Speedo is about 10% over

[AzzA SP20]

+1 to whatever he said..

Similar Calibration units are used by police for calibrating high performance vehicles however they do cost a fortune..

I wouldn't even worry about it. As I said earlier, it's the analog speedometer. If you check the data logs through Cobb, you will see the correct speed..

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To get somebody to do it and certified costs around the 600 mark.

The unit its self is about $200 of that.
and you can make your own for about $40.

but I wouldn't bother lol

[slixx]

+1 to whatever he said..

Similar Calibration units are used by police for calibrating high performance vehicles however they do cost a fortune..

I wouldn't even worry about it. As I said earlier, it's the analog speedometer. If you check the data logs through Cobb, you will see the correct speed..

Sent from my GT-I9100 using Tapatalk 4

Yeah I know
My Cobb is out now coz of my wheels

[RedDjinn]

This won't work. It's out by a percentage figure, not a standard variance throughout the whole speed range.

I disagree the faster you go the more correct our speedo is after 100kph

[bodyboardingbum]

I disagree the faster you go the more correct our speedo is after 100kph

... Not sure if serious, but that's not how it works.
If troll, well done - it worked :P

[GibbA]

Yeah @RedDjinn if you weren't trolling, just say you were because you're way off the money there :-P

I just know the percentage difference of my wheels compared to stock and just multiply vehicle speed column by it in excel to see actual speeds

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[RedDjinn]

... Not sure if serious, but that's not how it works.
If troll, well done - it worked :P

I am dead serious! My gen 2 is more accurate than my the gen 1... get on the track get too 150 or 200 kph have a look at it i beat you its reading closer!

[GibbA]

Have a look at it next to what?

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[GibbA]

I can see reason for it to get a tiny bit faster, and that's because the tyres have a bigger circumference at 150-200 but not increasing at a greater rate than the difference between speedo and actual speed...

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[RedDjinn]

I can see reason for it to get a tiny bit faster, and that's because the tyres have a bigger circumference at 150-200 but not increasing at a greater rate than the difference between speedo and actual speed...

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speedo vs GPS, I know i have been there i did it .. That's how i know its not a percentage thing, as i argued and thought long and hard as i wanted to correct it. One day i went out testing and found out!!

[AzzA SP20]

speedo vs GPS, I know i have been there i did it .. That's how i know its not a percentage thing, as i argued and thought long and hard as i wanted to correct it. One day i went out testing and found out!!

errr... hate to break it to you... It is a percentage thing!

our speedo's are controlledby variable reluctance magnetic sensor, which reads the speed of the passing teeth on a gear in the diff (works from electro-magnetic pulses). The sine-wave signal generated is converted to a certain amplitude of pulse depending on your speed. This is done via your computer, and this signal is sent to a stepper motor which moves the needle with digital accuracy.

when you have such multiplication processes, your accuracy will be based upon a percentage.

even old school eddy current needles have a percentage of error using your speedo/ ring gear system.
anything that uses some form or ratio's or multiplication of another dependent value will have a percentage of error.



your theory is severeley flawed as Gibba pointed out.

at 200km/h you are travelling at 3333.3' m/min

if you are on stock size rim (225/40/18) your tyre has a circumference of 2.0018m.

meaning per revolution of your tyre your car has travelled 2m (unless wheel spin )
anyway... your wheel is now doing 1666.6' rpm.

by the time you factor in your rotational mass variances at such high speeds aswell as the mass ammount of extra heat generated... your tyre has now expanded (and by a fair bit).

once your tyre expand... Its now travelling slower than it would be if it was cold (due to diameter increase).
which your speedo which was reading 106km/h at an actual velocity of 11km/h is now reading slower than it was when cold... mking your speedo reading say... 101km/h at an actual velocity of 100km/h.

BOOM! SIENCE BITCH! rofl

[bd581]

For those of us who have been around here for a long time.

I think we have our new nexus in training.
technical enough of an answer, but not quite long enough

[AzzA SP20]

For those of us who have been around here for a long time.

I think we have our new nexus in training.
technical enough of an answer, but not quite long enough

Not sure If bad thing, good thing or I look like a tool bag...

I'm guessing all lol

[bd581]

Here's some interesting figures on things like the difference tyre pressure and temperature makes
http://www.adrawa.com.au/Speedometer%20Accuracy.pdf

And also, the actual rules
"18.5.1.1.2. indicate the actual vehicle speed, for all speeds above 40 km/h, to an accuracy of ± 10 percent"
Vehicle Standard (Australian Design Rule 18/00 - Instrumentation) 2006

[AzzA SP20]

Here's some interesting figures on things like the difference tyre pressure and temperature makes
http://www.adrawa.com.au/Speedometer%20Accuracy.pdf

And also, the actual rules
"18.5.1.1.2. indicate the actual vehicle speed, for all speeds above 40 km/h, to an accuracy of ± 10 percent"
Vehicle Standard (Australian Design Rule 18/00 - Instrumentation) 2006

That's some good reading there

especially about the whole infringement stuff.

[bd581]

Not sure If bad thing, good thing or I look like a tool bag...

I'm guessing all lol

Yeah all of the above
He was an interesting chap (especially in person) very, very switched on, but all his answers were in essay form and required a thesaurus to fully understand

[AzzA SP20]

Yeah all of the above
He was an interesting chap (especially in person) very, very switched on, but all his answers were in essay form and Required a thesaurus to fully understand

well I am more trade background... so I try my best for an answer along with an explanation..
(just an answer alone is worthless).

But I do also try keep it short...ishhh lol.

[slixx]

Unless the dial of the speedo is out! Haha

I notice that the increments increase as the speed get higher

Cobb said that then speedo can be calibrated, but the reading from the ECU cannot be. Damn.

[RedDjinn]

errr... hate to break it to you... It is a percentage thing!

our speedo's are controlledby variable reluctance magnetic sensor, which reads the speed of the passing teeth on a gear in the diff (works from electro-magnetic pulses). The sine-wave signal generated is converted to a certain amplitude of pulse depending on your speed. This is done via your computer, and this signal is sent to a stepper motor which moves the needle with digital accuracy.

when you have such multiplication processes, your accuracy will be based upon a percentage.

even old school eddy current needles have a percentage of error using your speedo/ ring gear system.
anything that uses some form or ratio's or multiplication of another dependent value will have a percentage of error.



your theory is severeley flawed as Gibba pointed out.

at 200km/h you are travelling at 3333.3' m/min

if you are on stock size rim (225/40/18) your tyre has a circumference of 2.0018m.

meaning per revolution of your tyre your car has travelled 2m (unless wheel spin )
anyway... your wheel is now doing 1666.6' rpm.

by the time you factor in your rotational mass variances at such high speeds aswell as the mass ammount of extra heat generated... your tyre has now expanded (and by a fair bit).

once your tyre expand... Its now travelling slower than it would be if it was cold (due to diameter increase).
which your speedo which was reading 106km/h at an actual velocity of 11km/h is now reading slower than it was when cold... mking your speedo reading say... 101km/h at an actual velocity of 100km/h.

BOOM! SIENCE BITCH! rofl

only if the numbers on the dash are in the correct place.. Have a look at the numbers see if there all spaced out correctly/ all the same (look 0-10kph, off memory a gen1 is different 0-10kph you have a gen1?).. Maths/Your correct in theory if everything is worked out correctly and is measured equally

- - - Updated - - -

errr... hate to break it to you... It is a percentage thing!

our speedo's are controlledby variable reluctance magnetic sensor, which reads the speed of the passing teeth on a gear in the diff (works from electro-magnetic pulses). The sine-wave signal generated is converted to a certain amplitude of pulse depending on your speed. This is done via your computer, and this signal is sent to a stepper motor which moves the needle with digital accuracy.

when you have such multiplication processes, your accuracy will be based upon a percentage.

even old school eddy current needles have a percentage of error using your speedo/ ring gear system.
anything that uses some form or ratio's or multiplication of another dependent value will have a percentage of error.



your theory is severeley flawed as Gibba pointed out.

at 200km/h you are travelling at 3333.3' m/min

if you are on stock size rim (225/40/18) your tyre has a circumference of 2.0018m.

meaning per revolution of your tyre your car has travelled 2m (unless wheel spin )
anyway... your wheel is now doing 1666.6' rpm.

by the time you factor in your rotational mass variances at such high speeds aswell as the mass ammount of extra heat generated... your tyre has now expanded (and by a fair bit).

once your tyre expand... Its now travelling slower than it would be if it was cold (due to diameter increase).
which your speedo which was reading 106km/h at an actual velocity of 11km/h is now reading slower than it was when cold... mking your speedo reading say... 101km/h at an actual velocity of 100km/h.

BOOM! SIENCE BITCH! rofl

only if the numbers on the dash are in the correct place.. Have a look at the numbers see if there all spaced out correctly/ all the same (look 0-10kph, off memory a gen1 is different 0-10kph you have a gen1?).. Maths/Your correct in theory if everything is worked out correctly and is measured equally

- - - Updated - - -

errr... hate to break it to you... It is a percentage thing!

our speedo's are controlledby variable reluctance magnetic sensor, which reads the speed of the passing teeth on a gear in the diff (works from electro-magnetic pulses). The sine-wave signal generated is converted to a certain amplitude of pulse depending on your speed. This is done via your computer, and this signal is sent to a stepper motor which moves the needle with digital accuracy.

when you have such multiplication processes, your accuracy will be based upon a percentage.

even old school eddy current needles have a percentage of error using your speedo/ ring gear system.
anything that uses some form or ratio's or multiplication of another dependent value will have a percentage of error.



your theory is severeley flawed as Gibba pointed out.

at 200km/h you are travelling at 3333.3' m/min

if you are on stock size rim (225/40/18) your tyre has a circumference of 2.0018m.

meaning per revolution of your tyre your car has travelled 2m (unless wheel spin )
anyway... your wheel is now doing 1666.6' rpm.

by the time you factor in your rotational mass variances at such high speeds aswell as the mass ammount of extra heat generated... your tyre has now expanded (and by a fair bit).

once your tyre expand... Its now travelling slower than it would be if it was cold (due to diameter increase).
which your speedo which was reading 106km/h at an actual velocity of 11km/h is now reading slower than it was when cold... mking your speedo reading say... 101km/h at an actual velocity of 100km/h.

BOOM! SIENCE BITCH! rofl

only if the numbers on the dash are in the correct place.. Have a look at the numbers see if there all spaced out correctly/ all the same (look 0-10kph, off memory a gen1 is different 0-10kph you have a gen1?).. Maths/Your correct in theory if everything is worked out correctly and is measured equally

[GibbA]

@AzzA SP20, my turn to say I hate to break it to you, but it's not science, it's maths :-P


This is my speedo, and on this all your maths holds true because it's all evenly spaced (neglecting 0-10km/h)
HOWEVER if as @RedDjinn said, the scale on which the speed is read from isn't equally spaced in the gen2 his point certainly could be very valid!

If the spacing between the values decreases proportionally to the error in calculation of the vehicle speed, than it would compensate for the growing error and in turn mean speed on the speedo is a close approximation to your actual speed.

This would then mean a device which corrects the error (by multiplication of a PERCENTAGE to the signal the motor on the speedo receives) would not work, because the scale is not constant.

It would need to use a function of a higher degree to multiply the signal to show the true speed on the speedo. (Ie the multiplication factor changes with calculated speed) This would be easy enough to figure out, just don't know how to program it into a device to do that. :-)

Maths bitch :-P

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[AzzA SP20]

1 maths is a science...

2 they are evenly spaced