Odell89

Guys I have a problem that is driving me nuts, my wideband gauge is reading a full point off from my afr in tunerstudio, the gauge is showing 12.4-12.7, and the gauge in tunerstudio is showing 13.4-13.7, I don't know if the question I'm about to ask is stupid, but if so, take your best shot per miataturboforun.com fashion 😂 here goes: Would my ground for my wideband have an effect on this reading? I have read that it would and I also have read that it wouldn't, tomorrow I'm going to bring home some wire and such and go directly to the battery with it. I installed my MS last weekend and it has literally fought me the entire time to the point of having thoughts of selling it. Thanks in advance.

Onyxyth

iTrader: (2)

That's pretty far off. Your grounding can definitely affect this. You should be grounding the WB directly to the ECU's sensor ground. I would start there.

My WB was also off .2 - .3 AFR even with the correct ground, and I fixed it by using the custom linear WB options and making adjustments until they agreed.

Odell89

When you say I should be grounding it to the ECU's sensor ground, that is something I read before and totally forgot, guessing I caught the dumb, where would that be? 1993, 1.6 'Yata, Stupid question, but I'm new to the MS, sorry.. And thanks for the reply!! It really became a nightmare today, man.

Onyxyth

iTrader: (2)

Depends on which MS you have, or how you're installing it.
For instance, I have a MSPNP2, and there is a sensor ground wire on the DB15 connector, as well as a WB02 "input" wire (0-5v). It's same for PNP models built by Braineack and Reverent too, I think. Other models may be different.

There's also a sensor ground location on the intake manifold in 1.8L NA's, not sure about 1.6's. Or you can wire it closer to the ECU itself, which is probably preferred, but I don't have an ECU pinout for 1.6's on hand to tell you which pin. You should be able to google it/search the forum.

Odell89

Apologies, I could've been more specific.. It is a mspnp2, the guy that helped do my install did more of the wiring than I did. So I'm not sure what he grounded and where he grounded it.

Onyxyth

iTrader: (2)

Man, if it was my car, I wouldn't want someone else doing the wiring and then not knowing what they did. At least write it down so you know how to troubleshoot it later.

Which board revision of the mspnp2? Does it have a DB15 or a DB26 on that back?

Early boards with the DB15, it's pin 15.
Later boards with the DB26, it's pin 22.
All of this can be found here: MegaSquirtPNP by DIYAutoTune.com

Odell89

And you are saying the gauge ground should be close to the ecu? The sensor itsself doesn't have it's own ground.

jstck

The gauge / wideband controller should be grounded close to the ECU ground. If they don't have a good common ground, the ECU can't reliably read the signal from the wideband (which is a voltage difference to ground). Any ground offset will also be an offset in reading the signal, causing incorrect values. Same thing goes for all analog signals coming in to the ECU.
Whatever goes on between the wideband controller and the sensor you shouldn't need to bother with.