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| Thread ID: 121597 | 2011-11-02 02:45:00 | New gearbox in car - speedo now reading fast? | wratterus (105) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 1241446 | 2011-11-03 02:17:00 | They are KNOWN to give a high reading. The amount of times I've gone past one telling me "60kmph" when my speedo says 45-50kmph - the gps different again. Calibrate it yourself - on a rolling road. Or a analogue version is hop on the mway and use the power poles - they are at set distances so you can work it out yourself. I don't believe they are known to give high readings. In Wellington if they work they seem ok. GPS speeds are only reliable for on the flat, in a straight line steady speeds. What set distances? I can find minimum distances from the edge of the motorway but the distance between poles is to suit local requirements. |
PaulD (232) | ||
| 1241447 | 2011-11-03 03:10:00 | They are KNOWN to give a high reading. The amount of times I've gone past one telling me "60kmph" when my speedo says 45-50kmph - the gps different again. I find that they actually read low. I have to be doing 56k to read 50 and it is the same for every one I pass so maybe your speedo is wrong? Cheers Billy 8-{) |
Billy T (70) | ||
| 1241448 | 2011-11-03 05:52:00 | I find that they actually read low. I have to be doing 56k to read 50 and it is the same for every one I pass so maybe your speedo is wrong? Cheers Billy 8-{) It's exactly the same for me. I find around 54k on my speedometer will read 50k on the electronic sign. I don't think they are known to read high. In the absence of evidence to the contrary I would trust the sign over my speedometer. |
george12 (7) | ||
| 1241449 | 2011-11-03 10:41:00 | I find that they actually read low. I have to be doing 56k to read 50 and it is the same for every one I pass so maybe your speedo is wrong? Cheers Billy 8-{) What you mean is when you're doing 50k your speedo is showing 56 which is in line with the idea that many countries require 0% under reading but allow over reading. With our car I've found that at 50 the speedo shows 54 but at 100 the speedo shows 104 instead of 108 as you might expect. On a trip of 120km the odometer consistently differs by less than .5km from a GPS tracker. |
PaulD (232) | ||
| 1241450 | 2011-11-03 19:46:00 | At 50k my car shows 46k and one of those trailer things. :) |
Trev (427) | ||
| 1241451 | 2011-11-04 01:19:00 | Road marker pegs on the main highway have a marked km peg every 1 kilometer. Find one and take the time it takes to travel at say, 50kph to the next peg. Divide 3600 by the seconds it took to travel that distance, this will tell you how many kph you were actually doing. eg = 3600 / 58 sec = 62kph. One old van i used to drive showed 100kph on the speedo when actually at 80kph.! |
BobM (1138) | ||
| 1241452 | 2011-11-04 07:08:00 | I neglected to mention that I set my speed on cruise control for those checks, so there is no chance that I can influence the outcomes. It is good to know the precise tolerances because the 'holiday weekend tolerance reduction' to 4km/hr over the limit is so easy to exceed. Cheers Billy 8-{) |
Billy T (70) | ||
| 1241453 | 2011-11-04 10:58:00 | Somewhere there's a university study that found that the closest that either cruise control or manual could keep to a set speed was about +/-1.5km/h on the flat. Your speedo fluctuations could be damped so this isn't obvious. If you were to get pinged for >4 over it would be a mistake to think you could cruise at 103.5 and be safe. | PaulD (232) | ||
| 1241454 | 2011-11-04 21:48:00 | Road marker pegs on the main highway have a marked km peg every 1 kilometer . That is actually incorrect or more precisely not the norm on New Zealand Highways . It was also good to see a poster point out about the accuracy of a GPS actually is more accurate on the flat than where hills are involved . Most people think in 2D unless they are pilots :) Since it was established the speedometer is electronic this next piece information regarding the speedometer head that is the drive unit into the gearbox from the cable would not apply . what I was going to point out that this ratio can also have an effect to speedometer accuracy . Something I have been investigating a lot recently on the three vehicles of the same make/model and age with 3 differing accuracy on the speedometers . One these vehicles is quite perplexing in comparison to the others with speedometer accuracy checked and validated on a rolling road and was puzzling until we investigated the speedometer gear head ratio . at 100kph the resulting speeds were 90kph, 97 kph and 105kph the interesting part was at 50kph readings of 40kph, 49kph and 50kph was returned on the respective vehicles indicating an error of 10kph, 3% and the 3rd vehicle that was underreading 5% being accurate at 50kph . At 30kph we came back with 20kph, 29kph and 28kph! Our first two vehicles was pretty consitant being 10kph and 3% overreading range the final vehicle well that defies logic it seems . Especially when we changed the speedometer unit and then found that went wildly out possibly as a result of an attempt to calibrate in the unit itself . So intereting situation when vehicle number 1 and 3 are driving in convoy at 100kph! The worse part though is vehicle 3 is a diesel and as a result that 10kph error being overcharged on RUCs . If only we had a set standard in this country for speedometer accuracy! |
driver (16592) | ||
| 1241455 | 2011-11-05 08:16:00 | Somewhere there's a university study that found that the closest that either cruise control or manual could keep to a set speed was about +/-1 . 5km/h on the flat . Your speedo fluctuations could be damped so this isn't obvious . If you were to get pinged for >4 over it would be a mistake to think you could cruise at 103 . 5 and be safe . Nah! I'm not that stupid . My normal cruise is about 95 actual and if there is no traffic around I go down to 90 because I'm rarely in a hurry and it makes for a significant improvement in fuel consumption . I can get over 850 km per tank (55 litre fill) on a trip . Around town I get 650-700km/55 litres (2005 Mazda 6 Sport-Wagon, 2 . 3 litre manual 5 speed) . I use the speed warnings in conjunction with cruise control as a speedo check, that's all . All speedos are damped anyway, digitals more so or they'd just read garbage, mine is analog . . Cheers Billy 8-{) |
Billy T (70) | ||
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