I need help from the STAR experts to know if it is possible to change the indicated speed closer to the actual vehicle speed.

Please see my posting at:
http://www.benzworld.org/forums/w204-c63-amg/2384857-speedometer-error-star-calibration.html#post12294153

Regards,
Brian

I read your detailed post. We must be on a similar wavelength as I have the exact same problem. I did similar tests and my speedo also reads about 7% faster than I'm actually doing. I find this unacceptable. About 2% is acceptable.

I complained to the dealer. They were no help at all and refused to do anything about it. The tried to tell me the Garmin I was using was inaccurate, they tried to tell me my tyres were worn and on it went. I debated their lame excuses with science and advised them the Garmin and the Mercedes GPS in the COMAND were identical and did the calculation to show the difference between new tyres and tyres worn to the tread depth markers.

I believe it 's a rort in that they are using the ADR's to their advantage by setting the speedos to read towards the end of the allowable range of 0% to 10%. It seems too much of a coincidence that 7%/8% seems to be quite common. Just think more servicing revenue as cars come in earlier. Also potentially lower resale value as your car will have 7% more km's than it's actually done.

Out of respect to other road users I don't want to be doing 56km/hr in a 60 zone. I do the same thing in that I set my CC to about 66 knowing I'm really doing about 61.

In the end I received a short email from the dealer saying the car complied with ADR's so go jump in the lake and live with it.

I have DAS/Xentry with developer mode and have searched everywhere to see if there's a factor that can be changed. So far I've had no luck.

The annoying thing is you can recalibrate for different tyres in my W639 Vito. The dealer told me it couldn't be done. In this case it was the other way as I changed wheels to 17" with 225/55 x 17 tyres from the commercial 195/65 x 16 van tyres. The speedo was reading about 5% slower than I was actually doing. It was non compliant to our ADR's. The dealer sent me away with a flea in my ear saying there was nothing they could do about it ... and in fact said they didn't even know how to do it. I might add the 225/55 x 17 is listed as one of the optional tyres on the tyre placard. I said my vehicle was illegal and they should make it legal again. They refused and said nothing could be done.

It was that reaction that made me take control. I got my own multiplexer and the STAR software. Chinese knock off system for about $350 delivered. Then I joined mhhauto and downloaded some older versions of Xentry/DAS that allow you to do more.

So I plugged the van into STAR, got into DAS and discover a drop down list of the optional tyres in the ECU and the instrument cluster CU and you select the tyre size. Not only that there's a manual entry where you can calculate the rolling circumference and input that in mm's if you're using a different size tyre. I selected the 225/55 and the speedo is about as accurate as you can get it. The speedo and the Garmin read the same.

I'm sure there's something in DAS/Xentry for the W204 ... it's finding it that's got me stumped.

You've got me motivated to have another crack at it.

Is there anyone out there who can point me in the right direction? I suspect there's a correction factor you can input in the instrument cluster CU.

 

Hi Scott52 thanks for the reply.

I have spent hours trawling through the STAR DAS XEntry in simulation mode and connected to my C220 but cannot find anywhere that the speedo can be calibrated. A search of the the Internet reveals many other M-B models analysed with STAR showing actual wheel speed sensor values and equivalent rolling wheel circumferences etc, but not the W204.

I will have another go tomorrow and see if I can find a list of optional tyres. I didn't think of searching on tyres (tires). I have searched on wheels, wheel speed sensors, Instrument Cluster, speedometer, Traction Control, calibration, ABS, but so far no luck.

Keep us informed how you go.

I don't suppose it's due to the fact that I haven't got Developer Mode on my Chinese STAR?

Regards from a cold Adelaide,
Brian

 

Yeh Brian you need developer mode. Join mhhauto and get a copy of Xentry/DAS 10-2008 and 01-2011. They're about the best before things started being locked out.

It's a once off $USD10 joining fee.

 

Thanks I will look into that.

The real issue is that the car measures the speed accurately as evidenced by the OBD Speed parameter but it gets it horribly wrong on the Instrument Cluster speedo display.

If that could be tweaked it would solve the problem.

 

Brian you galvanised me into action last night. I was in simulation mode (DAS Golden Version 10-2008) and decided to look into the ECU as I realised that's where the tyres sizes were listed in the W639.

In developer mode under actuations and "Explicit Variant Coding" ... there are two lengthy drop down lists of tyre circumferences (mm) for the rear and the front. It's called the "Tire Factor". You can't enter a number you have to select the closest number to your calculation from the list.

This, old son, may be the beginning of cracking the latest German Enigma Code.

I'm hoping the "Tire Factor" selected is communicated through the CAN and central gateway into the IC. That circumference would be required for the ESP, TC, ABS, EBD, Axle torque limit and the instrument cluster.

I had a search through the coding of the IC CU and there's no "Tire Factor" list that I can find. So I'm hoping it comes from the ECU.

I'll go live with the car today and see what I can find.

By the way it's cold over here to.

Scott

 

wallyp post transferred from the AMG C63 Forum.

There are settings on the car (not using STAR) to calibrate the GPS where you select the tire size and new vs. worn tires - that should get you closer.

Hi Wally,
Can you please provide further details as to how to do this?

As far as I can tell there is nothing in the W204 C-Class to let me do this.

Did you mean it is possible on the W220 S-Class? Even so I have never seen this capability and would be interested for my S500.

Having said that my S500L speedometer reads within 1% of my Smart Phone GPS values. The GPS also agrees with several overhead speed test signs which we have here in Australia to allow drivers to check their speedos. There is one on the Western Freeway just near Ballarat, Victoria, which we go under a dozen times a year. The S500 will be showing 112 Km/h when the GPS is reading 112.6 Km/h and the overhead sign 113 Km/h which is close enough for me.

In the C-Class I always use the Smart Phone GPS Speed as the car is just so far out. If I remember correctly the C220 will be showing 121 Km/h (in a posted 110 Km/h Speed Limit zone) when the GPS is showing the actual vehicle speed as 112.6 Km/h and the speed check overhead sign is showing 113 Km/h.
Regards,
Brian

 

Brian I went through all the sub menus in the instrument cluster SCN coding and discovered a heading "K-Zahl" with a drop down list of four possibilities ... K-Zahl 1, K-Zahl 2, K-Zahl 3 and K-Zahl 4.

I had actually seen it before but didn't know what it was so thought best to leave alone. It was set on 1. Using Google translate "Zahl" is number. I Know correction is Korrektur so I deduced it was "Correction Factor" or "Correction Number". A bit more searching confirmed the Germans do use that term K-Zahl as the correction factor for the speedometers.

The trouble is I don't know what the background factor is for 1, 2, 3 and 4. So I set it on 2 and did a test drive and it was far worse. Indicated 65k/hr COMAND GPS about 55k/hr. I then tried 4 and then 3. Unfortunately there doesn't appear to be much difference between 1, 3 and 4. I've left it on 3 as I think it's slightly better. I did a longer test and was indicating 75k/hr vs COMAND GPS 71km/hr. That's about 5.5%

I set my wheel circumferences at U2030 rear (calculated 2026) and U2010 front (calculated 2001). They were set at U1970 front and rear which I don't understand as the car came with 17'' rims with 225/45 tyres. That gives a circumference of U1993. I ditched those 17's and have since put on a set of staggered 18's.

Umfang is circumference in German which they abbreviate to "U".

I did the Umfang correction first but it appeared to make no difference to the speedo reading. I guess it's only about 2.5% difference from the U1970.

I think I'm on the right track. I'm going to compare the reading against my Garmin as that seems to give a more accurate figure. I may try even larger Umfangs to see what happens. I'm not sure if it will bugger up the ESP, TC, EBD etc.

Look for the newspaper headline:

"Perth man in Mercedes loses control on freeway ... hits bus load of orphans ... 17 dead"

...

 

Well done Scott you are making amazing progress.

I have now discovered that my STAR C3 does have Developer Mode activated and I have spent all day trying to understand what it all means.

Our W204 wasn't available to do real tests so I have been using simulation mode.

What was really helpful was a post by BenzWorld Member, Ex-Fed here "When you start Xentry/DAS, you get a nag screen in German after the NOTES screen. "Ihr System ist mit der Berechtigung "Developer-Kit" ausgestattet. {Your system is equipped with the permission "Developer Kit".}".

"Developer Mode is in German because it’s meant for factory techs only. It allows delving into factory level settings/programming on about everything in the car. You can do some interesting things but be warned, you can make your car a smoking hole too."

I have spent all day translating the German for some of the Development Mode Items and put the results here in the W220 Wiki Encyclopedia.

I also found the unloaded and loaded specs for my 205/55 R16 91V tyres.

In summary:

• Tyre width: 205mm]
• Tyre height: 55% of width = 112.75mm
• Inner rim diameter: 16” or 406.4 mm
• Wheel unloaded diameter: 2 x 205 x 55/100 + 16 x 25.4 = 631.9mm
• Wheel unloaded radius: 315.95mm
• Wheel unloaded circumference: 3.141592 x 631.9 = 1985mm
• Wheel loaded circumference: 1852.0mm
• Wheel loaded diameter: 1852.0/3.141592 = 589.5mm
• Wheel loaded static radius: 294.8mm

The loaded values were obtained from the etyrestore.com.au on-line calculator and the change in circumference unloaded to loaded was 6.7%.

It is interesting to compare the spec values with what I measured under load. The results all seem to make sense.

These are the measured wheel loaded radius and a calculated circumference:

• With minimum tyre pressure of 15 psi: 280mm and 1759.3mm.
• With normal tyre pressure of 27 psi: 290mm and 1822.1mm.
• With maximum tyre pressure of 46 psi: 299mm and 1878.7.

Keep up the good work,
Brian

 

Brian I've done more work on this today and thanks for the translation service. It's good being retired 'cos I do the interesting things I want to do.

With the tyre calculations my Engineers brain tells me the fact the tyre radius is different when it's loaded doesn't come into it. The reason being is the tyre has a contact patch. It's not like a line touching a circle where the contact patch is a single point the size of an atom.

So the first calculation of the rolling circumference is all that's needed as the complete circumference has to travel over the road surface. Imagine if you stick a drawing pin in the tread. That pin would move forwards in a circular motion until it strikes the pavement. It then moves horizontally for say 150mm before leaving the pavement and resuming it's circular motion. So the initial calculation of 631.9mm rolling circumference is all you need to do. That drawing pin would travel 631.9mm for every revolution of the tyre.

Being a motorcycle road racing veteran I've been doing tyre and gearing calculations for decades and reckon I've looked at all possibilities.

I've done about 20 laps around the "Grand Prix" circuit in my suburb today. The neighbours are probably thinking "there's that mad bastard testing his Mercedes again".

The K-Zahl numbers are definitely correction adjustments for the speedo. K-Zahl 3 I can confirm makes the smallest adjustment. Forget 2 as that's about 20%. I checked the UN design rules for speedo errors on cars (our ADR's are the same and we are soon to adopt the UN rules anyway). A speedo has to be within a tolerance of 0% to 10% plus 4km/hr. So the manufacturer has a huge tolerance to play with.

The USA has more leeway ... 0% to 10% plus 5mph.

I tried many different tyre "Umfangs" from U1944 to U2083 and it doesn't seem to change the speed at all. Somewhere there are some hard coded numbers in the software.

I ended up setting my tyres to U2030 for both front and rear and settled on K-Zahl 3. This appears to give a fixed difference of 2 to 3km/hr no matter what your speed.

At a steady 60km/hr indicated the Garmin would oscillate between 57/58. At 70km/hr indicated it would oscillate between 67/68.

I need to get out on the freeway after peak hour and try it at 100km/hr.

All this was done using DAS Golden Version 10-2008 with the developer key. It's worth getting yourself a copy as I've been able to remove the torque limit and change the throttle pedal curve to a more direct more sporty feel.

Here are some screen shots:

You can't do this in Xentry. You have to use DAS which is better, easier to use and gives you more access to change things.

I'll do some more experimenting next week.

I'm off to do 2 days intensive training on a Kawasaki ZX6RR race bike at the F1/Motogp Sepang circuit in Malaysia. Should be a great experience. I'm hoping to be the fastest veteran with a Seniors Card. I've been hydrating as the weather is stifling up there.

 

I tried many different tyre "Umfangs" from U1944 to U2083 and it doesn't seem to change the speed at all. Somewhere there are some hard coded numbers in the software.

Does it not maybe change the odometer readings? I have fitted much bigger tyres on my W163 ML, and now I must multiply the distance indicated with 1.04 to get the correct distance travelled. I have done over 150 000 km's with similar sized tyres so I have actaully covered 156 000 km's!

I want to correct that and was thinking that changing the Umfangs with Star might correct it. My OE tyres was 255/50/17 and now I have 265/65/17.
What formula should I use to get the correct Umfangs amount?

 

Brian,

My apologies for taking so long to get back to you - life gets busy.

On my 2003 S430, USA version:
System on.
Press NAV.
Go to SETTINGS at the bottom.
Go to CALIBRATION.
Press START.
Select NEW TIRES or USED TIRES, then proceed to select tire size, etc.

 

Hi Wally,

... On my 2003 S430, USA version:
System on.
Press NAV.
Go to SETTINGS at the bottom.
Go to CALIBRATION.
Press START.
Select NEW TIRES or USED TIRES, then proceed to select tire size, etc.

That is very interesting.
On my 2003 (Update) S500L, Australian version, there is no CALIBRATION setting available. Unless I am missing something.

Regards,
Brian

 

But the OP's odometer only changed by 4%!!!

 

That's because the buggers read about 8% too fast in the first place. My theory is MB take advantage of the broad tolerance allowable -0 to +10% + 3km/hr or 4km/hr.

That's 8% more servicing revenue as the national fleet all comes in earlier than needed. It's also annoying when you have 100,000km on the clock you really only have 92,000km.

The speedo and odometer data comes from the same place being the wheel speed sensors. When I tested my car both the odo and speedo were out by the same percentage.

 

Hey Brian,

I just came across this thread and was wondering whether you ended up working it out?

I am currently in a similar predicament where I have put bigger wheels on my C207 and the speedo has gone out, I have Xentry, C4 and developer mode however not sure where to look.

 

It's in the ECU under variant coding. What version of Xentry do you have. After 01-2011 they started locking things down allowing you do less and less.

 

I couldn't find out how to calibrate the W204 C220 CDI speedo using SDS and still don't know if it is possible. I got around the problem by fitting slightly different size tyres with the help of the tyre fitter and the speedo is now within 1%.
My W220 S500 is within 0.25% and is basically spot on.
Brian

 

I tried looking at doing this as well but my only option was to go lower profile tyres (25) which is going to make a very harsh ride.

It's in the ECU under variant coding. What version of Xentry do you have. After 01-2011 they started locking things down allowing you do less and less.

I have both 01-2011 on a harddrive and 2018.09 on another harddrive. I found another one of your posts that mentioned this as well, but I couldn't find the "ECU" settings. I have a C207 and I can't connect to it using DAS it automatically switches to Xentry - could this be why I can't find it or am I just looking in the wrong place?

 

Now I want a Star Machine! (Sometimes I wish I could sort out the good vendor(s) on AliExpress)....

Hoping you guys find the setting!!!!

 

The whole Star Diagnosis System (SDS) program is very confusing and at the moment I do not have time to connect to our W204 C220 CDI and find out what control module Scott52 is referring to. When I get more time I will return to trying to adapt my W220 S500L for Distronic which I have now fitted. If you want to see examples of the SDS terms used here is my work in progress on attempting to program the W220 for Distronic https://w220.ee/WIS_30.30_Cruise_Control_(CC),_Distronic_(DTR)#Activation.2FAdaptation.2FCoding_.E2.80.93_Distronic_.28DTR.29

Further to my post #21 above, I did fit Pirelli P7 215/55 R16 91V tyres in place of the OEM Pirelli P7 205/55 R16 91V. The new tyres increased the rolling radius by 5mm. But I must admit that I was too lazy to do a full test and measurement. My quick test with the new tyres showed that the speedo error had reduced to about 1% and I was very pleased with the result. You have inspired me to finish the full tests which I will do asap.

I used this on-line tyre size calculator during my research into candidate tyres. ETyreStore Home - Welcome To The Revolution

This Calculator Shows Width, size differences, and circumference with vehicle weight factored in.
Here are the results for my OEM and candidate tyres.

Brian

 

i have a 2006 slk amg 55 and my speedo needle reads differently to my digital display by 7 mph at 60mph, it also shows a fault code, and i can't get any service data to show, any idears

 

So you are saying that your speedometer needle in the car's Instrument Cluster is different to the digital speed display in the car's Instrument Cluster? The error is 11.6% which is huge!
Has it always been like this or did it just recently occur and if so what else has recently changed.
If not, something has gone wrong somewhere and could be a faulty speed sensor. Do some more research and see if there are separate sensors for the speedo and the digital readout.
Which one is correct? Compare the car with a smart phone navigation app which shows your speed via GPS and is extremely accurate (as long as you travel at a constant speed).
Diagnosing the fault code with a STAR SDS is the only real way to proceed.
In my W220 S500 I get a small variation (less than 2 Km/h) between the speedo needle, the digital speed display, the speed limiter, the Distronic speed and the car's computed average speed data, none of which agree with each other. I cannot fathom why there are differences. The only value which really concerns me is the digital speed which is accurate within 0.5Km/h at 100Km/h as measured using the GPS test. That is, when the car's speedo is showing 100Km/h, I am actually travelling at 99.5Km/h as measured via GPS.

 

my car is a Japanese import, and it was like this when i bought it, the digital reading is right but the needle is wrong

 

I am sure it can be fixed by diagnosing the fault code with a STAR SDS.