C7 Posted September 6, 2004 Share Posted September 6, 2004 How do you calculate the pulses-per-mile for feeding into an electronic (eg VDO) speedo, when you've changed the wheels, gearbox and basically buggered everything up? Edited by - JimBean on 7 Sep 2004 13:26:54 Edited by - JimBean on 7 Sep 2004 13:27:30 Link to comment Share on other sites More sharing options...
Colin Mill Posted September 10, 2004 Share Posted September 10, 2004 Hi Jim What about checking its calibration against a hand-held GPS? Nearly all of these will display ground speed to the nearest 0.1 mph and they are accurate. Colin Link to comment Share on other sites More sharing options...
Chelspeed Posted September 10, 2004 Share Posted September 10, 2004 Measure the tyre circumference, ie X metres per turn of the wheel. Work out turns per mile by 1600 / X. Work out pulses per turn of the wheel. This depends where the pulses come from. It would be 4 if it's the front disc bolts used by Stack or similar speedos. Or 1 if it's a magnet glued to the rim like a push bike speedo. Or if it's on the propshaft it's the number of pulses that the prop makes per turn divided by the diff ratio. Then multiply these two together to get pulses per mile. Link to comment Share on other sites More sharing options...
Mick Day Posted September 10, 2004 Share Posted September 10, 2004 Basically follow the following. This is assuming you're taking the input from the front hub; ie 4 pulses per revolution. P= total pulses over 1 mile D = diameter of wheel & tyre. P= 4x1760x36/3.142 x D P= 3716 for 185x60x13 P=3476 for 185x70x13 Or see here for instructions: http://www.merlinmotorsport.co.uk/vdotech.htm Link to comment Share on other sites More sharing options...
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