[WolfPlayer]

Originally Posted by O6STi

My AFR's before a Stock ECU (red)and after a ecutek reflash(blue). This was runninig catless and without rear o2 sensor.

WOT has nothing to do with this post. It's AFRs in CLOSED LOOP with the rear O2 removed. Your post is a WOT dyno run in OPEN loop when the O2 sensors aren't doing squat (the ECU isn't looking at them because they are totally inaccurate at WOT when the the AFRs are that rich).

t

[R4ND0M_AX3]

I've decided that instead of welding a second O2 bung in my DP I'm going to just use the analog output from the LC-1 to simulate the rear O2. I'm tired of this rich idle.

[WolfPlayer]

Originally Posted by R4ND0M_AX3

I've decided that instead of welding a second O2 bung in my DP I'm going to just use the analog output from the LC-1 to simulate the rear O2. I'm tired of this rich idle.

Yup. That is something that I was going to do IF the location in the APS outlet was too close to the turbo.

t

[STLSTI]

Originally Posted by R4ND0M_AX3

I've decided that instead of welding a second O2 bung in my DP I'm going to just use the analog output from the LC-1 to simulate the rear O2. I'm tired of this rich idle.

Did it work?

[R4ND0M_AX3]

Originally Posted by STLSTI

Did it work?

I got a ps3 and have been distracted.

[STLSTI]

Originally Posted by R4ND0M_AX3

I got a ps3 and have been distracted.

NICE.

[jfitzpat]

Hi,

Sorry to wakeup an old thread, but this thread was linked to in another forum. A few things to keep in mind:

* Rear narrow band sensors are normally post cat. They are not there to monitor lambda (AFR), but to look for the removal of hydrocarbons.

* UEGO sensors (wideband or narrow) oxidize a test chamber, so when measuring on the rich side of stoichiometric (nominally 14.7:1), hydrocarbons are required for the measurement (on the lean side of stoich the sensor basically measures excess oxygen).

So, if the cat is working, and the engine is running in the normal ranges (peak and ROP), all wideband controllers will get some measurement error post cat. The direction and size of the error depends on cat efficiency (which changes continuously) and the measurement principle used by the controller - but there is always an error. Also:

* Most wideband vendors make it clear what the max gas temperature that the sensor is rated for (typically 800-1000 degC) but don't always publish the max bung temperature rating for the sensor - which is typically 300-400 degC cooler.

* Exceeding this spec shortens sensor life and also generally erodes the accuracy of the measurements, at least those a bit away from stoich (peak). However, it also has a tendancy to create tiny fractures in the sensor.

* All current based wideband controllers have some gas pressure related errors on the rich side of peak, but the errors are generally small. However, heat fractures can make the sensor very sensitive to lower gas pressures and pressure changes.

None of this nec. invalides the test or conclussion. I just thought it was worth noting that:

1. Post cat is a bad place to run a wideband for logging and tuning purposes because the cat alters the composition of the gas in precisely a way that effects UEGO measurements.

2. If you 'cook' a UEGO sensor near a turbo, it is very common for the readings to be very unreliable when the sensor is then used in a cooler, lower gas pressure, situation.

Best Regards,
-jjf

Edit: WolfPlayer, yes, you can most certainly program a LC-1 analog output to simulate a narrow band sensor. However, if the LC-1 is pre-cat I would be hesitant to use a narrow band simulation to feed a cat efficiency monitoring circuit.

Edit: Christian, the LC-1 does not have a significant pressure error. See the Innovate patent for details.

Edit: LukeSkyWRX, with a heated sensor, no additional heat is required, they will read calibrated gasses at room temperature quite accurately. Excess heat (outside of the rated EGT and bung limits) can lead to structural failure in other portions of the sensor (ex. ceramic) and problems for the heater control circuit.

[R4ND0M_AX3]

Thanks for chiming in Joe.

My LC-1 is pre cat (there aren't any) and several feet from the turbo.

[jfitzpat]

Originally Posted by R4ND0M_AX3

Thanks for chiming in Joe.

My LC-1 is pre cat (there aren't any) and several feet from the turbo.

If you don't have a cat installed, I don't see a problem with programming one of the LC-1 analog outputs and using it. If you put an LM-1 or LC-1 behind a cat, you will generally get readings that are .1-.3 AFR leaner, with the error falling off fairly sharply as you move away from stoich.

As far as location, if you are using a Bosch sensor both the LM-1 and LC-1 will throw an error if the bung temp limit or gas temp limit is exceeded. The only time I would worry about bung temp is when using an LM-1 with an NTK sensor. The LM-1 will still throw an error when gas temp is exceeded, but doesn't have a way to monitor bung temp.

Regarding the specific problem you are having, I'm sorry to say I don't have a clue why the ECU is idling rich. Rear O2 sensors typically aren't part of any AFR learning algorythm. But I only have a little bit of experience with the 16 and 32 bit ECUs in question.

-jjf

[flatthump]

Originally Posted by jfitzpat

I'm sorry to say I don't have a clue why the ECU is idling rich. Rear O2 sensors typically aren't part of any AFR learning algorythm. But I only have a little bit of experience with the 16 and 32 bit ECUs in question.

-jjf

The fuel trim corrections are made from the FRONT o2 sensor..

[R4ND0M_AX3]

Originally Posted by flatthump

The fuel trim corrections are made from the FRONT o2 sensor..

Maybe you haven't been following the issue. We're getting rich idle only when there is no rear O2 signal. We are as supprised as you.

[jfitzpat]

Originally Posted by flatthump

The fuel trim corrections are made from the FRONT o2 sensor..

Uh, OK. I thought that was my point ("typically aren't part of...") Post cat, O2 measurments typically aren't very meaningful for adjusting air fuel mixture (since the cat is working to remove the hydrocarbons the sensor needs to measure relationship to stoichiometric).

But I don't have an explanation for the phenomena already described, so I said so. It seems to me that the behavior of an ECU doesn't always have to make perfect sense when viewed as a black box. I could certainly envision firmware where a missing sensor causes problems in a seemingly unrelated system.

Think of someone yanking out your colon. Most of us consider our mouths and our rectums to be wholly seperate systems. But I'll bet if someone started embalming, most of us would be hard pressed speak in our normal calm clear voice...

On the flip side, there could be a problem with the measurements themselves. But, again, I'm not in a position to say one way or another.

-jjf

[WolfPlayer]

I wish people would stop filling up this thread with wrong information.

Subaru uses the rear O2 for fueling corrections. However, the roll the rear O2 plays is SMALL in comparison to the front O2. Simple as that.

t

[jfitzpat]

Originally Posted by WolfPlayer

I wish people would stop filling up this thread with wrong information.

Subaru uses the rear O2 for fueling corrections. However, the roll the rear O2 plays is SMALL in comparison to the front O2. Simple as that.

t

I'm sorry, I certainly didn't drop by to spread "wrong information". But, frankly, I don't find your statement any more compelling than flatthump's.

Flatthump doesn't really explain R4ND0M_AX3's experiences, and you are failing to quantify and elaborate on something that would be fairly unique and somewhat at odds with the physics involved.

I know you don't see it that way, but from my point of view you are saying "removing the defrost switch does effect fuel pump pressure". Yes, you are talking about two O2 sensors, but they generally serve two very unrelated purposes.

I'd like to understand, so I could better predict if R4ND0M_AX3's intended work around will be successful. But, if people are just going to throw absolutes at me - particularly ones that I don't really even see as being directly related to my comments, there is very little I can contribute.

Best Regards,
-jjf

[daemon]

Originally Posted by jfitzpat

Yes, you are talking about two O2 sensors, but they generally serve two very unrelated purposes.

I'd say "usually" rather then "generally". I've always sort of read this thread and thought there is a chance that Subaru might use the rear as a sort of check up on the front. It isn't unheard of for the 02 sensor to die. If they say the rear "should be about this much different" from the front and it isn't, then maybe they compensate a tad "just in case".

I honestly have no idea, but I don't find the two 02 sensors as unlikely to be related in some minor fashion as the defrost switch and fuel pressure.