Schroedinger

Background: I already have a LC-2 wideband installed in my 1992 1.6L. When I installed the WBO2, I pulled a ground wire through the firewall and to the driver-side engine block ground (below the master cylinders) because the Miata wiring diagram showed the ECU ground terminating at “right rear engine compt on engine block” and apparently I don’t know my right from my left.

As I’m planning my MSPNP2 install, I’m getting some conflicting information from the various install guides and the forum searches I’ve done here.

Question 1, Grounding:

Here is my view of Good/Better/Best. Is this the correct view? Can I get away with “Good”, or should I just jump straight to “Best”.

Good- leave it grounded to the driver side of the engine block.

Better- Move my ground wire to the passenger side engine ground where the ECU is grounded. If so, where the hell is this ground on a 1.6L engine?

Best- Pull the ground wire back into the cabin, and T-tap it into the black wire at pin 2A/B of the ECU harness (which seems like it would have a lower potential for voltage offset?


Question 2, Wideband Signal:

The MS-PNP install guide says:

“There are two ways of connecting the controller to the MSPNP2. You can either connect the analog output to the pin labeled Oxygen Sensor input of the option connector, or you can cut and splice the oxygen sensor signal wire to the analog output. If you use this pin for wideband input, you must disconnect the stock oxygen sensor. Do not ground the oxygen sensor wire if you disconnect it YADA YADA YADA”

I’ve read this twenty times, and it makes no gotdam sense to me. I think I should run the LC-2 signal wire (yellow) to Pin 21 on the MS-PNP2 Options port (oxygen sensor input), and not screw around with the stock O2 sensor at all, because I didn’t cut and splice from the harness. Am I correct, or should I sell this car and take up scrapbooking?

Many thanks in advance.

Schroedinger

Not to bump my own OP, but...

After further reading of the tea leaves, it sounds like the ECU signal ground on an NA6 is actually the black/green wires on pins 2C/D, rather than the power ground I referenced above (black wires on 2A/B).

I noticed in the wiring diagram that the power grounds go to a terminal (JC-03), the signal grounds go to an adjacent terminal (JC-02), and both terminal ground at the same spot on the engine block. The FM instructions for installing the Link ECU says to cut the signal grounds (black/light green wires) and reconnect them to a different spot thank the power grounds. The spot they recommend: the grounding strap on the driver's side that my LC-2 is currently using. This strikes me as being a pretty good idea, because I suspect a lot of noise comes over the power grounds.

So, as to my options above- Good, Better, Best, and

Bestest- move the ECU signal ground (black/green wires on pins 2C/D) to the driver's side grounding strap, away from the power ground, and where my WBO2 ground currently resides.

It strikes me that these posts are probably rhetorical. At least I know where to look to find my own thoughts. However, please feel free to chime in and tell me that I'm wrong or stupid.

Schroedinger

While I'm writing my little soliloquy here... I found this quote in a different thread from Braineack:

I hadn't considered the combined heater/signal ground of the LC-2, and the possibility of heater noise entering the signal ground. It's hard to know which is the higher priority- preventing voltage offset between the WBO2 and ECU ground planes, or preventing heater noise from entering the signal ground. At least the WBO2 heater is DC, unlike the vacuum tubes I'm used to dealing with. I'm guessing it's loaded with other electrical noise though.

I'm leaning towards "Good" is the leading candidate now- leave the grounding as it is, and try it. Which is cool, because I'm lazy. If I have issues, I'll try one of the other options.

ICE-.-

Well as solo conversations go this one was pretty darn helpful!