Front O2 sensor limit

merchgod · **Joined:** Thu Mar 30, 2006 2:38 am **Posts:** 5336

Jon [in CT] wrote:

The US 2002-5 WRX models all use the same sensor. The 2006+ WRX models switched to using the planar wideband found in the US STI.

Right, I should have clarified that. All 16bit ecus that I've checked have the same scaling for the front o2 and obviously the 32bit are different (in fact, the 06 wrx was the first rom I checked for the previous table shown earlier in this thread).

Jon [in CT] · **Posted:** Mon Mar 19, 2007 9:37 pm

merchgod wrote:

Here is the 16bit ecu front o2 scaling with the axis converted to mA. Ziggyrama did some logging for me and his A/F current #1 would go down to as low as -15 mA.

That scaling seems compatible with what Denso has published for that type of AFR sensor. However, I don't have much hope that this sensor will have any accuracy below about 11:1 AFR. I expect that when AFR is below 11:1, the sensor will always report roughly the same amperage, regardless of how rich AFR is.

Ziggyrama · **Posted:** Tue Mar 20, 2007 3:05 am

Here's output from a pull I recorded today. The O2 column is the stock sensor reading, WBO2 is my LM-1 reading. As you can see, the stocker goes flat below 12:1.

Code:

Load   RPM   TPS   WBO2   O2
33   2915   12.94   14.56   14.81
32   2935   12.94   14.44   14.59
32   2916   13.33   14.52   14.7
83   2925   38.43   14.52   14.7
86   2963   81.96   15.08   15.16
41   2952   100   12.4   11.83
99   2971   100   11.92   11.25
69   2986   100   11.16   11.25
41   3052   100   10.88   11.25
61   3060   100   11.2   11.25
51   3070   100   11.24   11.25
35   3114   100   11.36   11.25
32   3163   100   11.56   11.25
22   3198   100   11.56   11.25
21   3242   100   11.64   11.25
48   3245   100   11.68   11.25
47   3299   100   11.68   11.25
42   3328   100   11.48   11.25
35   3352   100   11.68   11.25
49   3392   100   11.6   11.25
52   3446   100   11.68   11.25
6   3464   100   11.64   11.25
71   3500   100   11.68   11.25
5   3541   100   11.56   11.25
44   3583   100   11.52   11.25
61   3594   100   11.56   11.25
72   3628   100   11.52   11.25
64   3656   100   11.28   11.25
53   3680   100   11.36   11.25
45   3731   100   11.36   11.25
49   3769   100   11.4   11.25
51   3780   100   11.44   11.25
51   3816   100   11.4   11.25
64   3842   100   11.36   11.25

WolfPlayer · **Joined:** Mon May 01, 2006 6:15 pm **Posts:** 126

The stock front sensor bottoms out at -1.375mA on my '05 STI. I have successfully rescaled this table. Previously, 12.5:1 on the wideband would yield 12:1 on my front sensor. It now reads 12.5:1 (like my wideband).

The last three lean columns are identical. That mean that you can shift the entire table over by 2 columns and put 2 more columns on the rich side (for more resolution). You can make a point for -1.38 (since the sensor goes down to -1.375mA).

This is a worthwhile modification IMHO for driveability/fuel efficiency in closed loop.

... now if I could just get rid of the FMIC rich spike

t

STIBungy · **Joined:** Wed Oct 25, 2006 2:10 am **Posts:** 45

Can you post up your table?

WolfPlayer wrote:

The stock front sensor bottoms out at -1.375mA on my '05 STI. I have successfully rescaled this table. Previously, 12.5:1 on the wideband would yield 12:1 on my front sensor. It now reads 12.5:1 (like my wideband).

The last three lean columns are identical. That mean that you can shift the entire table over by 2 columns and put 2 more columns on the rich side (for more resolution). You can make a point for -1.38 (since the sensor goes down to -1.375mA).

This is a worthwhile modification IMHO for driveability/fuel efficiency in closed loop.

... now if I could just get rid of the FMIC rich spike

t

LGT-3-6 · **Joined:** Thu May 25, 2006 12:11 am **Posts:** 205

WolfPlayer wrote:

This is a worthwhile modification IMHO for driveability/fuel efficiency in closed loop.

... now if I could just get rid of the FMIC rich spike

t

How does this effect closed loop? Not at all I'd imagine.

root · **Joined:** Sat Dec 23, 2006 12:42 am **Posts:** 51

My stock front O2 sensor (2004 STi) is located post-turbo. So are we saying that if I change the Front Oxygen Sensor Rich Limit to 10 and rescale the Front Oxygen Sensor Scaling map so that the lowest amperage is roughly matching the denso plot from earlier in this thread which aligns to the 10:1 AFR reading (somewhere around -1.8 mA?), that I should be able to log down to 10:1 using the normal stock sensor logging?

FWIW, here is a comparison plot of the OEM sensor vs. my LM-1 with the OEM sensor post-turbo. From this, if the ECU can handle it and log it, it would almost seem that post-turbo, the sensor might be useful below 11:1.

Jon [in CT] · **Posted:** Thu Apr 03, 2008 12:43 am

root wrote:

My stock front O2 sensor (2004 STi) is located post-turbo. So are we saying that if I change the Front Oxygen Sensor Rich Limit to 10 and rescale the Front Oxygen Sensor Scaling map so that the lowest amperage is roughly matching the denso plot from earlier in this thread which aligns to the 10:1 AFR reading (somewhere around -1.8 mA?), that I should be able to log down to 10:1 using the normal stock sensor logging?

Yay! Is your STI 2.0L or 2.5L? Where is your OEM AFR sensor mounted and where is your LM-1 sensor mounted? If you have the 2.5L STI (North America) why did you move the front OEM front AFR sensor?

So, if you have the 2.5L STI, then you want to shift everything over two slots to the right in the sensor scaling map.
url=http://www.romraider.com/forum/download/file.php?id=1901
That'll open up two slots on the left to scale below the stock 11.15 AFR, using as a starting point, the graph at:
http://i15.tinypic.com/4d45u7c.gif

root · **Joined:** Sat Dec 23, 2006 12:42 am **Posts:** 51

Jon [in CT] wrote:

Yay! Is your STI 2.0L or 2.5L? Where is your OEM AFR sensor mounted and where is your LM-1 sensor mounted? If you have the 2.5L STI (North America) why did you move the front OEM front AFR sensor?

It is a USDM 2.5L. Both sensors were mounted less than a foot from the turbine in the downpipe. The sensors were within a few inches of each other.

The reason I moved the stock sensor is because I installed the Full Race twin scroll kit and that's where they moved it to (rather than sticking it on just one of the runners leading into the turbo).

I'd be pretty happy if I could indeed log the stock sensor down into the 10s.

Jon [in CT] · **Posted:** Thu Apr 03, 2008 1:10 am

root wrote:

It is a USDM 2.5L. Both sensors were mounted less than a foot from the turbine in the downpipe. The sensors were within a few inches of each other.

You're our Man! Please tell us you have a Tactrix cable.

If you do, then you want to shift everything over two slots to the right in the sensor scaling map.
download/file.php?id=1901
That'll open up two slots on the left to scale below the stock 11.15 AFR, using as a starting point, the graph at:
http://i15.tinypic.com/4d45u7c.gif
The idea is to end up with a least squares fitted line with a slope of 1 between 10:1 and 14.7:1 with minimal variance (chi squared). So eliminate everything higher than 14.7:1 from you logs.

root · **Joined:** Sat Dec 23, 2006 12:42 am **Posts:** 51

Jon [in CT] wrote:

You're our Man! Please tell us you have a Tactrix cable.

Is it good to be (the collective) your man? I know it is good to be the King. Not so sure about your man though.

Yes. I have a Tactrix cable. The only immediate problem is my car is in a few pieces and I can't do the testing right now. I definitely want to try to make this work though once I'm back in a state to be able to start playing with it.

WolfPlayer · **Joined:** Mon May 01, 2006 6:15 pm **Posts:** 126

root wrote:

Jon [in CT] wrote:

You're our Man! Please tell us you have a Tactrix cable.

Is it good to be (the collective) your man? I know it is good to be the King. Not so sure about your man though.

Yes. I have a Tactrix cable. The only immediate problem is my car is in a few pieces and I can't do the testing right now. I definitely want to try to make this work though once I'm back in a state to be able to start playing with it.

Darn people not installing bungs when they should have

BTW - I realized I never posted my scaling in this thread. However, I did post it in another thread.

http://www.bescaredracing.com/sti/ecu/t ... escale.JPG

t

Jon [in CT] · **Posted:** Thu Apr 03, 2008 1:48 am

WolfPlayer wrote:

BTW - I realized I never posted my scaling in this thread. However, I did post it in another thread.

http://www.bescaredracing.com/sti/ecu/t ... escale.JPG

But you haven't relocated your front AFR sensor to be downstream from the turbo, right?

Jon [in CT] · **Posted:** Thu Apr 03, 2008 1:52 am

root wrote:

Jon [in CT] wrote:

You're our Man! Please tell us you have a Tactrix cable.

Is it good to be (the collective) your man? I know it is good to be the King. Not so sure about your man though.

You're our Man is short for you're our Man of the Year.

root · **Joined:** Sat Dec 23, 2006 12:42 am **Posts:** 51

WolfPlayer wrote:

Darn people not installing bungs when they should have

<cough>

Quote:

BTW - I realized I never posted my scaling in this thread. However, I did post it in another thread.

That pressure sure does screw with the sensor output.

RomRaider

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