Speed channel 22 on Climatronic - speed difference(video)

[Ignas.quattro]

Hi all ,
recently I found out that it is possible to trace speed on Climatronic channel 22 , but I noticed that there is quite big difference between what the speedometer and what speed is show in climatronic. For example when I drive ~60km/h(according to speedometer) , the climatronic shows about 52km/h , when I drive 120km/h(speedometer) on highway I get about 104km/h on climatronic. Why there is such a big difference and why there is a difference at all? Which one shows the true speed?
If you need any videos , I will make tomorrow
Today I have only one video , made with my mobile phone , if needed

[André]

In my opinion the true speed (oder nearest to this) is shown by the climate control unit.
The speedometer often runs forward something by 10% or more (although such a great difference is not allowed (in german "street law")).

<i>Why</i> there´s such a big difference is not comprehensible for me, because the source is the same.

Ciao
André

[mAARk]

Hi Ignas,

The speedometer is normally manufactured with a safety tolerance, to make sure that it does not indicate too low. This means that, on average, the speedometers of our Audis indicate about 10% too high (to the best of my knowledge). Some indicate less than 10% high, and some even more than 10%. So probably yours is on the high end of the factory tolerance.

Similarly, the climatronic could be a bit low. These two errors now add up.

Probably, the climatronic is more accurate, because it involves no mechanical parts.

When your speedo shows 120 and the climatronic shows 104, I guess that your true speed is about 108.

Cheers,
Mark
P.S.: in my C4, the climatronic and the speedo are never more than 2 km/h apart, and both are very close to the speed indicated by GPS. So I'm lucky...

[Ignas.quattro]

aha , OK , but if our audis have approx 10% factory tolerance , why then the speed shown in your speedo and in clima are so close?
oh damn , so when I was going at 185km/h according to speedo , I thought that I was going 175-180km/h for real , but now I see that there will be 160 km/h at best... so damn , it means that my engine is sooo "dead"...
My car is full of high factory tolerances - speedo , engine...
Rust protection probably was at the lowest tolerance point possible

[Bastian]

in my aggregate experience, after owning about ten of these cars:

- the speedometer errs on the side of caution, and the deviation gets higher the faster you go.
- the climate control readings are WAY too low across the board - here also, the margin of error gets higher with speed
- the most accurate speed reading is using the "average speed" function of the trip computer (just reset it while going at a constant speed).

In my current V8, the numbers are:

speedometer....: 60 | 100 | 130 | 285
climate control..: 55 | 92 | 119 | 240
trip computer....: 59 | 97| 126 | 261
----------------------------------------------
GPS nav system: 59 | 96 | 124 | 255

advice:
- get hold of a good GPS system (preferably with external antenna; the more satellites it can use the more accurate the speed reading) and do a comparison test run OR
- go to your local auto club; they should offer a test on a dyno that gives you the speedometer deviation. ADAC in Germany does that for free...


regards,
Bastian

[Ignas.quattro]

Unfortunately , my car doesn't have neither Autocheck , nor board computer...
I made a small video of this topic , please watch it
http://www.youtube.com/watch?v=dVdh6OjgD94
By the way , I did the same speed reading in my friends Audi V8 3.6 mechanic and I could say , that the difference between speeds is more or less the same as in my car...

[Olaf Henkel]

Hi,

take it as is!

I made the same experience, and I measured it with GPS.

The real speed ist exactly between the speedometer and the climate control.

Here are some examples:

Speedometer: 50
GPS: 44
Climate C.: 41


Speedometer: 120
GPS: 110
Climate C.: 100


Speedometer: 200
GPS: 185
Climate C.: 169


Besides, the climate control doesn't need the exact speed. It only needs speed > 0 or not.

Strange thing: If you will be trapped by the police due to speeding, the climate control shows the exact value, that you will be offered later. Thats because the police has to go down a little for the tolerance.


greetings Olaf

[Ignas.quattro]

Well , in my case , it's more or less the same as with your speed difference... Do you really think that if your real speed is exactly between the speedo and the climate control , mine should be the same?
Well , to be honest , I had some thoughts , that the real speed might be something in the middle between the speedo and climatronic , so those thoughs might be true now
hmmm , but where can I measure my real speed I don't have a GPS... haha , I should stop at the police car and ask them to "shot" me with their radar and then tell the speed
And in Lithuania , sometimes when people get trapped by the police , policemen show much higher speeds then the drivers saw in their speedos and that is the way , how some policemen get money "to have something to eat"

[mAARk]

aha , OK , but if our audis have approx 10% factory tolerance , why then the speed shown in your speedo and in clima are so close?

I said: on average, our Audis have 10% factory tolerance. And any system of averages has its exceptions - some high (like yours), some low (like mine).

(Or perhaps the Speedo in my C4 was actually calibrated by the previous owner... but I doubt this, because he is not that type of person.)

Ciao,
mAARk

[Ignas.quattro]

so It seems that this little problem cannot be solved...
so never mind that

[Ignas.quattro]

Yesterday I accidentally found out that one friend of mine has a GPS , so I told him to watch the speed as we were going on a motorway and so it happened as I thought - the real speed was more or less about the middle between the speed in speedometer and in clima

[Olaf Henkel]

Hi,

I think I told you before....didn't I?

greetings Olaf

[Ignas.quattro]

Hi,

I think I told you before....didn't I?

greetings Olaf

Hi ,
Oh yes you did