Let me start off by saying that this is what will hopefully get me by until I get the Raspberry Pi setup going.

I have added a fuse box with the goal of powering gauges and other stuff as I go. I've heard conflicting information on where to ground the wideband O2 sensor. I've heard to ground it to the common ground for the ECU which is a stud on the back of the intake manifold. The instructions say to ground the wideband to the negative battery terminal.

Since the wideband O2 is wired to the fusebox I added, I grounded the fuse box to the stud on the rear of the intake manifold.... So far the fuse box is only powering the MTXL & boost gauge.

Can someone let me know if I have wired this correctly? This is my first attempt of wiring anything of this level when it comes to cars. I am not trying to short out the ECU, nor anything else lol

I have turned the key to the on position, but have not cranked over the car. So far the fuel pump primes, and both of my gauges light up like normal.


Please excuse my chicken scratch handwriting & poorly drawn schematic.

 

That's all correct. 85 doesn't need to go to the battery. If your relay has a metal mounting tab, I often just make a small loop that goes from 86 to the mounting tab and into one of the many available m6 threaded holes in the Miata chassis.

The ground location depends on your wideband. The good ones (in my opinion) have a separate power and sensor ground. Your MTXL combines them both, I'm assuming through some sort of filter circuit, that they're trying to maximize by going directly to the battery. That's a little inconvenient on a Miata, I think what you're doing to the engine is the right move. That's a giant aluminum ground through the block, trans, PPF, and then directly to the battery, so you're not far off the instructions.

 

Thank you for reviewing my wiring job. I will adjust 85 to go to an M6.