Terrano Speedo

Lazy-Ferret · 17-02-2017, 01:54

Not sure if this has been mentioned before, but as we all know, the standard Terrano speedo seems to show you are travelling at a higher speed than you really are.

We have a Dashcam in the car, with built in GPS, which displays your live speed, and as said many times, the car speedo always shows 10 to 12% faster than the GPS speed. In the case of Suz's T2, when we are travelling at 70mph on the GPS, the Speedo shows 82MPH.

I have recently got a Bluetooth OBD2 module, so today we were going over to Suz's dad, a distance of 65 moles, and involved 40 odd miles on the M25, I had a chance to play with the OBD reader I have downloaded to my tablet.

It was interesting to see things happening real time, to get a feel for how things are working when the car is running perfectly, but it has raised a few questions as well.

The first is the fact that the speed is output from the ECU in KMH, and when you convert the reading to MPH, or change the GPS to display in KMH, the two readings match exactly... So it is the actual Speedo that is displaying the wrong speed, not the car incorrectly reading the speed.

Weirdly, the RPM reading also reads low as the revs increase, so when the REV counter was showing 2500RPM, the ECU was only showing 2250RPM.

Anyone else noticed this?

Banshee · 17-02-2017, 09:49

Quote:

Originally Posted by Lazy-Ferret

Not sure if this has been mentioned before, but as we all know, the standard Terrano speedo seems to show you are travelling at a higher speed than you really are.

We have a Dashcam in the car, with built in GPS, which displays your live speed, and as said many times, the car speedo always shows 10 to 12% faster than the GPS speed. In the case of Suz's T2, when we are travelling at 70mph on the GPS, the Speedo shows 82MPH.

I have recently got a Bluetooth OBD2 module, so today we were going over to Suz's dad, a distance of 65 moles, and involved 40 odd miles on the M25, I had a chance to play with the OBD reader I have downloaded to my tablet.

It was interesting to see things happening real time, to get a feel for how things are working when the car is running perfectly, but it has raised a few questions as well.

The first is the fact that the speed is output from the ECU in KMH, and when you convert the reading to MPH, or change the GPS to display in KMH, the two readings match exactly... So it is the actual Speedo that is displaying the wrong speed, not the car incorrectly reading the speed.

Weirdly, the RPM reading also reads low as the revs increase, so when the REV counter was showing 2500RPM, the ECU was only showing 2250RPM.

Anyone else noticed this?

I noticed this when I was on 17" rims but since having the 33's on, Sat Nav, Dashcam and Speedo all read the same

macabethiel · 17-02-2017, 10:09

Mercedes Benz like most manufacturers make their vehicle speedometers so they over estimate the speed. This is not poor design it's a conscious effort linked to some issues where a driver could blame the vehicle makers for speeding.

Mercedes also have Telematics date storage built into the ECU that can be accessed by the Manufacture. When a Mercedes is involved in a fatal accident and the vehicle is extensively damaged the data is used to help understand the cause and improve design and in some cases used as evidence by courts and insurers..

When Princess Diana was killed in the Mercedes S class it had a comprehensive set of data that was used during the enquiry.

GPS systems do not have these built inaccuracy in issues as they work via the satellite signals.

Monaro Pete · 17-02-2017, 18:09

What I would like to know is "how far in distance is a mole"

jims-terrano · 17-02-2017, 18:21

I like this over reading that pretty much all my cars have done. Gives me the confidence to know that I'm less likely to get a ticket. Long may it be until we get in built dynamic speed limiters in our vehicles.

Monaro Pete · 17-02-2017, 19:14

Quote:

Originally Posted by jims-terrano

Long may it be until we get in built dynamic speed limiters in our vehicles.

It'll be a long time and if the truth be known........ The government want you to speed, speeding uses more fuel = more cash & there's the chance of you getting caught which is more money for them.
Speeding doesn't cause many accidents, driver unawareness does.

It's the same with smoking, they don't want you to give up, because that again is less in taxation.

They just have to be seen to be discouraging you.

emjaybee · 17-02-2017, 20:17

Quote:

Originally Posted by Monaro Pete

What I would like to know is "how far in distance is a mole"

About twice the length of a stat, but not as long as a ferret.

Thought everyone knew that.

elty001 · 17-02-2017, 20:31

Quote:

Originally Posted by emjaybee

About twice the length of a stat, but not as long as a ferret.

Thought everyone knew that.

Ah but Is that a metric or imperial mole??

Monaro Pete · 17-02-2017, 21:17

emjaybee · 17-02-2017, 22:54

Quote:

Originally Posted by elty001

Ah but Is that a metric or imperial mole??

Now you're just being ridiculous, everyone knows moles are metric, that's why they have five digits per hand.

Monaro Pete · 18-02-2017, 12:18

Quote:

Originally Posted by emjaybee

Now you're just being ridiculous, everyone knows moles are metric, that's why they have five digits per hand.

So if moles are metric in measurement, because they have five digits per hand & there's 65 of them. Would you times the 65 by four? Or do the back legs have feet & not hands!!!

Lazy-Ferret · 18-02-2017, 16:15

You lot are insane...

I was reading this thinking, What??? had to re-read my post twice to see the typo..

But you are all wrong, as Moles have an extra thumb on the front feet, so they use the Duodecimal system on the front and Decimal on the back...

This reminds me of the great Jasper carrot sketch...

https://www.youtube.com/watch?v=fePU5CIHpas

emjaybee · 18-02-2017, 17:12

Quote:

Originally Posted by Monaro Pete

So if moles are metric in measurement, because they have five digits per hand & there's 65 of them. Would you times the 65 by four? Or do the back legs have feet & not hands!!!

Pay attention, I don't want to have to keep repeating this every time the subject comes up:

A mole is about twice the length of a stoat and are decimal (thumb not counted as all thumbs are fingers, but not all fingers are thumbs), the back limbs don't count as they are feet and that would be imperial.

FERRETS are imperial as they are 1 & 1/3 yards long because they have four feet.

I'm not sure what keeps tripping you lot up.

I mean, I can explain it to you, but I can't understand it for you.

jims-terrano · 18-02-2017, 17:33

So are you saying MPH is moles per hour?

If so is that how many moles per hour you run over, is that a constant one mole after the other or does it include the distance travelled to swerve between moles.

emjaybee · 18-02-2017, 17:34

Quote:

Originally Posted by jims-terrano

So are you saying MPH is moles per hour?

If so is that how many moles per hour you run over, is that a constant one mole after the other or does it include the distance travelled to swerve between moles.

No mate MPH is miles per hour.

Which planet are you on?

17-02-2017, 01:54	#1
Lazy-Ferret Senior Member Join Date: Jun 2012 Location: Sevenoaks, Kent Vehicle: Terrano 2.7TDi SE Touring Posts: 5,221	Terrano Speedo Not sure if this has been mentioned before, but as we all know, the standard Terrano speedo seems to show you are travelling at a higher speed than you really are. We have a Dashcam in the car, with built in GPS, which displays your live speed, and as said many times, the car speedo always shows 10 to 12% faster than the GPS speed. In the case of Suz's T2, when we are travelling at 70mph on the GPS, the Speedo shows 82MPH. I have recently got a Bluetooth OBD2 module, so today we were going over to Suz's dad, a distance of 65 moles, and involved 40 odd miles on the M25, I had a chance to play with the OBD reader I have downloaded to my tablet. It was interesting to see things happening real time, to get a feel for how things are working when the car is running perfectly, but it has raised a few questions as well. The first is the fact that the speed is output from the ECU in KMH, and when you convert the reading to MPH, or change the GPS to display in KMH, the two readings match exactly... So it is the actual Speedo that is displaying the wrong speed, not the car incorrectly reading the speed. Weirdly, the RPM reading also reads low as the revs increase, so when the REV counter was showing 2500RPM, the ECU was only showing 2250RPM. Anyone else noticed this?

17-02-2017, 10:09	#3
macabethiel Senior Member Join Date: Aug 2008 Location: Derby Vehicle: Freelander & Jeep GC 3.0 Posts: 4,416	Manufacturer Liability towards Speeders. Mercedes Benz like most manufacturers make their vehicle speedometers so they over estimate the speed. This is not poor design it's a conscious effort linked to some issues where a driver could blame the vehicle makers for speeding. Mercedes also have Telematics date storage built into the ECU that can be accessed by the Manufacture. When a Mercedes is involved in a fatal accident and the vehicle is extensively damaged the data is used to help understand the cause and improve design and in some cases used as evidence by courts and insurers.. When Princess Diana was killed in the Mercedes S class it had a comprehensive set of data that was used during the enquiry. GPS systems do not have these built inaccuracy in issues as they work via the satellite signals.

17-02-2017, 18:09	#4
Monaro Pete Senior Member Join Date: Apr 2016 Location: Nr J28 M1 Vehicle: 03 Terrano 2.7 TDi Posts: 995	What I would like to know is "how far in distance is a mole"

17-02-2017, 18:21	#5
jims-terrano Senior Member Join Date: Sep 2004 Location: UK Posts: 12,965	I like this over reading that pretty much all my cars have done. Gives me the confidence to know that I'm less likely to get a ticket. Long may it be until we get in built dynamic speed limiters in our vehicles.

17-02-2017, 21:17	#9
Monaro Pete Senior Member Join Date: Apr 2016 Location: Nr J28 M1 Vehicle: 03 Terrano 2.7 TDi Posts: 995

18-02-2017, 16:15	#12
Lazy-Ferret Senior Member Join Date: Jun 2012 Location: Sevenoaks, Kent Vehicle: Terrano 2.7TDi SE Touring Posts: 5,221	You lot are insane... I was reading this thinking, What??? had to re-read my post twice to see the typo.. But you are all wrong, as Moles have an extra thumb on the front feet, so they use the Duodecimal system on the front and Decimal on the back... This reminds me of the great Jasper carrot sketch... https://www.youtube.com/watch?v=fePU5CIHpas

18-02-2017, 17:33	#14
jims-terrano Senior Member Join Date: Sep 2004 Location: UK Posts: 12,965	So are you saying MPH is moles per hour? If so is that how many moles per hour you run over, is that a constant one mole after the other or does it include the distance travelled to swerve between moles.