I need to dial in my carb and want to use a wideband O2 sensor as a diagnostic device. The sensor only needs to mount temporarily. Since the car has 3" exhaust with cutouts, I ordered a set of header reducers and a walker 2.5" pipe with an O2 bung pre-installed. The other option was a unit that mounts an O2 in the tailpipe but I figure the cutouts get me closer to the engine.

The plan was to hook up the O2 to a basic multimeter, which would work for narrowband but apparently not for the wideband. So, back to the drawing board. I'm searching online for a cheap wideband gauge but that isn't going so well. The least expensive seems to be the AEM 30-4110 at around $170, which I have a hard time justifying. I'm thinking there HAS to be a super cheap way to link the O2 to either my phone or a laptop with basic freeware that will give me a digital AFR readout.

Again, this is a temporary, less than ideal hook up for the sake of having an extra layer of feedback for carb tuning. I know very little about oxygen sensors or electronics so whatever you suggest will have to be simple to operate. I'd like to use a LSU 4.9 sensor, which seems to be the standard in 2023. From what I've read, the 4.2s need to be calibrated, while the 4.9s do not.

Thanks

Here you go, $95 plus post, some soldering required. Add $30 to not solder with the model up

Thier real products look pretty good too, have seen very frew negative remarks for thier products

https://www.14point7.com/products/sigma-lambda-controller-free-2 $45 without the sensor

I don't think using a cut out and short length of tube will work the best. One of the reasons the sensor is meant to be as close to the port as possible is to avoid outside air contamination from the end of the exhaust system

If you're already playing with Arduino style stuff you might get out of it cheaper than that, but at the expense of time and faffing about.

I have ran O2s for years. First with narrow bands and then with the wide bands. In my opinion, this is a subject that is hard to be only a little bit pregnant in. The varying amount of alcohol affects the reading, you have to really know the carb's circuits in order to know how to make the necessary changes, you need the right carb that has all the changeable bleeds and jets or have a good set of tiny drill bits and taps and all the bleeds and jets to go with those tools. It can be expensive and exhausting to start.

You didn't say whether you were tuning primarily for track or street. They are typically 2 different tunes. The cruise and WOT settings are usually not real hard if the carb is the right one for the job to begin with. The closer the carb is to being right for the application, then the less mods will be necessary to bring it in.

The idle, just off idle, and transitions before the main circuits come in are the real challenges to tune. This includes the emulsions. They overlap so much and there are not a lot of carbs that have screw in bleeds and such in those circuits. Now those circuits are usually not as important on a track car. Pump shot alone can cover up a lot of ills in that area when the throttle only goes from fast idle to WOT. But on the street, those circuits are absolutely critical. Some cars even end up cruising on the idle and transition circuits. That is a real can of worms to sort out and means that major compromises must be made.

Obviously, I don't have any advice on a cheap wide band. I just thought it was important to touch on a few of the issues surrounding using one.

The carb is a 800 cfm Edelbrock AVS2 on a dual plane 440, which is reasonably close to OE application. I am tuning for the street, which as you point out is much more involved than how I would have tuned the thing in my younger years when it was either at idle or I had my foot in the water pump. I'm especially interested to see what's going on from off-idle to light cruise in real time, something I'm not going to get from just reading plugs. I've driven carbureted vehicles for a long time so I'm not expecting miracles. What I am expecting is to have some real data to guide me instead of just a shot in the dark.