01-26-2017, 12:42 PM | #23 |
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My question is: does it just show a couple extra MPH on the speedo but the computer has accurate MPH? Dunno...
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01-26-2017, 01:21 PM | #24 | |
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Next time out, I'll try to remember to do a timed run between mile markers. One mile traveled at 60 MPH indicated should take exactly 60 seconds. Probably set the cruise control to 60, first. And for what it's worth, every car I've owned during the past 20+ years has had an optimistic speedometer, including my current MB GLK-350.
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01-26-2017, 01:36 PM | #25 | |
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1). To account for the loss in rolling diameter as a tire's tread wears (lower rolling diameter = faster RPM = higher speedometer reading) 2). To prevent lawsuits and such against car manufacturers, municipalities, states, etc. for false speed readings that lead to unlawful behavior, i.e. speeding tickets Most U.S. law enforcement agencies are instructed to NOT pull over vehicles that are traveling less than 10 percent over the posted speed limit. Why? A combination of three reasons: 1). User error/improper calibration of speed-reading apparati (timers, laser/radar, etc.) 2). The aforementioned speedometer calibration tendencies 3). The relatively low income that comes from most low-level speeding tickets (i.e., below 10 MPH, not in a construction zone, etc.), and the likelihood that income will be mitigated by defendant challenge in court. In other words, it's simply not cost effective. Most modern cars' gauges are computer controlled, so what the OBDII says (and what the digital readout would say if it's coded) is almost certainly going to mirror what the analog gauge says. That's definitely the case with the speedometer on my P3Cars gauge, which is an OBDII device. And now y'all know.
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01-26-2017, 01:42 PM | #26 |
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Not sure if it's a "mandate" but in PA at least you really have to be cooking to get a real ticket. I got pulled over doing 95 in a 70 and they wrote me for the highest possible speed for the lowest possible infraction - believe it was 79. Logic being you get no points, pay a fine, and it's not worth your time to fight it. I am sure someone did some major statistical analysis along the lines of $100 no points collect 95% of the time, $300 + points collect 25% of the time, so EV of smaller tickets higher.
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01-26-2017, 01:48 PM | #27 |
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Precisely. So basically you can travel 77 MPH in a 70 MPH zone and be golden; a cop won't touch you unless you're doing something in addition to the speed (i.e., weaving, taillight blown out, what have you).
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01-26-2017, 01:53 PM | #28 |
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They did keep me sitting at the side of the road for half an hour and yelled at me for laughing the whole time. The cop apparently didn't find the humor in the absurdity of a 36 year old getting pulled over for "joy riding" in a station wagon with temp tags that belonged to my father. Also was not amused when I told him I had no choice but to test the car properly, that I just had Dinan Stage 1 installed and needed to make sure it was working properly before I returned the car to dad. You know, for safety purposes.
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01-26-2017, 01:56 PM | #29 | |
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01-26-2017, 10:23 PM | #30 | |
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This actually makes sense since the OBD reads the value directly from the wheel speed sensor while the speed correction happens at the instrument cluster (and can be coded off by coding KOMBI). |
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01-26-2017, 10:57 PM | #31 |
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I'd heard that BMW set their speedos low, didn't realize it was across the industry, so neat trivia. Gabrola's info is in line with my expectations - I would assume that the gauge is biased, but that they have reliable accurate info for the computer to use to calculate MPG etc. (or it would also be 10% off).
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01-27-2017, 01:47 AM | #32 |
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App-based 0-60 times are widely inaccurate-- the GPS hardware is just not meant for something like this. Someone on this forum also claimed their m235i with a few mods was getting 3.6 seconds when measured with an app. Keep dreaming. If you want to know your time, go to a track or get a real accelerometer. Here's one that has been consistently accurate (i.e. before mods it consistently registered 4.6 seconds, and after Dinan mods is consistently showing 4.3 - 4.4):
K.A.T. Matrix 3-Axis Car Performance Accelerometer - ~$110 on Amazon, though out of stock at the moment |
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01-27-2017, 08:46 AM | #33 | |
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01-27-2017, 09:28 AM | #36 | |
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But why.... http://www.2addicts.com/forums/showthread.php?t=1317455 |
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01-27-2017, 09:50 AM | #37 | |
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Would the digital speedo that can be coded for the center cluster display match the analog speedo or the OBDII data?
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01-27-2017, 11:45 AM | #38 | |
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01-27-2017, 12:53 PM | #39 | |
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01-27-2017, 01:54 PM | #40 | |
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and the vehicle is consistent (remember its stock), my best run and 60 foot - 1/8 mile were achieved about 5 runs in (getting used to launch control) Did you click on the link and look at my time slip? |
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01-27-2017, 04:18 PM | #41 | |
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01-30-2017, 11:28 AM | #42 | |
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01-30-2017, 11:37 AM | #43 | |
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01-30-2017, 11:40 AM | #44 |
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I concur that BMW speedometers are off by about 3-5% which is 2-3 mph at most normal road and highway speeds. This is true for each of the 5 BMWs that I've had since 2007.
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