Darkspeed
Club Retro Rides Member
Posts: 4,864
Club RR Member Number: 39
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From >35% it appears to decrease to <23% as speed increases so a really wide range of over read tolerance. You are over reading at 28 mph by 43% and the upper limit is 33% but if they cannot test it accurately...
indicated v actual
35 = 26 40 = 30 50 = 39 60 = 48 70 = 57
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Gearing only affects the slope of the curve, from the data above it looks like most of the issue is a fixed offset, I used to fix this by tweaking the needle on the speedo head, not sure if that is possible here.
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Last Edit: Jun 13, 2018 9:46:36 GMT by kevins
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Is there a long waiting list for test slots now you have all the fixes applied?
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Jun 13, 2018 12:25:28 GMT
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Speedo hard to test accurately unless I can do a steady 20 or 30 mph for around 20 secs or so as Satnav is not accurate without a longer period of reference. Original gears on motorway will read 60mph at a satnav indicated 58mph - so perfectly accurate - as they should be as it was worked out by the speedo people who supplied the gears. I have ordered another speedo drive gear with 2 less teeth which should make the speedo read 64mph at a satnav 58 mph (similar to Mondeo overread) for long term usage. If gears arrive before test date I can swap them in & retest, but tester really wanted to see an overread, so current ones will satisfy that itch, lol. I'll try to retest current gears again, but its difficult to find a road where you can drive at 20mph for long periods.
Retest date is July 10th.
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Jun 13, 2018 12:36:12 GMT
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My Mk2 Focus with the optional 17" wheels on it reads 30 but on a road speed trap the car is doing 28
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Darkspeed
Club Retro Rides Member
Posts: 4,864
Club RR Member Number: 39
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Jun 13, 2018 12:49:10 GMT
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Being an all mechanical drive we checked ours purely by calculation of Tyre Circ, gear ratio's and the Tach and it was exactly same as the results when tested. I put all the numbers in Gearcalc - Jacked up the rear run it through the gears and took the readings. Tach we knew was accurate. I seem to recall ours over read by a constant 5mph or so throughout. Nice simple fix on the tow hitch and a mirror fix to reduce those rear fender repairs - all good
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Jun 13, 2018 12:51:29 GMT
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Hmm....is gearcalc an online thing? I can run car up in garage much more easily.
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Darkspeed
Club Retro Rides Member
Posts: 4,864
Club RR Member Number: 39
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Jun 13, 2018 13:01:49 GMT
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Jun 13, 2018 15:22:43 GMT
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Thanks Andrew, thats a neat program. I predict my neighbours may hear some engine revving tonight
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jamesd1972
Club Retro Rides Member
Posts: 2,916
Club RR Member Number: 40
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Thanks Andrew, thats a neat program. I predict my neighbours may hear some engine revving tonight Those lucky lucky people !
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jamesd1972
Club Retro Rides Member
Posts: 2,916
Club RR Member Number: 40
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Thanks Andrew, thats a neat program. I predict my neighbours may hear some engine revving tonight Those lucky lucky people !
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Jun 17, 2018 18:47:50 GMT
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Had a play today with rpm/speedo readings. The main problem is that under 20mph the speedo does not really work very well. Due to the 2 reasonably tight bends in the cable it struggles to turn smoothly at low speeds and the needle wobbles around a bit until you get to about 20-25mph, by the time its at 30 it is nice and smooth. It reads under at low speeds as it is struggling to overcome the friction in the cable. It's not massively out with the wrong gears - around 300rpm off (low) at 30mph so I think I'm going to risk these gears rather than fit the correct ones for the retest.
Had a play with the jets in the secondary throttles and also the primary metering rods, a little richer in the rods and a little leaner in the secondary's and it seems to run even stronger. Still has a hesitation under initial W.O.T but its getting smaller, so steps in the right direction.
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Jun 17, 2018 19:52:32 GMT
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Mark
Could you fit a longer cable to reduce the 2 tight bends?
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Jun 17, 2018 20:16:54 GMT
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It's not cable length thats the problem, its a big engine in a little car issue. Just no more room.
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Jun 17, 2018 20:49:29 GMT
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It's not cable length thats the problem, its a big engine in a little car issue. Just no more room. Are there not GPS Speedometers that could be used if it is a dire problem?
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Jun 17, 2018 20:59:19 GMT
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It's not cable length thats the problem, its a big engine in a little car issue. Just no more room. Are there not GPS Speedometers that could be used if it is a dire problem? I don’t think GPS speedos are allowed for IVA (?)
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Jun 17, 2018 21:04:29 GMT
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Correct, GPS not allowed.
I don't think its a problem - must not overthink it as test was far less onerous that I imagined, so hopefully the overread will be absolutely fine.
It's certainly not a problem for me as the end user as it works fine over 25mph and who needs to know if they are going slower?
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glenanderson
Club Retro Rides Member
Posts: 4,315
Club RR Member Number: 64
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Jun 17, 2018 22:36:44 GMT
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GPS isn’t allowed, I presume, because it won’t work when the antenna can’t see the sky.
You could fit an electronic one though, with either a sender screwed into the gearbox where the cable used to go, or a pickup on the prop.
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My worst worry about dying is my wife selling my stuff for what I told her it cost...
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You could fit an electronic one though, with either a sender screwed into the gearbox where the cable used to go, or a pickup on the prop. Yep, that's what I did, pickup on one of my drive shafts.
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Darkspeed
Club Retro Rides Member
Posts: 4,864
Club RR Member Number: 39
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.... test was far less onerous that I imagined.... You did revise quite a lot
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