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29th October 2021, 18:16 | #1 |
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Rover 75 Tourer CDT Join Date: Apr 2014
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digital speedometer
how accurate is the digital speedo compared to the speedo in our cars just curious thanks
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29th October 2021, 18:40 | #2 |
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Rover 75 Conn SE V6 / MG ZT 260 SE V8 / MG ZT 180 SE V6 Join Date: Feb 2007
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On all three of my ZTs it is spot on when compared to my road angel speed camera detector which uses GPS signals for speed, but on both my 75s it reads about 3mph higher than actual when cruising at 70. The speedo needle indicates 77mph when actually driving at true 70mph on the 75 too.
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29th October 2021, 18:43 | #3 |
I really should get out more.......
Rover 75 Saloon Join Date: Jul 2011
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Not as accurate as the GPS but better than the analogue, having a hard time putting a number to it but say the analogue is 10% over GPS, then perhaps 5%. I'll try and remember to check next time I'm out and give you some real numbers unless someone beats me to it.
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29th October 2021, 18:46 | #4 | |
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29th October 2021, 18:51 | #5 |
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If I compare my speedo to speed over ground on satnav its 8 - 10% fast depending on speed travelling. The digital speed readout reflects what the sat nav reads so I have made the assumption that that is more accurate. Of course I could be completely wrong, be good to understand where the digital speed data is generated.
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29th October 2021, 19:41 | #6 | |
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The most accurate speed measurement would be physically measuring the distance travelled, through a doppler radar system or something. In answer to the digital speedo though, mine also tends to show a couple of mph between that shown on the speedometer. I assume that it's the same signal that goes to both, and obviously there is a slight error in the digital to analogue conversion. |
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29th October 2021, 19:45 | #7 |
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Rover 75 Tourer 2.5KV6 Connoisseur SE Join Date: Mar 2013
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Analogue speedometers are always faster reading because they are required to always keep you within speed limit. Around 10% faster at true 30mph.
Digital relies on the same pulse source as the built in analogue, namely the reluctor ring in the wheel hub. I believe PhilT4 was the inventor. |
29th October 2021, 19:54 | #8 | |
I really should get out more.......
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29th October 2021, 20:56 | #9 |
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my dash cam seems to be the most accurate followed but the digital speedo then the analogue speedo. I use my dash cam as my speedo so travel faster then what I would do using the cars two speedos and I have never been flashed or done by any speed camera as a result of using the dash cam.
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29th October 2021, 21:14 | #10 |
Posted a thing or two
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will someone correct me if i am wrong. but is the correct wheel diameter the main player in this .. i did read somewhere that wheel sizes are set via the options on t4. 15/16/17 ... etc. if they are then that would account for the differences on some vehicles. ...
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