Will stock O2 sensor read down to 11 AFR if moved after turbo? Any negatives?

[smithsrsn]

Basically it's related to the ECU code that normally causes the AFR to oscillate a few percent rich and lean while you're in cruise (it's an emissions thing). With no rear O2 sensor the ECU gets stuck in the 'rich' mode. But there's a table that can be used to disable the oscillation completely, and one guy has reported that he removed the rear O2 without running rich that way. Before we can be sure it will work for everyone, we need some more people to verify that.

 

 

Do you find that you can feel the car accelerate/decelerate slightly with the AFR oscillations?

I used to think it was my cruise control causing it but since I installed my WBO2 gauge, I now believe that I can actually feel the oscillations while driving with constant throttle.

I would love to get rid of these oscillations. Very annoying.

[NSFW]

I don't notice any issues related to the AFR oscillations.

 

I get a bit of hesitation between 2000 and 2500 RPM but that happens even if I force the ECU into open loop, which disables the oscillations. If you want to try that yourself, here's a how-to:

 

http://www.romraider.com/forum/viewtopic.php?f=33&t=7897

[fahr_side]

Just for reference, the 5th gen LGT has the front O2 sensor right behind the turbo flange in the cat pipe. I guess there's nowhere in the stock header the sensor would get a sniff at the gas from all four cylinders.

[ClimberDHexMods]

Just for reference, the 5th gen LGT has the front O2 sensor right behind the turbo flange in the cat pipe. I guess there's nowhere in the stock header the sensor would get a sniff at the gas from all four cylinders.

 

I think that's more common than not.

[fahr_side]

I think that's more common than not.

You're probably right, given that most turbo cars don't have a very long collector before the turbo. Ours are special.

[hadvw]

I was just looking at PLX devices new SM-AFR combo, and with their controller, they offer both a 5v "wideband" out, AND a 1v "narrowband" out.

 

If I understand correctly, this would mean you could use the WB02 as your everyday O2 sensor - hook up the 1v output to the ECU, and use the 5v output for logging.

 

I did not realize (until now) that our stock O2 is in the UP, which is (from what I can tell) not useful for WB02 logging. So, in that case, still need a WB02..

[ClimberDHexMods]

Afraid you can't use the PLX AFR outputs with stock front O2 input, unless yuou setup a custom signal converter. But you can output the PLX 0-5V to a TGV sensor input (I have this on my car with AEM output) so you can log raw voltage.

[hadvw]

Afraid you can't use the PLX AFR outputs with stock front O2 input, unless yuou setup a custom signal converter. But you can output the PLX 0-5V to a TGV sensor input (I have this on my car with AEM output) so you can log raw voltage.

 

What are the TGV sensors normally used for? Is this only if you did the TGV delete?

 

As for the PLX question, what am I missing?

From: http://www.tunergalleria.com/latest-news/plx-devices-supports-battle-of-the-bimmers-at-bimmerfest-2012

 

The wideband analog output is ideal for interfacing with aftermarket ECU's and data loggers. The narrowband output is ideal for stock narrowband oxygen sensor replacement where the simulated narrowband analog output is fed back into your ECU to make it operate as if the stock narrowband oxygen sensor is still installed while running the PLX wideband setup. All three outputs can be used simultaneously.

[fahr_side]

The stock O2 sensor system reads current, not voltage.

 

Option 1: Leave the stock O2 sensor in the UP to run CL fueling, add a WBO2 to the DP to log OL AFR via it's analog output to your laptop.

Option2: As above but use the TGV sensor channel to log WBO2 sensor voltage direct from the ECU.

Option3: Move the stock O2 sensor to the DP, let it control CL fueling like stock but trust it's logged output down to 11.2 AFR in OL.

[ClimberDHexMods]

What are the TGV sensors normally used for? Is this only if you did the TGV delete?

 

They sense the position of the TGVs Yes, they are left unplugged when you delete your TGVs.

[hadvw]

They sense the position of the TGVs Yes, they are left unplugged when you delete your TGVs.

 

So, if I haven't deleted the TGVs, I can't use those sensors to log WBO2, correct?

[fahr_side]

So, if I haven't deleted the TGVs, I can't use those sensors to log WBO2, correct?

 

If you still have the TGVs and their motors, you need the sensors in place to let the ECU know the position of the valves. If you delete the lot, the sensor cables can be used log WBO2 voltage (or any other 0-5v analog signal) by running the WBO2 controller's output through the existing wiring. This lets your logger see the data on the ECU instead of a separate input you might have to configure via a plugin etc. You might want to do this for example to avoid dragging any cables into the cabin through the bulkhead or if your WBO2 controller isn't supported by the logger you want to use.

[hadvw]

If you still have the TGVs and their motors, you need the sensors in place to let the ECU know the position of the valves. If you delete the lot, the sensor cables can be used log WBO2 voltage (or any other 0-5v analog signal) by running the WBO2 controller's output through the existing wiring. This lets your logger see the data on the ECU instead of a separate input you might have to configure via a plugin etc. You might want to do this for example to avoid dragging any cables into the cabin through the bulkhead or if your WBO2 controller isn't supported by the logger you want to use.

 

That's what I thought. Thanks for confirming it.

[EpicRasta]

If you still have the TGVs and their motors, you need the sensors in place to let the ECU know the position of the valves. If you delete the lot, the sensor cables can be used log WBO2 voltage (or any other 0-5v analog signal) by running the WBO2 controller's output through the existing wiring. This lets your logger see the data on the ECU instead of a separate input you might have to configure via a plugin etc. You might want to do this for example to avoid dragging any cables into the cabin through the bulkhead or if your WBO2 controller isn't supported by the logger you want to use.

 

Ok, so here is an update for me. I finally got a chance to finish my build. My problem is this: I’ve spliced the driver’s side 0-5v TGV signal wire (not sure if it’s the “left” or “right” tgv according to the AP). The wire I’ve spliced it to goes to the 0-5v “output signal” on my prosport controller box. I’ve confirmed that the wire going to the controller box is in fact reading 5 volts. So now when I go to my AP to view the voltage, it only reads 0. Shamar (infamous) is tuning my car, so my question is whether he has disabled the AP to read the tgv’s since I told him that I have tgv deletes. Also if that’s the case, if the tgv’s are enabled, is that going to throw a CEL? And since the tgv is a part of the emission control, if we were to enable the tgv's through the AP/ecu, that’s going to put the car in limp mode right?

 

So for those of you who have used this signal to log, please help! I actually just got off the line with Cobb and they said they’ve never heard of people logging via the tgv’s although it’s a “great idea.”

[EpicRasta]

So, I just got off the phone with Cobb, and their rep said he checked with one of their engineers and he was mistaken...logging through the AP via the tgv's is something they do with frequency. So I concluded that it comes down to either a) the ground i'm using is no good (which is the cig lighter) or b) the prosport black box.

 

However i'm thinking my logic may be incorrect because. Both tgv banks read 0 volts according to the Accessport. However, both tgv banks read ~5 volts with the volt meter when the ignition is on. I'm really wondering if theres something fishy with my AP.

[thefoos]

I have a scatter plot somewhere that shows the stock sensor and my PLX wideband reading within about 3% of each other, and I haven't noticed any drawbacks at all.

 

I have done the same as I now have my o2 sensor in the downpipe on my EFR setup. The front o2 was at worst 4% off of what my AEM/bosch setup is. Most of the time it was 0-2% variance.

 

I will say on my previous setup, I moved the front o2 into the bottom port on my TurboXS downpipe and in closed loop the ecu was chasing its tail. So there is a volume / time constant involved that we don't have access to. So if you do this, you need to place the sensor as close to the turbine as is reasonable.

[EpicRasta]

Sheesh, I FINALLY figured it out...lol i had the 0-5v output signal of my wideband spliced into the 0-5v output of the tgv's. Boy was that stupid. Anyway, thanks for everyones help.....now on to figure out the excel conversion. :-)

[Guest]

I tried to get it to read lower than 11.2, but I haven't figured it out yet. I changed the scaling and the 'rich limit' (there's a table for that in RR) and an undocumented limit, but it still won't read lower. The limit might be related to the sensor itself, but there is one more place in the ROM that I want to check - the code that reads the sensor signal. Problem is, I haven't found that code yet.

 

With 16-bit ECUs, disconnecting the rear O2 has no ill effects, but people with 32-bit ECUs have reported that their cars went rich after disconnecting it. However a couple guys at RR seem to have found the solution to that problem:

http://www.romraider.com/forum/viewtopic.php?f=34&t=8131

 

Basically it's related to the ECU code that normally causes the AFR to oscillate a few percent rich and lean while you're in cruise (it's an emissions thing). With no rear O2 sensor the ECU gets stuck in the 'rich' mode. But there's a table that can be used to disable the oscillation completely, and one guy has reported that he removed the rear O2 without running rich that way. Before we can be sure it will work for everyone, we need some more people to verify that.

 

Not that if you have a catted exhaust for emissions reasons, this will reduce the effectiveness of your cat, so if you're a tree-hugger like me you should keep your rear O2 in place and operational. But if you're a catless bastard then that sensor isn't doing any good anyhow so you might as well tune it out.

 

I can post find the oscillation table for A2WC522N pretty quickly I already have that ROM "under the microscope" so to speak. Other ROMs would take some work but if anyone wants to be a guinea pig let me know. But

be prepared to wait a while.

 

Bump!

 

Did you find it in A2WC522N? I need yet to parse the RR's thread...

 

EDIT: found it: 2DF2C

 

Man, I don't even want to remember how much grief this thing has given me. Eventually Chris @ EFI mostly work around that issue, but it was never completely solved.

 

If I were checking forums more often I would have found it year ago....

[JMLegacy]

MY JDM LGT has this sensor in the Downpipe..stock. In the ROM the rich limit is set at 12.0 Is this the parameter that can be changed to 11.2 ?

[NSFW]

Probably.... try it and see.

[LatentWagen]

Might do this when I next replace my o2 sensor. Subscribed for later!

[Xplosivo1]

Sheesh, I FINALLY figured it out...lol i had the 0-5v output signal of my wideband spliced into the 0-5v output of the tgv's. Boy was that stupid. Anyway, thanks for everyones help.....now on to figure out the excel conversion. :-)

 

Which wire did you use from the TGV plug to get the correct reading?