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I tried this today and I want your opinion people, if you see the picture, the gps is giving a reading of 212KM, while the car speed meter is giving 220km, so which one is the correct one and why?
 

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a GPS's speedometer is always going to be slightly off at higher speeds.. it's using satelite to guestimate where you are, whereas the speedo in your car is pretty precise..
 

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Yup I would definitely say the car is right. Gotta give the GPS a second to bounce off the satellite ;)

Unless you have the wrong tire size..

In any case..

HOLY CRAP ARE YOU NUTS?!?? That's a good way to lose your Cruze!!!!!! Or a life..
 

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Now, I have the other opinion. I think the GPS is more reliable because it has no influence from your tires, such as wear, inflation, brand. These things do affect the OD of the tire.
This is assuming good signal strength and steady speed. If you are accelertating briskly maybe the speedo will be more accurate due to the processing cycle. not sure, thats just specualtion on my part. I dont know how fast my GPS cycles that info. I know Im not exactly running an i7 in there!
 

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Discussion Starter · #6 ·
its good to try once in a life time, i wish i can add the video of that , but its a big file
 

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Now, I have the other opinion. I think the GPS is more reliable because it has no influence from your tires, such as wear, inflation, brand. These things do affect the OD of the tire.
This is assuming good signal strength and steady speed. If you are accelertating briskly maybe the speedo will be more accurate due to the processing cycle. not sure, thats just specualtion on my part. I dont know how fast my GPS cycles that info. I know Im not exactly running an i7 in there!
100% on board with you here. GPS is hands down more accurate than electro-mechanical for the same reasons you listed. your speed is greatly effected by tire overall diameter (different between brands by as much as a 1/4 inch), wear over time, inflation pressures, wheel slip, etc. While a GPS device only calculates distance over time and isn't instantaneous, it isn't effected by external sources. it's not a guess of where you are, it's an exact position down to a 4ft radius of the device, or better. depending on the refresh rate of the GPS (i've seen devices that refresh their position 10 times per second, and they are inexpensive), i'd say they are a heck of a lot more accurate than a working tire.

OP: try 160mph. with 2 less wheels.
 

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It ain't smart, but we have all done it. Boys are dumb.
I guess that's why I haven't done it.. Cause I'm a girl and like my car/life ;)

Plus I'm a chicken-$h!t. I used to cruise on the highway at 140. Then that whole '150 km/h roadside suspension and vehicle seizure' thing came about and I've been verrrry careful since.
 

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OP is definitely crazy, but at least he got to push his Cruze to it's limits.

I'm not going to lie, but I also have done this in a few cars (dumb indeed) and i notice some cars feel stable no matter how far you push it, yet some feel really unstable at high speeds of 120 MPH or more. How did the Cruze feel going 220 KM/H?
 

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Discussion Starter · #11 ·
remember guys iam the one who posted the nitrogen tires thread, as u can c , with a normal inflated tires u will never reach that speed , the tires are still new as the car is still new , but still i beleive the GPS is more accurate than what the car is showing , my GPS devise is Garmin and its an expensive toy , but why it always show 8 km difference , this is what i dont know
 

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Discussion Starter · #12 ·
OP is definitely crazy, but at least he got to push his Cruze to it's limits.

I'm not going to lie, but I also have done this in a few cars (dumb indeed) and i notice some cars feel stable no matter how far you push it, yet some feel really unstable at high speeds of 120 MPH or more. How did the Cruze feel going 220 KM/H?

it was gr8 , somehow quiet and stable , tires are inflated with 35psi nitrogen , may be this is why, but its not fun to try and i dont advise anyone to do it more than once thats if u like to hear your heart beats
since any sudden movement you are history
 

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it was gr8 , somehow quiet and stable , tires are inflated with 35psi nitrogen , may be this is why, but its not fun to try and i dont advise anyone to do it more than once thats if u like to hear your heart beats
since any sudden movement you are history
Im not sure how nitrogen would make a difference, since when did you start using nitrogen? Have you noticed any difference between nitrogen & regular air at regular driving speeds?

For a while now i wanted to fill my tires with nitrogen but never got around too it since i have easy access to a air pump. hearing from someone experienced will help me!


I believe if your heart is beating while going that fast.....it's fun :)
at least back in the days when i went that fast it was fun


just like the OP's suggestion, DO NOT go that fast. Not worth the cop trouble, and risking your safety.
 

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Car speedos just about always read on the high side due to liability issues. A GPS is way more accurate, trust me. I am a Telephone Network Engineer with experience in network synchronization. The digital public switched telephone network is "in-sync" via timing from the same satellites. These satelittes have expensive Cesium clocks in them... the same type of clocks that keep the current time at the US Naval Obsevatory. Well actually there are a bunch of clocks there. Your location is calculated using triangulation from the millisecond delay between the different satelites and your location.
 

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Discussion Starter · #15 ·
Im not sure how nitrogen would make a difference, since when did you start using nitrogen? Have you noticed any difference between nitrogen & regular air at regular driving speeds?

For a while now i wanted to fill my tires with nitrogen but never got around too it since i have easy access to a air pump. hearing from someone experienced will help me!


I believe if your heart is beating while going that fast.....it's fun :)
at least back in the days when i went that fast it was fun


just like the OP's suggestion, DO NOT go that fast. Not worth the cop trouble, and risking your safety.

go back to 7th of february and check my post about maximun speed
 

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GPS is slower than your ECU reading the frequency of your WSS or the speed sensor in the tranny (I'm not sure which one GM uses for the Cruze). I've worked with a lot of GPS equipment in aviation and it's nowhere near as accurate as what your devices on your vehicle are telling you. The information has to be relayed between 4 points before a position is determined. And there is always a delay. Remember the US GPS system is shared by many users as well. Also all civilian receivers are severely dumbed down so they can not be used above certain speeds and certain altitudes.


PS: OP please slow down.
 

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GPS is slower than your ECU reading the frequency of your WSS or the speed sensor in the tranny (I'm not sure which one GM uses for the Cruze). I've worked with a lot of GPS equipment in aviation and it's nowhere near as accurate as what your devices on your vehicle are telling you. The information has to be relayed between 4 points before a position is determined. And there is always a delay. Remember the US GPS system is shared by many users as well. Also all civilian receivers are severely dumbed down so they can not be used above certain speeds and certain altitudes.


PS: OP please slow down.
Wrong! There is a delay using GPS, so during acceleration, your car speedo is more accurate, but during a constant speed, the GPS is much more accurate. I would bet any amount of money on it.

Trust me... I have worked with Symmetricom, the major manufacturer of cesium and rubidium atomic clocks.

I hate when people talk about things they really know nothing about.
 

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Car speedos just about always read on the high side due to liability issues. A GPS is way more accurate, trust me. I am a Telephone Network Engineer with experience in network synchronization. The digital public switched telephone network is "in-sync" via timing from the same satellites. These satelittes have expensive Cesium clocks in them... the same type of clocks that keep the current time at the US Naval Obsevatory. Well actually there are a bunch of clocks there. Your location is calculated using triangulation from the millisecond delay between the different satelites and your location.
Tell THAT to the cop that pulled me over and said radar clocked me at 128 whilst my speedometer was at 119 with cruise-control on and my GPS read 117!

Regardless, you used a lot of big words so I believe you :p
 

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I hate when people talk about things they really know nothing about.
7 years experience as a helicopter crew chief/technician. I have first hand experience with government grade GPS equipment, avionics as well as airspeed indicators.

I know absolutely nothing about what I'm talking about you're right.

Tell me what's faster. Civillian grade GPS's relay of information between 3-4 satellites and the ground receiver(through disruptive conditions[ionsphere]). Or a direct DC frequency read from a MPG/Hall Effect sensor through a few feet of wire to an ECU, computed, then sent do a dial indicator.

edit: I do agree with you that between car and GPS at a high constant rate of speed the GPS will be more accurate. In low speeds and changing conditions the vehicle sensors are more accurate. 130mph is relatively slow. I also agree that cars speedometers read high at higher speeds. I'm just talking about the relative information being sent between indicator and indicating source
 

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Im not sure how nitrogen would make a difference, since when did you start using nitrogen? Have you noticed any difference between nitrogen & regular air at regular driving speeds?

For a while now i wanted to fill my tires with nitrogen but never got around too it since i have easy access to a air pump. hearing from someone experienced will help me!


I believe if your heart is beating while going that fast.....it's fun :)
at least back in the days when i went that fast it was fun


just like the OP's suggestion, DO NOT go that fast. Not worth the cop trouble, and risking your safety.
Nitrogen is pressure stable over a much wider temperature range. The nitrogen molecules are also larger than normal air, so tires leak less over time.

Costco Tire Shops now use nitrogen, and use green valve caps so you can tell.
 
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