Datalog MPH
 

I have a NA6 with swapped NA8 motor running a DIYPNP (MS2 equivalent). From my understanding, I need a variable speed sensor to be able to read miles per hour. My goal is to run a tablet, or something of the sort to replace my whole cluster...how were some of you able to get your cars to read speed (if at all)? Or am I the only one to not have this function working?

You would need to swap in a NB speed sensor and run the wires for it. The bigger issue is what are you going to do for a fuel gauge?

Thankfully I'm only in the planning stage 😅. I imagine I'd need to do something similar. Anyway, thanks for the input! More research to do now.

You can disassemble the NA6 instrument and keep just the part that converts the cable speedometer to a pulsed signal. There's a writeup on here on where this is, but I don't think it mentions how to disassemble the cluster, I just know my roommate did that.

https://www.miataturbo.net/megasquir...6-miata-82518/

Fuel gauge needs a pull-up to 5V to create a voltage divider. I would recommend a 150 ohm pull up, this seems to offer the best compromise of resolution (using most available voltage range) and reducing current through fuel sender. It's a 10-110 ohm resistive sender. So when the tank is full and the sender is at 10 ohms, it would be a total resistance of 160 ohms, so 5V/160ohm = 31milliohms. When the tank is full, the signal should be 0.41V, and when full it should be 2.5V.

Lower resistance pull-up and the current exponentially rises (heat in fuel tank = bad, as well as battery drain). Higher resistance pull-up, and the difference between the full and empty voltage reduces, so the resolution is worse.

If you want to do stuff like this, I would recommend looking into an MS3 upgrade. You'll run out of inputs/outputs real quick on a DIYPNP. Or look into a adding JBPerf expansion board to your DIYPNP.

Ok, that link to Aidan's thread is farking forum gold mine.

You all are freaking AWESOME! The MS3 is a definite possibility as I'm slowly working on an 11.5:1 piston upgrade (spare motor; slow build as supporting mods are quite expensive as well, gives me time for more tuning the nut behind the wheel). Will also definitely look into the JBPerf expansion. Thanks for the inputs!

I would go MS3X well before I spent any money on a JBPerf expansion board.