Discussion
I can't get the speedo to work below 20mph (not that important, but doubt if acceptable for SVA). I'm using a VDO electronic speedo (same as factory) and the inductive sender supplied by factory picking up on six lugs on a ring fitted inboard on driveshaft. Tried adjusting gap etc, no joy. I think I just need to get stronger pulses, any ideas?
I have the same setup. I haven't got it fitted yet so I can't offer any concrete advice but I have used inductive speed sensors in the past. Like Andy says the gap is critical. I haven't been able to find the spec of the VDO sensor but these things ususally need to have a gap of about 1mm before they will reliably see the teeth. I noticed that Ultima have changed the design of the cutter plate from what is shown on my build manual. The old design was a disc with teeth missing whereas the new one has teeth that stick out. The new design will probably be less noise prone. Which design are you running?
Another area worth checking is the cabling. At slow speeds the signal is going to be very faint which is why Ultima include a screened cable in the wiring loom. It would be worth checking that this is undamaged particularly the screen and possibly resoldering the connection.
It strikes me that VDO are maybe being a bit optimistic expecting a passive inductive sensor to work at low speeds under a car bonnet. Perhaps a pulse amplifier of some sort is needed close to the sensor? As this would require a bit of rewiring of the instruments I doubt that this is usually needed. It's probably just not adjusted quite right yet.
Is the cutter plate concentric on the driveshaft? If the gap is varying a lot for the different teeth then this will confuse the electronics in the speedo.
Another area worth checking is the cabling. At slow speeds the signal is going to be very faint which is why Ultima include a screened cable in the wiring loom. It would be worth checking that this is undamaged particularly the screen and possibly resoldering the connection.
It strikes me that VDO are maybe being a bit optimistic expecting a passive inductive sensor to work at low speeds under a car bonnet. Perhaps a pulse amplifier of some sort is needed close to the sensor? As this would require a bit of rewiring of the instruments I doubt that this is usually needed. It's probably just not adjusted quite right yet.
Is the cutter plate concentric on the driveshaft? If the gap is varying a lot for the different teeth then this will confuse the electronics in the speedo.
Dave,
thanks for advice. I have got it sorted by varying gap and alignment, speedo works fine even at low speeds now. I have the new disc design (six teeth sticking out). I had to bend the Ultima supplied bracket a bit to place the sensor directly in line with the disc and changed the lock nut on the sensor for a spacer to get the thing as close as possible to the teeth.
thanks for advice. I have got it sorted by varying gap and alignment, speedo works fine even at low speeds now. I have the new disc design (six teeth sticking out). I had to bend the Ultima supplied bracket a bit to place the sensor directly in line with the disc and changed the lock nut on the sensor for a spacer to get the thing as close as possible to the teeth.
Glad you've got it fixed. After I posted I dug out my bits to have a look at how they fit together. Like you say the lateral alignment of the sensor w.r.t. the disc seems to be very critical. Most other inductive proximity sensors I've met have been much smaller diameter than the VDO part. I think that it is basically the same internal design but potted into a larger more robust housing.
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