Data logging is something that anybody with a Subaru should be able to do in my opinion. It will show you many issues with your car that can occur over time or when doing modifications – be it if they show up as detonation events, air/fuel errors, or boost errors. There are several devices which you can use, but I only plan on focusing on two of them: the OpenPort/Tactrix cable (OP2) and the Cobb AccessPort (AP).
OpenPort 2.0 (OP2.0):
This is an ‘open source’ cable that you can buy premade from Tactrix. It is around $200 new currently, and I’d suggest just buying it instead of downloading the hardware design. There are a few older versions (and knock off versions) which will work with ‘older’ models (pre-CANbus – around 05 to 06ish). It allows you to read data or ‘re-flash’ your cars ECU with a new ‘map’ or tune. The newer 2.0 version brings with it a few perks such as standalone logging to an SD card (no laptop required! Woo!). It also takes advantage of the newer CAN bus found on modern vehicles… which is fast.
Cobb AccessPort (AP):
This is a ‘plug-n-play’ tool for Subarus. It comes preloaded with some Off-The-Shelf (OTS) maps that are good for stock cars, cars with intakes, downpipes, or some common mods. They also provide a means for professional tunes. They are similar in function to an OP2.0, with some slight differences. I don’t personally use one of these, so my definitions may be slightly different than theirs.
You need to decide on a purpose of your log before you start. You may be investigating your cars boost control, fueling, or just a general check for any detonation. Each one will require specific parameters. You cannot usefully log every parameter at once – you lose resolution (datapoints/time) with every added parameter. The OP2.0 will give you a much better resolution on a CAN bus equipped vehicle… where as the AP you will have to give your chosen parameter list a bit more thought.
If you are using an AP, jump to the next reply. I’m going to use the rest of this reply to go over configuring an OP2.0 for standalone logging.
To configure your OP2 for standalone logging, some tech savy-ness is in order.
First, you should get the most recent version of ECUFlash so you have the most recent drivers/firmware for your OP2. If you go to Help -> About EcuFlash... I have Version 1.43.3252 showing. It works with my LC-1, which was my primary issue with the version on the Tactrix website. I got this one off of an Evo forum actually. After installing it, connecting your OP2 to your laptop and going to Help -> Licensing should apply the new firmware I think.
Next, open up your tune in EcuFlash. If you don't have one, hook it up to your car and read it. If you have definition problems - you are outside the scope of this write up. Either go to RR forums or shoot me a message and we'll get you up and going. Open up the 'ROM Info' section and write down your ECU ID (mine is 7412597007). Next look at the bottom of the entire scroll box for a "Patches" menu - check that and reflash your tune to your car. That will enable you to read various parameters much faster using the CAN bus.
Alright, now you need your microSD card and a bit of patience. You'll need to move a logconfig file onto the root directory of your nice new microSD card. I'll attach mine for reference. Don't rename it. Don't put it in a directory. The catch here is that mine is made for my ECU ID. All of the values read from the ECUs RAM (xFF or most floating values) are specific to an ECU. You will need to go through your EcuFlash or logger definitions and find yours. I can help with this, but it is a good practice to learn how these files work. Ctrl + F will be your friend.
Set your trigger at the bottom. I either use the defroster or RPM > 0. You'll see that I include both in my file and comment out ( the one I don't want.
One last interesting note - you'll notice the scaling in the log config file is in Reverse Polish Notation (RPN). I'd recommend giving it a wikipedia read. I am a bit partial to RPN calculators after getting the hang of them.
Any more detail about the OP2 config file is a bit out of the scope. Give it a go, and I can help you out if you post up your ECU ID and your current file. It takes some work and was fairly frustrating.