Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

AFR Logging Options Subaru STI

General Tuning Discussion

Forum Posts



Tech Articles

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads


So my car currently has a AEM Wideband installed in the car but its just running independently from the ECU on the car (came with the car).

After looking into things a bit it seems like as is this can only be used as a visual reference as there currently is no way to get a data stream from it with the current set up. So far it seems like my options are

1.) Pull out that entire AEM Wideband and wiring setup installed in the car and replace it with something like this iwire kit


Seems like a nice clean solution and I wouldn't need to leave the redundant factory o2 sensor in place, but I'd end up re-buying an AFR gauge and sensor I already have since they dont sell it as just a harness.

2.) Do something like this: https://forums.nasioc.com/forums/showthread.php?t=2805570

Which involves leaving what I already have in place (including the OEM o2 sensor), but tapping a 5v output wire from the AEM Wideband into the factory harness.

Seems cheap and easy but I'd like to avoid creating a rats nest of random wires if I can and this seems like a step in the wrong direction potentially?

3.) Wire up some kind of serial output connector from the aem wideband to an output port so that the signal can be logged separate from the main ECU logging output. Not sure how this would work or whether ecuflash/romraider would support integrating a separate signal like this into a log but seems like it would be possible in theory.

Interested if anyone has some experience with these different options or perhaps might recommend some other solution I haven't thought of.


Reflash based tuning options:

If you have the 30-0300 with gauge, an iwire PnP harness for that eases install and allows you to ballpark the analog error and adjust your assessment of data or your data scaling accordingly. You can monitor error at stoich idle, then a brief temporary rich idle condition at the end of the range you plan to operate the vehicle. Observe the difference between AFR on the gauge face, and logged data, to determine analog offset.

The inline unit without gauge doesn't give you a great method to identify analog error unless you wire in and use serial comms on your laptop, and it sounds like you already have a wideband so I wouldn't switch unless switching to something much better.

Alternatively you can wire in a Ballenger AFR500v2 which outputs control low and high voltages every startup, log that, and account for the analog error quickly, more accurately, and easily verify at each startup.

Standalone tuning options:

Get a CAN based wideband. Analog error doesn't exist. Link and Motec to name a few.

You can use the serial wire (blue wire) and the ground wire (black) of the AEM Wideband to log directly into RomRaider.

Note that I have a serial port on my laptop and I'm using a 30-0310 AEM Inline Wideband. I'm pretty sure you could use a Serial to USB cable if you don't have a serial port. It's very straightforward to set in the software and it won't be affected by analog offset.


I do already have a AEM 30-0300 with a gauge, but not one from an iWire kit. Unfortunately it looks like iWire will only sell you the PnP kit with an AEM 30-0300 included so If I wanted the PnP harness I would be re-buying an AEM 30-0300 even though I already have a working one with a gauge. Basically Im just trying to figure out if the PnP kit would offer me anything other than just ease of install compared to routing the 5v analog signal output of my existing AEM 30-0300 (which is already installed on the car) into the OEM o2 sensor harness on the car instead since I dont particularly want to re-buy the wideband and gauge just to get the PnP harness unless I have a good reason to.

Im assuming I could perform the exact same type of analog error compensation adjustment/testing If I just wired the 5v output of my current 30-0300 into the oem o2 sensor harness no?

Probably not going to be jumping on a Motec just yet but digital CAN communication does sound like the best solution to all of this :).


Just did a bit more digging on Serial data logging vs analog and some of the info I'm seeing is saying that (at least with the AEM 30-0300), that

- Serial output: 10hz, 3 digit data only (eg: xx.x)

- Analog output: 500Hz, 10 bit resolution. Also apparently has "differential analog output" that can help compensate for ground offset errors.

Have you had any issues with the lack of frequency or resolution w. serial data?


Depending of the ECU and the numbers of parameter you are logging, it's unlikely you get a rate of more than 10hz with Romraider. CAN ECUs are faster but again it depends of the number of logged parameters.

Here's a screenshot of a log I made with the Wideband connected via the serial port of my computer. This is a GD Subaru, not a CAN ECU. I think it's quick enough to tune with it. It's unlikely you have a big swing in lambda that won't be registered at 10hz.

I agree that the 30-03xx have dedicated analog sensors ground that help with offset error, but in my experience you always have to tweek a bit so there is 0 error.

Finally, the X-Series AEM Wideband can be connected via CAN. The AEMnet+ and AEMnet- are just CAN High and CAN Low in AEM lingo.

Hope it helps,


Attached Files

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?