Thought I had a speedo error once in the Magnum and then I checked with GPS. The highway signs were off, I guess the truck that set those out had a speedo off.
That was how they used to do it 20 to 30 years ago, I think they use GPS now days.
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| Trip Mileage Report/Odometer Error http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=8261 |
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| Author: | Cowcatcher [ Sat May 06, 2006 10:12 pm ] |
| Post subject: | Trip Mileage Report/Odometer Error |
I took a road trip today of about 300 miles on wide, well maintained, two lane state roads traveling 55>65 95% of the time. The terrain was rolling hills most of the way with the caveat that our average elevation is around 2200 ft but on four occassions the roads drop to perhaps 800 feet to cross rivers, then back up again. I figured this would be a good CRD mileage test but over night it got windy and I was bucking a head wind of 20>30MPH and for a while it was probably over 40MPH. On the return the winds had died to 10>15 MPH. I also check my odometer several times on different roads against the state mile markers which I have generally found to be reasonably reliable. What I noticed on a CRD Limited with stock tires was that I was consistently running between 6.5% and 7% slow. With that adjustment I ended up with a 29.86 MPG average as measured by the EVIC with about 8800 miles driven to date. I wonder about the odometer error. At first I was thinking that since I have a Limited perhaps the odometer was programmed for the 17" wheels but unless I am thinking wrong that would make the odometer read even slower as the tire would be of greater radius and would make fewer rotations per mile. It would be interesting to see what other CRD owners are seeing regarding odometer error with stock tires and compare the year and the model, Sport v Limited. |
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| Author: | oldnavy [ Sun May 07, 2006 10:16 am ] |
| Post subject: | |
If your truck was programmed for the larger tires and then they put on the smaller tire it would speed up the speedometer and show more miles traveled then actual and it would increase you MPG reading. What has most likely happened is you truck has a need of reflash to cure inproper programing. The reason I say that is I seem to remember seeing a TSB mentioning this problem, I could be wrong and it could be on a different vehicle. |
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| Author: | Jacobi [ Sun May 07, 2006 7:56 pm ] |
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I constantly compare my speedo to my gps, only when gps is tracking 4 plus sats (for 3d fix) and I notice when I'm doing 65, the gps says 65.8-66.1. Interesting. -Barry |
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| Author: | Zonie [ Sun May 07, 2006 11:36 pm ] |
| Post subject: | New 2006 with same problem? |
I picked up my 06 Limited Saturday and put 500 mi. on it in the last 2 days. On the 1st tank, the EVIC reported 28.5 mpg. When I used a calculator, it was actually 24.7 mpg. It has stock tires 225x75x16. Looks like I need to get the GPS out..... This one came off the assembly line April 18. It needs to be flashed already? |
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| Author: | Taz [ Tue May 09, 2006 7:22 am ] |
| Post subject: | |
After reading this I started checking my spedo vs. those speed indicating signs on the sides of the roads. There are 2 of them on my drive from work. According to the signs my KJ is reading about 5% high on the spedo. |
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| Author: | oldnavy [ Tue May 09, 2006 8:11 am ] |
| Post subject: | |
Thought I had a speedo error once in the Magnum and then I checked with GPS. The highway signs were off, I guess the truck that set those out had a speedo off. That was how they used to do it 20 to 30 years ago, I think they use GPS now days.
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| Author: | Cowcatcher [ Tue May 09, 2006 9:46 am ] |
| Post subject: | |
Somewhere I have a first generation GPS unit. I should get it out and check with it but then it might not be anymore accurate then the state PU. I did my test drive on 4 or 5 different stretches of state highway and accross nearly as many highway districts and the results were very consistent. What was inconsistent was my punching the trip odometer since the electronic one does not change when you push it like the mechanical ones do. Still, when meassured over 10 > 20 miles that error is minor as it would diminish with miles traveled. |
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