Today I.....

birtyA2 said:
Bit of a drama getting the MOT this year

1st test failed on fast idle CO emission with an advisory of the under tray being fitted. Never understood why that gets picked on, it’s part of the car. This was despite a dose of Cataclean and a bit of a spirited drive before hand. New NTK lambda fitted (2nd one - measuring blocks didn’t show any movement so perhaps tired rather than failed; no DTCs) and all good
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That’s ridiculous for the undertray should be the other way round for not having one. I wouldn’t go back that MOT centre


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Today, Oxted in Surrey to Maidenhead round the M25 and M4, a distance of 46 miles at a cruising speed of 65-68mph:

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So far since filling up I’ve done 95 mostly motorway miles like this and CDIS says I have a range of 695 miles - I think given I have another 400 motorway miles coming this week and next, I should be able to crack 700 on this tank before the low fuel warning scares the hell out of me reminds me to start thinking about filling up when passing a cheap source of diesel 😆

I’m not sure why Audrey is giving me such good returns in the colder weather but I am most certainly not complaining. For the record, I always fill the tank to the brim using the burp toggle, which means I can fit in about 45 litres from the range reading zero miles.
 
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dj_efk said:
Today, Oxted in Surrey to Maidenhead round the M25 and M4, a distance of 46 miles at a cruising speed of 65-68mph:

View attachment 134368

So far since filling up I’ve done 95 mostly motorway miles like this and CDIS says I have a range of 695 miles - I think given I have another 400 motorway miles coming this week and next, I should be able to crack 700 on this tank before the low fuel warning scares the hell out of me reminds me to start thinking about filling up when passing a cheap source of diesel 😆

I’m not sure why Audrey is giving me such good returns in the colder weather but I am most certainly not complaining.
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Always check withe the tank neck to tank neck fill in the same place / filling station & cross reference, a good calibration check.
 
dj_efk said:
Today, Oxted in Surrey to Maidenhead round the M25 and M4, a distance of 46 miles at a cruising speed of 65-68mph:

View attachment 134368

So far since filling up I’ve done 95 mostly motorway miles like this and CDIS says I have a range of 695 miles - I think given I have another 400 motorway miles coming this week and next, I should be able to crack 700 on this tank before the low fuel warning scares the hell out of me reminds me to start thinking about filling up when passing a cheap source of diesel 😆

I’m not sure why Audrey is giving me such good returns in the colder weather but I am most certainly not complaining.
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Is your wheel/tyre combination, (circumference), as the OEM spec?
Mac.
 
Took delivery of this nice promotional material which I believe was sent to German Audi customers to entice them to come try an A2 at their local dealer.

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ChatGPT translation of the letter:

Welcome to the world of the Audi A2!

You probably know this feeling yourself: the curiosity about what others think of something you are particularly proud of. That’s how we feel about the new Audi A2. Because this car offers a wealth of new perspectives, it is innovative and versatile, it is many things – but one thing it is not: ordinary. The pictures of the Audi A2 are meant to give you a first impression of it.

What you cannot take from the enclosed brochure is the feeling that only arises at the moment of encounter. We are sure that experiencing the Audi A2 live is something special. That’s why we invite you to get to know the Audi A2. Visit us – we look forward to seeing you.

Your Audi Partner

Cheers,

Stuart
 
PlasticMac said:
Is your wheel/tyre combination, (circumference), as the OEM spec?
Mac.
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It’s slightly larger Mac as I’m running 185/60/15 instead of the OE 175/60/15. The speedometer is ever so slightly optimistic according to the GPS speed on google maps.
 
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Yes by a small tiny margin Mac and less so than OE.

Also, I’ve adjusted the consumption calculation with CDIS so that the average of what it says I do over a tank roughly matches with the at-pump calcs. So it’s as accurate as it can be.
 
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But you can't "adjust" the odometer.
The speedo is deliberately set to over read, as we know, but that "calculation" is not applied to the odometer. It records acurately, but only if the rolling circumference is to the OEM standard.
Even brim to brim consumption calculation, the gold standard, depends on the odometer being accurate.
Even tiny errors become significant, when they are cumulative.
Mac.
 
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The tyres on the car are slightly larger -meaning they rotate 2% less per mile as below - or to put it another way, when the car has travelled 100 actual miles, the odometer will read 102, assuming as you say that it reads dead-accurate when the car is on the OE 175 size - Correct?

I can live with that as a margin of error.

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dj_efk said:
The tyres on the car are slightly larger -meaning they rotate 2% less per mile as below - or to put it another way, when the car has travelled 100 actual miles, the odometer will read 102, assuming as you say that it reads dead-accurate when the car is on the OE 175 size - Correct?

I can live with that as a margin of error.

View attachment 134372
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100,000 real miles = 102,000 dj_efk miles.
Mac.
 
I'm no expert and more practical than technical and certainly wouldn't argue the point as I honestly don't know but my 'common sense' thought process would suggest that if the manufacturer deems it necessary (or is legally obliged to) build in a tolerance allowing someone to fit oversized wheels/tyres as large as are physically capable of being fit to the car without the speedometer over-reading then wouldn't the same tolerance be applied to the odometer too, so potentially the mileage stated is a greater distance than we have actually travelled, I don't know, it doesn't work off GPS so how accurate is an odometer when the car leaves the factory?
Then there's also the anomaly with the different sized factory wheels specified on the A2, 15", 16" and 17" and although the tyre sizes are altered to make the rolling circumference as close as possible to being the same, they are still different. If you check, 175/60/15, 185/50/16 and 205/40/17 sizes, they will be different, not massively but is the odometer calibrated for each vehicle when the tyres are specified/chosen when built but the speedometer isn't, I have no idea? 😊
 
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The odometer, and all ECU calculations, RPM, distance driven, etc, are calculated from the crankshaft ABS sensor, (except early car with gearbox drive).
The over read factor, applied to the speedo reading, (to save us from ourselves), is, I believe, an instrument controller function, and not applied to the odometer.
I wouldn't think there was any tolerance for fitting wheels, or tyres, that were not on the OEM list at the time of build. Why would there be?
I don't have any knowledge of the CDIS, but it's raw data source can only be the ECU.
Mac.
 
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PlasticMac said:
The odometer, and all ECU calculations, RPM, distance driven, etc, are calculated from the crankshaft ABS sensor, (except early car with gearbox drive).
The over read factor, applied to the speedo reading, (to save us from ourselves), is, I believe, an instrument controller function, and not applied to the odometer.
I wouldn't think there was any tolerance for fitting wheels, or tyres, that were not on the OEM list at the time of build. Why would there be?
I don't have any knowledge of the CDIS, but it's raw data source can only be the ECU.
Mac.
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RPM, gearing etc is all altered by wheel/tyre size (rolling circumference) along with the speedometer and the tyre sizes I've quoted are the factory specified one's 👍
 
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A2Z said:
RPM, gearing etc is all altered by wheel/tyre size (rolling circumference) along with the speedometer and the tyre sizes I've quoted are the factory specified one's 👍
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The only thing that is not a variable is the relationship between the ABS sensor, and wheel rotation.
(I had originally, mistakenly said crankshaft sensor, and I've edited my posts, and apologise),
The ECU uses the ABS sensor, together with the standard wheel circumference, which for all originally listed wheel/tyre combinations is, very similar, (I was going to say the same, but didn't, but to all intents and purposes, they actually are), to calculate distance driven, and display that on the odometer.
If the wheel/tyre circumference is different from the OEM figure, then the odometer, and anything derived from it, such as mpg, will not be correct.
Mac.
 
PlasticMac said:
The only thing that is not a variable is the relationship between the ABS sensor, and wheel rotation.
(I had originally, mistakenly said crankshaft sensor, and I've edited my posts, and apologise),
The ECU uses the ABS sensor, together with the standard wheel circumference, which for all originally listed wheel/tyre combinations is, very similar, (I was going to say the same, but didn't, but to all intents and purposes, they actually are), to calculate distance driven, and display that on the odometer.
If the wheel/tyre circumference is different from the OEM figure, then the odometer, and anything derived from it, such as mpg, will not be correct.
Mac.
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I think it's the 'correct' term that's the issue as I don't think it actually exists.
I don't think there is anyone more OEM or originality obsessed than me (or possibly someone slightly more 😊 but I am) and it's the 'incorrect' over-reading speedometer from the factory with factory specified tyre sizes (which I referenced above) that annoys and bothers me, hence why I sought to use slightly oversized tyres in an attempt to correct this as much as possible and make it read as accurate or 'correct' as possible but not at any compromise such as safety, handling, comfort and most importantly any fouling or rubbing. I will never go up more than one step in sidewall size as that is the max in my opinion (and sometimes potentially too much) and never up a size in the width combined with this too and is why I get on the defensive when people recommend using them, I've tried most combinations and know what works and what doesn't and the effects of that!
When keeping with the original factory sidewall depth (or aspect ratio) then I do find it beneficial to go up one (and sometimes possibly two width sizes on wider wheels) but this is dependent on other circumstances, wheel width/J and offset/ET etc. and I find this can not only improve or lessen the considerable factory over-read but improve comfort and handling too and actually also help a little with noise at motorway speeds by lowering the gearing and thus the revs, actually increasing mpg just as @dj_efk has done.
If I'm honest I've never actually considered the effect on the odometer until you brought it up a few posts earlier but as I said before if it was checked with the various sized factory specified tyres don't believe there would be a 100% 'correct' reading anyway as they are slightly different 👍
 
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Quick change of service parts to my (new to me) tdi90, had a spare hour so got to it and changed air filter, fuel filter and the hardest job of the three coolant temp sensor. Such a swine locating the clip in position do all you tdi owners agree?
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No wonder my temp gauge wasn’t working!
 
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