More accurate readings w/o Wideband?

[SlightlyEvil]

Seems the stock sensor goes batshit from what I'm told while the car is in boost, and doesn't render accurate readings (says 11.14 when I log but Im told by someone I trust that could be from 9-12:1), so is it possible to calculate a more accurate AFR based on other readings from sensors that DON'T go nutso?

 

The car is going to be protuned in two weeks, I'm just wondering if in the meantime it's possible to get a more accurate picture of what's going on while in boost.

[rao]

No. The stock sensor is very accurate down to ~11.2, but after that it is not. I posted a comparison with an actual wideband a long time ago, which just confirmed that it was on target until it ran out of its range.

[gianspi]

Nope. Just pick up a wideband. $167 for an LC-1 is pennies compared to the cost of a new engine.

 

http://tinyurl.com/3lkjpc

[Infamous1]

Do NOT try and monitor with the stock wideband under WOT. The ecu will not monitor ranges below 11.14 or so. The problem is not the sensor it is the location it is in. The exhaust pressure is too high, you need a wideband placed downstream of the turbo.

[LittleBlueGT]

The OEM O2 is very accurate compared to a WBO2, I actually find it quicker to respond, and a little more stable.

 

I think I explained it to you before, it is the PRESSURE in the exhaust stream that skews the readings.

 

Here is a pic of a WOT run that I recently did:

 

http://i248.photobucket.com/albums/gg194/littlebluegt/OEMO2vsWBO2.jpg

 

In other runs I found that you could kinda estimate the actual AFR from the OEM O2 by looking at its readings and comparing it to the pressure. I am sure there is a mathematical formula for it, but then you would need to know exhaust pressure (pre-turbo).

 

1-Is the OEM O2 accurate? Yes.

2-Is it accurate when their is pressure in the exhaust? NO!

3-Can it read lower then 11.02? yes.

4-You can log lower then that if you change a table in the ECU that cuts it off at 11.02.

5-Is it accurate below 11.02? I don't know. I have changed the scaling of it and it did read lower, subjectively I feel it can read lower to reasonable accuracy (see #2)

[Jon in CT]

Have an exhaust shop install an O2 sensor bung in the downpipe. Relocate the front AFR sensor to new bung and plug old bung with bolt. Now you have accurate AFR logging down to 0.76 lambda (and it's no big deal, safety-wise, if you're richer).

 

How the front AFR sensor used with the 32-bit ECUs works:

http://www.denso.co.jp/ja/aboutdenso/technology/dtr/v07_1/files/dissertation5-i.pdf

[biz77]

LBGT, I rescaled the front O2 and adjusted the min value down. I'm still seeing the 11.02 cap. Any ideas?

[LittleBlueGT]

LBGT, I rescaled the front O2 and adjusted the min value down. I'm still seeing the 11.02 cap. Any ideas?

 

I looked for my logs, but couldn't find them. I did my testing a long time ago (before I bought my WB).

 

Sorry.

[LittleBlueGT]

LBGT, I rescaled the front O2 and adjusted the min value down. I'm still seeing the 11.02 cap. Any ideas?

 

Can you post a screen shot of the O2 scaler?

[biz77]

[Table2D]

-1.38 -1.30 1.10 -0.87 -0.47 -0.14 0.00 0.10 0.24 0.39 0.53 0.64 0.74

10.98 11.15 11.67 12.17 13.18 14.19 14.70 15.21 16.22 17.23 18.25 19.26 20.28

[NSFW]

;1910348']Have an exhaust shop install an O2 sensor bung in the downpipe. Relocate the front AFR sensor to new bung and plug old bung with bolt. Now you have accurate AFR logging down to 0.76 lambda (and it's no big deal, safety-wise, if you're richer).

 

How the front AFR sensor used with the 32-bit ECUs works:

http://www.denso.co.jp/ja/aboutdenso/technology/dtr/v07_1/files/dissertation5-i.pdf

 

 

Has anyone actually done that relocation with a USDM BL/BP and verified it against a wideband? Does it idle smoothly?

[Infamous1]

If I remember correctly groff relocated his, however not sure if there ever was ever a comparison.

[NSFW]

 

Here is a pic of a WOT run that I recently did:

 

[snipped]

 

 

Is your WBO2 in the downpipe?

[Long Island Legacy]

why does my AP read 20.4 when i lift after WOT? is this another foul-up with the stock sensor or is my car running seriously lean?

[BlackHole]

Standard ECM behavior to cut fuel on decel - thus the lean condition. No big deal.

[LittleBlueGT]

Is your WBO2 in the downpipe?

 

Yes, right in the top of it, COBB DP.

[BlackHole]

Has anyone actually done that relocation with a USDM BL/BP and verified it against a wideband? Does it idle smoothly?

 

Yes and yes. I looked it up on RomRaider last night but don't have the link handy, sorry. FWIW, the OEM JDM twin scrolls evidently have the O2 sensor in the DP.

[NSFW]

I think I know the thread you're thinking of. I remember some theorizing that it should work, but I don't remember anyone actually trying it.

 

I know the JDM's are that way from the factory, but I don't know if there's anything different about the sensor or (more likely) the tuning that would cause trouble if we do this on a USDM (like lower gains in the feedback loop to compensate for the increased delay by reading downstream).

 

It would be great to save money on a wideband but it would suck to do this and get inaccurate readings. Because if I have to buy a WB02 to verify, then I don't save any money. It would make logging a little simpler though, it would be nice to get good AFR data using any SSM logger.

[mickeyd2005]

root on romraider has a twinscroll setup and a WBO2. His WBO2 and his stock O2 sensor match but the ecu won't report lower than 11.02 even if it is rescaled.

 

AFAIK, all twinscroll setups have their front O2 sensor in the downpipe. Otherwise, they would need two front O2 sensors.

[LittleBlueGT]

I know the JDM's are that way from the factory, but I don't know if there's anything different about the sensor or (more likely) the tuning that would cause trouble if we do this on a USDM (like lower gains in the feedback loop to compensate for the increased delay by reading downstream).

 

You bring up a good point. TTBOMK we cannot yet control the gains on the loop for AFR learning, but if you have your intake finely calibrated (like mine, AFR learning over the course of a year has not changed by more then 3% on A and 1% on the rest) and you change the upper and lower limits of AFR learning to about 7% or so or less, it may help improve and possible driveability problems.

[Ridgeracer]

Has anyone replaced the rear o2 sensor with a wb that has a narrow band secondary output for the ecu?? I want to aviod getting an o2 bung welded into the shorty dp.

[Ridgeracer]

Yes, right in the top of it, COBB DP.

 

LBGT...I think you answered my question. Are you using the narrowband output for the ecu??

[LittleBlueGT]

LBGT...I think you answered my question. Are you using the narrowband output for the ecu??

 

I actually seriously thought about that, but wasn't sure if it would work.

 

I am using OEM O2 in OEM location (well in a header) and a PLX WBO2 for tuning in the DP.

 

In all honesty I think I could tune my car with the OEM O2 (assuming installed in the DP) as long as it was my alky tune, seeing that AFRs are in the high 11s-12.

[Ridgeracer]

Thought you had the WB in the stock rear location