cars sold in the USA) can never under-report the speed, including in circumstances where, for example, snow tires of a different size (but still within specs for the vehicle) are used.

The US Government could not give a rat's ass where a car is manufactured, the rules for cars able to be sold in the USA are the same, regardless of where the car comes from.

It IS true that European manufactured cars TEND to over-read the speed MORE than cars made elsewhere. There is a lot of misinformation on the web about this topic, and if you googled what you put in here, you stumbled onto some of it.

It is also true, that VWs tend to read accurately, even though they are made, or the company hails from, Germany. It is also true, that BMW is among the most pronounced in overstating from the true MPH, in all circumstances, and that most or all (at least USA-based) BMW dealers will not code out the speed error intentionally put in there by BMW.

It is also true that Carly for BMW, among other coding tools, will allow you to "UN-CORRECT" the intentional speed over-correction on at least some BMWs in the digital readout, which readout may or may not be present in a given car (can be coded "IN" in all BMWs with the capability, if I recall correctly). For example, my old Z3M Coupe does not have the display to read out digital speedo readings, however it is spot on with the Analog readings.

My point, if you would reread my post, is that the intentional speed error put in there by BMW can be coded out on E82/E88 cars, but from what I have been able to find so far, it cannot be done in the F87. Hopefully someone will show that it in fact can be coded out here, and will contribute further to this thread.
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      12-13-2017, 05:36 PM   #11
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To each their own, but does it really matter if the speedo reads 78 when you're really doing 75? Personally I have better things upon which to dwell.
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      12-13-2017, 05:44 PM   #12
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Quote:
Originally Posted by Wharf Rat View Post
To each their own, but does it really matter if the speedo reads 78 when you're really doing 75? Personally I have better things upon which to dwell.
Thought the same thing, I can barely see the gauges anyway, but at least now I know I can go a little faster to offset the error.
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      12-13-2017, 05:56 PM   #13
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My experience with newer BMWs is that they all read 5% high. So the faster you go, the higher the delta. This is how I mentally compute the delta at any speed:

1. Divide your speed by ten. Easy to do. 40mph -> 4
2. Divide that value by 2. Easy to do. 4 -> 2.

So at 40mph, it will read 42.

At 75: 75 -> 7.5 -> about 3.5 So it will read 78-79mph at 75 mph.

I did very well on a Time-Speed-Distance rally using a late-model BMW with a HUD and mentally performing the math on my speed using the 5% value.
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      12-13-2017, 06:57 PM   #14
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My F10 M5 is spot on, up to 55mph. After that it is 2mph over at 60 mph and then 3 mph over up to 100 mph.
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      12-13-2017, 07:23 PM   #15
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Quote:
Originally Posted by ibimmer346 View Post
My experience with newer BMWs is that they all read 5% high.
This is/was my experience on my X6 50i: at a speedo readout of 105Km/h, the actual speed was 100Km/h.

Interestingly, I changed the tyres over to Conti's (the Bridgestone stuff that was on the X6 when I got the car 2nd hand was total rubbish) and the delta on the speedo changed too! Now a speedo readout of 104Km/h on the X6 gives me an actual speed of 100Km/h (error = 4%), so a change in tyre can potentially account for a 1% change in the indicated speed.

My LCI M2 has a smaller error: a speedo readout of 102Km/h is actually 100Km/h (i.e. error = 2%).

Note: I've measured the actual speeds with CoPilot GPS on an iPhone
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      12-13-2017, 07:33 PM   #16
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Not for nothing, speedometer error drives me absolutely crazy. Accuracy in this category would be a blessing.
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      12-13-2017, 07:34 PM   #17
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Quote:
Originally Posted by ibimmer346 View Post
My experience with newer BMWs is that they all read 5% high. So the faster you go, the higher the delta. This is how I mentally compute the delta at any speed:

1. Divide your speed by ten. Easy to do. 40mph -> 4
2. Divide that value by 2. Easy to do. 4 -> 2.

So at 40mph, it will read 42.

At 75: 75 -> 7.5 -> about 3.5 So it will read 78-79mph at 75 mph.

I did very well on a Time-Speed-Distance rally using a late-model BMW with a HUD and mentally performing the math on my speed using the 5% value.
Although I love doing the mental math, the built in speedo error is total BS.
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      12-13-2017, 11:14 PM   #18
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My Golf R consistently gives the accurate speed that I am doing on its analog AND digital speedometers. Every time I compare it to what i get with a GPS app or a Garmin, it is within 1/2 mph, consistently, regardless of what speed I am going.

All of my recent vintage BMWs (1M, 2013 135i Coupe, 2013 135is Convertible) read from several to more mph fast, increasing the error with increasing the actual speed. If I correct out the intentional error as shown on the digital speedometer with Carly, then at least the digital speedo reads accurately.

This is not brain surgery. This is intentional CRAP.

Where I do most of my driving, the state police and the county sheriffs will allow you 5 mph over before they contemplate writing a ticket, should you happen on one of their radars. 6,7 or 8 mph over, and you are taking a chance, and above that a ticket is pretty much guaranteed.

So for me, I'd really like to know what speed I am actually doing by just looking at the speedometer on the car, which is the easiest way for me to ascertain that. All the rest of this discussion to me is an excuse justifying why the lawyers that BMW employs use the algorithms that they use to fool us into thinking we are going faster than we really are.

Peace.
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      12-14-2017, 07:58 AM   #19
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Interesting. I knew this was a glaring behavior on my E46, but also knew that the ODBII port output was the real speed. I did the same check on my M2 and thought, great, it's fixed. I guess not.

Validating the real speed is a lot trickier. I wouldn't trust those "courtesy" radar units. They're often portable, banged around and even the stationary ones have no good reason to be kept calibrated. You could have someone with a known accurate speedo pace you to verify, but how does that one become a known good? Same problem.

I think the most accurate way would be if you had a buddy in law enforcement to use his (radar) gun on you. They're not perfect but are periodically calibrated as their readings are often used in court.

I'm going to see what my handheld GPS tells me. That might be pretty accurate too.
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