Hi,
I need some help to calaibrate my speedo please.
I have an inductive sensor at the prop shaft .
The manufacturers data says, measure the circumferance of the tyre by rolling the whell 1 full rotation.
Done that = 181 cm. this equates to 552.486 revs per kilometer?
Then the diff ratio is either 3.62 :1 or 3.38:1
The manufactures equation is
number of prop bolts X distace tyre travels in 1 kilometer x diff ratio.
Is it as simple as 4 X 552.486 X 3.62 ???
Please help this is the last item to get bagged off before the SVA on Tuesday.

Yes, that's correct. You're looking for pulses per kilometer:

552 revolutions of the tyre per kilometer

x diff ratio gives you numer of turns of prop per kilometer

x 4 gives you numer of times a bolt passes sensor per kilometer.

Its the diff ratio i am having problems with.
Do i just multiply using the 3.62 or 3.38, depending on what diff i have.
Yep its a dumb question , my brain is mush at the moment!!!!!!!!!

Yes, that's right.

3.38 diff means the prop rotates 3.38 times for one turn of the wheel.

I had a similar problem getting to grips with the calculations for my Veypor - the instructions refer to the magnet being mounted on a wheel, yet mine was on the prop adaptor. What it was asking for was the circumference of the wheel without factoring in diffs etc as for a bike.

I eventually did a very vague Google search and found the Veypor forum. It put it in really simple terms - measure the distance covered (in inches or mm) for one rotation of the prop if you have one magnet. You then enter this in to the Veypor. I will fine tune using the GPS speedo on my sat nav.

Link added:
http://veypor.com/forum/viewtopic.php?t=592

[Edited on 19/4/09 by slimtater]

[Edited on 19/4/09 by slimtater]

Does your diff have the tag on it still? That should give you the ratio. If not it may be a good idea to calculate the settings for both ratios , you may be able to reset at SVA if the speedo is out ?