From the pics I see, the rear o2 sensor is before the last cat, or in the front 1/3rd of the cat. I'm kind of confused, as I thought the purpose of the rear sensor was to tell if the cats were working...in that case, shouldn't the sensor be behind the cats? Or is it just a temperature of the cat type of sensor? Reason I ask is I am ordering a stromung high flow cat mid pipe (pics of this pipe also appear that the bung is before the cat), and would like to add an auxillary bung to it, for a permanant wideband sensor, and was wondering why the stock senor is where it is?
What kind of car? In the 2.0L WRX's there is a cat in the up-pipe. Front o2 sensor before the 1st cat (in the up-pipe). The rear o2 sensor is before the rear cat (there are 2 cats in a "full" down-pipe"). See Unabombers FAQ on exhausts on Nasioc (has a nice diagram). http://forums.nasioc.com/forums/showthread.php?s=&threadid=447182
To get an accurate reading from a wbo2, you shouldn't be behind any cats. If you are only replacing your mid-pipe, you should probably place your bung on the exhaust headers.
02' WRX So with the rear o2 sensor being before the cat I will be adding (going to be no cats before the high flow unit in the midpipe) it will still trigger a CEL, and will have to be turned off when tuning...which leads to the question: Could I just not use the rear sensor, and use that bung for a wideband, or would if F something up?
My understanding is the rear o2 sensor is used _only_ to determine if the cats are working. I have disabled the CEL(s) it with no noticeable ramifications. DISCLAIMER: Some people suggest that the rear o2 affects fuel trim.
Yes, you can leave out the rear 02. It may trigger a code or two until it is turned off by tuning. Mine (in my 03) is unplugged, as I am always running a WBO2.
What kind of car do you have? Removing the rear O2 in a 16bit ECU won't affect much. However, if you have a car with a 32bit ECU, some of your fuel trims will get skewed.
And you definitely do NOT want to put a aftermarket wbo2 BEFORE the turbo. The pressure will skew the readings making them about as useful as the rear sensor. Always install the aftermarket wb02 in the bottom of the dp or before any cats. You can install it after a cats, but your cruising afr will be a bit laggy. WOT afr will be fine. Russ
Has anyone here used an LC-1 (I'm sure others do this also) to get a narrowband o2 signal out of the sensor to send to the ECU while still reading wbo2 data with your laptop/gauges/etc? Is it tricky/hastle to configure a wbo2 like this? I was intending to install a bung near the top of my downpipe & leave the rear o2 installed (ECU cell fix). But I was basing this on my impression that you want the wbo2 as close to the engine as possible for an accurate/instant reading (this is not so much the case with a catless system?).
The biggest thing with installing the wbo2 right next to the turbo is the heat. The all the wbo2 sensors have a recommended heat reange that they work in, and if it is too hot (right next to the turbo) the sensor life goes down. I have had my sensor in my cat pipe for 40k, and still works fine. You do want it as close to the motor as possible, but within reason. pressure will skew the reading, so anything before the turbo is out and your next concern is too much heat. If it is something you will be dailing driving with the sensor in al the time, I would just install it at the bottom of the dp or in the cat pipe. Russ
My WB is half way between where the downpipe goes parallel to the ground and the midpipe. I wanted the sensor to last as long as possible. On light cruise there is a small delay, but at any decent load, its pretty fast.
