2 hours ago, xman said:

 

As you also know VAG never lie about anything.

 

60 mph is taken from the speedo which might be 55mph.

 

Don't **** on my parade, 6.52 is official. The Speedo is 100% accurate lol

It's quite easy to correlate a steady state 60mph GPS with whatever the equivalent number is on the speedo and then go up to whatever that number is.

Brochure quoted times are 0-100km/hr i.e. 62.15 mph

 

There are many potential sources of error some subtle, some not so subtle.

 

The obvious ones first

 

1. Speedo is 0% to 10% fast, by law. Likely to be midway 5%

 

2. Was the run on a perfectly level road, not downhill or up and down

 

3. No assistance from wind, aerodynamic effects from other vehicles etc.

 

4. There are always effects known as slip and creep between a driven tyre and the road. Varies depends on tyre construction, pressures and road surface but under powered acceleration, the powered tyre is always spinning that bit faster than the road passing under, 5% or more is perfectly possible and likely and that's passed onto the speedometer data (which is filtered before it gets to the dial)

 

https://www.sciencedirect.com/topics/chemical-engineering/tires

 

5. Software - app - is not a lab instrument. Written by happy appy people. How do they look at the trigger start/end points, most likely wont start timing until you reach 3 or even 5 mph. Lots of time is in initial take off. How filtered and skewed is the speedo data taken from canbus and is the data "real time" (never really possible) and not skewed or subject to dynamic errors. And Apps on phones or your infotainment centre multitask, time slots are not guaranteed, without special dedicated hardware, timing cannot be guaranteed.

 

Proper accurate measurement needs to be independent, requires a surveyed test track and things like 5th wheel etc

 

For information, for a few years, I designed electronic test equipment and wrote software for statutory dynamic brake testing and learnt a lot of this stuff working alongside HSE scientists, who were always that bit cleverer than me.

 

Edited 21 October, 20187 yr by xman

1 hour ago, Wino said:

It's quite easy to correlate a steady state 60mph GPS with whatever the equivalent number is on the speedo and then go up to whatever that number is.

 

Not if you think about it, carefully, even if you ignore most of the other factors I've mentioned.

 

Acceleration slows dramatically with speed, its not linear, neither is it a simple mathematical relationship as the engine characteristics also have to be modelled.

 

Simply put, that last 5 mph takes a lot longer than any of the previous 5mph slots. And if you only have a 0-55 mph time, it would be difficult to extrapolate that to 0-60mph with any degree of certainty.

 

Edited 21 October, 20187 yr by xman

You're overthinking this dramatically. It's just not that important.

6 minutes ago, xman said:

 

Not if you think about it, carefully, even if you ignore most of the other factors I've mentioned.

 

Acceleration slows dramatically with speed, its not linear, neither is it a simple mathematical relationship as the engine characteristics also have to be modelled.

 

Simply put, that last 5 mph takes a lot longer than any of the previous 5mph slots. And if you only have a 0-55 mph time, it would be difficult to extrapolate that to 0-60mph with any degree of certainty.

 

Mercedes E63S accelerates from 0-160mph in 19.4 seconds. Bet that doesn't feel like it is slowing down much. 0-60mph in 3.3 seconds.

Edited 21 October, 20187 yr by shyVRS245
wrong letter

5 minutes ago, Wino said:

You're overthinking this dramatically. It's just not that important.

 

Its not important to me at all. Just saying that the 0-60 app should only be for entertain purposes and is likely to be at least 10% optimistic, which makes people happy, but is a lie.

 

0-60 drag runs on public roads is also a questionably dangerous thing for app developers to encourage.

2 minutes ago, shyVRS245 said:

Mercedes E63S accelerates from 0-160mph in 19.4 seconds. Bet that doesn't feel like it is slowing down much. 0-60mph in 3.3 seconds.

Comparing apples with wet cod.

Edited 21 October, 20187 yr by xman
Low flying golf balls

2 hours ago, Wino said:

You're overthinking this dramatically. It's just not that important.

Thank you...... some very serious people on here. A bit sad really lol

Jeez this got very serious very quickly,who gives a f@#( how accurate the app is ?

For us normal people it's going to be an accurate enough barometer,

In my case 9.55 -9.9 either or is damned impressive for the little sewing machine which was the point of my original post.

On 20/10/2018 at 21:27, 181ce said:

25000 up on mine now perhaps degree of use ?

Possibly.  Mine only has just 4,000 miles.