How accurate is the Defi A/F gauge (D-Gauge)
 

I'm about to install the a Defi D-Gauge Air to Fuel gauge in my car. I'm wondering how accurate the reading really is. It taps into the stock O2 sensor. Of course it's now going to be like having a WB, but I want to hear others' experiences before I go to the trouble of wiring this thing up. Thanks in advance guys.

-Scott

You pretty much answered your own question. ;)

Accurate enough to tune by? No
Accurate enough to give you idea of what's going on? Possibly

My understanding of a narrow band a/f sensor is that it essentially has two readings, rich and lean, so it pretty much just bounces between the two if it's anywhere near stoich. I had one installed before and if you're running super rich it'll just be pinned to the rich side, same with lean.. So it COULD give you an idea of what's going on with your motor, however even with Defi's reputation, I don't see how they could give accurate readings from a source that can't provide it. As much as I love Defi's I'm going to have to believe that their narrow band a/f gauge cannot provide any more accuracy than an autometer a/f gauge..

That's what I was wondering. I wasn't really asking if the Defi guage specifically was accurate; I was more interested in how accurately the stock sensor would be at provide a reading.

narrow band O2 sensors only work very close to stoich. if it's too lean or too rich it will read incorrectly. I can't seem to remember which it defaults too (i think lean). so as everyone else has said it's definitely not accurate enough to tune by but it will give you some idea what's going on.

Its as accurate as your 02 sensor is. It looks sweet though.

Yup - it's pretty much just a (nice looking) voltmeter. Even a $10 eBay gauge would be accurate enough here.