Elise S1 Stack gauge speedo signal

[tobyc]

Hello everyone,

This site has already helped me a lot for my quest to get a S1 Stack gauge working in K series engine swap Mini. Me and my friend have used pinout diagrams found here to work out the lights like indicators, oil warning etc. The tach works off the ECU (Mems2J) signal but the speedo has us utterly stumped. 

We found information suggesting the signal needs to be 10.14hz per MPH and that the stack dash takes a signal directly off the speed sensor and not off the ECU. As I understand the speed sensor is a hall effect with toothed trigger wheel. I have tried sending it square waves, sine waves in various frequency ranges at 0-5v but nothing moves the needle. If I touch the speedo input to ground temporarily the speedo needle does move so I know it is fundamentally operational.

I dont know what else to try, my friend suggested adding a second sine wave 180 out of phase with the first because its the cross over point between the two waves that is the signal trigger. Another suggested it might need a -5 to +5v signal. Someone else said 12v signal. I even found a service manual with the dash schematics but it doesn't tell us anything about voltages or wave forms or frequency.

Please if anyone has any information about how the speed sensor works and what signal the stack dash wants then please please post. Sadly I don't have an Elise I can hook an oscilloscope to read the speed sensor. 

[tobyc]

Can anyone confirm what type of speed sensor the elise uses?
 

[MG4Lotus]

Hi Tobyc

I don't have an Elise but I have found this on Deroure

Parts Shop - Bell and Colvill

Item 32 is the Speedo Driven Gear Assembly. I don't know if that is the answer you are looking for or do you need something more technical?

[MG4Lotus]

If that is what you are after it is "no longer available" from Lotus, but I searched the part number and you may be able to get one from here SJ sportscars

pdf.brochure.php

 

[Lithopsian]

Not Hall effect.  It's a reluctance sensor, so should be a sine wave.

Edit: the voltage will vary with the wheel speed so it probably isn't too critical as long as it is in a sensible range.  Could be anything from a volt or two to several tens of volts, but who knows depending on the sensor.  I also think it is going to be more than 10Hz.  I think you're working from 43 teeth per rev, so work out the circumference of your wheel (I calculated 838 revs/mile) and it seems like more than 10Hz.

Lastly, the sensor seems to read a voltage on the signal pin when there is no load (but connected to the Stack).  I don't know if that is meaningful or not.

Edited September 12, 2025 by Lithopsian

[dobbo]

Not sure if this question is still needing an answer.  If so, this is what the wiring diagram shows.  I don't know what the two 'infinity' signs indicate, I'm afraid.

EDIT - quick Google search suggests it indicates that the cores are shielded.

Edited October 12, 2025 by dobbo