speedo ratio

Rev Counters, Speedo's, etc..

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jonnyr48
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speedo ratio

Post by jonnyr48 » Wed Feb 26, 2014 11:19 pm

hi dudes, has anybody got any idea what the speedo drive ratio is on a dnepr mt11? and what do people think about using a mph speedo with a diesel on the continent - presumably it will give a (very!) rough indication of km/hr?
cheers, jonny

gilburton
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Re: speedo ratio

Post by gilburton » Thu Feb 27, 2014 8:50 am

Depending on the countries you are going to convert some standard kph speed limits to mph and stick some lines at the ones that correspond to your mph speedo.
I doubt if motorway speed limits will worry you too much but you do get restrictions for road works etc. the same as here.
As a starter an easy comparison is 80kph =50 mph so 40kph would be 25 mph etc. but you'll get a more accurate idea using a converter once you know the common kph speed limits.
I would suggest a small satnav as they can be converted to kph but I know they are illegal in France if they show speed traps. Don't know about other countries??

http://www.which.co.uk/cars/driving/dri ... mh-to-mph/

or if you are going for some time get one of these and mark it for 30/40/50 mph etc for uk use??

http://www.ebay.co.uk/itm/Speedo-With-T ... 4d18915d69

gilburton
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Re: speedo ratio

Post by gilburton » Thu Feb 27, 2014 11:27 am

or these

http://www.ebay.co.uk/itm/KPH-stickers- ... 258418a43b

http://www.ebay.co.uk/itm/SPEEDO-OVERLA ... 461b2f7bf4

I prefer the second example as it has the speeds in groups of 10 whereas the first one although cheaper misses out some vital speeds. It also has alternative sizes so may fit your speedo better and still show the mph numbers clearly.
Say for instance you used the small kph ring.
All you have to do is align it centrally with 80kph opposite 50mph or use 0 to align. Simples lol

pietenpol2002
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Re: speedo ratio

Post by pietenpol2002 » Thu Feb 27, 2014 11:55 am

Ron
Goshen, IN USA

jonnyr48
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Re: speedo ratio

Post by jonnyr48 » Fri Feb 28, 2014 3:02 pm

errrrmmmm, thanks guys, but i actually live in spain now, and true to my normal bodging style im trying to figure out how to use a new speedo marked in mph to give me a vague idea as to my actual speed in kph, given that my engines revving roughly 1/3rd less...... but i need to know what ratio speedos i can look for, and therefore also what ratio my speedo is running at now...? it looks to me as if i would need to take 10kph off what the lashed speedo would show, no? theres only 1 speed camera on the island, so the speedos only really for the mot test :D

gilburton
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Re: speedo ratio

Post by gilburton » Fri Feb 28, 2014 3:11 pm

Ah I presume the Ural speedo is driven off the gearbox but that shouldn't be affected by the engine swap assuming you are still using the original gearbox/drive/rear wheel?? The speedo takes it's readings from the rear wheel/output shaft rotations.
An easy way to check would be to use a sat nav and note the local speed limits against your speedo readings.
Another slightly cruder way would be to get someone in a car to pace in front of you at the various speeds you want to check??
Start with the car at 80kph and if it matches 50mph on your speedo then the speedo is reading correctly just mark your speedo out using the mph/kph conversion tables :)
Last edited by gilburton on Fri Feb 28, 2014 3:29 pm, edited 3 times in total.

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coachgeo
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Re: speedo ratio

Post by coachgeo » Fri Feb 28, 2014 3:24 pm

find a road with a row of cell towers to improve accuracy and use a cell phone with a speedo app. There several free speedo app's. Go to an art store or an office store and get some stick on numbers. Then you dont have to do any math. Find out what speed is the typical three speeds of the area (35mph? 55mph, 75mph if it was US) with the app; read them with the phone and note them on the speedo. Then stick the markers in appropriate matching places on the speedo

jonnyr48
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Re: speedo ratio

Post by jonnyr48 » Fri Feb 28, 2014 9:48 pm

thanks guys,the thing is i need to have a speedo that shows kph, even if ive painted it on! im not too worried about the accuracy - my current one is wildly inaccurate. ive changed the gearing in the back wheel, to make up for the low revs, so the speedo drive will have been thrown out by that. im really after the original speedo ratio so that i can work from there...any dnepr mt11 owners out there who've sorted this one out?

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