[Dutch Nitro]

I have noticed that the KM/ph indicator is not correct. According to my GPS (TomTom) my Nitro runs 128 km/ph, but my Nitro indicates a speed of 120 km/ph. My Nitro always indicates less than the real speed. I think that is unusual. I have to take care by passing speed controls!
Do you have the same problem? Does this only happens on km scales up to 240 km?

 

[Waldorf]

I have noticed that the KM/ph indicator is not correct. According to my GPS (TomTom) my Nitro runs 128 km/ph, but my Nitro indicates a speed of 120 km/ph. My Nitro always indicates less than the real speed. I think that is unusual. I have to take care by passing speed controls!
Do you have the same problem? Does this only happens on km scales up to 240 km?

hey Dutch,
How do you know the TomTom is correct? what else have you check the speed against?

 

[Dutch Nitro]

I'll try other methods to check the speed soon. I don't know the Tomtom is correct. That's why I ask for your experiences. But I believe a GPS is reliable, or am I wrong?

 

[Waldorf]

I'll try other methods to check the speed soon. I don't know the Tomtom is correct. That's why I ask for your experiences. But I believe a GPS is reliable, or am I wrong?

I'm guessing you may be correct. I'm just asking the questions too! How reliable are vehicle speedometers? Are they less accurate at higher speeds than lower speeds?

 

[Pshrynk]

The speedo is out by 3 or 4km/h and the Tom Tom is out by 3 or 4 and that there is the crux of the problem.

 

[Waldorf]

The speedo is out by 3 or 4km/h and the Tom Tom is out by 3 or 4 and that there is the crux of the problem.

there you go, I guess we will all have to make a trip to Bonnevile Salt Flats for Speed Weeka dn get a true speed reading!!! :chuckle:

Now who has the "Fastest Indian In The World"?????????????:Racing:

 

[Dutch Nitro]

Do you mean that the speedometer indicates about 3 or 4 km less and the Tomtom is about 3-4 km optimistic?
I thought most speedometers are optimistic. In my case I have to pay attention for speeding by accident, because I drive faster than the speedometer indicates. Good to know!

 

[MFPITA]

I'll try other methods to check the speed soon. I don't know the Tomtom is correct. That's why I ask for your experiences. But I believe a GPS is reliable, or am I wrong?

well dutch, I have been in the army for 8yrs now and I can tell u that GPS well are great usually tend to be slightly wrong when judging speed, mainly do to the fact its tracking a signal, and not tied in to ur vechiles system.

 

[Waldorf]

well dutch, I have been in the army for 8yrs now and I can tell u that GPS well are great usually tend to be slightly wrong when judging speed, mainly do to the fact its tracking a signal, and not tied in to ur vechiles system.

that's what I was thinking when Dutch first brought up the speed from the TomTom. There's no way it can be MORE accurate that the vehicle sppedometer. The speedo could be out too.

Myabe you can get somebody else to drive at the same speed as you, in a different kind of vehicle and then see what they say?

 

[Dutch Nitro]

I have a better idea: come visit Europe. In Germany on most "Autobahn" there are no speedlimits. I'll buy you a drink. How about that?

 

[MFPITA]

I have a better idea: come visit Europe. In Germany on most "Autobahn" there are no speedlimits. I'll buy you a drink. How about that?

I spent 3 yrs station in germany, lol it was great times, but Im a red white and blue guy at heart lol,

 

[Dutch Nitro]

You mean you are Dutch at heart?

 

[KenCary]

I have noticed that the KM/ph indicator is not correct. According to my GPS (TomTom) my Nitro runs 128 km/ph, but my Nitro indicates a speed of 120 km/ph. My Nitro always indicates less than the real speed. I think that is unusual. I have to take care by passing speed controls!
Do you have the same problem? Does this only happens on km scales up to 240 km?

8 KM / 128 is only about 6% error. That is pretty close. My guess is that the GPS is not 100% accruate either so this could simply be "tolerance stack up"

If you really want to check this out, look for a Measured KM mark. I don't know if you have them in your contry, but here in the US we have "measured mile" signs on parts of out interstate road systems for the purpose of checking speed.

One more thing that you can do is to look up the exact diameter of your tires, mulitiply it by PI (3.14) to get the CM/ rotation than divide this by your final drive ratio and top gear ratio and appropriate decimal conversion. This will tell you RPM/KM/Hr which will be a further check of the speedo acuracy.

Also keep in mind that if you changed to tires that are larger diam than the stock tires, your speedo will read lower than actual. The same calculation can be used to make this correction.

 

[Waldorf]

8 KM / 128 is only about 6% error. That is pretty close. My guess is that the GPS is not 100% accruate either so this could simply be "tolerance stack up"

If you really want to check this out, look for a Measured KM mark. I don't know if you have them in your contry, but here in the US we have "measured mile" signs on parts of out interstate road systems for the purpose of checking speed.

One more thing that you can do is to look up the exact diameter of your tires, mulitiply it by PI (3.14) to get the CM/ rotation than divide this by your final drive ratio and top gear ratio and appropriate decimal conversion. This will tell you RPM/KM/Hr which will be a further check of the speedo acuracy.

Also keep in mind that if you changed to tires that are larger diam than the stock tires, your speedo will read lower than actual. The same calculation can be used to make this correction.

what do I look like a blue faced rocket scientist??????

 

[adot45]

Nitro speedometer dead on with stock 16's

I went for a drive on the freeway today and noted 2 different "tests" for the Nitro.
test 1 Nitro's reported speed 72mph
speed reported by Magellan 72mph
one mile time 50 seconds = 72mph

test 2 Nitro's reported speed 65mph
speed reported by Magellan 65mph
one mile time 55 seconds = 65.45

stock 16" wheels and tires. I'm more than happy with the accuracy of the Nitro's speedo.

 

[Waldorf]

I went for a drive on the freeway today and noted 2 different "tests" for the Nitro.
test 1 Nitro's reported speed 72mph
speed reported by Magellan 72mph
one mile time 50 seconds = 72mph

test 2 Nitro's reported speed 65mph
speed reported by Magellan 65mph
one mile time 55 seconds = 65.45

stock 16" wheels and tires. I'm more than happy with the accuracy of the Nitro's speedo.

thanks for the testing adot! :rep:

 

[adot45]

Thank you for the rep points Waldorf :wavey: , I saw the Dutch Nitro post just before we left and thought it would be an interesting thing to do. I wish I would have remembered my camera, the fall colors were astounding.

 

[Waldorf]

Thank you for the rep points Waldorf :wavey: , I saw the Dutch Nitro post just before we left and thought it would be an interesting thing to do. I wish I would have remembered my camera, the fall colors were astounding.

np adot! effort gets recognized around here! I bet the colours are great now. Get some pics tomorrow if you can. It's really windy here in Ontario today and the leaves are finally falling!

 

[Dutch Nitro]

Thanks guys, I'll try to find a clear road (at night?) to do some test you advised.

 

[Paladin021]

I did 5 different passes at 5 different speeds (ranging from 35 mph to 85 mph) and mine is right on the money each time - tested with a Vascar speed timer and a 14 year veteran cop over a 0.0380 mile distance (200 feet)

The Vascar was calibrated last week.

Hope that helps.