Modifying catalyst efficiency thresholds

[repoman89]

Anyone know what values or maps need to be modified to “turn down” the rear O2 sensors? My SSv1 cats are not strong enough to not trigger the catalyst efficiency codes when combined with CSL software (they were fine with stock US more emissions friendly software). I looked for a while in XDFs and couldn’t narrow it down, and eventually just turned off the DTCs. However it would be nice to have an indicator of catalyst health and turn their sensitivity down 30-50% or so.

[EthanolTurbo]

In for details

[R3Z3N]

Not sure about changing the efficiency, but you can simply disable the DTCs so that it no longer reports, which it seems you did. The rear O2 sensors do not affect engine running:

https://github.com/saildot4k/MSS54-X...-Sensor-Delete

[Stack]

Have you thought about just adding in a bung ?


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[SliM3]

You should be able to adjust post cat values using Lambda_POST-CAT (NKAT) SENSOR VOLTAGE (USM)lean (K_LANK_USM) & Lambda_POST-CAT (NKAT) SENSOR VOLTAGE (USF)rich (K_LANK_USF).

Max allowable value is 1000mV.

[repoman89]

You should be able to adjust post cat values using Lambda_POST-CAT (NKAT) SENSOR VOLTAGE (USM)lean (K_LANK_USM) & Lambda_POST-CAT (NKAT) SENSOR VOLTAGE (USF)rich (K_LANK_USF).

Max allowable value is 1000mV.

Thank you!! So presumably those are the thresholds around 0.45V that the DME uses to determine whether a crossing event occurred. I’ll give it a bit more leeway, 0.35 and 0.55 or so and see what that does with the DTC reenabled. I should probably log the readings too and see what nearly new SS/HJS 100 cells look like on the current tune.

[Tbonem3]

Ss hjs cats are 100 cell for most applications, but alpinerider confirmed that cell count is 200 specifically for e46 m3 hjs catted sect 1 (2.5" & 2.365).

You don't need to mess with o2 sensitivity, you'll pass. Get them well warm just to be sure.

[repoman89]

Ss hjs cats are 100 cell for most applications, but alpinerider confirmed that cell count is 200 specifically for e46 m3 hjs catted sect 1 (2.5" & 2.365).

You don't need to mess with o2 sensitivity, you'll pass. Get them well warm just to be sure.

good info about the cell count.

I don’t have smog or OBD emissions period anymore (15 year rule in MA). More want the cat monitor working as designed but for my specific hardware because it feels like a hack to just disable the DTC ... especially since I went through all the effort of putting the post cat O2 hardware in. I didn’t get the DTC with the stock US tune but do get it pretty quickly with my PCS CSL tune, until I disabled it of course.

Just call it software/electrical engineer OCD to have a non functional system in the car

[repoman89]

So far so good with the codes turned back on and lean/rich thresholds given another 0.05V of leeway. I haven’t driven it a ton but the catalyst efficiency code used to appear pretty quickly.

[ELEM3NT]

Noob question incoming....best tool for this BMW flash, mssflasher, INPA, other? Thanks in advance.

[repoman89]

Noob question incoming....best tool for this BMW flash, mssflasher, INPA, other? Thanks in advance.

TunerPro combined with the XDFs in @R3Z3N’s sig. mssflasher will correct the screwed up checksum in the binary when you go to flash your changes.

[ELEM3NT]

TunerPro combined with the XDFs in @R3Z3N’s sig. mssflasher will correct the screwed up checksum in the binary when you go to flash your changes.

Thanks! Appreciate the info. I'm looking to make the same adjustment but have not used any of these tools to this point.

[heinzboehmer]

I did this for my SS HJS cats, but eventually just turned the post cat O2s off entirely. The light would come back on after longer highway driving and I got bored of messing with it.

[repoman89]

I did this for my SS HJS cats, but eventually just turned the post cat O2s off entirely. The light would come back on after longer highway driving and I got bored of messing with it.

Yep, it doesn’t work. You can go almost as wide as you can on these thresholds and the HJS cats will still throw the code on long highway drives. Anyone who says they have “turned down” the sensors in the tune has just turned off secondary O2 monitoring. They must not get up to a high enough temp on those light load situations when the catalyst testing is running.

Who cares I guess, the catalysts are there and working regardless of the idiot light test. I just pretend it’s a pre-OBD2 car from the 90s.

[heinzboehmer]

Yep, it doesn’t work. You can go almost as wide as you can on these thresholds and the HJS cats will still throw the code on long highway drives. Anyone who says they have “turned down” the sensors in the tune has just turned off secondary O2 monitoring. They must not get up to a high enough temp on those light load situations when the catalyst testing is running.

Who cares I guess, the catalysts are there and working regardless of the idiot light test. I just pretend it’s a pre-OBD2 car from the 90s.

Yeah, it's unfortunate cause I don't love to turn fully off features that could be useful (like you mentioned), but it just wasn't worth my time. My nose can be the cat efficiency light from now on.