Considering doing a LS Swap into a NB2 using a Haltech. Rather than using a Dakota Speedometer box, is it possible for the Haltech 2500 to output the required signal the stock NB cluster needs? .

 

You’d have to have a speed input to the ecu first, to have it output a signal. It would probably be easier to keep the stock sensor and wiring to keep the stock speedo working, and tap into the speed sensor at the trans for your ecu.

 

I won't be able to use the stock sensor as i'm running a T56 transmission.

For speed input, I have it covered, https://www.tickperformance.com/tick...-tr6060-4l80e/ will be used in the stock T56 sensor location. It will go straight from the transmission sensor to the Haltech.

For VSS to gauge cluster, I was thinking if the Haltech could send out an appropriate VSS signal to the NB Gauge, or if I would need to splice into the VSS signal from the sensor into a Dakota Speedbox into 3M pin of the gauge cluster.

 

It won't work. The stock speed sensor is a variable reluctance sensor that outputs an AC signal to the gauge cluster. Then the gauge cluster has a circuit that converts the signal to a square wave.
Just get the Dakota digital box and you can send the square wave to the box and the box will convert it to the AC signal and allow you to calibrate the speedo.

 

It looks like it just might be possible actually.

https://www.miataturbo.net/ecus-tuni...-sensor-85749/

Referring to the read above, it looks like I can send wire 2M (orange wire) of the gauge cluster a 0-5v square wave (If i'm reading this correctly, I know basically 0 about electrical work), The Haltech's DPO can send a ground trigger, 5v, or battery voltage as an output.

I'm not really sure what a square wave is but I'm imaging I don't need the 5v pullup and resistor in the circuit as the Haltech can already send a 5v signal as an output.

If the above is true and the DPO does what I need, I need to start figuring out the actual settings required.

 

The NB speedometer sensor outputs a VR signal so a square wave is unlikely to work, but not impossible.

 

I 90% got this working. In case anybody is wondering, I used a generic DPO (in my case DPO2) directly to pin 2M of the gauge cluster wiring.

The setting in Haltech is...
-Active State = Low
-Pull Up Voltage = +5v
-Signal Type = Frequency
-Mode = Table
-Duty Cycle = 50%

In the actual Table, set it Duty Cycle (Y Axis) vs Vehicle Speed (X Axis)..

Saying this, one thing I noticed that is weird, high up in the frequency range, if I turn on anything from the steering wheel stalk (turn signal, headlights, etc) the mph needle jumps for a second and then goes back to normal.. Either way, pretty happy it's somewhat working

 

Made an account to say thanks for the update. I checked this forum a year ago when I was first trying to figure out details of a digital speedo swap to my FC and wanted to go from trans to Haltech to new speedo. Finally came back around to figuring this out!

 

For more clarity, i'll post screenshots as somebody recently asked.

Modifying the values in the bottom row is how you adjust the speedometer.
The easiest way to test is to change the 0mph value (in my case 13) to different numbers and write down what it shows on your speedometer.
So if I change the '13' in the 0mph column to '89' and the speedometer showed that I was at 40mph, I would write that down and enter it under the 40mph column. That way I can map what value matches what speed without having to drive around. You might need to fiddle a bit but you'll at least be pretty darn close


If you want to emulate the speedometer going through the entire range, you can change the Vehicle Speed (MPH) axis to throttle position. Pressing the throttle will move your speedometer.

 

^Awesome info, thanks for posting!