jon85
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| posted on 22/4/12 at 07:18 PM |
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need help with speedo calibration
hi all,
kit car going in for iva test in 2 days and iv just been told that the speed sensor cant be on the front wheel, something i shouldve looked into more
:/
anyway iv now wired the speedometer to the speed drive on the type 9 gearbox. i now have problem calibrating it as i cant find any info on the
settings.
i have a smiths classic speedo with 10 switches on the back.
can anyone please help or point me in the right direction?
iv worked out some info i need but now im stuck.
tyre circumference - 73.7
tyre turns per mile - 860
diff ratio - 3.4
prop shaft turn per mile - 2958.4
another thing is im not sure how many pulses the sensor gives out per mile on a type 9 gearbox.
i could even mount a speed sensor to pick up directly from the prop shaft if its easier.
any help would be very much appreciated.
jon
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SteveWalker
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| posted on 22/4/12 at 07:58 PM |
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When I took mine for SVA I had the Caerbont speedo, which I think is the same as your Smiths one (although I was sensing the propshaft bolts). I set
up an approximation and left the bracket off the back of the speedo. The speedo came with a sheet of switch settings, each of which related to a
decimal multiplier. I programmed a quick and dirty Basic program into my ancient 8Kb hand held computer and they were happy for me to see what the
indicated speed and actual speed were, stop, do a quick calculation, pull out the speedo, look up the decimal number, adjust the switches and then
re-run the test.
I was nearly caught out though and they were about to fail it on the third try, when I realised that the switches were in the reverse order to that
shown on the sheet! After that it was a doddle.
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mad-butcher
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| posted on 22/4/12 at 08:17 PM |
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By far the easiest place to mount it, and the easiest calibration.
[img]
 
Rescued attachment speedo pickup mount.jpg
[/img]
only drawback it took 4 days to stick magnets on using the original 24hr araldite not the rapid stuff
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jon85
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| posted on 22/4/12 at 09:11 PM |
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good of them to let you do it in the test, was hoping they would let us make adjustments.
think il go ahead and mount it on the prop.
my problem is i got no switch settings, if the caerbont is the same do you think the switch settings will be?
i was hoping to find some sort of table with the settings but the only calibrations i find online are requesting to send it in to them.
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MkII
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| posted on 22/4/12 at 09:41 PM |
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If you go to caiguage.com and then to there q&a page it tells you all
you need to know about doing the calcs and setting the dip switches. .m.
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blakep82
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| posted on 22/4/12 at 09:54 PM |
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this table here
http://www.caigauge.com/page20.html
can't decide whether you should use 2955 or 2966 pulses per mile, but one will read slightly over actual speed, the other under
is it a ford electronic sensor? i got a ford one from burton, think its 8 pulses per mile
[Edited on 22/4/12 by blakep82]
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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jon85
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| posted on 22/4/12 at 10:11 PM |
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thats exactly what i was looking for thanks
but wouldnt i multiply the prop rotations/revs by 4 as it will be picking up 4 prop bolts per turn?
thanks for all your replies
jon
p.s i think its a ford sensor and looks like a genuin part but not 100% as it came with the gearbox
[Edited on 22/4/12 by jon85]
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jon85
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| posted on 26/4/12 at 09:24 AM |
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thanks for the help guys,
ended up using the sensor that was in the gearbox. 5 pulses every 2 rotations.
took her for the test and the speedo was bang on
didnt do too bad either
n/s/r wheel binding, think the half shaft seal is leaking.
headlights were designed for left hand drive, something to do with the light.
front indicators need to come up 50mm.
the bar on brake pedal needs to be fixed not adjustable.
rear wheels locked up before the front.
also on our way there we couldnt get 5th gear so box needs stripping.
then the enjoyment of coming home in hail stones and heavy rain with just a pair of sunglasses.
at 70mph, shotgun to the forehead is an understatement.
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