2001 Mazda Miata Wideband Install - Which Ground to use?

Hi everyone. So I'm trying to find the best grounding location for the Innovate MTX-L I have for my turbo build. I have researched and think I found two grounding points that should work. I have read that the wideband should be grounded at the same ground as the ECU. My question is, which of the two grounds (if I'm correct) should I use? I have linked an image of them both; one right behind the oil dipstick and one on the upper right of the TB. Can I just crimp the wideband ground to a ring terminal and bolt it down on top of the other ground?

https://imgur.com/a/lzQbIlF

Thanks!

That should work. 

Just make sure all the surfaces are clean.   Shine them  up with sandpaper and bolt them together.     

In reply to jharry3 :

Thank you! Is there one of the two grounding points you would prefer over the other? Just want to get the wiring right; I've never been great at wiring.

You only have to worry about the ground point if you are using an analog output. Batt negative is generally the best spot. 

In reply to Paul_VR6 (Forum Supporter) :

Gotcha, thank you! Yeah I am using an analog output for the AFR gauge (have it wired to the signal wire of the old O2 sensor connector that I snipped per megasquirt's instructions).

FWIW, if you want to get the most potential out of the sensors, you should plan on having a data acquisition system.   Visually, you will be able to notice the longer term trends, but it's unlikely that you will actually see what happened when you have some kind of hesitation or fault.  Let alone be able to pair that with a cause.

Let alone, many times when you are actually needing max power or perfect driveability- you are distracted with the driving (or you should be focusing on the driving vs how it's running).

Having dealt with a/f meters in cars for many, many years, the number of times I actually looked at the live a/f data was pretty darned few.  And that was not even hard driving- I was totally focused on how the vehicle was running.

In reply to alfadriver (Forum Supporter) :

Just for some more understanding, when you say data acquisition system, do you mean something that can log what the car is doing and how its running?

alfadriver (Forum Supporter) said:

FWIW, if you want to get the most potential out of the sensors, you should plan on having a data acquisition system.   Visually, you will be able to notice the longer term trends, but it's unlikely that you will actually see what happened when you have some kind of hesitation or fault.  Let alone be able to pair that with a cause.

Let alone, many times when you are actually needing max power or perfect driveability- you are distracted with the driving (or you should be focusing on the driving vs how it's running).

Having dealt with a/f meters in cars for many, many years, the number of times I actually looked at the live a/f data was pretty darned few.  And that was not even hard driving- I was totally focused on how the vehicle was running.

A wideband isn't just for a meter, though. It can also be an input for an aftermarket ECU. I don't even have a wideband display or a visible boost gauge on my turbo Miata because my ECU is the one monitoring those inputs.

The big thing about the ground is that you don't want power grounds (ie, O2 sensor heater) and signal ground to share the same point. Ideal is the ECU signal ground (again, not the ECU power ground), but it's more important to have that separation.

Japspec said:

In reply to alfadriver (Forum Supporter) :

Just for some more understanding, when you say data acquisition system, do you mean something that can log what the car is doing and how its running?

Exactly.  Using a visible meter to see it's output is a very limited way of seeing it's full capabilities.  Even if it were an input to the ECU, the primary way I would use one to see what's going on is with data instead of a visual gauge.

Keith Tanner said:

alfadriver (Forum Supporter) said:

FWIW, if you want to get the most potential out of the sensors, you should plan on having a data acquisition system.   Visually, you will be able to notice the longer term trends, but it's unlikely that you will actually see what happened when you have some kind of hesitation or fault.  Let alone be able to pair that with a cause.

Let alone, many times when you are actually needing max power or perfect driveability- you are distracted with the driving (or you should be focusing on the driving vs how it's running).

Having dealt with a/f meters in cars for many, many years, the number of times I actually looked at the live a/f data was pretty darned few.  And that was not even hard driving- I was totally focused on how the vehicle was running.

A wideband isn't just for a meter, though. It can also be an input for an aftermarket ECU. I don't even have a wideband display or a visible boost gauge on my turbo Miata because my ECU is the one monitoring those inputs.

The big thing about the ground is that you don't want power grounds (ie, O2 sensor heater) and signal ground to share the same point. Ideal is the ECU signal ground (again, not the ECU power ground), but it's more important to have that separation.

Do you happen to know on a NB2 where the ECU signal ground runs? I was looking in the FSM, and it looks like a ground from the PCM runs to the front of the Intake Manifold.

I don't recall offhand. Just don't use the same ground point as a power ground.

In reply to Keith Tanner :

Thanks! I'll have to figure out whether the ground I found is a power ground or not.