ULTM8Z

Where does the WB sensor get it's sensor ground from? Through the sensor body?

A couple of years ago, I started questioning the grounding of the NB sensor through the headers... so I hooked up a braided ground strap from the sensor body to the back of the cylinder head (effectively bypassing the header) and ended up having to recalibrate the fuel trim as a result. The car ran significantly better.

So the other day I decided to do the same thing on the WB. All of a sudden now the WB is reporting damn near the same AFR as the commanded AFR (within about a 1/2 point). Am I imagining something or does the WB sensor actually ground through the sensor body such that this ground strap actually did something? I don't remember having done anything else.

It's been a while since I've been doing serious tuning on the car (since about early last year), but last I remember I was having to program in about a point a half lower AFR to get what I want (i.e., I want 13.0, I have to program in 11.5)... So this is now a marked improvement in the tune-ability of the system...

???

iTrader: (5)

if it's an lc1 or lm1. back when I first got mine, I read tons of stuff on their boards about grounding and it was always use the main engine ground at the back of the head for the + and - of the wideband controller. never anything about the o2 sensor. since they work not even in the exhaust pipe. their free air cal and exhaust tip clamp

so I'd say no, but maybe your created a ground loop that changed things? they tend to warn about that too for using 2 many different ground points.

ULTM8Z

Mine is a AEM... but now the ground wire and the sensor body are the same ground potential. It must matter for sensor performance I guess....

???

iTrader: (5)

if it works it doesn't really matter, but just for the heck of it. you could check for a voltage drop with a meter from main engine ground to ungrounded o2 and see if there's any voltage drop with and without the ground?

interesting

???

iTrader: (5)

don't know how you made the ground connection, but I remember innovate sold a small plate that went between the sensor and the bung to use as a heat sink, if you used a stock manifold hole and Heat thru off the sensor reading. any chance your ground is changing Temps?

ULTM8Z

Basically I took a braided ground strap and clamped it to the sensor body tightly with a hose clamp. The other end of the strap I terminated with a ground lug and bolted to the back of the cylinder head.

The other thing that occurred to me is that the sensor may not have been reporting the correct AFR at all... so my example of wanting 13.0 and programming in 11.5..... the 13.0 reported AFR may not have been correct itself...

ULTM8Z

The other thing I just thought of was that this could be contributing to the difficulty I was having trying to get TunerpoRT to see the WB sensor. I'll have to revisit that and see this change makes any difference with that...