Steve Lovelock
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| posted on 15/4/08 at 02:57 PM |
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Setting speedo for SVA
I have an electronic Smiths speedo which works but is not calibrated. How can I do this when I can´t drive on the road? I am about to apply for SVA
and would appreciate the wisdom of others who must have overcome this issue.
Cheers
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worX
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| posted on 15/4/08 at 03:02 PM |
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Could you contact Smiths to ask for the relevant percentage increase/decrease to be applied to the settings?
Alternately you could go to a local garage with rollers and ask them to check it for you.
You could take the car to a private area and doa couple of respectable runs to do it yourself.
And lastly there is the obvious, not recommended, never done by any other members, trick of just driving it on a quiet road local to you...
Steve
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DaveFJ
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| posted on 15/4/08 at 03:06 PM |
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I am in the same situation as you and I'm not sure how i am going to sort it either....
Although I could do a few runs on a local airfield, it's getting the car there in the first place! (I live in town and there is no way i could
get away with driving it) 
Dave
"In Support of Help the Heroes" - Always
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Steve Lovelock
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| posted on 15/4/08 at 03:11 PM |
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Well living in sunny London has its good points but driving a unregistered Luego on the local roads would not be amongst them. I have no trailer
either.....
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02GF74
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| posted on 15/4/08 at 03:22 PM |
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I don't understrand what the problem is.
If the Smiths is like other electronic speedos it works but counting pulses.
The pulses are generated by some sensor on the drive train.
The speedo usually needs to know how many pulses there are in a given distance, usually a mile.
Knowing this info. it can the work out distance travelled (odometer reading) and speed.
What you need to do is it to find out what information the speedo needs - usually pulses per mile then using some simple math work out diameter of
wheel, diff ratio and so on to work out the distance your car travels for one pulse.
Dividing this number into 1 mile gives you pulses per mile; program this number into your speedo but at about 1-2% less so it over reads and job
done.
You don't need a rolling roll or even move the car.
Or am I missing something fundamental? (like the Smiths speedo is programmed in some other weird way, if so, should have bought a RaceTech  )
[Edited on 15/4/08 by 02GF74]
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DaveFJ
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| posted on 15/4/08 at 03:24 PM |
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Mines Teleflex so may be a bit different but, the instructions give settings that are slightly vague and therefore I really want to test for real to
make sure that it is not under-reading before the test....
I could leave this for the trip to SVA but it's cutting things a bit fine!
Dave
"In Support of Help the Heroes" - Always
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David Jenkins
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| posted on 15/4/08 at 03:25 PM |
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Does this help?
Greengauges speedo guide
Greengauges/CA/Smiths are all the same, IIRC.
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02GF74
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| posted on 15/4/08 at 03:32 PM |
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quote:
Originally posted by DaveFJ
Mines Teleflex so may be a bit different but, the instructions give settings that are slightly vague and therefore I really want to test for real to
make sure that it is not under-reading before the test....
I could leave this for the trip to SVA but it's cutting things a bit fine!
you can always set up speedo on SVA rollers.
but by jacking up the rear wheels (remove tyres to reduce rotatin mass) use the rev counter in different gears to see how it tallies with speedo
reading.
If you see 300 mph in 1st gear at 2,000 rpm, you should start to have doubts about the speedo.
You should be able to work out speed from rpm/gear/wheel diameter/diff ratio.
This does not mean you will get it right for SVA but a) you should get it close and b) have some experince setting up the speedo - make understable
notes so in the heat of the moment as SVA you can program it.
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ditchlewis
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| posted on 15/4/08 at 03:50 PM |
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i have telemetric speedo and attached are the instructions i found on the web.
hope this helps
ditch
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Schrodinger
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| posted on 15/4/08 at 04:15 PM |
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For Smiths Speedo
http://www.caigauge.com/speedofitheader.htm
Keith
Aviemore
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Johneturbo
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| posted on 15/4/08 at 05:13 PM |
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I was planning on taking the laptop with me and using the speedohealer program, not sure if the tester would be happy with that!
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James
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| posted on 15/4/08 at 05:52 PM |
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My gauge manufacturer told me the number to plug into my speedo once I'd told him gearbox ratio, wheel size and diff' ratio.
I checked it using a TomTom or similar.
HTH,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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caber
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| posted on 15/4/08 at 07:51 PM |
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I worked out the wheel rpm for 20 30 and 60 got a laser tachometer cheap off ebay jacked up one side and chocked the front wheels and revved un til I
go the right speed at the wheels then set the speedo adjustment to show the correect speed. It didn't seem right then I realised with one wheel
off the ground it was going twice as fast! I reset everything and still had to tweak it at the test!
Caber
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