Logging Wideband O2 Via The TGV Sensor Input

is AEM's claim of "no fresh air calibration required" worth the extra $45? I found the AEM controller on amazon as well.

 

Yes. Yes it is.

So, if I'm understanding this correctly, you'd route the WB Sensor to UEGO box output through the non-unused TGV connector (presumes TGV deletes are in place), so you'd be able to read the WB data, via your OBDII connector, on your AP, or BtSsm? I'm seeing a lot of algebraic formulae and wondering where that all goes, since I don't use RR, or other datalogging software.

Yes. I would take the 0-5V output from the UEGO box and wire it to the TGV 0-5V input. Logging software takes the 0-5V from the TGV sensor, via the ECU, and converts it to a value for the TGV flapper. Using the equation given by heiche (and AEM), you can convert that same 0-5V from the TGV sensor into a WB AFR value.

 

BtSsm allows custom fields (I'm sure RR does too). You give it a memory (?) address (where to get the information from, so the 0-5V) and an equation to convert the value in the memory address into a usable value, which in this case is AFR. I think RR does this in its XML logging definitions, BtSsm has a GUI for it in the android app. I'm not sure how you would do it with the AP.

 

 

Turkeylord: where is your sensor located? Mine will be in the Cobb bung, though some places say it should be further from the turbo. Also considering the idea of a sensor heat sink but haven't seen much online about that.

My sensor is in the Cobb bellmouth bung. That sounds dirty.

all I can think of is King Cornholio.

 

...are you threatening me?

Well if I moved the sensor downstream I would definitely need TP (threaded plug) for my bunghole.

http://vignette1.wikia.nocookie.net/beavisandbutthead/images/0/08/Cornholio101.jpg/revision/latest?cb=20060701030018

Also considering the idea of a sensor heat sink but haven't seen much online about that.

 

from what I've heard/read, it's more about protecting the side of the sensor that's not in the exhaust from heat, so it's not a heatsink, it's more of a heatshield. deflects heat from the exhaust pipe away from the sensor. either wrap, coat, or add a little round heatshield (washer) under the WB02.

 

Edit for clarity, the "washer" shouldn't/doesn't need to be thick (no fender washers). just drill a hole for the O2 sensor in some thin steel and then cut the outer edges to your preferred geometric shape. round just sounds less likely to cut/poke any electricals or hands.

Edited July 15, 2015 by Flinkly

^ That makes sense. The stock one had a little shield.

My sensor is in the Cobb bellmouth bung. That sounds dirty.

 

So it doesn't really need to be much farther down the downpipe than the bellmouth? I thought I read the AEM sensor, and innovate for that matter, are supposed to be ~2ft from the turbo.

My AEM manual says 18" is ideal. I'm going to stick with the bellmouth because it's simpler. <shrug>

 

 

 

*EDIT*

 

FailSafe manual says:

Locate a suitable place in the exhaust system to install the included oxygen sensor weld bung. On nonturbocharged

engines, mount the oxygen sensor in the exhaust system at least 18 inches downstream

from the exhaust port. On turbocharged engines the oxygen sensor must be installed after the

turbocharger, ideally 18” downstream from the turbocharger exhaust housing. NOTE: If the sensor is

mounted before the turbocharger the pressure differential will affect the accuracy of the unit. For

accurate readings, the sensor must be mounted upstream of the catalytic converters and/or auxiliary air

pumps. To prevent collection of liquids between the sensor housing and sensor element during the cold

start phase, the installation angle should be inclined at least 10° from horizontal with the electrical

connection upwards, see image below.

 

That inline sensor manual says:

A weld-in UEGO bung is supplied for sensor installation. Mount the UEGO sensor in the exhaust system at least 18 inches downstream from the exhaust port. If you anticipate high EGT's (over 800C), run a turbocharger, run at high RPM for extended periods of time or plan on running leaded race fuel then you must mount the sensor at least 36 inches or more downstream of the exhaust port as all of these can cause the sensor to overheat. On turbocharged engines the UEGO sensor must be installed after the turbo charger, if not, the pressure differential will greatly affect the accuracy of the unit. For accurate readings, the sensor must be mounted before catalytic converters and/or auxiliary air pumps. To prevent collection of liquids between the sensor housing and sensor element during the cold start phase, the installation angle should be inclined at least 10° from horizontal with the electrical connection upwards, see Figure 2.

Edited July 15, 2015 by Turkeylord

oooooooh, could use the rear "O2" input AND location for a wideband. already removed it's contribution to the ECU/Tune and it's CELs anyways.

 

is there a rear O2 logging param in RR? (my logging laptop is in the Subaru ATM...)

also what I'm going to do (cobb bellmouth). Just ordered AEM my sensor kit from amazon

 

The issue isn't the accuracy of the readings, but instead the life of the sensor may be shortened by the heat.

 

so, sensor wire to TGV sensor wire, brown to TGV ground. Not having done much electrical in this car, I need to read up where to find best ignition switched 12V, which they suggest putting an inline 5A fuse for.

I tapped off the cigarette lighter personally, with a little 4 place fuse block for my gauges and failsafe relay.

http://www.romraider.com/forum/viewtopic.php?f=7&t=6430&start=15

 

someone talks a little bit about using WBO2 in the rear O2 location in this thread

Thanks, I was just going to get that.

For anyone interested, the relevant pages in the service manual are WI-77 & WI-86. I've attached them to this post.

2005 Legacy GT Service Manual TGV.pdf

Since my setup is going to be contained to the engine bay, i'm not sure the lighter is as available. but i've gotta do some searching. i don't even know where that is right now (physically)

Is ACC power alright for this? I was going to try to tap the 12V ACC in this thread:

 

http://legacygt.com/forums/showthread.php/ignition-12v-engine-bayi-115414.html

Fixed my ground issue!

 

Soldered.

http://i.imgur.com/WBNfgbc.jpg

 

Heat shrunk & zip tied.

http://i.imgur.com/MoIZQcr.jpg

 

Looking better.

http://i.imgur.com/lLUpz1M.png

 

Formula needs a little tweaking, I'll try bnguyenbb6's values and see how it looks.

So it doesn't really need to be much farther down the downpipe than the bellmouth? I thought I read the AEM sensor, and innovate for that matter, are supposed to be ~2ft from the turbo.

 

Keep in mind that AEM is assuming that the turbo is located just inches from the exhaust ports, because most turbos are mounted right at the exhaust manifold's collector. Subaru turbos are two or three feet downstream of the exhaust ports, so most of us put our WBO2 into bungs that are right on the bellmouth.

I have this exact gauge in the car wired to my passenger side TGVs. I use 2.375x + 7.613835. From my experience, trying to calibrate it with the front O2 is hard due to the delay and the slow response of the front o2. I had better results moving the Front O2 into the down pipe but it was still off a bit.

 

Good point about moving the stock front O2 sensor into the downpipe before making comparisons. The stock location (pre-turbo) makes it inaccurate under boost.

 

On the other hand, if you can get the WBO2 to match the stock sensor at idle and read what the manufacturer expects when you lift the throttle (16:1 or 20:1 or whatever) that should be enough to get the multiplier and offset correct. Since it's a linear equation, two points should be all you need. That said, the further apart your known values are, the better.

 

And to whoever asked about TGV deletes and cold starts, mine has been tested down to low-single-digit farenheit, and the car starts fine.

Keep in mind that AEM is assuming that the turbo is located just inches from the exhaust ports, because most turbos are mounted right at the exhaust manifold's collector. Subaru turbos are two or three feet downstream of the exhaust ports, so most of us put our WBO2 into bungs that are right on the bellmouth.

 

Ok well then I guess I'll only have to unwrap the top of the downpipe. You guys have a picture of what orientation yours is welded in? I've seen them in a few different orientations. Not sure if one is better than the other.

Yeah I had my TGVs deleted all of last winter in that pretty terrible Boston winter. Didn't really notice much difference. You get a little oscillation on cold-start-idle but otherwise no issue